Pontiac Street Performance
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password

 All Forums
 Pontiac Performance
 Intake / Carb and Fuel Delivery Tech
 Disappointed
 New Topic  Reply to Topic
 Printer Friendly
Next Page
Author Previous Topic Topic Next Topic
Page: of 2

mrryals
Tribal Scout

USA
11 Posts

Posted - 10 Aug 2013 :  1:10:05 PM  Show Profile  Reply with Quote
Just rebuilt 1970 400 balanced blueprinted. 6.625 eagle rods .30 over 670 heads ported flow of 248 224. comp cams 274 xe roller rockers. Performer rpm port matched holley 750 dual feed. forged hei with msd upgrade kit.Engine broken in and dynode. 373 horsepower 427 torque. Was expecting at least 400hp and maybe 500tq. Where is my weak link

Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 10 Aug 2013 :  4:23:37 PM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Do you have a copy of the dyno sheet? At what rpm did the test begin and end? What was the peak torque and at what rpm? What was the peak hp and at what rpm. What kind of exhaust? What was the mechanical advance at the peak rpm?

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 10 Aug 2013 :  4:26:39 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Well it sounds like you have an engine with a good CR, and good flow. I like my XE cam, and liked the one in my 428 but they're low compression setups from what i read/understand. I'm just a parrot of others findings, but it's my opinion that those cams wake up lazy smog era pontiacs. Don't get me wrong, a 450HP 455 from a 250ish horse one is a big jump, but it's not to 550HP+ like the aluminum headed roller motors either. I'm no expert, and again just repeating what i read here and there, but i'd bet money someone comes in and says 60919 cam.

Do you have your dyno sheets? What RPMS was max torque and HP at? would tell others more knowledgeable than I where your engine is making power and if it's taking advantage of those ported heads or not. Lastly, 375HP and 427tq, especially if it's all under 5000 or 5500 RPMS sounds like a sweet street motor.
Go to Top of Page

Blued and Painted
Chief PONTIAC

USA
3406 Posts

Posted - 11 Aug 2013 :  03:26:59 AM  Show Profile  Reply with Quote
It's not so easy to get in the 1 to 1 club on the home page. Look at some of there combo's. But thats OK. It's not easy to get 1 to 1 torque out of a SBC either.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 16 Oct 2013 10:21:03 AM
Go to Top of Page

Phil
The Great White Buffalo

USA
7219 Posts

Posted - 11 Aug 2013 :  10:57:03 AM  Show Profile  Reply with Quote
What pistons with those 670's? Your compression may be easily in the "10's" if using good flat tops (not the "rebuilder kit" cast flat tops with double eyebrows).
Maybe not the best cam choice for higher compression setups but I try to stay away from staring into the Sun (cam recommendations=nasty behavior on many forums from the many "walking ego's")

Tell us what was done to optimize tuning regarding the carb and timing curve.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 11 Aug 2013 10:59:35 AM
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 11 Aug 2013 :  11:03:07 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I would guess, if really a high CR AND an XE cam, that maybe they couldn't really get that much timing in. Who knows though, i got lots in on the 428/670s with the XE262, but like i mentioned before, i don't know why that setup worked, and i tore it down for other reasons.
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 11 Aug 2013 :  11:53:36 AM  Show Profile  Reply with Quote
Test started at 2800 rpm408 tq 219 hp ran 5500 . Timing set to 35deg. Tq peaked at428 @3600rpm. HP373 at5300. Forged trw flat top pistons. Vacuum advanced disconnected. Advised to leave it disconnected due to the high compression this came from a chevy guy. Change distributor spring to white one he had in shop said it was coming in to fast. That resulted with best pull the one above
Go to Top of Page

Phil
The Great White Buffalo

USA
7219 Posts

Posted - 12 Aug 2013 :  06:01:33 AM  Show Profile  Reply with Quote
So many variables yet to address. You have alot of fine tuning to do to optimize any new engine including the actual break-in of the engine. It's like buying a new guitar and trying to play it without tuning it. Oh, and a "Chevy guy" is never a good thing to have around anything but a Chevy.


Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.

