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PontiacLars
Tribal Scout

11 Posts

Posted - 04 Sep 2019 :  2:35:54 PM  Show Profile  Reply with Quote
I would like som opinions on what to do next to make my engine produse more power.
Current set-up:

400 block bored +0.30 2-bolt mains
Speedpro 4 valve relief pistons
Eagle H forged rods
Original crank ground down 0.20
All balanced
#46 iron heads. New guides and 2.11+1.77 valves. Mild portwork.
Crane full roller 1.65 rocker arms
Comp cams XE284H camshaft
MSD distributor with mallory ignition box and coil.
Hooker headers
2x2,5 exhaust pypes race pro

This engine sits in a 4 speed Trans Am with 3.42:1 gears, Max rpm 6750 now.

This combo did not give the power I was expecting and
I am considiring a 461 stroker kit from Butler or KRE High Port heads or Edelbrock E heads.
What would be your choice? The cost is about the same..

tjs44
Crazy Horse

USA
627 Posts

Posted - 04 Sep 2019 :  3:30:51 PM  Show Profile  Reply with Quote
KRE D ports and the stroker kit.In for a penny in for a pound!Depending on how much HP you want that combo can make close to 600 HP.With the D ports you wont need new headers,cam and rockers will work.Tom
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 04 Sep 2019 :  11:35:50 PM  Show Profile  Reply with Quote
Which 46 heads are on that. What cc? Are they the 80cc. Which intake valves, 45* or 30*? Compression?

Are you looking at out of the box aluminum heads? Jay

Edited by - Corncob2061 on 04 Sep 2019 11:41:59 PM
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PontiacLars
Tribal Scout

11 Posts

Posted - 05 Sep 2019 :  04:55:04 AM  Show Profile  Reply with Quote
Both stroker and aluminum heads are out of my budget now, that is why I am wondering what is the best to start with.

I did not know there was 46 heads with 80cc? Are they not all 72cc?
I have Ferrea valves 45 degree.
I am looking at out the box alu heads but would like to reuse my valves and springs if possible.

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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 05 Sep 2019 :  10:38:47 AM  Show Profile  Reply with Quote
There was some made in 73-74 that were bigger cc heads. 69 had the small chamber.

With the 4 speed the better heads might be a better way to go, the extra tq of the big cid pushes what most 4 speeds will handle. Unless you have a HD 4 speed or a modded one. Jay
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 05 Sep 2019 :  12:24:32 PM  Show Profile  Reply with Quote
Right off the bat you can forget High Port heads as they have a lot of valvetrain mass and need quite a bit of spring pressure to control it. The intake valves typically use 2.200" diameter and valve length around 6.200". And require a minimum bore size. That and the claimed 330 cfm and large runner volume will be way over kill.

The valves that are used in the heads assembled from Edelbrock come in a length for a 1.800" installed height, the length depends on the chamber size. Keep this in mind if you want to order raw castings.


.
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 05 Sep 2019 :  1:49:37 PM  Show Profile  Reply with Quote
"Max rpm 6750 now"

Curious, are you suggesting the engine is currently making power toward that number or suggesting it can safely rev that high with the components in use ?



Edited by - Steve C. on 05 Sep 2019 1:50:19 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 05 Sep 2019 :  4:05:36 PM  Show Profile  Reply with Quote
Am I recalling that correctly that the small chambered 46 and number 15 heads run about upper 70s to 80 instead of 72? IRC, 16 and 48 run close to 72, 62 and 13 run closer to 75-78, and the small valve 15 and 48 in 1968 and 69 just about 80cc. Then 73-74 there was a 46 that ran mid 90s. No number published like that that I know of, it is what folks have measured them at.

We have never ran a 69 casting 46, but the everything I have seen they react well to the bigger valves and port work.

If the 46 heads are close to 80cc, that puts the compression down to the lower 9s. Might be asking a lot to push the rpms much past 5500 with that combo if I am correct on that. Maybe some else can verified the 80cc, I could be wrong, going off memory on that... Jay

Edited by - Corncob2061 on 05 Sep 2019 4:07:38 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 05 Sep 2019 :  4:25:42 PM  Show Profile  Reply with Quote
I can't offer up a 400 Pontiac dyno sheet indicating peak power rpm but I did read a tech article where a short stroke Small Block Chevy combination with the XE284H cam and aftermarket cylinder heads went to 6200 peak rpm. And this with Comp Pro Magnum roller rocker arms, valvesprings with 153 lb seat pressure and with titanium retainers on the springs. All revolving around a small block Chevy valvetrain weight. And the cylinder heads on that specific SBC combination had longer, thus heavier valves, I presume it's valvetrain mass was probably lighter than the Pontiac.

And as another example, here a Comp Cams "dyno sheet" for 3.480" stroke Chevy 350 with aftermarket heads and single-pane intake with the XE284H cam .... peak power at 5800 rpm.

https://www.compcams.com/xe284h

Here below is a dyno proven 400 combo from SD Performance many years ago with more intake duration than the XE284H cam and a single-plane intake... peak power right at 6000 rpm.

