Compression Ratios

[NYTSKY]

Hi all,

I will be having my engine rebuilt with all the goodies and i have a question on CR.

What would be the average amount of material shaved off both the head and the block. 4 thou off each??

When the head and block gets shaved,so as the gasket can seal correctly,will my CR rise alot?

I have ordered CP pistons at 9.0:1 CR (stock RB25 CR) and a 1.2mm Cometic headgasket (stock thickness)

CHEERS

[The Mafia]

well, you have no choice but to get them done just enough so they are flat.

So just do that and then do a mock build and measure it? Depends how good you want it to be.

You could end up with 9.1:1 maybe, but thats a good thing I say.

[Guilt-Toy]

use a cometic 3 layer head gasket that will bring it down a little

[RB30-POWER]

was interesting to read old mate post the other day, that he had to remove the head again to fit a thicker gasket after a rebuild on rb25 because the engine was detonating and not able to make the power it was previously. was well over 500hp or so from memory, thread is on here somewhere.

depends on what power you want and what fuel you plan to use i suppose.

but the average build/engine will not have a problem at all with such a little increase in cr.

[NYTSKY]

use a cometic 3 layer head gasket that will bring it down a little

The Cometic gasket i will be using is a MLS 3 layer metal type.Maybe i should have ordered the 1.3mm instead???

[Risking]

run it around 9.2-9.3.

the results will all come from whoever you choose to tune it but.

sammy will only take off what needs to be taken.

Id say dont deck the block unless it needs to be. You need to have this engine put together and measured correctly. It needs to have the squish bands etc all measured as well and piston to valve clearances set properly.

Several mock up assemblies will be needed to get it all correct.

Edited March 7, 2008 by Risking

[NYTSKY]

run it around 9.2-9.3.

the results will all come from whoever you choose to tune it but.

sammy will only take off what needs to be taken.

Id say dont deck the block unless it needs to be. You need to have this engine put together and measured correctly. It needs to have the squish bands etc all measured as well and piston to valve clearances set properly.

Several mock up assemblies will be needed to get it all correct.

Want to make a couple of extra dollars Brad?? With the amount of goodies going into this motor i want it done correctly.

[Risking]

if sammy is machining it all up there is no problem with me showing you how to do it.

Better you learn whats involved rather than paying someone to wack together an engine.

Next time I meet up with you tell me exactly whats being done and will go from there.