Edited by - Phil on 12 Aug 2013 06:02:27 AM
Go to Top of Page

Cliff R
Cochise

USA
535 Posts

Posted - 12 Aug 2013 :  06:51:27 AM  Show Profile  Visit Cliff R's Homepage  Reply with Quote
I hope it was a chassis dyno.

With 250cfm head flow a 455 with 10 to 1 compression will make 450hp/540tq pretty easily. The numbers will be down slightly if it has lower compression.

A few years ago we built a 455 with unported #46 heads from a 350 engine, Crower 60919 cam, stock intake, q-jet, and it cranked out 440hp/530tq.

My own 455 with 10 to 1 compression, same cam, and 232cfm head flow made 455.4hp/540tq on the same dyno. An XE274 cam in the same exact engine will make 400hp/490tq, pretty much done by 4800-4900rpm's. The larger XE284 made 430hp/499 tq in a nearly identical engine. All of these were ran on the same dyno, so the comparisons are pretty close.....Cliff

If you can read this, thank a teacher. If you can read this in English, thank a Veteran.
Go to Top of Page

Phil
The Great White Buffalo

USA
7219 Posts

Posted - 12 Aug 2013 :  07:22:11 AM  Show Profile  Reply with Quote
Cliff, he seems to be running a 400. Still could be a little better.

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
Go to Top of Page

Phil
The Great White Buffalo

USA
7219 Posts

Posted - 12 Aug 2013 :  07:24:22 AM  Show Profile  Reply with Quote
mrryals, what's a "forged hei"?

Bowties are for Pee-wee Herman. "Chevy": even the name sounds cheap, but not as cheap as your Pontiac will be with an LS transplant.
Go to Top of Page

Cliff R
Cochise

USA
535 Posts

Posted - 12 Aug 2013 :  07:52:29 AM  Show Profile  Visit Cliff R's Homepage  Reply with Quote
Thanks, I miss-read and thought it was a stroker set-up. Still pretty "weak" for a 400 in both areas. 400 engine with a smaller cam and unported heads we made 419hp/453tq at 10 to 1 compression. The cam was a Crower 60916, 221/229/112. With a larger 60243 cam with 228/235/112 424hp/465tq. With unported KRE aluminum heads the same cams made 440hp and 450hp respectively......Cliff

If you can read this, thank a teacher. If you can read this in English, thank a Veteran.

Edited by - Cliff R on 12 Aug 2013 07:53:30 AM
Go to Top of Page

Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 12 Aug 2013 :  09:16:26 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Should we assume these numbers were with tube headers in play?

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 12 Aug 2013 :  09:28:40 AM  Show Profile  Reply with Quote
what octane fuel? i am assuming the CR is about 10.5:1??

Edited by - ledhed76 on 12 Aug 2013 09:31:29 AM
Go to Top of Page

sixt8bird
Chief Many Horses

USA
1114 Posts

Posted - 12 Aug 2013 :  11:28:43 AM  Show Profile  Visit sixt8bird's Homepage  Reply with Quote
Ditch that comp cam and put in one that has at least mid 20s and 30s and you will be happy!!226-234 on 114 is everything I could have hoped for. Idles good, sits in traffic all day nice and cool nd has one hell of a throttle response.Even with lean jetting Im at 400+. 12.5 second 1/4 mile times with nothing special or super tuned as some may call it. And it loves just pump gas. Bummer about the numbers.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 12 Aug 2013 :  12:40:00 PM  Show Profile  Reply with Quote
there is clearly an issue here that is more than cam selection
Go to Top of Page

