I just assembled my shortblock.

Want a torque monster for my '69 Fury 727 w/2.76 diff.

Recommend head gasket?

Compression Ratio?

Cam for cruising on the highway? Voodoo 60302?

400 block 4.375 bore 3.75 stroke. Diamond 52407 pistons -12cc dished .010 below deck. 915 heads, DP4B intake. HP ex. Man. 2 1/2" ex.

I rec a steel shim as that will give you the most comp. ratio

I'd also go standard blue Permatorques. It yields 9.6.1:1 static, with a .050 quench. The quench is not optimal, but it will still help. This also allows you to run a smaller torquey cam the gearing and weight need. You will want to run something cam-wise with at least 225°@.050.

I'd use a gasket that will net you .035" to .040 quench(piston to head). Here is a quick & easy CR calculator. http://kb-silvolite.com/calc.php?

What's the average 915 head volume? If I put 78cc in the calculator w/a .039 gasket, I get a CR of 10.055:1

4.375 X 3.750 x 78cc head x .010 below deck x 4.375/.039 gasket x 12cc piston dish

Sound right? I'd like to get better quench. Any 4.375 gaskets in the .025 -.030 range?

I think the 915's average 80 CC's. www.cometic has different thickness gaskets & there are others(which are probably cheaper) & getting proper quench is CRITICAL.

Thanks!

you're welcome!

Since the pistons a dished, it may be a little difficult to get a full quench. Also are there valve reliefs? If not you will have to clay it to see your clearance. Steel shim will give you .030 quench (prob. too tight) but more than .040 in the dish area. If you can get .030 gaskets, at least the edges will have quench.

I'm thinking the area around the dish will concentrate or squish the charge into the dish. Kinda like a diesel piston. The dish area is directly below the open area of the head's chamber with the flat portion of the piston matching the flat area of the heads.

Depends on the Dish shape....a D dish like these will allow full perimeter quench....The last set of Diamonds had a smaller D dish as well which would quench with a closed chamber head.

That's what I have. I just think that perimeter would "squish" the charge to the dish and make a nice kerplosion. Or maybe I don't have a clue.
Thanks for the informative discussion. Much appreciated.

That oughta quench fine.

yes a D dish will quench fine. For some reason I erroneously got to thinking that you were talking about just a regular dish piston with the thin perimeter around the dish which you were not.

Okay, I think we got the piston and gasket thing ironed out.

How about a cam? I,m leaning towards the 60302 Voodoo.
C-body w/2.76 gears.
What do you think?

Enough duration?
220 int./226 exh. @ .050

Yeah you're right in the ballpark for your gearing and weight, I'd prefer to run a 3.23-3.55 ish type gear unless you're building it for 90% highway driving....the extra revs won't hurt mileage that much and the extra piston speed will greatly enhance your roll-on throttle torque....

10:1 compression + iron heads + small cam, not sure how well that's gonna work with you on pump gas. The quench will help, but that cam with that combo will build a lot of cylinder pressure.

But as for torq/mileage it should work well with your combo in that respect. Proper tuning will be necessary to get it to run w/o detonation.

I can only seem to find .020 steel shim or .039-.040 head gaskets. .010 deck clearance.
.049-.050 quench too much distance to work for my intended purpose?
.030 too tight?
Other cam ideas? Bigger w/Rhoads lifters?

Much help given so far. Thanks
More discussion welcome.