4.150 bore
3.750 stroke
Eagle 6.625 rods
6X factory heads / 9.3 cr / 260 cfm
Comp P296-AH-8 hyd flat tappet cam
246/253 @.050" / 108 LSA / 104 ICL
0.544" / 0.560" (1.6 ratio)
Torker II intake w/ 1-inch spacer
Reworked Holley 800 cfm carb
1-3/4" headers

459 hp at 6000 rpm


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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 05 Sep 2019 :  10:47:24 PM  Show Profile  Reply with Quote
I see one company is offering forged cranks with Pontiac 2.25 journals, (gasp!) 3 inch mains again in 4 inch and 4.21 stroke for $597 with free shipping( shipping usually adds $140), throw in a set of $300 speed pros with the rods out of the 400 it would be a smoke n cheap stroker engine. I am even tempted to switch out my 4.21 N crank for this, thought these were discontinued...Must be a fresh batch, or someone opened a lost shipping container..lol...jay

https://www.ebay.com/itm/PONTIAC-400-455-4340-Forged-Steel-Crankshaft-ST-4-210-M-3-00-RJ-2-25-RMS-2Pc-Ext/302396623474?hash=item46683e4a72:g:zJIAAOSwI59aBA42

Edited by - Corncob2061 on 05 Sep 2019 11:10:14 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 05 Sep 2019 :  10:52:38 PM  Show Profile  Reply with Quote
And the 4 with Pontiac journals, man I might have to get one of each, $597 that is cheap with free shipping.

https://www.ebay.com/itm/PONTIAC-400-455-4340-Forged-Steel-Crankshaft-ST-4-00-M-3-00-RJ-2-25-RMS-2Pc-Ext/302749066100?hash=item467d402374:g:AOsAAOSw~Q9bBz3x


I would guess these might be similar to star galaxy ???

Edited by - Corncob2061 on 05 Sep 2019 11:21:03 PM
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Lee
Sitting Bull

193 Posts

Posted - 06 Sep 2019 :  09:46:59 AM  Show Profile  Visit Lee's Homepage  Reply with Quote
Define "power".

Going with more cubes will give you more TORQUE, but horsepower will remain virtually the same with the same heads & other components - it will just occur at a lower RPM.

Going with better heads will give you more HORSEPOWER, and help the torque as well.

CURRENT: '73 T/A clone, starting to get less boring!...
67 Firebird (sold) 11.27 @ 119.6 Feb. '05 issue HPP
69 Falcon wagon, 10.51 @ 130mph Feb. '10 issue PHR (sold)
72 Cutlass Convertible, first car, owned since '82, now with a 6.0 LS, mild, putting just under 400 hp/tq to the wheels.
www.LNLPD.com
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tjs44
Crazy Horse

USA
627 Posts

Posted - 06 Sep 2019 :  11:08:11 AM  Show Profile  Reply with Quote
I ordered one of their 4in stroke 2.25 cranks,when it arrived it was a BBC J.They paid the shipping back.FWIW,Tom
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 06 Sep 2019 :  11:21:05 AM  Show Profile  Reply with Quote
Two interesting points of view, one from a street perspective and another from a race perspective.

From the street....

"Since larger motors produce more torque, and horsepower is nothing more than torque multiplied by rpm, they can make the same horsepower as smaller displacement motors without having to turn as many rpm. The net effect of keeping the rpm down is vastly improved valvetrain reliability, smoother idle quality, and the ability to run taller gearing for more relaxed freeway cruising and increases in fuel mileage. Likewise, turning fewer rpm means that you can get by with a less aggressive camshaft, which substantially improves driveability in addition to fattening up low and midrange torque. Consequently, if you use the largest cubic-inch short-block that you can afford as the foundation for your engine build, it's hard to go wrong. Our goal is to design a motor to be as efficient as possible for the rpm range we want to run it in, then to use the best cylinder heads available. That way, you don't need to run a big cam, which makes an engine combination much more streetable."

From the race....

"There are much more cost-effective ways to tailor an engine's torque curve than to use a long stroke crank and small bore block. The intake manifold, cylinder head runner volume, and camshaft timing all have a much more significant impact on the torque curve than the stroke and are much easier and less expensive to change."

And as typical by me this material is offered for general interest only, with no intention of right or wrong presented. Nor which might be more cost effective :)


Edited by - Steve C. on 06 Sep 2019 11:26:09 AM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 06 Sep 2019 :  1:48:45 PM  Show Profile  Reply with Quote
quote:
Originally posted by tjs44

I ordered one of their 4in stroke 2.25 cranks,when it arrived it was a BBC J.They paid the shipping back.FWIW,Tom




Why am I not surprised. Too good to be true. Still cheap though, be worth considering for bbc rods. They claim they are good for 1400 hp. Seems like a pretty big number.

