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Lines4life
Tribal Scout

6 Posts

Posted - 07 Feb 2017 :  7:02:15 PM  Show Profile  Reply with Quote
I am editing my original post(story) to keep the confusion down. I have 70 tempest sport convertible. I have a .030 over 400 I plan to use in it. The block has been in storage for a long time. Before it was stored it was hot tanked, got new bearings in it and replaced stock bolts with ARP bolts. I have a iron heads that won't work due to CR concerns. I want to be able to run it on 91. Just looking for a mean street car that will see little highway use. Not shooting for specific numbers but I'm hoping to come in around 450HP. I am looking for reccomendations for a good roller cam set up for this combo. Any help would be greatly appreciated.

70' 400 block bored .030 over
Piston to deck height: .003
Planned gasket thickness: .039
3.90 posi in the rear
Manual transmission
Power disc brakes

Right now this is what I have:
- stock cast crank
- eagle 4340 Hbeam rods (ordered)
- Speed-Pro Power Forged Pistons (6.7cc eyebrows)
- I have a stock iron intakes and I also have a Elderbrock performer
- 750 Holley carb
-stock exhaust manifold
-MSD everything for ignition

Proposed list of parts:
-Elderbrock performer heads
- all new valvetrain
- set of 1.5 roller rockers
-set of Dougs Headers, long pipe
-full 3 inch exhaust
- roller cam

So, that's what I'm working with now and will begin buying parts as soon as I have a build sheet of everything. I'm just not sure what would be a good fit for this set up. It seems like I'd have to lower SCR down to around 9:1 to achieve a good DCR for pump gas. I know the aluminum head like to between 10:1-10.5:1.

Edited by - Lines4life on 09 Feb 2017 11:50:11 AM

Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 07 Feb 2017 :  11:26:49 PM  Show Profile  Reply with Quote
Welcome Lines4life
A roller set up would definitely take advantage of the high flowing e-heads. The 400 with good rods and pistons will rev high enough for the 3.90.. The elderbrock intake may be the choke point.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Steve C.
Crazy Horse

1672 Posts

Posted - 08 Feb 2017 :  09:21:05 AM  Show Profile  Reply with Quote
stock rods are proposed
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cortcomp
Coyote

USA
5335 Posts

Posted - 08 Feb 2017 :  10:39:51 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
No matter the cam, you can run a lot more compression with the alum heads. Not that i'm a big XE fan when you're spending the money on nice heads, but i wouldn't be afraid to run 10:1 with those heads. I'm running a lunati grind in my SBC because i didn't want to risk the comp XE clacking and it's been good.

If you're considering roller though, and you don't mind spending the money, focus there and forget about the hyd tappets. If nothing else, avoid any chance of wiping a cam lobe, or at least drastically reducing the change of valvetrain issues. (I know there are still noisy or garbage retro rollers, but there are many running happily too.)
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 08 Feb 2017 :  10:48:12 AM  Show Profile  Reply with Quote
Im curious about the pistons used in the short block build. The 8 eyebrow jobber pistons can make the engine detonation sensitive.
The first links below show the 4 eyebrow style that came in many pontiac's
Second is the less desirable 8 eyebrow. They will fit the pre 67 valve angle cylinder heads or the more modern valve angle heads These will lower compression and trap a percentage of the air fuel mixture in the outer edge bevel.

http://www.ebay.com/itm/L2262F-TRW-FORGED-PISTON-SINGLE-NON-COATED-SKIRTS-400-PONTIAC-030-OVER-/311769145410
http://www.ebay.com/itm/400-pontiac-speed-pro-pistons-set-of-8-411np-0-30-/252759433982


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

Edited by - Blued and Painted on 08 Feb 2017 10:59:38 AM
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Lines4life
Tribal Scout

6 Posts

Posted - 08 Feb 2017 :  6:45:04 PM  Show Profile  Reply with Quote
The pistons are the 4 eyebrow style. These are the Pistons that are in it now,

https://www.summitracing.com/parts/trw-l2262f30?ibanner=MobileSwitchNo

Edited by - Lines4life on 08 Feb 2017 7:03:20 PM
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Lines4life
Tribal Scout

6 Posts

Posted - 08 Feb 2017 :  6:50:49 PM  Show Profile  Reply with Quote
I figured the performer intake would be gasping for air for my set up. Will most likely be upgrading to an RPM intake
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Phil
The Great White Buffalo

USA
7214 Posts

Posted - 09 Feb 2017 :  10:23:34 AM  Show Profile  Reply with Quote
I haven't heard of any RPM related hood clearance issues on the 70 A-Body's but it's best to do some investigating before buying the intake. In either case, those E-intakes need a little work to fit well and get the most out of them. On your 400, I'd use a 68-72 factory intake (iron or HO) hands down before the Performer.