Steve C.
Crazy Horse

1675 Posts

Posted - 12 Aug 2013 :  2:38:37 PM  Show Profile  Reply with Quote
Probablt take it to a another chassis dyno and get completly differant numbers.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 12 Aug 2013 :  3:38:02 PM  Show Profile  Reply with Quote
im thinking this was done on an engine dyno??
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 12 Aug 2013 :  3:54:09 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I was assuming engine dyno too, if that was chassis dyno, those are good numbers.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 13 Aug 2013 :  10:07:23 AM  Show Profile  Reply with Quote
I think with that cam, 500 lb/ft is a little high for torque expectations
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 13 Aug 2013 :  12:45:34 PM  Show Profile  Reply with Quote
Thanks for all the posts. I had hooker super comp headers but a had a problem installing them in my 68 firebird. GM hei with msg up grade kit coil rotor cap and module
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 13 Aug 2013 :  12:54:17 PM  Show Profile  Reply with Quote
Thanks for all the posts. I had hooker super comp headers on the dyno but a had a problem installing them in my 68 firebird. GM hei with msd up grade kit coil rotor cap and module. Engine was broken in on dyno than made four pulls. I didn't want to get caught with the numbers but after planning the build I was hoping for higher numbers. Especially after reading about other builds. 10:1 compression 93 octane.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 13 Aug 2013 :  2:17:11 PM  Show Profile  Reply with Quote
Personally i think the torque number is fine....the hp number is what is jacked up.....with that cam i am thinking around 425hp maybe....must be an ignition or fueling issue....
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 13 Aug 2013 :  3:27:23 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
To be cautious, i have a 462 with the bigger XE284 and ported heads, with the chassis dyno numbers, i estimate i'm getting 430-450HP (500 ft lbs torque). I would estimate the smaller XE274 and less cubes could be 400HP conservatively? Just a guess.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 13 Aug 2013 :  3:57:44 PM  Show Profile  Reply with Quote
I have the smaller xe262h in my 400 with unported heads and 9.3:1....camquest says i should be around 370 hp and 460 lb/ft.....
Go to Top of Page

Cliff R
Cochise

USA
535 Posts

Posted - 14 Aug 2013 :  06:10:22 AM  Show Profile  Visit Cliff R's Homepage  Reply with Quote
Numbers are low, even for that cam. One of our customers built a 400 with mildly ported 6X-4 heads milled for 8.8 to 1 compression, XE274 cam, etc. He made 375hp/440tq on the dyno, and was pretty pleased with the results.

Where the cam was degree'd at will have a significant impact on power production, especially with one on a tight LSA with short seat timing. If you close the intake valve too soon, they never do make any power....FWIW.....Cliff

If you can read this, thank a teacher. If you can read this in English, thank a Veteran.
Go to Top of Page

Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 14 Aug 2013 :  07:43:17 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
With ported 670 heads, this high compression-headed 400 should develop over 400 hp @5000 rpm. Hmmm....

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 14 Aug 2013 :  07:53:55 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Did you guys degree the cam? My new comp cams double roller set was 6* off. I degreed it carefully over a dozen times. Put a new sealed power regular timing chain on, degreed it several times, right on.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 14 Aug 2013 :  09:19:19 AM  Show Profile  Reply with Quote
quote:
Originally posted by Cliff R

Numbers are low, even for that cam. One of our customers built a 400 with mildly ported 6X-4 heads milled for 8.8 to 1 compression, XE274 cam, etc. He made 375hp/440tq on the dyno, and was pretty pleased with the results.

Where the cam was degree'd at will have a significant impact on power production, especially with one on a tight LSA with short seat timing. If you close the intake valve too soon, they never do make any power....FWIW.....Cliff



chassis dyno or engine dyno?
Go to Top of Page

Bill Boyle
Horse Feathers (Charter Member)

USA
4794 Posts

Posted - 14 Aug 2013 :  09:29:15 AM  Show Profile  Visit Bill Boyle's Homepage  Reply with Quote
Degreeing in a cam isn't difficult. However, if you haven't done it or haven't done it in a long while it takes time to be certain of the sequence and your measurements--as will as doing basic math. A multi-position sprocket can be deceiving as well as being off. The first time I performed the procedure I was doubtful about my results so it was done over. A half a degree reading off here and there will goof you up. I use a narrow pointer to get accurate readings.

"Dedicated to keeping the classic Pontiac engine alive."

