I finally got down the IPD big bore piston set with one slightly damaged by
impact with a 5/16" hex nut.
This is for a 6 bolt, 2130cc engine, 92mm/3.622" bore.
| = perpendicular to wrist pin, - = parallel to wrist pin

Skirt | = 3.619, - = 3.605
between rings 1 and 2, | = 3.604, - = 3.603

Then I got out the Elring headgaskets that I got 3 of for $5 (plus shipping).
The cylinder sealing rings (metal) exactly fit over the tops of the pistons,
no interference and no apparent clearance. Uncompressed thickness of these
rings is 0.035" so I suspect that they compress to 0.032"/0.8mm

My conclusion is that if the overbore is exactly concentric with the gasket
pattern, and there is no throw of the pistons above the deck, these gaskets
would be usable as high-compression, big-bore gaskets for STD 2130 size,
not for overbore above the 2130 size.

Is this a call to "blueprinting"?? Or maybe a very slight chamfer to the top
of the piston?
--
George Downs, Bartlesville, Oklahoma, Central US

Lets say the blocks bores do match the gasket bores. If there is no apparent clearence between piston and the metal gasket rings, I'd think you'd have a problem once the gasket is chrushed. It will indeed crush to 0.032"/0.8mm and when it does it will, like Phil already said, indeed decrease the bores diameter.

But lets say you'd have a block decked so the piston are clear with the deck. When revving it the pistons will rise .030-.032" (Phil's numbers). What would happen if one would just cut the piston a bit, so the top .035" of the piston or so will have a smaller diameter, lets say 3.600" ?

Or will this back-cut area be filled up with carbon deposits in no time and still cause a problem at high rpm's? (when constantly revving it to high rpm's there will no problem (I think). But what happens when this engine would be a daily driver and only once in a month be revved to those high rpm's?
But then again, it's exactly the same situation with the carbon that's on the head's quench area is it not?
--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)

The 6 bolt pistons that ipd had made several years ago were a teeny bit larger than the more common B21 piston retrofit. Unfortunately, I don't have any of the specs handy for either variety. What I wonder is this: is it possible that there's a headgasket that's suited to the (slightly smaller) B21 piston that would happen to be slightly too small for the (slightly larger) ipd 2200cc piston?

About the only idea I'd have would be to sacrifice one gasket by installing and crushing it; then hand turning the engine through a couple revs, then disassembling it for inspection. This *might* tell you if the piston is contacting the gasket (and it might not); but it _won't_ tell you whether the piston will or will not contact the gasket when the engine is running.

I guess my short answer is: I'm not sure. If it were me, I might check with ipd and see if they can offer some comparative measurements.

Best,

Cameron
Rose City

As you can see from the dimensions, these are 2130 cc pistons, not 2200s.
I think I will go ahead and try it, unless the bore job I get is not concentric
with the gasket rings. The pistons are pretty sturdy (if they can mash a 5/16"
hex nut down to less than 1/8" thick without more than the most minor damage)
so I don't think I am putting the pistons at serious risk. It will be a while
before I get to it. Many thanks for the comments.
--
George Downs, Bartlesville, Oklahoma, Central US

My question is whether the gasket rings will interfere with the pistons when crushed. I can picture the ID narrowing when that happens. ???

For efficient combustion, we like having the piston-to-head clearance at .030-.032" in a blueprinted motor (meaning the rods and/or piston have been corrected so they all come out the same). That means a zero deck height with the gasket in question, assuming it does crush to .032".

The reason we don't go tighter than that on the clearance is because we allow .030" for so-called rod stretching at high temps/rpm. Under those conditions, the clearance is essentially zero.

Point is that the pistons will definitely need to come up through the gasket without hitting it.

Point taken. Many thanks!
--
George Downs, Bartlesville, Oklahoma, Central US