There has been several dyno tests were they left everything the same, cam, heads, compression ect and change only the stroke. Most of the time the stroker engine comes out on top big on tq, and some gains hp to. I read one 350 sbc verse 427 sbc that the 427 was close to 30 higher. Engine masters ep18 had a shootout of a 360 mopar LA versus at 410 mopar LA and the 410 beat the 360 by 8 hp with a lot less torque. Never seen a Pontiac comparison like that, likely similar results, some how the longer stroke manages to pull a little more air in at peak power. So it is anyones guess which is right, stroke or heads. Seems like the combo that can not miss is the one Tom said earlier...Cubes and heads win/win..Jay

https://www.hotrod.com/articles/stock-vs-stroked-horsepower-test-engine-masters-ep-18/

Edited by - Corncob2061 on 06 Sep 2019 1:50:16 PM
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i82much
Cochise

USA
224 Posts

Posted - 06 Sep 2019 :  7:25:01 PM  Show Profile  Reply with Quote
I'd make darn sure my 400 was tuned properly and didn't have any issues first. Yes, you can go faster by throwing parts at your car, but making sure the parts you already have are performing optimally is fun, free or at least cheap, and what you learn by doing it will help you if you decide to throw parts at your car later.

That being said, you can change the heads in a weekend and be back on the road. On the other hand, the stroker is going to give you bigger bang for your buck from the "seat of the pants" perspective. A 400 with nice flowing heads needs some rpm to make power.

Steve
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PontiacLars
Tribal Scout

11 Posts

Posted - 07 Sep 2019 :  12:21:13 PM  Show Profile  Reply with Quote
I am not sure where power drops of. It hits the revlimiter quick with the current gearing.
It cerntenly needs rpm to make horsepower. Not much happening before 3000 rpm and the driveability in low revs are not good, jerky and rough.

Anyone have experience with 4.5 inch stroke? With my current bore (4.150) this makes a 7.982 CID engine. With the right dish on the pistons this could work with my current heads and maby the camshaft works better with the larger CID engine?
Block casting is 481988 so strength should be ok?
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phil400
Crazy Horse

Canada
515 Posts

Posted - 07 Sep 2019 :  12:41:44 PM  Show Profile  Reply with Quote
That seems like a big cam for a 406,I've only read of guys running it in 455s, which would explain doggy below 3k. It might want more gear.

78T/A 4-SPEED/Original Paint/ Mine since '99 Third and final owner as long as I'm alive.
77 T/A Sold
85 Monte Carlo SS Sold
83 Mustang GT Sold
"Let me tell you what Melba toast is packing"
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 07 Sep 2019 :  1:32:38 PM  Show Profile  Reply with Quote
4.150 bore and 4.5 stroke crank would be 486 cubic inches.
Do your homework regarding a 4.5 stroke crank in a factory block.... steel aftermarket caps, stud kit, filled block, etc.


Reminds of the bicycle pump and small runner volume cylinder heads....

The longer stroke will make the engine sensitive to under-flowing heads. To illustrate, grab a bicycle tire pump sometime, and first try to operate it as quickly as you can. Then, slow down the pumping action. You will notice that it is far easier to move the pump handle slowly. Your engine is no different- slow down the piston, and the engine has less work to do. Again this condition is aggravated by high RPM conditions. The important thing to remember is that no matter how fast or slow the piston goes, the engine moves exactly the same amount of gasses during the same number of crank degrees.

And this.....

"With the high piston speeds involved it will obviously require much better than production reciprocating parts. Good quality light 6.700" rods and lightweight pistons. Also it's more sensitive to detonation, as well as sensitive to under-flowing heads so watch compression with the iron heads, and they will certainly benefit from good quality port work."

Ray T. Bohacz
"Long Armed and Dangerous"
June '02 High Performance Pontiac Magazine

Edited by - Steve C. on 07 Sep 2019 1:35:11 PM
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PontiacLars
Tribal Scout

11 Posts

Posted - 08 Sep 2019 :  06:26:42 AM  Show Profile  Reply with Quote
I have been doing some reading and the ones who have done it says it works fine with 4 bolt main upgrade. Is block filling that common if the rpms are kept at arond 6000 max?
What are you guys experience with compression ratio? Will 10.5:1 work on premium fuel with iron heads? I know that piston stand still time increase with the added stroke and that can lead to detonation.
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 08 Sep 2019 :  10:00:20 AM  Show Profile  Reply with Quote
Yes, 4-bolt main caps.... but I hope you would not attempt it with factory caps & bolts ! Install Pro-Gram Engineering 4-bolt steel main caps on the center mains with oversize dowel pins to locate them. Purchase and use a ARP stud kit. The last time I did that work at least 15+ years ago just the main cap installation labor, they have to be fitted and the thrust cap has to be machined, and honing labor alone was about $500 at the time. That didn't include the costs for the parts. No telling what that labor would be at today's shop rates.
Filling the block to the freeze plugs has noting to to with intended RPM. The pressure or load on the outside of the cylinder wall is very high and increases with the larger 4.500 stroke. The cylinder wall starts to distort from the outward force caused by the rod angle as the piston stops and begins the upward movement.

