Can anyone tell me the benefits or disadvantages of having thin walls where the pushrods are supposed to go through? I'm looking at a set of C heads that I may purchase off of craigslist but they have been opend up and the walls for the pushrods are thin i'm told and come with sleeves.

Can someone elaborate?

 

I'm guessing that the prior owner was using larger diameter (and thus stiffer) pushrods?

 

also its been know to enlarge those holes after a HUGE amount has been milled off!
Better ask more questions -- and especially get the seller to verify that there are no cracks in them -- or promise a full refund including return shipping if you test them and find cracks!! i learned that lesson the hard way with a set of "C" heads I bought off of a seller right here on CLASSIC OLDS - not even Craigslist!!

 

When using stronger valve springs and higher lift cams a thicker larger diameter rod is cheap insurance. Bending rods loose power and can fail.