picky775

I got my engine re-built roughly 2 years ago,i got unfinished cosworth racing pistons,so block had to be re-bored to fit pistons.Ever since ive had the engine back ive been gettin a metalic rattle under load what i think is pinkin.resulting in 4 blown head gaskets.Since converting to efi and having it mapped on the road weve found its got nothing to do with fuel or timing,ive been told the piston crowns shouldnt have valve cut outs in them,they chould be flat.So do these pistons need to come back out and get the tops taken off to make them flat?????

turbo.jon

When i had mine for my cvh turbo they come unfinished and need skimming to get the required compresion they then cut in some valve cut outs..Im sure i have read somewere that they are a bit noisy compared to std pistons so that might be what noise is?

jon

picky775

cheers fella ANYONE else with any views on these pistons????

picky775

ANYONE?????

pa_sjo

That's a load of bollocks. Pistons don't rattle because they have cut-outs. If it's detonating, then sure skimming the piston could stop that.

IANS2RST

iTrader: (1)

they look like the standard style pistons that have been skimmed to reduce the compression ratio.
race pistons may rattle due the positioning of the gudgeon pin. standard pistons have it offset to reduce noise where as some race pistons move more towards the centre of the piston as iirc it gives some performance benefit but at the cost of increased noise.
it is also possible that the pistons may have been fitted the wrong way round which means that the pin could be offset the wrong way drastically increasing the noise.
which side of the piston has the larger cutout? inlet or exhast?

picky775

The cut outs are both the same size,im thinkin the compression may be to high because i cant understand why it kept blowin gaskets,i never take it past 4500 revs anymore because of it and its drivin me mad.