Edited by - Steve C. on 08 Sep 2019 10:04:27 AM
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PontiacLars
Tribal Scout

11 Posts

Posted - 08 Sep 2019 :  10:14:45 AM  Show Profile  Reply with Quote
I see that program engineering main caps come as single part number for the front cap, the three in the middle and the rear one that holds the rear seal. The rear cap costs the same as the three in the middle..why is that? Is replacing the three in the middle enough or do one need all five?
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tjs44
Crazy Horse

USA
627 Posts

Posted - 08 Sep 2019 :  10:54:19 AM  Show Profile  Reply with Quote
If your going to do all 5 billet caps and a 4.5 crank your better off with a aftermarket block.Kind of like putting lipstick on a pig.10.5 CR with normal pump gas is pushing the envelope with detonation.Dave at SD kind of uses 10.25CR for alu heads.Tom
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 08 Sep 2019 :  11:45:33 AM  Show Profile  Reply with Quote
For your intentions billet front and rear caps would not be necessary. And a fwiw, Billet SpeedWorks has acquired Manufacturing Operations of Pro-Gram Engineering. And as I eluded to, the Pro-Gram Engineering billet 4-bolt steel caps have .020"extra material on the thrust cap for finish and they must be machined. Also the process is more difficult on a Pontiac than on other engines because the dowel pins used to align the main caps are like fingerprints - no two are exactly alike. Buy and fit oversize dowels, I think Butler sells them as do others. Once this is done and the new caps are fitted, the block is align-bored. According to one well respected Pontiac source... the proper way to line bore a Pontiac block is to first put the block on a milling machine and register all four corners. Then you need to take a light (usually about .003) cut down the center only in the area the caps will seat in. This is required because most blocks have taken a "twist" from front to back over the years. Also, most main webs have developed a "crown". Now with the block surface prepared, you can skim the bottoms of the caps and proceed with the line bore. This gentleman charged $585.00 to do this, but it's done right. And that cost was in 2003!

A fwiw, I have installed Pro-Gram Engineering billet caps on two different factory blocks, but not involving a 4.5" stroke crank. Thus this material posted by me is offered for general interest only. I'm not here to suggest the use of the 4.5 crank OR to do so in a factory block. I agree with Tom and personally I would use a IA2 block IF going to a 4.5" stroke.

Edited by - Steve C. on 08 Sep 2019 12:36:28 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 08 Sep 2019 :  12:07:33 PM  Show Profile  Reply with Quote
I know you do not intend to build such a higher horsepower combo, but for interest to support some comments here....

"When you add 5 steel main caps, a lifer bore brace and Block filler cement to make a stock block live to 700 ish horsepower. It can weigh in at 220 lbs. The cost to modify a stock block is around $2,200.00 to $2,500.00 bucks."
Bob C.
ALLPontiac.com

Been there, done it. Just as Bob described with 700 hp, and before the aftermarket block was available. Also others will disagree THAT much money to prep a stock block is involved.

Edited by - Steve C. on 08 Sep 2019 12:11:41 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 08 Sep 2019 :  5:33:08 PM  Show Profile  Reply with Quote
Most of the engines I have built or am building for one of my own cars are what would be considered high compression cast iron headed pump gas engines. I look at SCR as a means to maximize or minimize other parts of the engines performance not as a number by itself. I know plenty of local engine builders that puts limits on the SCR, usually at 9.5 for pump gas with cast iron heads. The cid, head and exhuast flow, induction and exhuast system, cam and compression all work best matched up together. If you push one element to far or not enough you can find yourself pissing into the wind trying to make hp. With lack of head flow on a big cid engine the static compression can be increase and increased and power output stays pretty much flat with only small gains. You can then add more cam if you choose, and add more compression yet, but if the heads are holding the big cid engine back you end up with about the same hp, less torque with a broader power band. So for what it is worth, if you want to do a big cid engine such as a 4.5 stroker with a set of average heads you could run 9:1 compression loose very little performance versus the 10.5:1 4.5 stroke street engine with the same heads. It is a similar effect to adding a bunch of compression to a smaller engine with a stock cam, the cam does not let the engine breath and the extra compression adds very little. Your probably the other way right now, you appear to have a decent cam and heads, but might be short some on compression depending on what cc the heads actually are.

But, as I stated, I push compression on my cars. It can be done. We have been up into the mid 10s scr with 455s. But it works best with fully ported cast iron heads, high flow induction and exhaust with a carefully chosen cam. Jay

Edited by - Corncob2061 on 08 Sep 2019 5:59:05 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 08 Sep 2019 :  8:10:58 PM  Show Profile  Reply with Quote
"I know plenty of local engine builders that puts limits on the SCR, usually at 9.5 for pump gas with cast iron heads."

