Pup1970

I bought a motor that was rebuilt but ran funny according to the guy I bought it off of. I have taken it apart and found a very loose timing chain. I pulled the cam out and ran the numbers. It turns out it a mondello grind .542 int .556 exh. Now the real question is it had stock rockers. I'm pretty sure that they can't handle the lift. If I'm wrong someone tell me how to make them work or let me know what route to take.

Thanx

svnt442

With that much lift you need to go to adjustable rockers...period.

slade69

If the timing chain is loose, something is wrong with it. Replace it with quality one and you also need to time the cam according to it's specs. Stock stamped non-adjustable rockers work up to 0,5" lift, not more. You need adjustable ones and right length pushrods to match and get the geometry right. When thaese are done, chances are it does not run "funny" anymore

olds 307 and 403

There was probably binding in the rockers. Hopefully the valve springs have enough installed height not to bind. How loose was the timing chain? How many degrees can it move before the gears and chain make contact? They do stretch a fair bit in a few miles.

joe_padavano

Lift has nothing to do with the need for adjustable rockers. Since the came likely has lobes with a reduced base circle, the lift means that you need custom length pushrods. Using adjustable rockers instead of the correct pushrods is a kluge that just screws up the contact at the valve tip. Yes, obviously you need to be sure the rockers and springs can accommodate that lift without bottoming, but the lift number itself does not require adjustable rockers.

Pup1970

Th timing chain was very loose to the point that I could squeeze the chain to get her and have about an inch bettthe two.

oldcutlass

I wonder if the block was align bored and needs an undersized timing set or perhaps not rebuilt at all and has the original timing set minus plastic teeth.

olds 307 and 403

Get a Cloyes Billet roller timing set, that sounds very loose.

svnt442

Everything I have ever read about factory Olds rockers is that .500 is the safe limit for lift with them. I pushed it with a .504 lift cam and would never think of going to .550 with factory rockers.
There is only so much travel in the slot and so I will have to disagree with you on this one Joe.
The lower base circle on the cam will require a longer pushrod to compensate, but that won't do anything for the amount of travel that the rocker can move before coming into contact with the bridge. All it will do is bring the rocker back into proper alignment with the valve tip.

Pup1970

Thanx for all the replies. I have decided to go with a different cam .488 .472. I don't need a radical cam for this build. Thanx again everyone