906 heads

[Animal]

Started to strip down the 383 & found that on each head,only 1 or 2 of the exhaust valves are a nice light brown colour,while all the others are black.Why would this happen if all cylinders are getting the same fuel air mix?
The engine was running headers.Would it be that these were the only valves open,as the engine has been sitting for nearly a year?Look forward to an explanation.Thanks guys.Adam.

[firefighter3931]

Why would this happen if all cylinders are getting the same fuel air mix?

Adam, what type of intake manifold are you using on this engine ? Don't assume that all of the cylinders are getting the same mix....that is usually not the case, especially with dual plane manifolds. A weak spark caused by fouled plugs or ignition wires that have excessive resstance will also create higher carbon buildup in the chambers.


Ron

[Chryco Psycho]

you coul dalso be pulling oil into the cylinders through the valve guide or past the rings

[Animal]

Thanks Guys,the intake is the original cast iron 4 bbl set up,with a holley 750 sec vac.Lot of carbon build up on those pistons & chambers tho.The 383 ran like a dog before it was hauled out.Thanks Adam.