Base Gaskets. Wondering if I should use thicker this time.

[AZRickD]

A couple of years ago I had the RB squish mod done and mounted the jug with the .3mm gasket (Permatex bringing it to about .35 as I measure it after today's tear-down). It have me a squish of about 1.1mm. I ride around Phoenix at 2000 plus feet or higher in other sections of the state. Premium pump gas around here is 91 Octane.

The piston is not nearly flush with the port so I am considering using a thicker base gasket set to raise it a few fractions of a mm (using either the .5mm alone or the .3mm and .5mm together).

I may (or may not) have the head re-cut by a local shop to adjust for this.

What engine behavior am I likely to get if I do raise the jug a bit (with and without the head being re-cut)?

Thanks,

Rick

 

[RBD]

Raising your cylinder will advance the port timing ,moving power band up in RPM range.

It is not always wise to make the piston flush with the bottom of a transfer port, as this will decrease the charge velocity of the transfer port. "The floor", of a port is not that critical as opposed to the "opening port time".

It is the opening of the port that is more critical and will have the biggest influence on the over out power specific out come!

Ron

 

[Stoby]

How then should you figure the best cylinder height adjustment via gaskets?
Stoby

 

[AZRickD]

Does the GG Cognosanti still recommend using Permatex on the base gasket?

The Legend was that this was a fix against the possibility that coolant would leak out the front.

 

[AZRickD]

Ron, given my riding style (I work the bottom revs off the 250), and my terrain (technical), My guess is that I'll keep the .3mm gasket rather than turnining it into a top-end screamer while at the same time removing all that nice compression you've carved into the head.

 

[socalscott]

Where to set the port height(timing)? The big GG mystery.

I've experimented with no port shrouding @ BDC and did not lose the tractor factor. I can't say what happened beyond the mid-range, as I was chasing the 300 phantom power loss.
I picked up a custom fat gasket to replace my multi-layered glued stack from the link below(contact the owner). It dropped back to maybe 1mm of port shroud and .065" squish. He offers two fat gaskets. I don't recall at what thickness. My bad.

http://stores.ebay.com/NORTH-TAHOE-...=1&_sid=53867201&_sop=1&_trksid=p4634.c0.m322

 

[Jakobi]

Ahuh! More base gaskets shifts the power up. You'll drop a little compression also which will also favour top end. Squish will still be acceptable even if you add an exta 0.5mm