Bad lifter question....

[RECHRGD]

As some of you may remember, I did a head/cam swap a few years back.  Although it jumped up the HP pretty well, I always thought that it should have had a little more.  I bumped up the compression about a point (10.5 for alum heads) but HP gains were marginal.  The best pull was 335 RWHP.  All the while after I did the swap I dealt with a noisy valvetrain that would seem to come and go.  I attributed it to bad header gaskets and an occasional lifter bleed down.  Last fall the bleed down problem increased to the point that I yanked out the Comp ProMagnum hydraulic lifters and put in Lunati lifters.  On one of the old lifters I could easily push the plunger down with a pencil while the remaining units would not budge.  With the new lifters the noise is greatly reduced and the idle is much smoother than before.  There actually seems to be a seat of the paints improvement in power.  Question:  Could the one bad lifter have been causing a power loss and rough idle even when it wasn't making the loud noise like it did when it would unmistakeably bleed down?

[elacruze]

absolutely.

[RECHRGD]

absolutely.

Well then, I guess a trip to the track is in order to see what kind of gains I might actually have.   Now if it would just stop snowing!

[firefighter3931]

A bad lifter will certainly affect performance, inmo 

Geez Bob....it's still snowing down there ? 



Ron

[RECHRGD]

A bad lifter will certainly affect performance, inmo 

Geez Bob....it's still snowing down there ? 



Ron

Well it sure feels a bit stronger but, I won't really know how much without another trip to the dyno or the track.  YES...6" so far this morning.  Winter has never hung on so long here that I can remember.  I think the north american ice fields are reforming!  It's supposed to be a good weekend though.

[firefighter3931]

Good luck at the track and hopefully that happens soon 

You should have enough steam to dip into the 12's as long as you get it to hook off the line 

It's been a cold & wet spring up here as well ! 



Ron

[Kern Dog]

Think of it THIS way.... If it was a bad INTAKE lifter, the Intake valve wouln't open fully and you'd be down one cylinder. If it was a bad EXHAUST lifter, when the piston tried to push out the spent gases, instead of them going out the exhaust, they would flow BACKWARDS up the intake path and contaminate the fuel/air mixture in the intake manifold. This would affect all cylinders.
The short answer to your question is.......Yes.

[RECHRGD]

Think of it THIS way.... If it was a bad INTAKE lifter, the Intake valve wouln't open fully and you'd be down one cylinder. If it was a bad EXHAUST lifter, when the piston tried to push out the spent gases, instead of them going out the exhaust, they would flow BACKWARDS up the intake path and contaminate the fuel/air mixture in the intake manifold. This would affect all cylinders.
The short answer to your question is.......Yes.

Thanks for that explanation.  I had always assumed that if the lifter was bad it would let you know via that lovely banging in the engine.  But, being that the idle was rougher than what I have now, (with the new lifters) even when it was quiet, I guess that's not the case.  Thanks, Bob

[Kern Dog]

I'm not nearly the hardcore gearhead that some are, but I have had experience with cams or lifters going bad. My first bad cam was in a '70 Chebby 350 motor waaay back in 1993.  3 intake lobes failed at the same time! The motor would run okay at low speeds, but would send a loud popping noise through the carb at anything over 1/2 throttle. I have had nylon coated cam sprockets fail, leading to bent pushrods and/or valves. I have had timing chains SNAP! Finally, with the change in modern motor oils, I have had NEW cams go bad in short time. NOW I am extremely diligent about using the proper oil and a high quality oil filter. camshaft/lifter break in is crucial to long cam life.