I'm not clear on the heads: what are you planning to use in the meantime until you upgrade to the E-heads later?

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.
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Lines4life
Tribal Scout

6 Posts

Posted - 09 Feb 2017 :  11:15:56 AM  Show Profile  Reply with Quote
I have a set of iron heads now but they CC'd in at 68 and need some work. I'm afraid we won't be able to achieve proper CR with them. They also need some work so I am just going to buy a new set of E heads. The engine is out of the car now and it will be a month or two until I order the new heads.
I wanted to get some advice on cam selection and CR to see if I should run the 72 or 87 heads.

Using a .039 gasket the 72cc heads would put me at at a SCR of 10.45:1 and the 87cc heads put me at 9.07:1. I've read that with the aluminum heads you want to run them at at least 10:1 to make up for the heat loss. With the reading I've done on DCR it seems like I'd have to run a lower SCR to keep my DCR at an acceptable range for pump gas, when running a roller cam. Is 9:1 to low for the aluminum head?

I just dont know enough to figure out what looks good on paper, and what will ACTUALLY work. I have a performer intake, and a set or two of iron already. Is the RPM the best option, assuming there are no clearance issues?
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Blued and Painted
Chief PONTIAC

USA
3404 Posts

Posted - 09 Feb 2017 :  11:56:23 AM  Show Profile  Reply with Quote
The aluminum 87cc heads work with the 455+ engines
9 to 1 with aluminum would be like 8 to 1 with iron. ball park.. Then cam selection would be limited.


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Steve C.
Crazy Horse

1672 Posts

Posted - 09 Feb 2017 :  12:44:36 PM  Show Profile  Reply with Quote
The 72cc chamber Edelbrock head will work fine on a 400 engine.

A fwiw, years ago when I was planning my previous 462 build with Edelbrock aluminium cylinder heads I contacted Dave Bisschop about compression ratios. At the time based on his dyno testing he was recommending a maximum of 10.25 compression with the 87cc Edelbrock chamber design and 10.5 compression with the 72cc Edelbrock chamber design. This was a general recommendation for engines leaving his shop to be used under all types of driving conditions, unknown gas quality, and not knowing how the end customer would tune and operate the combination. Obviously under the right conditions it could be higher but like most engine builders they typically are not going to suggest pushing it for most people with a lot of unknowns.

Again, this is with the typical wedge chamber design used on the Edelbrock 'round port' cylinder head. The 'heart shaped' combustion chamber design on the aluminium d-port type heads is a different situation. They allow the use of higher compression.
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Phil
The Great White Buffalo

USA
7214 Posts

Posted - 09 Feb 2017 :  1:06:59 PM  Show Profile  Reply with Quote
Agree with Steve. I kept my CR to 10.3:1 by having Ross fine tune the pistons during the ordering process.

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.
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Lines4life
Tribal Scout

6 Posts

Posted - 09 Feb 2017 :  5:19:09 PM  Show Profile  Reply with Quote
So when using aluminum heads, do the same rules apply to DCR when picking out a cam? In other words can I run a cam that gives me say a 9:1 DCR vs 8:1, when aiming for a pump gas friendly engine?
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Steve C.
Crazy Horse

1672 Posts

Posted - 09 Feb 2017 :  6:36:15 PM  Show Profile  Reply with Quote
The biggest problem with DCR based theory is that it only truly relates to what is happening when the engine isn't actually running.

Once the engine is actually running, all bets are off, as numerous other dynamics come into play that the DCR calculations cannot even begin to account for.

That's the point that Harold B. is often trying to get across when he dismisses the whole DCR thing as a waste of time.

And I believe that's what Paul (gtofreek) was talking about too.

Cylinder filling dynamics in a running engine are based on far more than just the things that DCR calculations account for, and that includes the IC event too.

So if you need to know what the DCR is for an engine while it's cranking over, then I guess DCR theory tells you everything you need to know.

Though it doesn't tell you much of anything useful beyond that.

DCR wont tell you how much HP a given engine may (or may not) make.

And it wont tell you with any reliable accuracy if you can run on a given octane fuel either...

FWIW

Bret P.

Source, and other fine comments here:

http://forums.maxperformanceinc.com/forums/showthread.php?t=716521&highlight=DCR
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cortcomp
Coyote

USA
5335 Posts

Posted - 09 Feb 2017 :  8:15:55 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
Honestly, unless you're doing something different, find a recipe with a roller and those heads that the owner reports has streetability that you'd like, and dyno numbers to prove, and go off that.
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Lines4life
Tribal Scout

6 Posts

Posted - 09 Feb 2017 :  8:38:37 PM  Show Profile  Reply with Quote
So when using aluminum heads, do the same rules apply to DCR when picking out a cam? In other words can I run a cam that gives me say a 9:1 DCR vs 8:1, when aiming for a pump gas friendly engine?
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