clio engine problem

[willzer]

after running a standard engine in our 172 for 3 seasons of tarmack rallying thought it was time for more power so we built up an engine using 287 cams high comp pistons ,steel rods and jenvey throttle bodies after a remap it was showing 235bhp at 7000 approx 30 miles into its first event it dropped onto 3 cylinders and was knocking from the top end after stripping it down we found the inlet valve on no1 cylinder had snapped and wrecked the head and piston
what i would like to know is are valves a prob with the f4r engine and also what should i set the limiter at [it was set at 7800] also will a head from a 197 fit my block
thanks for any help
will philip

 

[Mark One]

It's never come up on here. Valve issues have never been a problem. Not sure about your cams, have you got stiffer/double valve springs in there?

 

[willzer]

we have stronger springs

 

[willzer]

dont know where i got the 287 from the camshafts are cat cams 423s 292/284 duration

 

[sideways danny]

there's a tech update from renault about valve heads. Seen a few fall off, but IMO it's from over-revving and bouncing off the limiter.

spoke to a guy from a works rally team that uses the F4 and he said they've had several failures due to heads falling off

 

[Tom84]

where bouts did the valve snap near the head or near the collet slot

 

[willzer]

it snapped near the head

 

[willzer]

some more info on our problem after a total strip down 1piston is u/s one valve has snapped near the head and the bore is badly gouged .The other 3 pistons have contact marks on the crown from valve contact ! any ideas why this has happened ? and any solutions?

 

[Scadden182]

timing jumped?