tap tap tap

[dustybarn]

The cam lobe and undoubtedly the follower surface is badly worn on #2's exhaust valve opening ramp. I finally pulled the valve cover again and carefully inspected each cam surface, rotating the engine about 45 degrees at a time. That explains why the clearances always checked OK. While it's a bit of a PITA to change the cam, it's not as bad as it could be. Thanks to all for your help.

[David T]

That is unusual. I would suspect the motor oil (wrong type) low motor oil, infrequent oil changes, etc. What is the history on the car? The B28F used in the Delorean does not have a lot of problems with the cams (unlike the previous, earlier versions). I would carefully inspect the other cam too. It wouldn't hurt to do a leak-down test on each cylinder and a compression test with and without oiling the cylinders to see if you have a lot of ring wear.
David Teitelbaum

[dustybarn]

That is unusual. I would suspect the motor oil (wrong type) low motor oil, infrequent oil changes, etc. What is the history on the car? The B28F used in the Delorean does not have a lot of problems with the cams (unlike the previous, earlier versions). I would carefully inspect the other cam too. It wouldn't hurt to do a leak-down test on each cylinder and a compression test with and without oiling the cylinders to see if you have a lot of ring wear.
David Teitelbaum

I checked leakdown on the affected bank, and they all were good and identical. I know that they are not stock cams, they're from Race Cams, Inc. of Ft. Lauderdale and probably are only a few years younger than the car. I plan on replacing both of them as a matter of course. The car has maybe 75000 miles on it.

[David T]

Well, that would explain it. The cams probably did not have the proper hardening. Best to get those cams out of the motor now. My suggestion would be to go back to stock, drive the car around 500 miles or so and then do an oil change.
David Teitelbaum

[Ron]

+1

[Azar]

Hello, bringing up this thread. Did it sound similar? It is louder when warm. Oil is fresh, Castrol GTX 20W-50. The oil pressure is very low at idle and warm though....
https://photos.app.goo.gl/hd1tysQgsW8xZsis5

Thanks!

[Azar]

here for example this owner changed Timing Chain tensioners, guides, replaced both heads, New Cams, and New Rockers, New Valve guides, and had the valves lapped in. Also replaced the pulley wheels - still same so he got a new engine!
https://www.youtube.com/watch?v=JFXllpATMdE

[mark w]

here for example this owner changed Timing Chain tensioners, guides, replaced both heads, New Cams, and New Rockers, New Valve guides, and had the valves lapped in. Also replaced the pulley wheels - still same so he got a new engine!
https://www.youtube.com/watch?v=JFXllpATMdE

i have a question too. if you change the cam, do you need to have the rockers machined to match?

[dmcman73]

i have a question too. if you change the cam, do you need to have the rockers machined to match?

No, unless they are warm then you replace them. Only the adjuster screw needs to be set according to the manual.

[Ron]

Azar,
As the engine warms, the valve train should get tighter (quieter), if anything. Since you have low oil pressure at idle (confirm with external gauge), I would suspect that the oil is getting thinner as it warms, reducing the oil pressure even more... Sounds like the upper half of the engine could be starving for oil because of components in the lower half is worn (crank/bearings/pump/etc).