----
400 bored +.030, forged TRW pistons, ported 62 heads, Hedman headers, 2.5 SS dual exhaust X Pypes, Comp 276AH10 cam, Scorpion 1.65 RR, 850 Q-jet, stock intake & tuned HEI; original owner.
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 14 Aug 2013 :  10:59:44 AM  Show Profile  Reply with Quote
Cam was degreed when installed. Maybe I need to experiment with different springs in the distributor and different springs in my carb need to figure out when vacuum secondaries are coming in. I appreciate all the information and help. Engine dyno with 1.44 inertia factor
Go to Top of Page

Mr. P-Body
Running Bear

USA
2258 Posts

Posted - 14 Aug 2013 :  7:53:42 PM  Show Profile  Visit Mr. P-Body's Homepage  Reply with Quote

Agreed. More to this than the cam. It should easily make 400 HP. With heads that flow like that, significantly more, IMO. We know of people using XE274H in high compression applications that are VERY effective, though it's in larger engines. I would think the 400 would "like" the smallish cam more. The key to using the XE grind in the higher compression is to be sure you have enough octane. Detonation is key to power, so with 10:1 and a fast cam, 100 octane is called for. Unlike the 041 and other popular grinds for "bleeding" compression (cylinder pressure), XE grinds don't do that, even at higher durations (in proportion to "conventional" grinds).

I would think, with heads flowing that well, 1.65:1 rockers are being used, correct?

Has a leakage test or static compression test been done? 210 lbs. should be "normal".

How much total timing is the engine getting? Does it make power to 6,000? It should with heads like that.

Secondary adjustments will make it more drivable, but, won't make any difference in peak power, unless it's WAY lean or WAY fat, having nothing to do with when it opens. You ARE sure the secondary DID indeed open, yes? I would prefer to see a well done Q-Jet or a good Holley performance (double pumper) 750 on there. Hard to beat Q-Jet for a vacuum secondary carb. Hard to beat an AED or Carb Shop 750 HO or HOM, period.

Jim
Go to Top of Page

Cliff R
Cochise

USA
535 Posts

Posted - 15 Aug 2013 :  08:36:05 AM  Show Profile  Visit Cliff R's Homepage  Reply with Quote
The 400 engine mentioned above with XE274 cam and 8.8 to 1 compression was ran on an engine dyno, not a chassis dyno. Made 375hp/440tq. Not too bad for that deal, and pump gas as well. Keep in mind the heads were ported, tight quench, etc.

With unported #16 heads we made 419hp/453tq with a Crower 60916 cam. The larger 60243 cam made 424hp/465tq. Adding unported KRE heads shot the numbers up to 450hp for the 60916, and 460hp for the 60243 cam.

Both of these cams have more off seat duration than the XE274 cam, and wider LSA, so they would have made more power in the same application.

We found out here with back to back cam testing, that even with "modern" lobes, installing a cam with LESS duration yields LESS power.

We dyno'd my own 455 with a Crower 60919 cam and KRE heads. 494hp/540tq. Installed a custom Comp 240/248 cam and lost 10hp/22ft lbs torque. Peak power fell from 5600rpm's, to 5200rpm's. The custom cam did have .060" more lift, but gave up over 20 degrees of off seat timing, so it just didn't move as much air thru the big 455, and ended up making less power.

I know this sort of goes against what the cam manufacturer's tell us, than the "modern" lobe profiles can get it done with shorter seat timing events and "better" lobe profiles. We just didn't see this on the dyno.

As part of the same dyno testing, we yanked out the custom flat cam, and installed a custom hydraulic roller cam, 231/240 with .361" lobes yielding over .600" lift. The engine responded with 3hp/4ft lbs more power than the Crower 60919 cam. We made a few other changes, which included an RPM intake, and ended up getting 514hp/587 torque out of the engine. Pretty nice improvement over our baseline numbers of 494hp/569tq with the unported KRE aluminum "D" port heads.

What we learned from the testing, is that the roller grinds are able to get it done with less seat timing, as the improved lobe profiles allow for more air to be moved thru the ports without as much duration.

As I have long suspected, the technology is pretty much "played out" with flat cams and stock diameter lifters. They just aren't able to move the air by reducing seat timing and going to faster ramps with more lift. The newer grinds to idle better, at least when comparing .050" numbers, but they do NOT make more power, at least in the testing that we did here......Cliff

If you can read this, thank a teacher. If you can read this in English, thank a Veteran.