I'm not a engine builder but I'm in that camp :) And that 9.5 number typically touted in many tech articles on the subject with iron heads. Similar situation with Dave Bisschop in relation regarding a general recommendation of the static compression ratio. He feels you can't protect all of these engines once they leave your shop so he purposely keeps it conservative for most that don't want (or shouldn't) push the envelope and stay on top of the tune, bad gas, weather, etc.

If your like Jay and can stay on top of things go for it, for the small difference.

Edited by - Steve C. on 08 Sep 2019 8:14:23 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 08 Sep 2019 :  10:09:17 PM  Show Profile  Reply with Quote
I built a bunch of 9.5 scr engines. It worked well for a lot of cast iron heads engines. Some engine builders have struggle though with some of the smaller short seat timing cams like the XE cams and aggressive small hyd rollers. With those cams 9.5 even became to high. With good heads and hyd roller cam combos like SD performance sends out I am on board with 9.5. :). Vast majority of combos 9.5 is a great place to put the SCR.

I do not have great examples for moving from a stock 3.75 crank combo to the bigger strokes, I have mainly built 455s. :). I am pretty sure Steve has example moving to a bigger cid engine with less compression and a smaller cam. :)

here is one of mine:

My 69 Dodge Charger we had a 450 cid with aluminum heads ran on race gas, ported by the famous hemi super stock guru Ray Barton, solid roller cam designed by Barton, 260/268 110lsa at .050 with .624/.624 lift. The head flow numbers were published in a magazine. They flowed 268 cfm intake and 210 cfm exhuast after Barton worked on them. It made 557hp at 6100 rpm and 567 ft lbs pretty much flat torque from 3000 to 5000. We had a 5000 stall and could hardly drive the thing. So we moved that engine over to a race car and built a 510 CID stroker engine, it was back when stroker engines where almost unheard off. We started out with 11.1 scr ported cast iron heads, dual plane intake and a cam similar to that XE 284. It ran good, but we had to run a blend race gas in it. It was about 465 hp @5500 going by et and mph. We then switch to a bigger solid cam, did more porting to the heads, dropped the compression to 10.5 and went to a single plane intake. It then made around 535hp @ 6000 on 89 octane pump gas by e.t. and mph against the other engines. About 20 hp less than the full roller 450 cid race gas engine at almost the same rpm with another 60 cubes and a 12 degree smaller cam at .050, but with a wider lsa and less lift. The oem fully ported cast iron heads outflow the Barton ported aluminum aftermarket heads some, mostly it is the 60 cid and the cam that made the difference. The stoker engine has a ton of seat timing compared to that roller, it fills cylinders in a completely different manor. I am sure I could do some more tuning or a cam with more lift it could match the hp of the 557 hp aluminum head roller engine.

As a side note, we ported the Barton heads on the 450 cid engine and changed cams, picking up close to 100 hp over what Barton did with no other changes. We had a fair amount of anxiety for fear of loosing head flow when we started porting on that one. We almost gave up porting that one, when we first started porting and put them on the flow bench for the first time we lost flow everywhere! Lol, thought we ruined our heads. We finally found some flow, eventually ported until we hit the steel spring retainers under the valve spring and had to take them to a tig welder. The engine ran totally different, we went from running with mid 10 second cars to keep up with cars in the upper 9s. Did not even sound like it was the same engine. It went from feeling like is barely went to 6000 to shift at 7000.

So, which way do you want to gain the power? Both ways work, do what you can afford.


Like Steve said, I go after every little hp on some things, cam, head flow and compression are the 3 main things I focus on. Hard to say what I gain sometimes, it is what it is. :) Jay

Edited by - Corncob2061 on 08 Sep 2019 11:38:42 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 08 Sep 2019 :  11:38:45 PM  Show Profile  Reply with Quote
Again, the 4.5 stroke will be sensitive to under-flowing cylinder heads, at least that's what is touted, but that said I've built nothing with more that the popular 4.250" stroke. And my current engine using it has only 10:0 compression with Edelbrock heads. Also I run solid roller cams... the obvious, when going from a hydraulic cam to a solid cam you should increase the amount of intake duration for similar results. Example the very popular Dave Bisschop Old Faithful hyd roller cam with 236 degrees intake duration would be similar to at least a Comp XE 242 solid roller lobe or even a bit more. And his popular Road Paver hyd roller cam with 246 degrees intake duration has a VERY SIMILAR lobe profile as the Comp Hi-Tech .420" solid roller lobe 4005 with 256 degrees intake duration. And those hyd roller cams are very popular in 455 based street/strip combinations.

