hi, I'm wondering what are the most desirable and best oval port castings to look for on a BBC. I prefer closed chambered to get my compression up on my stock 8.5:1 402, but if I could find a good set of open or semi-closed chambered heads, I could probably angle mill them to a desired CC. Also, What kind of potential does the "820" castings have? Those are the heads I currently have. Is it worth it to work w/ these heads? Thanks for any help. Eric

I have several sets of closed chamber heads. Email me direct at 81vete4speed@cox.net and I'll tell you about them.

820 is one of the better open chamber castings to work with. The ports aren't quite as large in stock form as some of the 454 castings; but they port up quite well. IMO they're one of the best for a street build.

You may find that closed chamber heads won't work with your pistons. The chamber shape is different (duh) so the dome may interfere. It depends on which pistons and which heads you use.

The 215 style head works super in the smaller BBs.

I would also like to know what's the best oval port heads to use on a 402. I know of a guy with a set of 280's, 290's, 390's, etc. I'm looking to get a 10.0:1 c.r. for pump gas use.

Originally posted by RB69SS396Conv:
820 is one of the better open chamber castings to work with. The ports aren't quite as large in stock form as some of the 454 castings; but they port up quite well. IMO they're one of the best for a street build.

You may find that closed chamber heads won't work with your pistons. The chamber shape is different (duh) so the dome may interfere. It depends on which pistons and which heads you use. I thought my pistons would have a dish instead of a dome because of the low CR, but I'm not sure, haven't taking off the heads yet. Does anyone know if I could use closed chambers on my stock pistons? Would some 702's work? Some guy wants to sell me a pair that's why.

You should be able to use early closed chambered oval port heads with flat pistons under 600 lift. I'd stay below 575 but you should check anyway. You'll get higher CR with the smaller chambers. Around 100cc you'll be between 9 and ten.

I like the 702s. 049s great open chambers. Also 241 and 781 as well as your 820s. Anything from 65 to 69 except ZL1s are closed. Just get your machinist to massage them.

is it possible to mount the mk VI heads on an earlier block?

If so the Vortec heads seem to be pretty stout.

Good info, thanks for all the replys. One more question, does anybody know the piston volume of the stock 8.5:1 piston in a '71 402? If not exact, does anybody have a ruff estimate. Thanks again, Eric

Don't think Vortecs wil work on a Mark IV. Vortec heads pretty much need flat tops for clearance.

Ok, I did a little search on here on if I have dome pistons, I think the 71/72 402's came w/ a .182 dome piston. I also looked up some replacements in the speedpro book, #L2246NF are the closes ones that came up. Now I'm a little worried w/ valve to piston clearances if I do install closed chambered heads w/ these pistons. I might be buying a closed chambered set of heads very soon, and want to make sure before I waste my money. Does anybody know, using my orginal 402 pistons w/ closed chambers will work w/o any problems? Thanks. Eric

I have a 396 with #215 heads and those pistons..no piston to valve clearance problems...thats how they came..stock .180 or so dome and used 101 cc chamber heads
Cam is 240/246 duration @.050

Correct 402 pistons are L2354 .188 dome, 19.8CC. I run those with 290 semi closed chamber heads. Interference occurs with closed chmaber pistons and open chamber heads near the exhaust side of the piston. But this is really only a problem with the 4.25" bore of a 427 or 454. A 402 will have more clearance due to the smaller bore and smaller piston dome.

Good info., but would I still have any problems w/ a 98cc chamber, even though it's only 3cc off from your guys heads, I'm thinking of some 702's. Thanks again. Eric

I just took apart a 72 402 that was running had the stock pistons std bore and had the #702 heads on it. The stock low HP pistons in a 402 from 70-72 were the same and in 70 they used a closed 101cc head #290 in 1971 they went to a semi open chamber dropping compression. bUy the #702 heads they help quite a bit by bumping compression. A lot of people like using them on stock 454 to bump compression, they really wake up with closed chamber heads and a mild cam.

Originally posted by supersport6667:
[QB]The stock low HP pistons in a 402 from 70-72 were the same and in 70 they used a closed 101cc head #290 in 1971 they went to a semi open chamber dropping compressionmy favorite cheap big block was a stock 72 402 shortblock that I bolted some #215's unto and threw in an LS6 cam..with an M20/4.10's it was a blast graemlins/thumbsup.gif

You really only need flat pistons with the 702s. The best thing to do is call the piston manufacturer, your machinist, or just ask others if you already have mild domed pistons. Somebody likely is running that combination. Then just check the clearance.

I just built a 454 with 702s. With the bigger valves they probably have a 100+ cc rather than the 98. With flat tops that's going to be in the 9.5 CR range. You can run up to a 600 cam with that with a street cam profile. A 540 cam with 1.8 rockers is 571 lift. That won't have any interference problems at all.