metal head gasket thickness

K

keeno

Member +
I am looking to buy a metal head gasket for my gt but I'm not sure
what thickness to get. The heads been off twice since I've had it so don't no how much has been skimmed off the head but I know the block was skimmed by 4 thou when she was re built, also I've got ross pistons, duno what compression ratio they are. Basically I know different thicknesses will change the comp ratio, but since i dont know the ratio at the moment what way should i go, thick or slim?

cheers
 
After-Glanza

After-Glanza

Member +
Thicker to bring the compression ratio back towards standard compression as the skimming of the block will raise the compression.
 
dantheman

dantheman

Member +
you need to find out if the pistons have the same cc as stock pistons,higher than stock,or lower than stock.. ross do make flat tops which are slightly higher cc than stock pistons, and with having the block skimmed aswell the cr is going to be a little high (assuming you have higher cc than stock), which is fine if thats what you want, but not if you want to run some big boost safely. you dont want to go stupidly low compression as it will leave you with an un responsive engine off boost.

so find out what pistons you have first :)
 
K

keeno

Member +
Yeah I have the flat top ross pistons, they oversized supposedly.
have a k24 turbo and was not really looking to run anymore than 1.2bar
boost.
 
rmsnoel

rmsnoel

Member +
Use an online calcultor, ross pistons have one on their site. Your engine builder should be able to tell you the inputs. Was the head skimmed, standard shes 39cc combustion chamber I believe. I did this last week for my trd gasket but Im uppin compression.
 
P

profane

Member +
keeno said:
I am looking to buy a metal head gasket for my gt but I'm not sure
what thickness to get. The heads been off twice since I've had it so don't no how much has been skimmed off the head but I know the block was skimmed by 4 thou when she was re built, also I've got ross pistons, duno what compression ratio they are. Basically I know different thicknesses will change the comp ratio, but since i dont know the ratio at the moment what way should i go, thick or slim?

cheers
Click to expand...

buy the thickest possible, which would be 1.2mm-2mm. this will ensure ur c.r stays low so u wont have problems will lower octane fuel.
 
azerty

azerty

Supermoderator
flat Ross piston have same cc ratio as standard piston. (not higher)
as your head has been skimed you might want to use 1.4mm metal headgasket if you want to stay closer to standard cc. if you use high octane fuel (over 98RON), I would keep 1.2mm one to get advantage of it :)
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
azerty said:
flat Ross piston have same cc ratio as standard piston. (not higher)
as your head has been skimed you might want to use 1.4mm metal headgasket if you want to stay closer to standard cc. if you use high octane fuel (over 98RON), I would keep 1.2mm one to get advantage of it :)
Click to expand...

thats correct!

i would do as lionel has suggested mate, ppl suggesting u use a 1.8 or 2mm hg are really suggesting overkill, yes ur pistons are flat top, but i wouldnt bother putting anything over 1.4mm if ur ony going for 1.2bar on the k24 :)

kon
 
P

profane

Member +
HYBRID said:
thats correct!

i would do as lionel has suggested mate, ppl suggesting u use a 1.8 or 2mm hg are really suggesting overkill, yes ur pistons are flat top, but i wouldnt bother putting anything over 1.4mm if ur ony going for 1.2bar on the k24 :)

kon
Click to expand...

its quite simple actually, the lower ur c.r the better ur car runs with lower octane fuel!
 
K

keeno

Member +
So 1.4mm would be the safe bet then, just in case I want more boost in the future?
I use 95RON fuel but put in silkolene pro boost on top of it which brings it up to about 98/99RON
 
Last edited:
P

profane

Member +
keeno said:
So 1.4mm would be the safe bet then, just in case I want more boost in the future?
I use 95RON fuel but put in silkolene pro boost on top of it which brings it up to about 98/99RON
Click to expand...


should be just fine. and running pro boost with every tank refill? for how long? better to build up thinking u have a shitty fuel at home so ur setup always turns out better with low octane fuel and probably best with hi octane fuel.
 
azerty

azerty

Supermoderator
95RON with octanebooster will probably do 96/97RON only.
yeah, best use 1.4 or 1.6mm hg then
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
well his other option (since he already has the ross pistons) is to send them off to an engineer to get them dished...

all he needs to do is take them + a stock piston & ask that the engineer machines them in the same fashion, but with more of a dish :) that way he can get a lower cr, & still be much safer than using a thick hg :)

kon
 
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