Edited by - Steve C. on 08 Sep 2019 11:44:20 PM
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i82much
Cochise

USA
224 Posts

Posted - 09 Sep 2019 :  1:16:08 PM  Show Profile  Reply with Quote
I would stick with the 4.25 stroke. Some have success with the 4.5 and some don't. If you are budget-constrained and the 4.5 stroke deal doesn't work out, what do you do then? Much safer to go with 4.25.

Steve
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DanM
Sitting Bull

190 Posts

Posted - 10 Sep 2019 :  1:04:13 PM  Show Profile  Reply with Quote
Lars,

Please take your car to a chassis dyno shop and get a couple measurements. We need specifics to accurately advise you. In my opinion you have far too large of a cam for that engine. 240 degrees of duration at 0.050" seems overkill. You talk about revving over 6000 rpm. I feel that approach is indeed consistent with such a massive cam duration but the heads will need more than just mild porting.

To that end can you provide measured flow bench numbers for your heads.

You are seeking more power but for what reason? If your goal is a better 1/4 mile time then it's possible you really want more average power in case that massive cam might be counter productive unless you have a very high stall rpm converter.

What are your 1/4 mile times? (and 60 ft, 1/8th mile, mph, etc.)

So without knowing all that, and having done the mechanic work myself I would advise (as i82much suggested) to get your 400 tuned first. It's a lot easier to change a cam than to change a crank shaft.

Meanwhile, I'm biased. I drive my car daily so I have no interest in revving to 6000 rpm with a 240 degree duration car. It would be completely undriveable. My instincts say to go to the track, swap in a milder cam, go back to the track and discover you went faster.

Sincerely,
Dan

71 LeMans Sport Convertible with 350,000 miles driven year round since 1994.
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 10 Sep 2019 :  8:08:53 PM  Show Profile  Reply with Quote
Here is a 400 Pontiac idling with a XE284. Sounds pretty spirited...

https://m.youtube.com/watch?v=HdURdhhRE1k


Not everyone is into bigger cams, I get that. Might consider what big cid does with cam size. Bigger cid engines swallow up the bigger cams like that xe284. My car that had the 510 cid engine and the cam similar to the XE284 had a best mpg average of 23mpg with an 850 holley on a mpg check during a 250 mile trip on a two lane blacktop. It average 17.8 in a different 360 mile round trip down the interstate with a bunch of rounds of 1/4 mile drag racing averaged in and included in the average (made it to the finals in a pro class). Some complaint about big engine using a lot of fuel, and supposedly the bigger cid and economy are two words that do not mix. That has not been my experience, but again, I typically push compression, and generally efficiency is one of the side effects. I like the 4.25 stroke engines across brands for street cars. I have a 4.5 inch mopar crank waiting for a project, we hope to put it in to use down the road, when I see engines with 4.5 cranks I try to take notes. We have a builder up by us doing Pontiac 4.5 cranks pretty frequently now. I would like to try one in a Pontiac, sounds like a worthy challenge I need to try. :) Jay

Edited by - Corncob2061 on 10 Sep 2019 9:02:44 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 10 Sep 2019 :  11:06:59 PM  Show Profile  Reply with Quote
Side topic... how about the enormous amount of torque in conjunction with a 4.5 stroke on the 4-speed transmission ?



.

Edited by - Steve C. on 10 Sep 2019 11:07:34 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 11 Sep 2019 :  09:12:54 AM  Show Profile  Reply with Quote
quote:
Originally posted by Steve C.

Side topic... how about the enormous amount of torque in conjunction with a 4.5 stroke on the 4-speed transmission ?



.



That is a good question. How much more torque will the 4.5 crank produce over say the 4.25? I do not think a stock st10 or m20, m21 or m22 would hold the 4.5 or a 4.25 stock. It would probably take some m23 guts to hold those bigger cubes, or on the st10 one of the steel mid plates (custom) or a cast iron mid plate and I think a couple gear inside on one of the clusters are made with a higher nickel content.

The m23 aftermarket trans would handle the bigger cid engines. The ones with the lower gear set with the wider jump between gears might like the bigger cubes. One of the five speeds should handle it to, not sure how you would set up the gears though?? J

Best way to make a manual survive IMHO is to build a high winding engine. I am doing a 450cid in front of a st10 with a cast iron mid plate upgrade. I will probably switch to a m23 if I get the money saved for it. Jay


Edited by - Corncob2061 on 11 Sep 2019 09:58:08 AM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 11 Sep 2019 :  10:11:57 AM  Show Profile  Reply with Quote
I thought this text my brother received from one of my friends was pretty funny regarding my 4 speed t/a. They both know how much time I have put into building the engine in it. Then a few weeks ago I had a custom roller cam ground for the engine, with the help of Steve C. :). They were texting about some car projects and it cam up that I was putting roller cam in that had .640 lift in my TA. lol, here is one of the comments said in fun...I got a kick out of it...:) jay

Quote:

Jay will be going along and will have the shifter in his hand but will not be attached to anything....

