I need help with my misfire/stumble...

[Blake]

I pulled this off of Crane's site:

Hydraulic Lifters

What happens if the amount of Hydraulic Lifter Preload is wrong?

If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter’s retaining lock, and this could cause the lock to fail.

If the opposite occurs and the pushrod descends too far (more than .060”), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause “backfiring” from the engine. How to correct this situation will be explained in the next sections.

This kinda sounds like what you were describing, like it wasn't making even power on all cylinders. Did you ever have any backfiring? Its amazing when you can look at something, do it over and over, still not know what's wrong. Then you take it to an experienced old timer and they figure it out right away.

Yours was a McCoy engine wasn't it? Did they use your old one as a core? Just curious if your old lifters made it back into it.

Blake

 

[TechWeasel]

That Crane site was very informative...

I'm sure I have the lash set properly, now that I know WTF I'm doing. According to my friend, a lifter that for whatever reason isn't "pumping up" would definitely cause the problem I'm having, since even with the rocker preload set properly, the valve spring would easily overcome the keeper spring in the lifter (if it doesn't have any oil in it) and the valve lift would be greatly reduced.

The kicker is that the other prime candidate for what's wrong is a manifold leak, and the act of taking the engine apart to get at the lifter valley is a certain cure for that as well. So either way, I'm probably not wasting my time.

Hopefully I'll get some useful feedback from the scope check, and I'll be able to pinpoint which cylinder is the offender. In theory, if there's a manifold leak, that cylinder should show a lean condition. I'm not sure just what to expect if it's a bad lifter, other than very poor cylinder filling.

And yes, it's a McCoy, and no, it wasn't my core. Only the upper and lower intake manifolds and tin are off the old engine.

 

[Blake]

Didn't mean to sound like I was bad mouthing them. I've seen a couple shops around here (Performance Engines and Rice's Engines)have reused hydraulic roller lifters under the thought that the things last forever when they should be replaced during the rebuild.
Please let use know what you find out.
Blake

 

[TechWeasel]

Ok, time for an update.

Yesterday I took my truck over to JBA Racing's shop. I ran into an aquaintance of mine over the weekend who manages the place, and told him about my situation. He told me to bring it on over and have his guys look at it.

They put it on the ignition scope, plugged in a scan tool, and fired up the 4-gas analyzer, then did about an hour's worth of poking and prodding.

Long story, writ short:

The scope shows all 6 operating normally. It's not an ignition problem, and it's not a fuel or vac problem that would show up on the analyzer. The scan tool shows nothing abnormal other than the idle hunting, but we knew that from before. The tailpipe sniffer also showed more or less normal readings, no high HC. Three different guys all heard the mechanical noise it's making, and independantly pointed to the driver's side valve cover area as the culprit.

Their judgement: A collapsing intake lifter in the odd-side bank. If the exhaust side was the problem, I'm told that would show up on the tailpipe test, and the O2 sensor wouldn't be cross-counting.

So, I guess it's time to pull the intake manifold and poke around in there... :roll: One good thing - at least I know I'm not crazy, and this is a hard MF to diagnose.

 

[TechWeasel]

Well, I finally got around to going in after the lifters. Only took me 2 hours or so to get down to where I could yank the intake manifold, too... I guess I'm starting to get good at this :roll:

The "bad" news is that there's nothing obviously wrong with any of them on the driver's side. I took them all apart tonight, gave them a good cleaning, and reassembled them. Once they were back together, I shot them with a little oil and did a "push test" to make sure none of them were getting hung up internally. All of them seem to be OK, and there's not a visual or tactile difference between any of them.

One thing I did notice when I was solvent-flushing the internal bores and upper cavities of the lifter pistons, though - there seemed to be a good deal of crud in them. Little bits of what I presume to be break-in metal, flushed out of all 6 of the lifters. Nothing was big enough to plug the oil passages, but I wonder if maybe that junk was making one of the lifter pistons hang up inside the body instead of "pumping up" like it should...

I don't want to put this POS back together without positively identifying why it's making a mechanical noise from the valve cover, and it's VERY frustrating to think I might have to pull the head and see if it's a bad valve seat or something wrong with a piston. While all the lifters are out, and consequently all the valves are closed, I think I'm gonna do a leakdown test on the odd side and see what that looks like.

Can anyone else offer things for me to look at before I put this all back together again and see if the problem magically goes away?

 

[TurboTony]

Any signs of rubbing in the valve covers themselves?

Sometimes the baffles in the valve covers for the pcv and breather will touch a rocker arm, gives some wierd nosies.



HTH

Tony

 

[E-Rue]

for what its worth.......

mccoy motors make a huge amount of what sounds like valvetrain noise. all of them do it. i kinda think they sound like deisel motors. but dave says thats piston slap......anyway if your not certain that there is more noise in the driverside valve cover than in the passenger side cover, you might be on the wrong track. also, there is gonna be a bunch of crap in your motor for a while. id change the oil more often than usual the first few times. i had a bunch of machining debree in mine. throw a big magnet on your filter, and keep a magnetic plug in your pan.

how about swaping ECM's from a known working truck.

also, are you sure that your injectors are compatible with the chip your running? i noticed your original post said you had new injectors.

although if it shakes like you say, and the plugs look really good after you drive it around a while, thats prolly not it.

id try another set of plug wires. just because.

i always thought the shakes were bad plugs or wires, but what about having one of your plug wires crossed? double check firing order against the top of your cap.

e

 

[just a 6]

Well here is some bad news for you, if you have a mechanical noise that goes away with disconnecting a spark plug, you most likely have a bad rod bearing or wrist pin. The reason is that under piston/rod assembly load by fireing in cylinder, if you have a to big clearens between rod bearing/crank or wrist pin/piston, that clearens is going to make a noise (knocking), but when you disconnect that hole, noise goes away due to that the piston/rod assembly just spinns around by the other 5 pistons and crankshaft, there is no load on it that can cause a knocking noise. The valve train will have the same load on it with fire in the hole or no fire, remember the valves are always closed while under ignition fire. So a noise (if it's knocking or tapping) that goes away if you disconnect the spark plug, 9 of 10 times is related to a bearing, piston or wrist pin.

After looking for intake leaks with carb cleaner for a while, he focused in on the mechanical noise I described earlier, and said it sounded like I might have a bad lifter. While he listened, I pulled the plug wires for the odd-numbered cylinders one by one. Just as before, the engine dropped on all three, but he noticed that the mechanical sound changed or went away entirely on #3.
...

 

[Blake]

Have you contacted McCoy? Sounds like if you have found nothing wrong with the lifters then the other (really bad) alternative is what Swede just described. You've gone through a lot of trouble to have a new engine with a bad connecting rod or bushing. There was someone else that got an engine from McCoy with problems but it was something crazy like $900+ for round trip shipping. I hate hearing stuff like this I would see if they will work something out on shipping at least. All the time you've spent putting it in (and possibly taking it out) has to be worth something.
Do you know if McCoy primes the engines (with oil) after they are built?
Your fuel pressure dropping down right after shut down won't cause the problem that you are describing.
Maybe they will let you take it somewhere locally and have it fixed and pay the bill? Just reaching. They will want to see it I'm sure.