I’ve a 496ci massive block Chevy that I constructed about 5 years in the past that has been on the road the entire time. I don’t drag race it, but it surely does get run fairly laborious each every now and then. The opposite day I began it up and see a slight ticking sound that was uncommon. The engine has a gentle strong curler cam, so I pulled the valve covers after it was warmed as much as examine the lash. I discovered a number of exhaust rockers free about 0.003 to 0.005 inch.
I used to be going to simply re-adjust all of them when a buddy stated that it could be good to do some extra investigation. He stated it may very well be I’ve a lifter or two going unhealthy. Is that affordable or is he simply making an attempt to scare me? Thanks.
D.E.
Your buddy is simply looking in your finest curiosity and that of your engine. It’s best to positively not even begin the engine once more and instantly take away the consumption manifold and punctiliously examine every of the exhaust lifters. Take away every lifter and search for harm or rough-rolling needle bearings within the curler portion of the lifter. I wish to roll the lifter throughout the within of my forearm the place the pores and skin may be very delicate. When you’ve checked all of the exhaust lifters, additionally examine the intakes as effectively.
What you might be searching for is any slight hitch or hesitation that may really feel like resistance to rolling. When needle bearings start to fail, typically one or two of the needles will stick or start to slip moderately than roll. This may occasionally trigger one of many needle bearings to create a small flat spot which can forestall it from rolling. That can trigger its neighbor needles to additionally resist rolling and it cascades right into a sequence of bearings that now not roll.
Generally in case you are fortunate, you’ll be able to hear this as a loud lifter or a ticking sound that’s sporting often the lobe on the camshaft or elsewhere that’s revealed as a rise in lash. So whenever you uncover that enhance in lash on a couple of lifter that could be an indication of elevated put on. That’s why it’s vital to right away examine the lifters for a foul curler.
The explanation that is so vital to catch earlier than the lifter fails is that when the curler bearings within the lifter fail, these tiny little needle bearings will fly round contained in the engine and trigger huge harm.
A fellow scorching rodder as soon as requested why I used to be so involved with these needle bearings. He stated they might merely get captured by the oil filter and never be an issue. That might not be farther from the reality. The truth is far worse. What occurs is when the needle bearings go away even only one lifter, they fly round contained in the crankcase and can ultimately get pinched between the piston skirt and the cylinder wall.
If the engine runs lengthy sufficient, (our guess can be most likely lower than a minute) it will trigger huge harm to the cylinder wall and in addition gouge a number of pistons. We all know this as a result of this occurred to a buddy of ours who then needed to rebuild all the engine, boring the cylinders out one other 0.010 inch to be able to clear up the mess. In fact this required new pistons, rings, bearings, and gaskets for the quick block and was fairly an costly lesson. In his case, the engine began to squeak however he continued to drive it for about one other two miles again to his store. These had been an costly couple of miles for comfort.
For those who discover no unhealthy lifters on preliminary inspection, it could be worthwhile to have the unique producer examine them and offer you their opinion. Many new mechanical curler lifters are actually fitted with pressurized pin oilers that assist to lubricate the rollers and prolong their life expectancy. Some are additionally rebuildable.
An alternative choice that can forestall needle bearing harm is to go for curler lifters fitted with bushings moderately than needle bearings. A number of lifter corporations like Comp, Isky, Morel and others provide these lifters. Our analysis nevertheless signifies that for a street-driven engine that the priority for bushing lifters has a lot to do with clear oil. The lifters will dwell an extended helpful life—however they have to be cared for with extra frequent oil modifications.
Clear engine oil is the vital level for ensuring these bushing lifters dwell an extended life. You will get away with soiled oil with a needle bearing lifter in comparison with a bushing lifter. I don’t have a upkeep schedule that has any which means since driving type and oil high quality have a lot to do with how typically you need to change the oil.
If the engine is pushed sometimes and isn’t allowed to come back as much as regular oil temperature of above 212 levels F, impurities will acquire within the oil way more rapidly than an engine that’s operated with the oil as much as working temperature of above this determine. When operated above 212 levels F, this enables the water within the oil to evaporate and take with it most of the impurities.
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Hopefully we haven’t scared you too badly with this reply. It’s additionally attainable that you’ll disassemble the highest finish of the engine and discover no issues and that every one the lifters look good. If that’s the case, reassemble the engine and punctiliously set the lash at working temperature. Make it possible for whenever you examine lash once more that you simply at all times examine it utilizing the identical process. If the lash modifications once more, there’s nonetheless an issue. If the lash is about precisely, it shouldn’t change except one thing is both shifting or sporting.
That is no small level. Some fans will attempt to let you know that the lash will change over time. If it does, one thing is sporting or shifting. That’s the one rationalization in the event you set the lash fastidiously and recheck it utilizing the identical process. We’ve a John Lingenfelter-built 420ci small-block that has seen over 25 years of racing abuse and each time we examine the lash, it has by no means modified. We ultimately modified the lifters solely due to the time issue concerned however they checked out high quality.
That ought to reinforce the purpose that the lash shouldn’t change if all of the elements are working correctly.
Hope this helps.
