[Z Code 400]

I just bought a complete 1970 400 (XH Code) with #13 heads. The engine is standard and has been in storage since 1991.

I paid $300 for the engine with a TH400 on the back of it. It was very clean inside and still turned over.

I was completely floored when I found it had 4 bolt main bearing caps. I have never seen a Pontiac with 4 bolt mains other than a Super Duty.

I picked this engine up to replace my damaged
'PWH' 400 block (broken main cap from rod shrapnel) in my 1979 Trans Am. I am looking for some answers on heads.

For my street driven WS-6 with 2.73 gears, I don't need big valves, headers or 10.00:1 compression. I will modify the engine to a streetable 8.75:1 to 9.25:1.

My question relates to cylinder head and intake manifold compatibility.

I must retain my EGR system on this California car. I have been told I cannot use the late intake with the #13 heads.

I have also been told by others that the late intake manifold will work with the #13 heads.

Can someone set me straight on this???...Robert

[Z Code 400]

I just bought a complete 1970 400 (XH Code) with #13 heads. The engine is standard and has been in storage since 1991.

I paid $300 for the engine with a TH400 on the back of it. It was very clean inside and still turned over.

I was completely floored when I found it had 4 bolt main bearing caps. I have never seen a Pontiac with 4 bolt mains other than a Super Duty.

I picked this engine up to replace my damaged
'PWH' 400 block (broken main cap from rod shrapnel) in my 1979 Trans Am. I am looking for some answers on heads.

For my street driven WS-6 with 2.73 gears, I don't need big valves, headers or 10.00:1 compression. I will modify the engine to a streetable 8.75:1 to 9.25:1.

My question relates to cylinder head and intake manifold compatibility.

I must retain my EGR system on this California car. I have been told I cannot use the late intake with the #13 heads.

I have also been told by others that the late intake manifold will work with the #13 heads.

Can someone set me straight on this???...Robert

[Skip Fix]

Look at the exhaust crossover area on the heads and intake, match them to a gasket. The 79(78) intake has small hole both sides that should match up to the head's crossovers.The 62s I have in the garage do.I think the problem is using the early intakes on the late heads because they have the extra opening above the actual crossover.

I never could figure out why the early heads have a small holes and the intake crossover has one large one and one small one??

[Z Code 400]

Thanks for the speedy reply. I will be mocking all the parts up today to check them for compatability. I will definitely look for that...Robert

[LouisianaGuy]

They supposodely put the 2 different size holes so that one could not use early style non egr intakes on Egr equipped cars, so as to keep everyone in the federal emissions standards, or so i have read. Best way to aleviate this problem if you wana run late heads and early intake is to just have a small piece of metal machined and welded into the intake side where the opening is too large and it will work fine ..that is what i had to do as im running a 68 intake on some 1974 heads
Mike

[Skip Fix]

But the early intakes with one big hole were made before they ever even made EGR intakes, and the head holes are small, so why one big hole in 1968-70?

[pontiarrg]

I believe this was done for heating on the older 4bbl cars. They were very hard to keep running in the winter for the first 10 min and had lots of flooding problems at shutoff. This heated cold and evaporated hot but it wasn't a good fix.

[Z Code 400]

Mounted the #13 head on a block and bolted the 1979 W-72 Intake Manifold on. It fits perfectly and there is a complete seal around the crossover when using the late style 1979 gasket...Robert

[Z Code 400]

Mounted the #13 head on a block and bolted the 1979 W-72 Intake Manifold on. It fits perfectly and there is a complete seal around the crossover when using the late style 1979 gasket...Robert