The V8 Owners Forum -

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 the rattle only comes on when up to temp. Research would suggest it is the pin fit in the piston that causes the issue. Probably abnormal expansion rates due to the bottom of the piston being hacked about so much.

It would seem that people fitting new pistons from the like of TVR Power have sorted it. My only concern is Powers pistons are like for like cast jobbies, although i suppose they may be a better quality than what TVR used.

So other than replacing like for like with more hacked about items i was wondering if anyone knew of a proper rod / piston combo that will fit the 90mm throw crank.

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.

Forged pistons tend to run with approx. 3.5 thou skirt clearance when cold and some piston slap may be heard until they get up to full temperature and given some work to do.
So, you may be swapping hot rattle for cold rattle.

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.

what's you end goal for your engine?
Unless your going high boost/nitros/high revs cast pistons should be fine.

Tom

SuperV8 wrote:what's you end goal for your engine?
Unless your going high boost/nitros/high revs cast pistons should be fine.

Tom

But the 500 displacement piston wise is achieved in a bizarre way by removing way to much skirt out of a 4.2 piston I would not be happy with this certainly not for hard use