On a trip to portland this weekend my cam decided to give up the ghost. I decided that in the interests of reliability I would replace it with a stock D fuel inj. one. Replaced cam,followers&pushrods,& oil pump. After a 12 hr. thrash on the street in the rain I realized I had changed the cam -dist. relationship but managed to get it running by changing plug wire position𖐬 deg. off]. After adjusting the valves I still had a knock , but a different one. It sounds like a rod bearing knock at idle but goes away if you rev it. 2 observations 1.I had to take up a lot of slack in the adjusters. 2.My mixture went from way rich to lean. I measured the old cam when I got home & got .405 in. gross lift & a 1.120 in. lobe circle. The parts came from IPD so the cam is an Isky. Could the lobe circle be smaller? A rebuild is in the works for next winter, but the house gets finished first so the cash isn't there for it now. Any ideas? Should I not drive it? It hasn't gotten any worse in the drive from portland to chelan-300 mi, but it concerns me . I don't want to do any irreversible damage. Thanks Mike M.

Did you put the spacer on the new cam? Very easy to overlook, as it may well stick on the nose of the old cam and not look like a separate part. The spacer is what sets the endplay of the cam, and if there is excess endplay, the lifters will definitely knock it forward and backwards at low rpm.

Doh! You mean the one I just picked off the old cam? Now does it go on the front or backside of the cam end plate? Thanks Phil, once again you come through!
Mike M.

There is room for it to fit in the brass retaining plate, so it goes on neither before or after plate, but with. Does that make sense?
You are lucky! When forgetting that cast ring, most fiber gears just shred their teeth because it locks the motor altogether.
shayne

May well be a rod knock - do you have an oil pressure gauge in the car?

The lobe circle could be smaller. The stock grinds (A, C, D) ipd carries aren't isky - the only isky cams are the 2A7001 and 2A7006.

I'd get an oil pressure gauge if you don't have one - this'll at least help you rule out one possibility...

Best,

Cameron
Portland

Oil pressure gauge says 60psi@1500rpms-45 at idle. Prior to repairs it was 35psi @idle & 45psi @ 2000 rpm. In my experience rod knocks will get louder on accel.,while this one disappears. Disconnecting plug wires to isolate it does not change it. The sound is more "rattley"than a hard knock.It's hard to pinpoint ,even with a stethoscope. I assumed that the cam in the Isky box was made by Isky. Sorry if I was mistaken in that regard.
Mike M.

Sounds like it's not an oil pressure issue at all - in fact, sounds like Phil nailed it in the post shown above.

Glad you're on the right track - just to be sure - please don't run the engine until that spacer's back in place!

Best,

Cameron
Rain City

You did just change the cam gear, but in my experience a worn cam thrust plate (or broken cam gear for that matter) will clunk like that at idle. At idle I think the valve springs can push the cam forward as the lifter passes 'TDC', then the cam pulls backward again as the next lobe starts lifting. Off idle either the drag from the oil pump or perhaps the dynamics of the valvetrain keep the cam under constant traction. The angled teeth of the cam gear means the back and forward torque on the cam at idle yank it forwards and backwards slightly. This won't make a sound unless there is room for the cam to slap to and fro.