For cosworth engine know alls

[stevedohc16v]

Put this on the RSOC BB and the opinion was that its been over revved at some time, what do you lads reckon, took the cylinder head off my 2wd sapphire today to do some work on it and the pistons all had 2 little marks on them where the inlet valves had obviously come into contact (or still are!) at some time, sorry for the pic taken by my cheapo digi camera you can just make out the dents.

http://media.turbosport.co.uk/2002/9/200293019202140316.JPG


Question is whats caused this? the cam timing looked spot on as per the manual, i was hoping to get the head checked/ skimmed but obviously this will make the problem worse, has it been skimmed too much in the past? are there any measurements i could take. Engine ran sweet enough and there doesn't seem to be any play in the pistons nor any damage to the valves.

Cheers for any help

Steve

[Andycos]

Hi Steve, although the valve's head look alright did they come out of the guide's smoothly, I ask this as i had to take some valve's out before that had been overevved which looked o.k visibly but the shafts were bent and had to be punched out( http://www.turbosport.co.uk/images/smilies/shocked.gif ) even though the car was still running well.
I guess its old damage that was put right, that is unless the marks on the pistons look shiney and fresh http://www.turbosport.co.uk/images/smilies/sad.gif
Yes the head can only take a couple of light skim's the details i have here say: Maximum material removable= 0.13mm. Minimum cylinder headheight after machining, measured between mating faces = 138.68mm.
From Vol 1&2 Workshop manual.. http://www.turbosport.co.uk/images/smilies/grin.gif
I'm sure some of the experts will have something to say... http://www.turbosport.co.uk/images/smilies/wink.gif http://www.turbosport.co.uk/images/smilies/wink.gif

[stevedohc16v]

Cheers Andy, haven't stripped the head yet but i'll be double checking everything.
Doh http://www.turbosport.co.uk/images/smilies/confused.gif never thought of looking in the manual for that info, cheers.

Steve

[Clint]

This is very common, nearly every engine I strip down has some piston to valve contact, it can happen for various reasons but is generally nothing to worry about.

[KAIBO]

thats common on cossie engines when you bend valves. on the timing has been a tooth out.or if the person rebuilding the engine has put the cams the wrong way around. (i know of few people that have done this) http://www.turbosport.co.uk/images/smilies/wink.gif http://www.turbosport.co.uk/images/smilies/clint.gif