So I just dropped a set of c-8 heads off at the machine shop and he asked me what valves I wanted put in. I said I wasn't sure and asked his opinion. He said as long as the valve seats were being replaced I might as well go with the larger valves. The valves he is planning on ordering are .100" bigger than stock. That is fine with me, but I was wondering if it will have any effect on my cam selection and will the engine perform any different? Thanks.

 

is he talking about .1" larger diameter or .1" longer valve stem, because he could be talking about either. the stock vavle size on the c8 heads is 2.08" and a common practice is to put the 2.19" valves in there. but the older heads used a .1" shorter valve stem then the later valves so he could be talking about either.

if it is a larger valve, on their own they won't do much good unless everything else is designed to utilize the larger valves. the intake valve pocket needs to be ported and enlarged to take advantage of the larger valve and more importantly the exhaust needs to be ported properly to get rid of the big restriction the exhaust ports have from the factory. without these two important steps, larger valves are like putting a fart can on a Prius. looks nice but its still a Prius.

then you can select the cam and headers and intake to take advantage of the larger valves.

so if you are just planning more or less a stock rebuild or mild performance upgrade, i wouldn't bother with a larger valve as you will not see a big difference for the cost involved.

rgds
Mike