Help with engine upgrades on my 70 gto

dwd70gto

New member
I currently have a 1969 400 350 hp engine with 6x-8 heads, I know that this has lower the compression down to about 7.5. The engine has the std cam and standard flat top pistons, a performer intake and a 750 q-jet carb. I have a HEI distributor and std exhaust manifolds . The car is a turbo 400 with the 355 posi
rear end. I was thinking about changing the cam and the heads and adding ram air manifolds (because I like them over headers). I was going to go with a Ram air 4 spec cam and some 80 to 85 cc heads. I want to run pump gas and I drive the car on the street all spring, summer and fall. Thanks in advance for your advice.
 

melsg5

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going for something like the Edelbrock aluminum heads with the round exhaust ports and 87CC chambers should be perfect. I would think real carefully about the RA IV cam with an automatic and stock converter. You may need to run Rhoads lifters to get it to idle properly. Reconsider perhaps going with the HO style 068 cam instead.
 

cammerjeff

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Belleville MI
I agree with melsg5 about the cam choice, the RA 4 cam's do not seem to like a auto trans with a low stall speed converter. I like your other choices, but if you do decide to go with 1.65 rocker arms you have to be very carful to check each valve spring for coil bind ( I have seen only 1 or 2 of the 16 have an issue with it) and also pushrod clearance on the head casting holes.
Going with aftermarket heads the pushrod clearance may not be an issue. Anouther set of heads to consider is Kauffman Racing's D port heads. They flow as well as the Edelbrock round ports and can save you $$$ by not having to buy the round port Ram Air manifolds. Just something to consider.

http://www.krepower.com/pontiac aluminum d-port cylinder heads.htm
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melsg5

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which ever head you decide on the manufacturer should be able to tell you the maximum lift that the springs can handle so you decide on which cam to go with. The Rhoads lifters can be noisy at idle.
 

dwd70gto

New member
With the 6x heads and stock cam the car is very slow to respond. If i put the 85 cc heads will that solve the response time. The 85cc heads should get me to 8.75 compression from the 7.5 I'm at now. The engine runs great just not the beast it should be.
 

cammerjeff

Member
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Belleville MI
Actually with aluminum heads you should be able to go to 10.0 CR without an issue, with cast iron heads I would not push the CR beyond 9.0 on a street car to avoid having to run race gas.
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dwd70gto

New member
I think I will stay with the 85cc Kauffman heads and use 91 gas. I think I will go with the HO 068 cam, because of the 400 auto and power brakes.
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bigwave01

New member
I use the 041 cam on all of my engines. staying with the 1.5 rockers will get you.420 lift. my auto GTO has #48 heads and will run pretty good on 93 octane but there is definitely a sweet spot in timing between starting easy and pinging but adding a gallon of racing fuel to your tank cures all. With 6x I think you would be fine. And yes I also use Rhoades lifters to tame the lope at idle.
 

melsg5

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I was going to ask how you got the 041 to behave and then I came to the last sentence. I made the mistake of installing it in my 455 HO with factory lifters and stock torque converter. it wasn't fun and was happy to go back to the 068.
 
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