Hi,
Just wondering how much can be removed off the faces of these heads to boost compression. I am looking at fitting a pair to my 5 litre EF and as it spends 95% of its time on gas I thought I would try and up the compression a bit.
I realise I may have to machine the bottom and sides of my intake to match and there maybe some valve clearance issues.

Thanks in advance.

Fitter

I'd do some research on this if i was you

The original gas when it first came out had a 100+ octane so lot of people boosted compressions up to get most out of it but now the octane is down around 93 somewhere i believe. I wouldn't go boosting compression too much otherwise will have serious pinging issue

The general consensis is can take off about 0.030" before you have to machine the inlet manifold. I took off 30thou off my E7TEs and my car spends a fair bit of time on LPG, plus I have a E303 and I wanted more compression to complement that. Runs very good on both gas and petrol.

Thanks for that info.
I will try 30 thou first and see how that goes. I took 60 thou off my 2V cleveland heads but it was a pain in the rear having to machine the intake to suit. It went well afterwards!!
I was going to get my standard cam reground to something a touch more violent so should hopefully all work well.
Cheers
Fitter