Edited by - Cliff R on 15 Aug 2013 08:39:34 AM
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 15 Aug 2013 :  09:50:50 AM  Show Profile  Reply with Quote
How did i know cliff was going to turn this into an XE bash session.....
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 15 Aug 2013 :  11:06:42 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
"The 400 engine mentioned above with XE274 cam and 8.8 to 1 compression was ran on an engine dyno, not a chassis dyno. Made 375hp/440tq."

I wouldn't say that part is bashing at all, that's what camquest pretty much says that cam will make in a low compression 400. Thats real HP, not pre-sae HP with no accessories i'm assuming. That engine will move. You basically ported smog era heads, slapped them and a cam in and went from 250HP to 375. With the cheapest most available head castings out there. If you didn't care about reliability because of bottom end, etc. you could take a junkyard motor, that cam and springs, port your heads at home, and get pretty close to that for like $300. That's like $2.50 per HP.

"With unported #16 heads we made 419hp/453tq with a Crower 60916 cam. The larger 60243 cam made 424hp/465tq. Adding unported KRE heads shot the numbers up to 450hp for the 60916, and 460hp for the 60243 cam."

Kind of apples to oranges, as you're adding a ton of compression going to 72cc heads. I'd be that the crower cams wouldn't do as well as the XE cams at 8.8 compression, and i bet the XE cam wouldn't do as well as the crowers at 10.1 or whatever those big valve 72cc 16's worked out to. Also, the 16s are rarer and more expensive if you're on a budget (that's what we always come back to right? budget and street performance? otherwise aluminum blocks and heads all around!)

I would like to see (and someone probably has posted it) how the crower grinds would do in the 8.8:1 setup without swapping heads to up compression. remember, there are 10,000 more low compression 400s and 455s and heads out there in station wagons, bonnies, gps, etc than 72cc heads from performance cars, and those smog era motors have nice bottom ends since they weren't revved up to 5k ever.
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 15 Aug 2013 :  11:09:07 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
also, unported 16 heads = 424hp, then KRE unported heads up to 460HP. $55.55 per HP. I know you got to pay to play starting right around 450HP. Getting up to 450HP being $2.50 per hp and moving past that $5.55 per hp (fast and loose math of course.). Big jump when you get into aluminum heads.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 15 Aug 2013 :  1:03:09 PM  Show Profile  Reply with Quote
quote:
Originally posted by cortcomp

"I wouldn't say that part is bashing at all, that's what camquest pretty much says that cam will make in a low compression 400. Thats real HP, not pre-sae HP with no accessories i'm assuming. That engine will move. You basically ported smog era heads, slapped them and a cam in and went from 250HP to 375.



i still think this engine should produce 400-425hp and be done around 6000rpm...i am going to put his head flow numbers in CamQuest when i get home and see what it says as an estimate...i bet camquest says 415hp and 440 lb/ft...
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 15 Aug 2013 :  1:48:41 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Oh i agree, i just wasn't looking for the 425-450 and felt that the 375 wasn't terrible, and only had to find some gremlins to get the last 25hp. Also this comment:

"I wouldn't say that part is bashing at all, that's what camquest pretty much says that cam will make in a low compression 400"

was the motor cliff tested, i wasn't referring to the original posters motor with higher compression. I would expect it to be done under 6k, but then again, being a 400 and not a 455, that will move the power up in the RPMS, correct?
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 15 Aug 2013 :  3:57:34 PM  Show Profile  Reply with Quote
Motor was ran up to 5600rpm. Not sure if secondaries kicked in will try different springs. I'll will also try different distributor springs. Waiting for headers so I can finish engine installation. Sounds like I need to test and tune, another learning experience. A carb change is possible not so sure about the cam at this point. Looking forward to driving it this year. It's just about the perfect time of year for driving your car here in upstate NY. I appreciate all the posts and information I've received. Anyone can own a chevy, but true happiness come from owning a Pontiac. I like to say a 68 firebird is a Camaro with attitude. Thanks once again
oo
o
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 15 Aug 2013 :  6:07:03 PM  Show Profile  Reply with Quote
wow i have to say i am surprised by the numbers on CamQuest...using his head flow numbers and guessing at a few other things, it says this engine should have 467 hp @ 6000rpm and 477 lb/ft @ 4000 rpn...
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 15 Aug 2013 :  7:34:31 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Really?? When i ran it with ported 6x head numbers, i got around 430. It was around 450 with edelbrock heads and the flow file for those that camquest provides.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 15 Aug 2013 :  8:12:43 PM  Show Profile  Reply with Quote
i used the following since he said in the original post they flow 248/224...the exhaust side of the camquest 6x file still has small valves and the flow is pretty low...


