New motor problems

C

cheese1

Member
The new motor is actually a rebuild that had not been installed, it sat on a pallet for 12 years. The engine has about 15 hours on it since install.
I have a knock that sounds like it is from the #1 cylinder. It is faint when the engine is cold and gets louder when it warms up. After installing cut out valve covers I noticed there are alot of lifters that are not rotating. The #1 cylinder in particular is the noisiest. When I lightly press a hammer handle on the pushrod end of the intake rocker it knocks like crazy. I installed a new lifter and it still knocks. I removed the intake lifter and pushrod to see if it would make a difference and the knocking went away.
Oil pressure on start up is 50 psi, when hot it is 10psi. Vacuum gauge shows 18", the needle is steady. Compression is 135# on all cylinders. There is only a puff of smoke on start up, none when idling or when revving the engine. The motor runs great, plenty of power, steady idle.
Does it sound like a bad cam, cracked piston, weak valve spring?
I am open to all ideas.
 
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My thoughts are the hydrolic lifters ar bad due to the motor sitting so long and the pressure from the valve train compressed the lifters to the point of they wont recover :mad2:
 
Chances are pretty good that the cam lobe is "flat" (or going flat). Not meaning all the way, but it is "down" by a few thousandths, enough so that the lifter can't compensate.

The original lifter that you replaced...what does it's base look like? I'd expect it show a show a slight "cupping" if the cam lobe is going away.

A correct new lifter will have a very slight crown to it's base, that is what imparts rotation, along with the actual angular profile of the cam lobe. See this thread:

http://www.forums.IHPartsAmerica.com/gas-engine-tech/2131-lifter-thread.html

And punch the links provided in that thread!

While it's certainly preferable that a fresh cam is installed with fresh lifters, in the real world that is simply never done by most folks! Thus we live with the consequences...sometimes it works, sometimes it don't! In my own personal rig, that is exactly what I did and have experienced no issues in 30k+ miles of severe towing duty....new lifters on oem cam with 100k+ on it. Engine has never been down/heads off/cam out.

On the other hand, I work with this stuff weekly under the same scenario where the cam is eating the lifter and visa-versa because the motor is not oiling correctly. Once the hard surface/wear-hardened cam lobe is cut through, it goes flat fairly quickly and the lifter base is destroyed also.

Replacing one pushrod with another part that is say...0.060" longer, will pre-load the lifter a bit more and prolly mask the problem temporarily. But then as the lobe continues to wear, valve timing on that cylinder becomes more out of sync resulting inna compression/vacuum issue on that one cylinder and resulting poor idle quality/performance.

Lifters that sit in an used engine can certainly "stick" internally, but the only way to remedy that is remove 'em, and disassemble/inspect/clean. But you have one assembly that you have identified as the problem by doing the correct diagnosis!

If you took the time to rig up a dial indicator directly on that new lifter pushrod cup and measured "lift", then did the same on a lifter that is not noisy, I bet you will see the cam lobe "height" difference! That wear is what we refer to as a "flat" cam...it does not have to be worn all the way down to the base circle.
 
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