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Tech Question
David Siddon, Kelowna, BC, Canada, 1975 Dart Sport 408
Hello Rick, and thank you for your great technical advice.
My combo is as follows: 360, .030 overbore, 4" stroker crank, mopar .508 cam and hydraulic lifters, 273 adjustable rockers and comp cams pushrods, stock replacement oil pump and stock oil pan. Oil pressure never drops below 20 psi at idle and is about 50 psi from 2000 rpm and up.
I put the engine together last year, broke in the cam with no problems and it ran great all summer. I broke it in with 10W30 regular oil, then switched to 10W30 synthetic. I put about 2500 miles on it last summer.
Part of my winter maintenance this spring was to pull the intake to block off the heat crossover. After hearing so many horror stories about bad cams I took this time to also inspect the lifters. They were all in beatiful shape with a slight crowning on the cam contact surface. I reassembled everything and lashed the valves just as I had on the initial assembly - by tightening the adjuster untill the lifter plunger is just depressed from its retainer and the one more half turn on the adjuster.
When I put on the intake I poured some oil over the cam to lube it, then ran the engine and everything seemed fine. I then drained the oil, refilled it with a cheaper synthetic (10W30) and replaced the filter.
I put the car back on the road for the summmer and noticed lifter noise the first day I drove it. It turns out the #2 intake seemed to have too much lash so I relashed it and put another 1/2 turn on all the adjusters. The noise was still there but slightly less.
Thinking that the cheap synthetic oil may have something to do with it I once more dumped the oil and changerd the filter, this time using mobil 1 10w 30 synthetic. There was mo metal in the oil when I changed it.
The noise is still there, seems to be coming from the #2, and if anything is getting slightly worse. It is possible that by disturbing the lifters I have had a lobe go bad, or is it possible that the change in oil has damaged a lifter?
What would you recomend I do next, and what procedure would you use for lashing hydraulic lifters?
Thanks for your time, David
David-
There can be several reasons for valve/lifter noise, but it is almost always lash-related. However, your "lashing" (actually, preloading) procedure is spot-on, althought I usually go about 3/4 turn, that doesn't sound (pun intended) as if that's the problem. And, for now, I'll take you at your word that the cam/lifter contact area looked OK quite recently, I can't see a "disturbance" causing a problem there, although I never say never. Which leaves only 2 likely possibilities:
Valve guide going bad. Check for excessive side clearance (i.e., wobble). If the springs aren;t 500 lbs., you can simply grab the retainer (at valve closed) and attempt to wiggle it by the retainer - compare with nearby ones.
Lifter bad (internally) or sticky (spec of dirt). They can be disassembled and cleaned. Sometimes extra detergent added to the oil will fix this, too (i.e., Marvel Mystery Oil, etc.) Of course, if you have to pull a lifter, you'll be able to inspect the wear surface, too, which can be crowned, or, after long use, flat, but NEVER dished - not even slightly.
Rick
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