juffer

im trying to work out my compression. could you please tell me the head chamber size in cc's and the head gasket thickness.

Christian and Beccy

iTrader: (14)

How sure are you that the head hasn't been skimmed?

I have the gasket thickness written down at work, I think its 1.3mm crushed.

Fiecos Dan

the head needs to be cc checked.

but i use the theory that a RST h/g is 1mm crushed, @ 5.4cc.

Christian and Beccy

iTrader: (14)

I measured the gasket that I removed at 1.6mm. Just checked on my notes this morning.

Fiecos Dan

but have you measured it when head bolts are torque'd?

i'll double check on my TT, as i need to strip the engine down over the weekend, and measure it before i take the head off.

juffer

thankyou for the information guys. If i use the details fiescos dan has give me then i have a compression of 7.7:1

The engine is standeard rs turbo with an overbore. now is this too low?

Fiecos Dan

if thats correct, then thats fine.

juffer

i know the engine can only take so much. but if the compression is lower can you put more boost in?

Fiecos Dan

std c/r is ok for 240 bhp, but best to drop to below 7.9:1 for above 200 bhp.

juffer

ok thanks for that. so at what point do you have top change rods, pistons and arp bolts?

Fiecos Dan

std pistons ok for 250+ bhp

std rods ok to 230+bhp

std rod bolts ok to 6000 rpm, above that best fit ARP.

steven botes

i have had engine failure due to std rod bolts faling , so now use ARP's only

std cc on the head is around 56cc unskimmed , and about 5cc for the headgasket , its the numbers i have used

std rods can be polished for extra safety