[junglejimbo]

With stock bore and pistons (88.9mm) and a gasket bore of 92mm, am I better off using a thicker gasket and having the pistons emerge from the cylinders to achieve proper squish, or thinner gasket with pistons slightly below deck at TDC? With bigger bore/pistons this wouldn't be an issue, but in this case I would be creating a >1.5mm ring of dead space (?) between the piston and gasket, which seems like it would be a carbon build up area, or something (which happened with the old thick gasket, although it looks like it was running quite rich). Anybody have experience with this?

 

[Phil Singher]

I'd use a B20B head gasket. The Elring ones advertised as .030" thick actually crush to about .034", and the bore is a bit less than 92mm. Deck the block so the pistons end up .002" above the deck, so you have .032" clearance. I've had engines where the pistons were all within one or two thousandths in height, but others where they varied a lot more than that, so take that into account. You can correct any overly tall ones by shaving the excess off the piston crowns.

 

[junglejimbo]

I'd use a B20B head gasket. The Elring ones advertised as .030" thick actually crush to about .034", and the bore is a bit less than 92mm. Deck the block so the pistons end up .002" above the deck, so you have .032" clearance. I've had engines where the pistons were all within one or two thousandths in height, but others where they varied a lot more than that, so take that into account. You can correct any overly tall ones by shaving the excess off the piston crowns.

Is that .034" consistent (not just an odd batch)?

 

[Phil Singher]

It's consistent. If you have any doubts, measure the thickness of the substrate where there are no features. It won't crush more than a thou or so there.

 

[junglejimbo]

It's consistent. If you have any doubts, measure the thickness of the substrate where there are no features. It won't crush more than a thou or so there.

Nothing beats experience! So glad you had this answer... Don't know why these specs aren't advertised. Haven't ordered gasket yet, and machine work will be happening within the week (before gasket would arrive to be measured), so needed some solid info.

Who cares to guess where this thing will end up power-wise? I'll be able to dyno tune it with the same guy who is doing the machining, so won't just be guessing. The details:
Stock 6 bolt B20 bottom end, decked per Phil's recommendation
Late non-US carb head, per other threads, milled to produce around 10.5:1 CR
Stock valvetrain (43mm intake valves) with fresh grind
Volvo K cam
123tune+ distributor and (?) hot coil
Stock SUs with fresh rebuild
stock dual exhaust manifold, exhaust tbd

I'm guessing it'll be in the 140-145 range, pulled straight outta my @$$

 

[junglejimbo]

BTW, I remember camping somewhere on Whidbey Island as a kid, and having the Blue Angels fly over. That was a long time ago....

 

[Phil Singher]

I don't think you'll see that much strictly in terms of horsepower, because that's a function of RPM and the K cam isn't all that high-revving. But I think you will see a higher and flatter torque curve than stock, which is much more important for performance.