Quote:
Originally Posted by Steve C.
Take this information with a grain of salt ! And further, this should be in the street section.
But like the above post another tid bit here for conversation.....
Years ago during a conversation with a Crower rep I mentioned that my car at the time was street driven only, typically weekends on occasions, and it often sat in the garage not driven.
This conversation was after I had bushed lifter failure. I mentioned our routine of monitoring spring pressure using a on the head valve spring tester and checking the valve lash.
We found no indication of issues with either.
Nothing was resolved as to why and not claiming this was the reason for the failure, but he did point out the following to me.
And with this in mind he suggested I go back to a needle bearing lifter for my particular application.
From the internet, not a quotation from Crower....
"Unlike needle bearings, which rely on tight clearances to naturally trap oil, bushing-style (bushed) lifters feature a larger surface-to-surface clearance that allows oil to drain out when the engine sits unused for extended periods"
.
|
Steve Morris just started using roller cam bearings instead of babbit bearings in his SMX engines used for drag and drive events. Logic for the choice was the roller bearings never let the cam actually drop down onto the babbit bearings with all the spring pressure when the engine was shut off and restarted. He went on to further explain that even if you used an oil accumulator to pressurize the system before startup the cam was still resting on the babbit bearings until it started to rotate and build a hydraulic oil wedge, causing wear every time the engine is shut down and restarted.
To prove his point he assembled the same engine with babbit bearings, and roller bearings then proceeded to use a torque wrench to record breakaway torque and moving resistance after breakaway was achieved. Turning torque was almost cut in half with the roller bearings. Breakaway torque was also less but only about 30% less than the babbit bearings.
He is betting that the roller bearings in this application will gain longevity in the overall life of the engine.
This theory is very similar to what you have heard about the roller lifter bearings, spring pressure has a bearing on how long you have metal to metal contact on startups. The roller bearings support the wheel even with little to no oil pressure, where the bushing style have metal to metal contact until oil pressure and rotation take up the clearance.
Steve Morris has no illusions that parts in a performance engine will break at some point, he'd just like to extend the breakage out as far as possible with small tweaks to the systems in a performance engine.