7500rpm

Hi

hi have a b20vtec with
rs machines pistons itr replica 85bore
b16 head
oem b20 head gasket
darton sleeves
eagle conecting rods

on the calculator it says 13.1 comp ratio, but it seems too hight to me
can you advise me a new head gasket so i can run it on a small turbo safely?
it will run on pump gas

i was thinking in 10.7 comp?

dcmatt

iTrader: (7)

You would be better off switching out the pistons.

wantboost

iTrader: (2)

Yea you can't run a headgasket that thick. the calculator will toss out a value between 13:1-14:1 for itr pistons depending on bore, stroke, and what head you use. the ctr pistons will spit out values almost 15:1

It would take a very thick hg to knock 3 full points off of the compression, you'd have a lot of issues

7500rpm

so...am i really runing those 13.1 comp ratio?
i've a friend with 11.5 wisecos(85bore) and the dome is pretty the same as my itr replica pistons.
he ordered the pistons to his b20vtec too



his block

mine

dcmatt

iTrader: (7)

I know the aftermarket pistons will have more valve relief so that helps drop em down. And it really doesnt take much. If you have the ross itr pistons they list them at 11.7-12.0 depending on which head you have. You might could get away with a slightly larger headgasket. Dont forget to figure in any decking on the block or head.

Muckman

iTrader: (2)

Which pistons exactly?
P73-A0 (USDM B18C5) = 12.6:1
P73-00 (JDM B18C5) = 13.28:1

Cometic has MLS gaskets all the way up to .140" so you could lower it a full 3 points with a thicker HG. I personally would rather run E85 before a ridiculously thick HG. Talk to your tuner first. I don't think you need to go that low on the compression, especially with a small turbo.

7500rpm

p73-A0

here in portugal we dont have e85, the best fuel we have on the gas station is 98ron.
so do you think it will be ok with 11.00 comp ratio on a .075 HG?

F22Master

You need to actually measure the C/R yourself to know exactlywhat it is. CC the chambers, CC the piston, and do the calculations. That is the only way to know for sure.

flavio

7500 our 98 pump gas its like the 93ron in the usa..

wantboost

iTrader: (2)

Just like excessive head and block milling can alter mechanical timing so can running a headgasket that's too thick.

once you go too far each way, too thick or too thin, the stock timing marks are no longer of any use. so if you go thick on the gasket you'll need to get a degree wheel and degree the cams to make sure the valve timing events are happening when they are supposed to

turbomaniac

i think that you can use your 13-1 pistins with max 1.5 mm gasket that will drop the CR to (more or less) 11.8-1 . If you use 1.5 mm gasket tighten the head bolts about 15% more.

7500rpm

i torque the arp headstuds with 110nm
do i need to torque it even more with 1,5mm HG?

wantboost

iTrader: (2)

Eh, I would say that's adequate