My plans were to do a complete performance rebuild on my 71 402. I still plan to do this, but for the moment would like to make the car mobile and focus on other parts of the restoration.

The engine is a stock 71 402 with 820 heads (larger than stock valves).

Have been looking for a pair of close chamber heads to bump the compression for the time being.

Would I really benifit from the reduction of chamber size? Any close heads I should look for or stray from?

Any cam suggestions? Plan to put the engine back in with new oil pump, air gap intake, small tube headers, and 750cfm vac holley. Will be in a 4sp car W/ 3:73 Like the idea of a lopey idle.

Thanks for any help, Kevin

i built a 402 for my chevelle. Well my engine builder did the short block but anyways... he was adamant about having closed chambered heads. I bought a set of 290 heads that allready had the 2.19 intake valve in it. My comp ratio should be around 10-1. For a 402 id say the only way to go would be closed chambered. you can flow all you want on those open chambers but if you dont have the compression it wont do you any good.

I have a set of venolia dome pistons and a set of big valve 781's for my rebuild, but currently have these stock pistons. Unsure what Cr I can get out of them.

Thanks for the reply, Kevin

anyone?

Not sure if this helps but I also used 290 oval ports on my 402. However I was told to keep the stock valve size because larger valves on a smaller bore engine are shrouded by the cylinder wall but also reduce velocity which makes the engine a dog in the lower rpms.

I guess that makes sense since I was advised to get small tube headers.

Thanks!!!

what dawg said is true, my engine builder cut a relief into the block for the valve. Not sure i used the correct termonology but oh well.

IS that the relief I see on the left side of the cylinder in my picture?

I think I've found a nice pair of 215 heads which should yield me @ 9.5:1cr I think . Should know soon.

Thanks again, Kevin

I have a set of 820's on my 454, 113 cc chamber, carefull
on the closed chamber heads on a 402, piston contact.
Unless you have pistons to match.

781's are 120 cc open chamber.
Real pleased with the comination of the 820's and the trw .125 dome pistons.. Just have hook up problems now.

I Am Also Running The 820 Heads And I Am Wondering If Milling Them I Could Get The Best Of Both Worlds Compression And Flow