0.100 105 0.100 80
0.200 165 0.200 140
0.300 210 0.300 185
0.400 240 0.400 214
0.500 251 0.500 225

Edited by - ledhed76 on 15 Aug 2013 8:16:33 PM
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 15 Aug 2013 :  8:13:47 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I just can't imagine almost 470 with a 400/XE274. I could be wrong though, someone may have done exactly that.
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 15 Aug 2013 :  8:21:17 PM  Show Profile  Reply with Quote
those are some serious flowing heads...
Go to Top of Page

Cliff R
Cochise

USA
535 Posts

Posted - 16 Aug 2013 :  06:41:46 AM  Show Profile  Visit Cliff R's Homepage  Reply with Quote
"Kind of apples to oranges, as you're adding a ton of compression going to 72cc heads."

Also consider that our #16 heads were not ported, not even intake gasket matched. One would think, at least from what we've been led to believe over the years, is that you can drop compression by over one full point, install a cam with "modern" lobe profiles, shorter seat timing, and tighter LSA, and make up all the power.

The same folks that make these statements will also tell you that there is only a few percent power loss in dropping the compression from 10 to 1 back to 8.8 to 1.

If my math is correct, the loss is considerably more than 4-6 percent, closer to 14 percent.

I would also mention, that we are also able to manage pump fuel on the 10 to 1 compression ratio engine with zero issues anyplace, as the larger cam on a wider LSA not only spreads power out considerably, it spreads out dynamic compression, and moves peak power (torque) higher in the rpm range. With the events happening much quicker, cylinder filling isn't as effective and less chance for detonation at any given octane.

We've been involved with quite a few higher compression ratio engines, 400's, 428's and 455's, and NEVER once have had any issues with pump fuel, even clear up to 11 to 1 compression. I'm not advocating this deal, just saying it can easily be done with careful parts selection, tight quench and full control of timing/fuel curves.

A little off subject, but here's Brett Flynn's Firebird making a 10.86 second run couple of nights ago. Very "basic" engine set-up, 455, flat solid cam, iron heads, Street Dominator intake, and topped with a 750cfm Pontiac q-jet:

https://www.facebook.com/photo.php?v=10201065459056206&comment_id=5530027&offset=0&total_comments=14

......Cliff

If you can read this, thank a teacher. If you can read this in English, thank a Veteran.

Edited by - Cliff R on 16 Aug 2013 06:43:06 AM
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 16 Aug 2013 :  10:25:34 AM  Show Profile  Reply with Quote
Sounds like if I want more HP need to change cam. Any suggestions on what duration I should be looking for. Probably won't change till next year due to financial constraints at this time. I will be doing some carb and dist. Tuning though
Go to Top of Page

Blued and Painted
Chief PONTIAC

USA
3406 Posts

Posted - 16 Aug 2013 :  11:15:42 AM  Show Profile  Reply with Quote
defining the goals and application:

406 @ 10+ to 1
Goal 400+ HP

Body type and weight?
Street or strip application?
Power Brakes Yes/No
Stick shift/automatic?
Plans for rear gear?
Plans for Exhaust system?


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.

