89mm Ross Piston C/R with...

[Steven]

The Ross 89mm piston is rated at an 11.2:1 compression ratio by Ross. Is this with the .020 base gasket and .025 head gasket?

The reason I ask is because I already purchased a Cometic gasket set for my 440 which has a .012 base (.010 crushed) and .025 head gasket.

This will further reduce squish, increasing the compression ratio correct?.

Anybody know where I might be on C/R with this combo?

Thanks, Steve

[Steven]

I know some of you have played with the c/r on the Ross 89mm piston....

anybody?

[eldoexrider01]

wish i could help ya man. im on here tryin to find out some info on piston comp.s cuz ive heard an 11 to 1 is not true 11 to 1 unless u get the gaskets n stuff rite. so im lookin. sorry i cant help i fig i would post cuz i hate when people ignore my threads .

[Steven]

you are right... my wiseco 89mm 11:1 was really more like 9.5:1 when i measured it... thats why I'm getting the ross.

[eldoexrider01]

if u read the dirtwheels wit the z440 and 440ex test they did, the piston mfg had the piston made custom for their shop and it was more than 11:1 and with the subtraction of actual comp. it might be close. jus and idea or suggestion.

[eldoexrider01]

sorry about that. it was the zuki that had the special made piston and it was 12:1. its been a long weekend.

[Steven]

Anyone else know the c/r of the Ross 89mm with a .010 base and .025 head?

[Steven]

bump

[Matt Fisher]

These sites have calculators to figure it out.

http://www.kb-silvolite.com/calc.phtml

http://www.rosspistons.com

Without figuring it out, I'd guess at about 11.9:1; as .025 makes about 1 full point in the CR.

You can get a special lightweight alloy wrist pin from Ross, btw. Saves about 20 grams, and it's only about $30. Just call Honda Jim @ 760-366-7879. He's the guy at Ross that designed the piston (as well as the JE ones in the past).

[Steven]

Thanks Matt.

Thats more than i wanted... I think I'll get the .020 base gasket from cosmetics.

[deansfastway]

Steven try out that trick preload head gasket 89mms from Cometic.