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Solution Posted by Justin VanAbrahams [Email] ![]() ![]() In Reply to: Clattering valve train - I think, Justin VanAbrahams ![]() |
I had a brief flash of creativity, and hoped against hope it was just really loud injectors, sticky from years of disuse. I replaced them with a brand new set of FoMoCo 24# injectors. No change.
I then hooked up an Autometer oil pressure gauge, and found ~12psi at idle, and ~40psi at ~2500rpm, which is pretty close to the Bentley-indicated spec of 39psi at 2000rpm. I compared against my SPG, using the same gauge, and it sees close to 50psi at ~2500rpm, which either means a healthier oil pump, or more clogged oil passages. Meh... it was close enough.
I then pulled the valve cover from my 1980 900T, which I remembered has a motor from an early 1988 SPG - with external oil rails. I compared valve covers between the two, and found a couple subtle differences. I thought maybe the oil rails were popping out under oil pressure or something. But no, new valve cover didn't help one iota.
I pulled the alternator out so I could inspect/replace the oil pressure relief valve. The piston was stuck in the bore, and after getting it out I was hopeful that maybe it was stuck part way into the "bypass" position and diverting oil pressure. I cleaned it up, replaced with good/used, and put it back together. It was apparently working fine. Still noisy lifters.
Since it was getting dark, I decided to try the last thing I could think of short of pulling the motor. I grabbed the cams and lifters from the "180 degree" engine, put them in the car, and started it up. It clattered like CRAZY, but I figured those lifters had been disused for 5 years, and it might take them a bit to loosen up. I eased the car onto the road and went for a low-RPM drive. Almost exactly 18 minutes after I left, the clattering quieted, then went away completely. Sweet!
Diagnosis: Most likely a stuck lifter. They all compressed with a screwdriver, but perhaps not quite easily enough for the hydraulics to do it, or perhaps one of them was not compressing fully. Whatever the case, I continued my drive and by the time I got back 30 minutes later, the car sounded fantastic again.
Very happy - now I just need to get it through smog... :)
posted by 75.45.108...
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