Head gasket/deck height

[dsommer]

Currently the engine is at the builder and he told me that the piston is SLIGHTLY above the deck (#6) by .003.

 

Block was decked but the builder did not request that it be zero decked.

 

Solution is to use a Felpro head gasket #1144-061 (or -053) to resolve any possible issue of piston interference.

 

Engine internals:

Eagle 4340 Forged Steel Steel Internal balance

2pc rear main seal 3.75†crank

Mahle Forged Racing Pistons 11:1 (.040 over bore)compression ratio Phosphate Dipped and Teflon Coated

6†Eagle ESP 4340 Forged Steel H Beam Rods with ARP 8740 Bolts

Mahle Moly Racing Performance Ring Set

King Race Bearings Rods and Main

ARP main studs

ARP head studs

 

My questions are:

Is this normal for the piston to protrude out of the bore?

 

If I use this gasket, is it made for the .040 overbore

 

Can anybody source these gaskets cheaper or recomend an alternative as these are expensive at $80 EACH!!!

 

Thanks,

 

David

[jt1]

When a block has been decked, sometimes pistons can wind up above the deck. It's really not a big deal unless it's excessive, and 0.003" isn't enough to worry about.

 

That gasket has a 4.2 bore and is 0.061" thick compressed, way overkill IMO. It's expensive and you lose all the quench benefits.

 

I would use one of the 0.041 felpro gaskets, like the 1003. That will give you a quench distance of 0.038, which is just about perfect. If you want a little more, Ferrea makes a 4.060 bore 0.045 thick head gasket which is very nice. You can get them from CV Products.

 

John

[Six_Shooter]

When a block has been decked, sometimes pistons can wind up above the deck. It's really not a big deal unless it's excessive, and 0.003" isn't enough to worry about.

 

That gasket has a 4.2 bore and is 0.061" thick compressed, way overkill IMO. It's expensive and you lose all the quench benefits.

 

I would use one of the 0.041 felpro gaskets, like the 1003. That will give you a quench distance of 0.038, which is just about perfect. If you want a little more, Ferrea makes a 4.060 bore 0.045 thick head gasket which is very nice. You can get them from CV Products.

 

John

 

 

Basically what I would have suggested, I just wouldn't have had any part numbers.

 

On most engines the general concensus seems to be about .040" quench distance as being good. On a race only engine, a tighter quench could be used, but requires very CAREFUL assembly and measuring process.

This is usually something (for a street engine) to err on the side of slightly too much quench distance instead of not enough.

 

I do agree .003" piston hight above the deck isn't much to worry about.

[grumpyvette]

jt1

gave you good info

.038 quench is almost ideal

having a performance piston extend a couple thousanths out of the bore is COMON

[Michael]

Measure the piston installed-height once the rotating assembly is together. In my engine I specified +0.001" installed height (piston above deck by 0.001") but in reality the flat part of the piston is at -0.004". These are mid-grade hypereutectic pistons, with significant graininess and unevenness on the flats.

 

When I applied clay to the piston to check quench gap and piston-cylinder gap, well, upon unbolting the heads the depth of the clay was 0.015" more than I expected from my calculations. Part of that may be elastic spring-back of the clay after the head bolts were untorqued.

 

Bottom line: small tolerances do matter when the gaps get close, but even a moderately large tolerance stackup should (I hope!) be OK when gaps are relatively large. My quench gap came out to 0.055" - while I was shooting for 0.040". The price, I suppose, is a slight decrease in combustion efficiency and concommittant increase in required timing advance.

[G.I.jonas]

Is it normal or ok for one piston to be sticking up and not the others?suppose one of them is 3 thousandsths of in the other direction,sounds like differing compression ratios to me but im no engine builder.

[pparaska]

Getting piston deck heights to come all within 0.003 or 0.004 of each other is pretty difficult. I'd go with the 0.038" as your smallest piston-to-head clearance and be very happy! That's about ideal!

 

I've had the tops of pistons cut down a few thous. to bring everything close using stock rods. With aftermarket rods, and pistons, it's usually easier though. I've also been known to take a few thousandths off the top of a piston myself, using a lot of checking (relative to the ring lands, valve pockets, etc.) by using sandpaper and a figure 8 motion. It takes a long time. That was because I had a piston that was 0.004" higher than all the others and it bugged me. I probably could have left it alone .