Thread: 402 BBC buildup - combos???

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them pistons you want to watch them that they do not hit the sides of the head camber if you use a close camber head O port heads. i did a set of 292 heads with big valves and was 103 cc when done i would loose the781 less you know the cc are. if they are cut like you said the ear on the head where it just cast would be level with the cut on the face of deck or damn close

I got a few other pictures of the chamber. Also, on the right image, as you said pat, its damn close to being flush with the cast. Ill keep that in mind

I'm wondering if cutting my intake out to 2.19 will be a problem with the deck of the heads. whether it will cut it off. what do you guys think?

I think your gonna have problems with your intake manifold bolts lining up. You may want to take these to a machine shop and see if they are worth using. Are you sure they are cut .065? I think that would be over the limit. As for the piston dome size, that is about the size dome I used in my engine with a closed chamber oval port head. The chambers cc'd at 96.4. The compression was a little over 10-1. You can find an oval port head with a 101cc chamber and that will work pretty good. They are from the late 60's and make good power. They are all over Ebay. Check on Mortec.com for casting #'s.

Originally Posted by 1JohnnyO

I agree.....Im just saying it's easier if you can start bigger. And how do you know the valves wont clear? We dont know for sure what pistons are in there, and it shouldn't be an issue if he doesnt get crazy with the cam.

Well, I've already been through all this before with my 396. I had a set of 2.25 valve rectangle port heads on my 396 with KB pistons with a 250 duration isky cam. I clayed the pistons to check clearance and there was none. The valves don't fit in the valve reliefs. I switched to a comp magnum 230 dur. with a 520 lift just to see where I was at and I only had .060 clearance. Which is bear minimum. So I went with different heads. KB, TRW, and Silvolite are the only manufacterers that make pistons for a 396. None of them are machined for 2.25 valves, 2.19 is the max. size valve.

Originally Posted by 69elko

I think your gonna have problems with your intake manifold bolts lining up. You may want to take these to a machine shop and see if they are worth using. Are you sure they are cut .065? I think that would be over the limit. As for the piston dome size, that is about the size dome I used in my engine with a closed chamber oval port head. The chambers cc'd at 96.4. The compression was a little over 10-1. You can find an oval port head with a 101cc chamber and that will work pretty good. They are from the late 60's and make good power. They are all over Ebay. Check on Mortec.com for casting #'s.

Yes, I'm a 100% sure the heads are decked .065. I got this engine from a buddy who decided he wanted to build a small block instead. (clearance issues) And he originally had planned on running E-85. So that is why he decked so much to get high c/r. I'm thinking on getting a new set of heads. Any body have a set in mind? I might just go to my local machine shop and get another pair of 781's, or 049s since they are the same. Whichever is cheaper.
Thanks

3909802 3917215 3931063 3964290 These are the head numbers I would go with. They are all 101cc chamber. I would use the thicker Fel-Pro .051" head gasket just to make sure you can run on pump gas. It will give you about 9.5 to 1 compression. Just making sure, but those pistons you have are made for a closed chamber right? It looked like it in the pictures but I wasn't positive. The heads you listed will need a huge domed piston. They are all 119cc and will give you 8.5-1 comp. or less.

With the 9.5-1 comp., a comp magnum 280H hydraulic cam, and all the bolt-ons, you should be right around 425-450HP no problem.

Originally Posted by 69elko

3909802 3917215 3931063 3964290 These are the head numbers I would go with. They are all 101cc chamber. I would use the thicker Fel-Pro .051" head gasket just to make sure you can run on pump gas. It will give you about 9.5 to 1 compression. Just making sure, but those pistons you have are made for a closed chamber right? It looked like it in the pictures but I wasn't positive. The heads you listed will need a huge domed piston. They are all 119cc and will give you 8.5-1 comp. or less.

With the 9.5-1 comp., a comp magnum 280H hydraulic cam, and all the bolt-ons, you should be right around 425-450HP no problem.

why go with the 101 cc heads? and a .051 head gasket .them domes will hit i bet you on 101cc. just get a set of 292 and be done with it

As long as those pistons he has are made for a closed chamber head they shouldn't hit. They look like the closed chamber type, I could be wrong though. Call KB and double check.

Originally Posted by 69elko

As long as those pistons he has are made for a closed chamber head they shouldn't hit. They look like the closed chamber type, I could be wrong though. Call KB and double check.

I'm very positive they're open chamber. I bought it from my buddy, and it came with all of the stuff. I'm pretty sure I'll be throwing the heads out. as I'm sure they'll have a problem with the intake lining up and id rather not have that milled down.

the 292's will work with your arrangement probably because of the extra shrouding around the exhaust valve. I have seen 292 casting heads on ebay many times. they are usually 113 cc. I believe they are the same combustion chamber as the 820 casting. They are considered by some people as the first gen smog head but most attest that they are great street heads. Run these with a small hyd roller.

i like them 292 heads have used them on some 454 to that work very good with just a bit of work