Closed Chamber Heads on a 400

[440+6]

I'm thinking about putting a pair of 516 heads on a 1972 400. My question is, about what will my compression be?

[dave571]

Assuming the pistons in your 400 are about .100 down the hole, std bore, .020 gasket, 4.342 bore, 3.380 stroke, 0 cc valve relief stock pistons, etc.

Your at 8.00:1 now (open 88 cc heads)

With closed 516 (around 78 cc's)

8.66:1

I used this calculator http://kb-silvolite.com/calc.php?action=comp

[DartGT66]

Make sure to measure the 516 chambers first. I have seen even 86cc chambers in them. In stock form, they have smaller exhaust valves than the stock 400 heads, and in any form they flow worse than the 400's stock heads with similar prep. Milling the closed chamber heads .040" will reduce the chamber size about 7 cc's, and milling the open chambers teh same amount about 10. So, with the commonly assumed 10cc difference, with 0.1" milling the chambersizes should be even.

I really don't know, where the assumed 10cc difference comes from, though. The cahmbers, valve depths etc are pretty much the same in both open and closed chamber heads, except the portion that is "open" in the open chamber heads. It's usually about 0.1" deep, and if you take a look at for example Edelbrock heads, they have both closed chamber, and open chamber versions available. The open chambers have been machined with pretty much the same depth open portion as in the production open chamber heads, but the advertised difference between the two is only 4cc's instead of the commonly assumed 10cc in production heads?

[dave571]

Originally Posted by DartGT66

..... I have seen even 86cc chambers in them.

I really don't know, where the assumed 10cc difference comes from, though.

I have never measured closed iron heads at more than 80 cc's. The ones I run now are 78 cc's bang on, with nail head valves, that take up a little.

Every set of open iron heads I've measured, came out to 88-90. Sometime with as much as 2 cc's variable on the same head .

I am wondering about the casting tolerances in early days(516's etc). Only because this is not the first time I have heard this brought up. Other members have posted measureing closed iron heads at over 84 cc's, while I have never seen a set that bad myself.

[ehostler]

Most opens tend to average 90cc. I've seen them as bad as 94cc; however, that is very rare.

[sundrop_440]

It is critical you find out how far down the hole the piston is, I have a 440 .030 over trw 2266 pistons, I had about 8;1 just a tad higher,my pistons were .092 down the hole. But I ported a set of 915's (closed chamber) 2.14 intake, 1.81 exhaust, I installed a .020 gasket instead of the .040 felpro I had, trying to do just what your attempting, I also replaced the cam with a Hughes 28-- something, I can't remember the last two numbers. I bumped my compression over 9;1, but, I ran into detonation problems, since then I've read, asked, probed,and found that you have to keep that closed end to around .040 to .060 or your going to have problems like mine, I was concerned when I did it, and I thought I'd try and if it didn't work I'd change the pistons, which is what my next step is.I hope this helps to save you from alot of poteintial grief. Sundrop_440

[daredevil]

are you removing 452s with a plunge cut and mild porting they flow good numbers

[Shaun]

Originally Posted by DartGT66

Make sure to measure the 516 chambers first. I have seen even 86cc chambers in them. In stock form, they have smaller exhaust valves than the stock 400 heads, and in any form they flow worse than the 400's stock heads with similar prep.

516's are good heads. The sets that I have had have all been under 80 cc's. The ones I run in my 440 are 78.5 cc's after polishing.
True,they did come stock with a 1.60 exhaust valve and the water passage runs right in it(preventing extensive porting there). However,you can put a 1.74 exhaust valve in it and can bowl port it,to an extent.
Flow worse in any form? Pretty broad there 66. I've had and seen more than a few 915's and 516's,and according to the experts,the ports are different,but not as much as anyone with 915's wants to think. My 516's were template ported using the MP templates,then hogged out(can't tell all). I have the stock valves for a 440-2.08 and 1.74 in them and with 28 inches of water(H20),they flowed 220 at .500 lift. Hmmm. That's better than a ported 915 head.
I run the 1009 Fel pro head gasket(.039),I'm down in the hole a few thousandths and at running temp,I have a head to piston clearance of .040. More secrets are involved here,but my CR is almost 11-1 and I run on 91 octane California pump gas. My cam is a 240*/246* at .050 with .501 and .507 lift Comp grind. I installed it retarded 2* from 106* to 108*.
I advise running a split pattern cam with the 516's,because of the limitations the water passages pose to your exhaust flow. But don't go bigger than 1 7/8 on your headers,or you will lose your velocity. You will go small to big,too quick. I run 1 3/4 for this reason and I get 12.30 in the 1/4 spinning(for now until I get her done and more weight transferred).