The Stovebolt Site Forums The Shop Area Engine Shop Camshaft Nightmare

Hello all. I've been away a long time. Nice to see you're all still here! Recently I've been having failed camshafts in my 235 1956 block. The zinc oil problem started this and then repeatedly I've had three brand new and one regrind fail at startup, despite using zinc additives and API SJ rated oils. I've cover all the basics and it appears that in at least one case the new cam did not have enough taper ground onto the lobes. I told the shop to regrind that with 0.002" taper all TAPER RIGHT, that is towards the rear of the motor. But here's the question...does the 54 to 62 235 Stovebolt originally have a MIXED TAPER CAM? There is a bolt on thrust plate on this cam assembly so I presume it is mixed taper and I screwed up telling the shop to go all taper right. Looking down the lifter bore holes it looks as thought the cam lobe offsets alternate from the No.1 exh. TL (towards the front of the engine) No.1 int. TR, No.2 int. TL and so on. Does anyone have any idea about the proper grind for these?! Thanks for any help you guys can give.
HT

Are you wiping out the same lobe on the cams?

It's possible your valves are sticking in the guides. It's also possible you've got the wrong valve springs, the springs have too much pressure because the spring seats are too high, or your pushrods are too long and you've got too much pre-load on the valves.

If you've wiped out four cams, something in the valve train is wrong.

-Brad

The cam that was in it originally went bad when the zinc was removed from engine oil which I was unaware of(SM vs. SJ oil). Then I put in another and some of the lifters failed to rotate at break-in. I pulled that one out and put in another (a brand new EGGE and still different lifters failed to rotate, different from the previous cam. I took it back to EGGE and they said it appeared it was produced with insufficient taper. So I asked them to regrind it with 0.002" taper, but asked for all lobes to be ground "taper right" (what I had "heard around"). I've got the cam back today and they did a great job. Only problem is I am looking in my lifter bores at the previous cam down in there and it looks like the lobe offsets are staggered, alternating. If that's the case, then I just had them grind the cam wrong!!! If the lobe offsets are alternating I think I need a mixed taper grind. I'm close to emotional break down on this one!

Not knowing for sure, but I would bet the cam should have a alternating taper, this would tend to keep it in the center and not force it to one side.

Glad you know about the rotating lifters, thats the fastest way to tell if a cam is good. I just pulled apart a Pontiac with half the lifters ground down. They quit rotating sometime ago, each one looks like you heald them up against a grinder wheel!
Joe

Have you had the block cleaned after the cam failures? And have you been putting new lifters in with each cam change? And last, are you using a hydraulic lifters or mechanical?