7 replies to this topic

[Kevybmini]

Hi all,

 

is 250 psi to high for a road car, head gasket has gone after 1,000 miles between 2/3 which is now 100psi 

[Aridgerunner]

If you want a head gasket that will not fail buy a Cometic multi layer steel gasket. They are expensive. But so is doing the job twice. I know I didn't answer your question but while 250 might be very high the Cometic gasket can handle that.

https://www.mgocspar.../4236/2050/4253

Edited by Aridgerunner, 10 May 2026 - 10:24 PM.

[timmy850]

While you have the head off it’s a perfect time to measure the actual static compression ratio.

Compression gauges don’t all give the same readings, but 250psi on my gauge would be a static ratio of way over 11.0:1 which is very high for a road engine

[nicklouse]

All depends on what cam you have fitted.

 

but as said work it out as a compression testers results depend on many external inputs.

[whistler]

My wife's 1330 with an EVO 001 cam and MG Metro head has 220psi compression and had no problems.

[coopertaz]

mine is 1330 and runs 230psi after having head skimmed twice. Been fine for years now just run on superplus all time and on standard composite gasket, I keep it away from E10

[ACDodd]

They will run ok if you're not developing maximum cylinder pressure at 220psi, but once you do, you will likely find it won't.

Ac

[ACDodd]

They will run ok if you're not developing maximum cylinder pressure at 220psi, but once you do, you will likely find it won't.

Ac