Edited by - Blued and Painted on 16 Aug 2013 11:19:12 AM
Go to Top of Page

mrryals
Tribal Scout

USA
11 Posts

Posted - 16 Aug 2013 :  11:35:18 AM  Show Profile  Reply with Quote
1968 firebird street no power brakes 4speed rear gears next year hedman husler headers 2 1/2SS dual exhaust. Comp cams cam Hp rates xe 274 at 369 horse power. Looks like crower 60243 next year
Go to Top of Page

ledhed76
Cochise

USA
304 Posts

Posted - 16 Aug 2013 :  1:03:02 PM  Show Profile  Reply with Quote
i wouldnt give up that easy on the XE274...there is another issue here other than cam selection...
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 16 Aug 2013 :  1:08:24 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
I think there's more to be had on that cam/setup, i think it can break 400HP no problem. I just don't know enough to point you in what direction. (when all else fails, blame it on the valve springs!)
Go to Top of Page

cortcomp
Coyote

USA
5335 Posts

Posted - 16 Aug 2013 :  1:29:03 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
"A little off subject, but here's Brett Flynn's Firebird making a 10.86 second run couple of nights ago. Very "basic" engine set-up, 455, flat solid cam, iron heads, Street Dominator intake, and topped with a 750cfm Pontiac q-jet:"

That car looks fast and light...what kind of numbers is that motor putting down? I have to assume that car is full race, gutted, cage, etc the way it launched and ran. I like the wagon next to it looking tricked out and ready to run a mean 1/4....until he's gone off the screen.




"The same folks that make these statements will also tell you that there is only a few percent power loss in dropping the compression from 10 to 1 back to 8.8 to 1.
If my math is correct, the loss is considerably more than 4-6 percent, closer to 14 percent."

Your math in this instance is VERY incorrect. You are comparing a low compression/cam-A setup with a high compression Cam-B and Cam-C setup. If we wanted to test for just the changes of compression, the following chart would be ideal. You are saying that you gain 14% going from 8.8 to 10:1 compression, but you're not telling the average car guy who doesn't get the details that you also switched cams to take advantage of that compression and get that 14% claim. Remember, in engineering, accuracy and completeness are laws.

8.8:1 HP | TQ
---------------------
XE274 |
60916 |
60243 |



10:1 HP | TQ
---------------------
XE274 |
60916 |
60243 |


Filling in those charts would tell you EXACTLY what percentage you lose lowering the compression, AND it would tell you that same info per cam model.



As one of the people who DOESN'T know any better, this next section is aimed at the people who read this and don't know any better either, not Cliff or Jim or anyone who knows cams or engine design or anyone else, because this will make it simple for the rest of us. This is for the guy who stumbles in here wanting to know where to begin on his first engine parts choices on his only car that he just got and he's lost. We get about 3-4 guys a month like this on this forum, and it always ends up back to the same cam wars and discussions:


Both sides make claims about loss with compression, or gains to had from compression, but neither side seems to tell the complete story:

Cliff/AntiXE or new lobe haters or whatever will tell you that lowering compression is more than a few % loss in power. What they're not telling you is that they're also switching cams when making those statements. If you had a 10:1 motor and ran, say the XE274 or whatever cam, then did NOTHING but dish the pistons down to say 9.3:1, i'd bet a chunk of money that you'd only lose a few percent as the new lobe/XE/fast ramp guys say. That's not to say then fine, run lower compression, because compression is ultimately needed to make power, now you have to decide how you're going to make it, budget, car use, etc. Both ways seem to work, and high compression motors do have 50+ years of being over 450HP under their belt, and others here are doing it with no issues so it obviously works for some or a lot.


new lobe/XE/fast ramp guys will tell you that it's ok to run at 9:1 compression for safety because you're only losing a few percent of power, but what they're not saying is that when you start getting to 10:1 that you open up a whole lot of cams up for consideration that just wouldn't play well near 9:1 and some of those (including tested and true older grinds) will give you more power than the newer lobes/xe series/lunati whatever would....AT THAT COMPRESSION ratio. So, yes, you do only lose a few percent by lowering compression, IF you're not open to changing cams at all, but who is planning a motor and not open to different grinds?


So, in conclusion, it always comes back to: CHOOSE YOUR CAM FOR YOUR COMPRESSION AND USE.
Go to Top of Page
Page: of 2 Previous Topic Topic Next Topic  
Next Page
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Pontiac Street Performance © 2006-2017 Go To Top Of Page
This page was generated in 0.44 seconds. This Site Sponsored By:
Powered By: Snitz Forums 2000 Version 3.4.05