RB26DETT Engine compression ratio?

[cbileske]

hey, im getting some new pistons for my RB and i am also gonna be getting a aftermarket head gasket, just want to make sure that the pistons are the same as stock for compression and such, and also how do u figure out what thickness you need??

[themadscientist]

If you are having the block or head decked or chambers reshaped you must take that into consideration.

[cbileske]

what di u mean by decked? the head will probbly just be pressure tested and the block just cleaned up, but it will be bored out from 86 to 87mm im pretty sure. is there any formula to make sure everything is good to go? (compression) also has anyone every ported and polished thier head? is it worth it? i was thinking even just a polish? Yes or No?

[themadscientist]

You should check the head and block surfaces for straightness. If there is a problem your machinist will "deck" or cut the surface to correct it. That process removes material and thus reduces the size of the combustion chamber and brings the piston closer effectively increasing compression.

[cbileske]

ohh yes, so then you basically have to make up that loss with a thicker head gasket? besides that is there anything to worry about, what if the boost is wayy higher then before shoudl there be any changes for this or will a good head gasket and stronger head bolts be good?

[themadscientist]

Just remember it is not boost that unseats head gaskets, it's detonation. I ran 8 years on a bigger turbo with the original HG. As soon as I pushed the fuel system past it's capability and leaned out POP!Metal head gaskets resist the destructive pressure spikes a bit better than OE but if your engine is knocking they pop just as easily. I would not recommend going with a thick gasket. The taller the gasket, the more it is exposed to the events in the combustion chamber. Also the gasket is not as rigid as the block and head castings which could allow things to shift. I would go with the thinnest gasket possible and get a compression drop from dished pistons or chamber work.RB26 head bolts are beef, you would be hard-pressed to lift the head if properly installed. Studs give you the advantage of locating the gasket during assembly and making the torquing more accurate. A bolt has two forces acting on it when torqued, stretch and torsion, the twisting force. A stud sees really just stretch and is thusly more accurate and stronger. It is by no means a requirement though, properly installed bolts get it done.