Mopar Action On-line – Tech Questions
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 .508cam and hydraulic lifters, 273 adjustable rockers and comp cams pushrods,stock replacement oil pump and stock oil pan. Oil pressure never drops below20 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 andit ran great all summer. I broke it in with 10W30 regular oil, then switchedto 10W30 synthetic. I put about 2500 miles on it last summer.
Part of my winter maintenance this spring was to pull the intake to blockoff the heat crossover. After hearing so many horror stories about bad camsI took this time to also inspect the lifters. They were all in beatifulshape with a slight crowning on the cam contact surface. I reassembledeverything and lashed the valves just as I had on the initial assembly – bytightening the adjuster untill the lifter plunger is just depressed from itsretainer 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, thenran the engine and everything seemed fine. I then drained the oil, refilledit with a cheaper synthetic (10W30) and replaced the filter.
I put the car back on the road for the summmer and noticed lifter noisethe first day I drove it. It turns out the #2 intake seemed to have too muchlash so I relashed it and put another 1/2 turn on all the adjusters. Thenoise was still there but slightly less.
Thinking that the cheap synthetic oil may have something to do with it Ionce more dumped the oil and changerd the filter, this time using mobil 110w 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 isgetting slightly worse. It is possible that by disturbing the lifters Ihave had a lobe go bad, or is it possible that the change in oil has damageda lifter?
What would you recomend I do next, and what procedure would you use forlashing hydraulic lifters?
Thanks for your time, David
There can be several reasons for valve/lifter noise, but it is almost alwayslash-related. However, your “lashing” (actually, preloading) procedure isspot-on, althought I usually go about 3/4 turn, that doesn’t sound (punintended) as if that’s the problem. And, for now, I’ll take you at your wordthat the cam/lifter contact area looked OK quite recently, I can’t see a”disturbance” causing a problem there, although I never say never. Whichleaves 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 valveclosed) and attempt to wiggle it by the retainer – compare with nearby ones.
Lifter bad (internally) or sticky (spec of dirt). They can be disassembledand 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.