Needs a midplate to keep the engine front falling out...

And last..he should carry a bag of floor dry in the trunk...lol


Edited by - Corncob2061 on 13 Sep 2019 11:06:44 AM
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PontiacLars
Tribal Scout

11 Posts

Posted - 11 Sep 2019 :  10:27:19 AM  Show Profile  Reply with Quote
Great discussion going on here with alot of knowledge.
This car is only a fun weekend car I have to smoke my friends cars and going to car shows, so no daily driver. I do however want it to be somewhat driveable and I feel that with my current CID and cam it is to rough in cruise speeds.

I have thought about driveline issues with going to a bigger cube engine and I belive my transmission is the weakest link.
Rear Axle is fresh built with 3.42 richmond gears and Auburn differential. Was told that too much traction would kill it, but I do not intend to run drag slicks.
Prop Shaft has new joints and new balancing.
Trans however is an Saginaw 4 speed. I know a guy who has been racing one in a 600 hp racecar for years so time will tell if it lives.

I have no flow Numbers on my heads as they are only bench ported by me. No professional shop.
I need to get my heads CC checked as this statement that some #46 heads have 80cc bugs me.
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 11 Sep 2019 :  11:12:38 AM  Show Profile  Reply with Quote
A fwiw, I've had a Auburn unit in my Trans Am for almost 20 years, still using it now and my current 505 makes over 600 ft.lbs.torque from about 4100 RPM up thru 5700 RPM. And with it the previous engine combinations have been 560, 600+ and 580 HP. The only time we took it out was to run a spool with the 700 HP 450 combo. And we have run slicks with it. That said, we have been damn lucky and honestly I'm very surprised it has lasted :) Also important to note that it's always been used with a automatic transmission and the proper converter to match the combinations in use. Now is this a recommendation.... NO, I won the Auburn differential in a raffle !

Edited by - Steve C. on 11 Sep 2019 11:16:26 AM
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tjs44
Crazy Horse

USA
627 Posts

Posted - 11 Sep 2019 :  11:50:20 AM  Show Profile  Reply with Quote
I would really worry about a Saginaw over 400 HP with sticky tires!Tom
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 11 Sep 2019 :  11:59:54 AM  Show Profile  Reply with Quote
Which Saginaw do you have? How many grooves on the input shaft? 1st gear is what breaks on those. There are 4 different gears sets, the lowest two gear set transmissions will not take a lot of abuse in first gear. The seem to take a fair amount of abuse in 2,3, and 4.

Since you did the porting yourself you might know where your main porting efforts were done. Where were your main efforts there? Jay
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DanM
Sitting Bull

190 Posts

Posted - 11 Sep 2019 :  12:53:51 PM  Show Profile  Reply with Quote
Fun weekend car. Ok. Noted.

Out of curiosity what springs are you using?
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PontiacLars
Tribal Scout

11 Posts

Posted - 11 Sep 2019 :  1:17:20 PM  Show Profile  Reply with Quote
I don't remember have many grooves on the input shaft. I always start in 2. gear when doing burnouts and only hammer it in 1. doing rolling starts. Maby that is why it still lives.
The bowl is what got most attention and the intake ports are a bit wider.
Springs I think is comp cams 995.

Sounds like the auburn diff is a solid unit!
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PontiacLars
Tribal Scout

11 Posts

Posted - 11 Sep 2019 :  1:19:19 PM  Show Profile  Reply with Quote
Dan, never tried the car on the drag streep so have no times to share unfortunatly.
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 11 Sep 2019 :  5:56:44 PM  Show Profile  Reply with Quote
A fwiw. A fellow on the PY board built a 463 using the cam XE284H cam. It was 9.25-1 compression, RPM intake with 1" spacer, 850 Holley, cleaned up heads 220 cfm...dyno'd at 440 hp.
It went 11.98 @ 109 @ 3680lbs.

The valve springs in the heads were not adequate. He used the 995 springs that after use they lost pressure down to about 95 lbs seat pressure if memory serves me right, and after that it was nosing over below 5000 rpm, 4700 or 4900 rpm, don't remember which.

Personally I would not always rely on the pressures from cam manufacturers. A good example in my opinion is the Comp 995 spring often regurgitated by them for use in a Pontiac applications at a pressure many would find inadequate. All too often the Comp Tech people, and depending on which work cubicle the call gets routed to, just regurgitate their standard recommendation and it's taken as gospel. I've known of many applications where they have lost pressure and the engine combos nose over at rpm.


Edited by - Steve C. on 11 Sep 2019 6:08:20 PM
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 11 Sep 2019 :  7:36:35 PM  Show Profile  Reply with Quote
Duplicate message by mistake. Sorry
Bill fell free to delete this.

