I've got a '76 Century with a 350, and stock cam. The engine is a rebulit long-block that was installed in the car about 9 months ago. The timing cover was replaced with a new one from Poston, Inc. and a new oil pump kit installed using the 60 PSI spring. All was fine until about 3 weeks ago, when it developed a lifter "tick" after about 10 miles of sustained interstate highway driving at 75 MPH. (It's got a 2.56:1 gear, so 75 mph is not super-high RPM) The noise gets worse with further highway driving, and the engine develops a pronounced "mis". If I then kick open the 4-Barrel, I get sputtering and light backfire back up thru the carb. Upon exiting the interstate, after about 3 minutes, all returns to normal, with the noise slowly going away, along with the "mis". If I drive it around town, or keep it under 60 MPH, I don't have any problems. No "tick" at idle. I can even do 1/4 mile drag-strip passes at full-throttle, with no ill effects. It's just prolonged mid-range RPM that causes the problem to appear. Last week, I installed another oil-pump kit, this time using the 40 PSI spring. The condition is slightly improved, and takes longer to appear, but did not go away. Anybody got any ideas?
ya know... you've changed the oil pressure bypass and a few other things... but when i had a problem on my 350 the exhaust manifold gasket blew out. and it does get worse while accelerating. (extra force on the exaust system when the engine torques over slightly) tempature also affected it. woulden't hurt to look. nate
The passenger side exhaust manifold does have a crack in it, so I am used to hearing the exhaust "tick". This other noise was definitely a lifter "tick", with the guts of the lifter apparently collapsing with sustained mid-range RPM. I replaced all 16 lifters yesterday, and the problem is now solved. I never could identify which lifter was bad... none had visible wear on the cam face, and I couldn't find one that the inner plunger compressed more easily than any of the others (using a pushrod, wrapped in shop-rag to push down on it as hard as I could). One of 'em was bad though, getting too much bleed-off at highway speeds, I guess. I wonder if the 60PSI oil pressure could have caused the premature failure? At any rate, I'm back to 40PSI, and a whole new set of good lifters, and Ol' Buford is back to running smooth.
