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Discussion Starter #21
Call Roy Johnson . He has 3 warehouses full of rebuilder inventory.
I got some stock 400 forged pistons . NOS . 1.714 Compression height . TRW IIRC

Price was good.


517-321-6460
Call Roy Johnson . He has 3 warehouses full of rebuilder inventory.
I got some stock 400 forged pistons . NOS . 1.714 Compression height . TRW IIRC

Price was good.


517-321-6460
Thanks LATECH..
I will call him.
What compression did you wind up with with those pistons and with what heads..if you don't mind me asking?
Thanks...Stan
 

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Discussion Starter #22
If you wish to keep the engine as a stock build I recommend the 068 cam. This was the factory cam for the 68 HO engine and is an excellent overall cam without going crazy with modified heads or special valve springs. Makes good power with the factory heads, intake and QJ. I paid $95 for a Melling SPC7 (068 clone) on line with O'Reillys.
Thanks o52..
I have heard that on here a couple of times. So the Melling cam is a good 068 clone?

I've was disappointed in Comp Cams clones for a big block chevy...

What heads and compression does you engine have, that has this cam?
Thanks...Stan
 

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There's no reason why you need to make any other changes than the forged pistons. I ran forged pistons with cast rods and stock heads for a long time. I
AND I didn't drive it easy. I did limit my RPM to 6000. Details are buried in "My Early GTO History"

My Early GTO History

Pontiac Jim is absolutely right about 4 reliefs in stock pistons. It's been so long since I ran them that I forgot.
 

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One question you have to ask is why your pistons are so far down in the hole. If there's some reason that your rods are shorter, then new pistons won't help. That's one good reason to buy new rods art the same time. I've never heard of a stock engine having that much deck height.
 

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Discussion Starter #25
Yes I agree, nor have I...good point!
The old machinist build sheet I have list the rods as OEM 6.625 rods. Is that a stock rod length? I'm not sure? .....but thought it was. I'm looking for the specs now.
 

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Discussion Starter #28
I'm looking this build sheet over for oddities for the umpteenth time. It's all pretty straightforward stock stuff.
 

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Discussion Starter #29
I guess 87 cc heads are like hens teeth to find...but looks like with them a 9.29 compression ratio engine could be built. Is there any downside to using them if I can find some?
Thanks...Stan
 

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Not as long as they have screw in rocker studs. They would be a great head. I know the '70 GTO heads (#64) would work great, but they are very scarce. IIRC they are 94 cc's.
 

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Stan, I used some 7H1 heads and milled the heck out of them,like .045 to get to 82 ish CC chamber size.

I have a pair of number 11 heads and they are 85 CCs stock, Pretty much perfect for a 400 build with flat tops.

The 7H1 started at 90 CC.

Maybe you can find a set of 11s and run them The 7H1 heads are fine but , i had one that was cracked. And I milled a LOT off of them , which worked good, but the rail that the intake valley seals on was pretty narrow after that, ans was a little tricky to get sealed well, but it did seal good . With heads that are already at 85 CC you would only need to mill them to flatten them .

Look for a set of number 11 s

My CR is at 9.4 to 1
 

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Here is a pair that would work well with a small amount of milling

OEM 1971 Pontiac #94 Matching Cylinder Heads 350cid Complete | eBay

I would ask if he can garantee they arent cracked. Or have him pressure test them at a machine shop.
Note that these have press-in studs and screw-in studs are what is wanted for a high performance build unless keeping the cam near stock on lift and using stock spring pressures.
These heads will also have the smaller intake valves which can be upgraded to the larger 2.11" intake valves.

Again, neither is an issue per say as you can have screw-in studs added as well as the 2.11" intakes and get a solid performance head with the cc's you are looking for. A good 3-angle valve job and some mild port clean-up would really help them breathe.
 

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So get a set of 7/16 CBB studs put in like I did. Get poly locks for adjustable valvetrain.
As far as I am concerned the smaller valve leaves more valve "unshrouded" and permits better flow at low rpms. Maybe I am wrong.IDK
My 389 runs the stock intake valves from the 7H1 (350 heads), but I have the 1.77 exhaust valves.Poncho motors need more room to exhale. Longer exhaust duration and the larger exhaust valves seem to help that. 2.5 inch mandrel bent exhaust with H pipe also gives a bit of help too.
My 389 runs pretty strong .
 
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