The V8 Owners Forum -

It's possible to fit 3.9 pistons into a 4.2 but you need to machine their tops to put them just below the deck. This then gives you a piston with a reduced dish and the compression ratio will be higher. I don't know the number though.

The top ring will however be closer to the crown but unless you ...

Give John Eales a ring. His brother does all his engine balancing and does it correctly with a proper individual internal balance. He did my TVR 5 ltr which needed a lot of metal removing from the crank and then a fair bit of heavy metal also adding. End result is super smooth. Wasnt expensive ...

Can't see it being your heads. Most likely is the inlet valley gasket leaking from the very corners and then the oil will be finding its way around the heads.

Did you use a little sealant in the 4 corners of the valley gasket where the rubber end seals fjt.

Yes very true. I've done some reading up on forged pistons and this would seem to be the case.

Well I guess its leave it alone and put up with it or replace with cast items for considerably less money than the forged jobbies and hope they do the trick.

Right I've been doing some research and a quick update for anyone reading in the future, RND Engineering do 6 inch rods and a forged piston that fit and are suitable for the tvr 90mm throw ctank.

My Griff 500 engine has the usual rattle on the over run at about 1800rpm even though i`ve just re built it. The only thing i didnt change were the pistons so presume these are the culprits. Not the end of the world as a lot do it but i`d rather it be quiet.

As per usual it is quiet when cold and ...