'71 402 engine questions

[72c20customcamper]

Not squabbling just a discussion.

[weq92f]

.

Pull the valve cover off to get the casting numbers of the heads. That will tell you Oval or Peanut.

If you have peanut port heads, that might explain why the engine runs the way it does and you'll need to pickup a set of #781, #049 or similar cast heads. I bought a set of #781s for 100 bucks off craigslist not so long ago.

Calculate your compression ratio.

Use that to select appropriate cam which will give you the necessary springs required and the data to set them up properly. Then the heads, springs and related parts to the machine shop to get refreshed ( 1000 to 2000 ). I did my #063 heads this way w/ stock valve sizes and walked for about 1400 w/new stainless valves ( et al ), valve job, the proper springs/setup and required machining ( includes the cost of the head parts ).

I went with a COMP 11-422-8 retrofit roller cam on my stock 402 bottom end at about 9:1 compression, Edelbrock Performer 2-O intake. Also installed the COMP lifters at the time. Recently I replaced those lifters with Howards 91161, which is what I should have used to begin with! Upgraded from manifolds to long tube headers as well.

This setup woke the thing up BIG TIME!

Hth,

-klb

[garyd1961]

Originally Posted by 72c20customcamper

K . But I dont think any reputable builder would put roller rockers on a flat tappet cam .

I have a roller cam with regular old stamped rockers, came from the factory that way.

[deadshort52]

Thanks for the good information. This is the type of post that I was looking for. Tell me what you didn't like about the Comp Cam lifters and what you liked about the Howards lifters. Did you leave the bottom end together or give it a re-ring kit?

Originally Posted by weq92f

.

Pull the valve cover off to get the casting numbers of the heads. That will tell you Oval or Peanut.

If you have peanut port heads, that might explain why the engine runs the way it does and you'll need to pickup a set of #781, #049 or similar cast heads. I bought a set of #781s for 100 bucks off craigslist not so long ago.

Calculate your compression ratio.

Use that to select appropriate cam which will give you the necessary springs required and the data to set them up properly. Then the heads, springs and related parts to the machine shop to get refreshed ( 1000 to 2000 ). I did my #063 heads this way w/ stock valve sizes and walked for about 1400 w/new stainless valves ( et al ), valve job, the proper springs/setup and required machining ( includes the cost of the head parts ).

I went with a COMP 11-422-8 retrofit roller cam on my stock 402 bottom end at about 9:1 compression, Edelbrock Performer 2-O intake. Also installed the COMP lifters at the time. Recently I replaced those lifters with Howards 91161, which is what I should have used to begin with! Upgraded from manifolds to long tube headers as well.

This setup woke the thing up BIG TIME!

Hth,

-klb

[davischevy]

I changed the cam in one stock 402 half ton. It helped some but still wasn't impressive.

The 402 I have now was built when I got it and has an unknown RV cam. I ran fine and had ok power, but leaked oil at the rear main and started missing a while back. I suspect a flat cam.

I thought about rebuilding it, but it cost no more to build a 454. I have a 454 with a set of 781 heads so I decided to build it. I am using a roller cam and rockers.

I will use the original intake manifold which doesn't make any sense except that's what I want.

[i82much]

Originally Posted by weq92f

.

Pull the valve cover off to get the casting numbers of the heads. That will tell you Oval or Peanut.

If you have peanut port heads, that might explain why the engine runs the way it does and you'll need to pickup a set of #781, #049 or similar cast heads. I bought a set of #781s for 100 bucks off craigslist not so long ago.

Calculate your compression ratio.

Use that to select appropriate cam which will give you the necessary springs required and the data to set them up properly. Then the heads, springs and related parts to the machine shop to get refreshed ( 1000 to 2000 ). I did my #063 heads this way w/ stock valve sizes and walked for about 1400 w/new stainless valves ( et al ), valve job, the proper springs/setup and required machining ( includes the cost of the head parts ).

I went with a COMP 11-422-8 retrofit roller cam on my stock 402 bottom end at about 9:1 compression, Edelbrock Performer 2-O intake. Also installed the COMP lifters at the time. Recently I replaced those lifters with Howards 91161, which is what I should have used to begin with! Upgraded from manifolds to long tube headers as well.

This setup woke the thing up BIG TIME!

Hth,

-klb

do you have an automatic and if so does it have a stock converter? curious how that cam would do with a stock converter. what’s your idle rpm?

from the original post it sounds like the heads would be original oval ports, i thought the peanut ports didn’t show up until the smog engines? also i think the peanut port heads have enough head flow for a 396, they actually make decent power on a 454 or 496. but i would imagine peanut ports from a smogger 454 would have abysmal compression on a 402.

[weq92f]

Originally Posted by deadshort52

Thanks for the good information. This is the type of post that I was looking for. Tell me what you didn't like about the Comp Cam lifters and what you liked about the Howards lifters. Did you leave the bottom end together or give it a re-ring kit?

Nope, we just did the top on this cash dump! Bottom has less than 10k ~easy~ miles on it

The COMP lifters made a lot of noise all the time whether hot or cold. I made several attempts at adjusting the preload -- 1/4, 1/2, 3/4. Decided miles might cure so drove it over 1000 miles at 1/2 turn... no change.

Some research indicated this was a common issue! Soon after deciding to swap them for something else, I was lead to Howards as a suitable replacement.

Hth,

-klb