Thread: 402 needs more power (heads & cam)

Tweet

Hi jerry yes I know.. but the covers are allright. And at home i have a plate to put on the manifold to lift the engine.

for what it worth many of the close chamber Gm /trw forged pistons 396/402 hi CR were made for the close chamber REC port heads not the close chamber oval port that could be less cc and could be more cc then the older close chamber REC port heads but the EX side of head chamber of the oval port head had small shape around the ex valve many times adding to engine sound to rod knock sound as the piston hit the chamber if not reworking the chamber . so chamber to dome is a good ideal to check even with after market heads. i know that Icon wiseco and others make a pistons for a open chamber heads on a small bore 396/402 big block . there is companys make smaller chamber heads afr .brodix and edelbrock to so there more then one way to go .if machine work is that much them you may be better to buy new heads ?i have a very hard time seeing that ? as i build sell and have a engine machine shop were much of the work is engines that are BBC or base off a bbc but all after market parts labor rate is that hi then i can seen why many of you guys buy engines from the USA .if your working thru this engine? no one said put a 454 or bigger like a 489/496 base off a good 454 blocks and parts maybe very hard to fined were you at. i build 489/496 street engine then the 396/402 i had some 396/402 and built some but over the years parts have not found there way for the much smaller bore 396/402 engine i not saying it can not be done. but things like as simple head gasket are all set to work base off the 4.250 bore 427/454 with head gasket fire ring size 4.370. for some over bore of the 427/454 bore and many head gaskets with a 4.540 fire ring as a stock gasket base off 125 over bore 4.375 and Gm 502 4.470 bore engines and much bigger as blocks after market can go to 4.625bore and head gaskets are easly had.the bigger fire ring and can add to your cc as your bore many be 4.125 or 4.155 that is about it on many 396/402 blocks can take for over bore. only for very few396 1965/67 4 bolt block s could take a over bore to the stock 427/454 4.250 bore this was done many years ago on some 396 . but the value of the blocks for the number guys in a restore should not be done or much think about. but if your looking at a full rebuild you may want to think about building a bigger big block by using a 4 inch stroke 454 crank you will need the 454 damper and fly wheel or flex plate for what ever your needs are for the type of trans your using as the 454 crank is external balance engine so with parts listed and a set of KB pistons for a 402 bore size and the stock size rod of 6.135 and the 454 crank of 4.000 can get you about 427 . on your heads. Gm did put a ex seat in some heads .many were induction heated the iron around the ex seat this made it hard...it would be hard for me to say what was done on the truck heads as i seen them both ways over the years

Yep---the 396/402 stuff I pretty much talk people out of unless its a numbers restore deal---------the 454 core block and stroker crank plus late alum heads, internal balance is an excellent way to go -------------with alum heads /manifold engines weight isn't too bad --------


thawing out any there in Michigan Pat??

Techinstructor, why is this info needed? Because I don't really want to tear down my engine and then put the same heads back on the block. Respectively I can remove them next autumn/winter, check all you need and then order the new heads and install them.
Which exactly are the needed information to choose new heads?
Piston and block casting? Something else?

I bought the engine from rockauto and it might be a marshall engine. Will take a look tomorrow if I have some specification from the manufacturer. I think there are the stock pistons in it.
When a block is honed, must there be bigger pistons or could you reuse the original ones?

Yes so when I need to decide between porting my heads for 2000$ or buy new heads for 2500$ I prefer the new lighter ones.
Or if I could take the 3964290 with 101cc closed chamber without modification (except valve springs) this would also be an option. But I think aluminium heads would give more hp.

I'll let you know that English isn't my native language, so sometimes I don't understand everything. So that's why I ask some questions twice

Tim