Edited by - Steve C. on 11 Sep 2019 7:38:35 PM
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cortcomp
Coyote

USA
5470 Posts

Posted - 11 Sep 2019 :  9:48:31 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I built almost the same motor. XE284, about 9.3:1, ported heads, 430HP. I never got more than one run in the 1/4 to see what it did, and on that run i locked up the shifter between 2 - 3. Same issue with the same springs, when we dynod the car on a chassis dyno after a few hundred miles or so, we noticed issues at the top that pointed at the springs. Pulled them and they measured in the 90s. Replaced with another brand (crower?) and i sold the car before i had a chance to dyno again.
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 11 Sep 2019 :  9:58:12 PM  Show Profile  Reply with Quote
You also have to pay attention with some Crower springs. Example the popular 68404 often used as a "stock replacement spring". Rated at 1.600" installed height, IF it's at or near that IH with some popular Pontiac flat tappet cams the distance from coil bind can be a lot !
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PontiacLars
Tribal Scout

11 Posts

Posted - 12 Sep 2019 :  12:10:53 PM  Show Profile  Reply with Quote
What are you guys thoughts on splayed vs straight billet main caps? Looks like splayed are out of stock everywhere..are they not in production anymore? To me going with straight when the block is to be machined anyway sounds like a bad idea.
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PontiacLars
Tribal Scout

11 Posts

Posted - 12 Sep 2019 :  3:18:07 PM  Show Profile  Reply with Quote
Guess I need to check my springs when dissambling engine then.
I have a nasty clacking sound coming from driver side rocker cover on warmup. Goes away when engine is semi-hot and hot. Crane full roller 1.65, are they junk?
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Steve C.
Chief PONTIAC

2054 Posts

Posted - 12 Sep 2019 :  4:00:33 PM  Show Profile  Reply with Quote
The upside is that the angled bolts are stronger then straight up. Probably overkill for your proposed goals, but that's a guess on my part.

Lee has pointed out that Pontiacs have dowels on the caps, which keeps the caps from moving in any direction other than down. The dowels pretty much eliminate the cap-walk issue that other brands can suffer from, and the reason most other brands NEED 4-bolt caps at lower power levels than do Pontiacs. But that also assumes a tight fit on the caps and dowels.


.

Edited by - Steve C. on 12 Sep 2019 4:23:03 PM
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Corncob2061
Crazy Horse

USA
535 Posts

Posted - 13 Sep 2019 :  11:00:09 AM  Show Profile  Reply with Quote
quote:
Originally posted by PontiacLars

Guess I need to check my springs when dissambling engine then.
I have a nasty clacking sound coming from driver side rocker cover on warmup. Goes away when engine is semi-hot and hot. Crane full roller 1.65, are they junk?



The cranes rockers should be fine for your engine, I have a set I have ran for years on different engines. The toughest are probably the Crower Stainless enduro, and second is probably the compcams Ultrapro magnum in stainless steel. The Harlensharps with their life time wareentee are to me top of their class in aluminum. The cranes are probably somewhere in the middle of the pack.


It sounds to me like the valve terrain noise is probably coming from the cam itself if it is quieting down after it warms up. A lot of XE cams do that. They shut the valves pretty hard, even more so with 1.65s. Kind of the difference between landing a fighter jet on a carrier versus landing on an airport runway. If they miss the landing a little the plane gets pretty big jolt on the aircraft carrier, not such a big deal on the full runway. As long as the noise quiets down after it warms up they seem to last along time. The lifters seem to compensate after the engine warms up. Some of them can be really loud on a cold day.

Probably should focus on the 3.75 stroke build with the Saginaw behind it. My opinion is the XE284 kind of fritters to much of the port flow on scavenging and not enough on filling the cylinders on heads where the flow is more limited. It works pretty good with the aluminum heads though with the bigger port volumes.

If you are running 45 degrees intake seats versus the factory 30s it will not take as much seat pressure for the same rpm. The effective force on the 30 degree seat by the springs is less, and the 45s seat better and do not have the tendency to bounce. But you do loose some low lift flow below .3 lift with the 45 seat angle, not enough to worry about though JMHO. Jay

Edited by - Corncob2061 on 13 Sep 2019 11:29:15 AM
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DanM
Sitting Bull

190 Posts

Posted - 13 Sep 2019 :  11:57:35 AM  Show Profile  Reply with Quote
Hi Lars,

Regarding the clicking when cold. Did you use "polylocks" or other adjustable rocker bolts? If so then you might be able to eliminate the issue that Jay was talking about by adding a little bit more pre-load to the lifter. A half a turn will be plenty, even a quarter turn might do the trick.

If you don't have adjustable rocker bolts then maybe get some.

Advice: go to the track and go to the chassis dyno. They are both inexpensive, super fun to do, and the data you get will be key to guiding you on your next move toward improving your car. Also you will be able to tune your carb better and could be up for a 10 HP gain at little to no cost.

Even for just a weekend fun car, "average HP" means a lot, maybe even more than peak HP.
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