Engine vibration at 2900-3000rpm - HEL

[kiltedrunner]

Engine vibration at 2900-3000rpm - HELP

Hi Guys,
First off, I should say that this was a major project for me. Everything changed on my car including suspension, engine, transmission, fuel system, cooling, and much of the wiring... with that said...

I purchased a used motor a few years back and it had lots of good parts on it. I never pulled the heads off, but did install a new cam, lifters and pushrods. I finally got the engine into my car last January. Overall, I am quite happy with the entire project, but as always there are some gremlins I'm working through. Mostly I have it all figured out, but unfortunately there's something causing a fairly major vibration between 2900-3000rpm. It smooths out below and above that rpm range. The engine consists of the following specs:

400 block mopar with a 440 crank ground to make 451ci
Electric waterpump & electric fans - only external items are alternator and power steering
​

Hydraulic roller cam and lifters - comp cams
B1BS aluminum heads
11:1 compression
EFI (throttle body) - EZ EFI 2.0
High torque starter - summit?
727 automatic trans with 3000 stall converter - ProTorque (New York)

I should also point out that the original engine had the oil passage ways blocked off for solid lifter use. I pulled all of that out - so I don't think I'm starving the number 1 cylinder - but it is the last cylinder to get oil on the bank.​

While the engine ran great overall, I noticed a few symptoms with the engine:

1. Starter slows down when turning over number 1 cylinder. The starter has a really hard time starting the engine if it has to start turning from cylinder 1, while it spins quickly on all other cylinders.
2. Engine usually stops spinning at number 1 cylinder when I shut the engine off.
3. I have a very high cylinder pressure - 220 on cylinder one - but lower on all others.
4. Vibration when revving engine to 2900-3000rpm while in neutral. I can't separate the converter from the engine because I need it for the starter. Converter company claims that it's balanced dynamically before shipped. It's not the drive shaft, because I have found this issue still exists while the trans is in neutral.
5. Lifters on cylinder one seem to bleed down - can't remember if it's intake or exhaust though.

I believe it could be one of the hydraulic lifters bleeding down that's causing this issue... but I'm not sure.

What do you guys think?

 

[racin-jj]

If the lifter simply bleeds down, this doesn't explain the variance in balance from lower to higher RPM. The engine would run rough but it should not cause the vibration only at one rpm range.

First, you need to isolate the problem to be sure it is the motor. Did you disconnect all of the belts and accessories that attach to the crank (including the water pump). If not, disconnect then and run again. A normal cause for this issue is a bent/uneven fan blade or fan clutch. A badly bent pulley could also cause this issue.

You seem pretty stuck on the #1 cylinder possibly being an issue. What was the compression of all the cylinders? You said #1 was high, but how much different is it? Here's a few other possibilities:
Have you checked the cam to see if there are any flat lobes?
Have you checked the valve lash for inconsistencies? Possibly looked at the valves to see if any are sitting higher (when looking at the top of the head surface).
Does the #1 cylinder have any excess oil inside that may be causing a tight seal = higher cylinder pressure while starting.
Have you disconnected spark to see how the crank spins continually with the starter.
If you remove the #1 spark plug is there still a drag near the #1 compression stroke?
If you remove all of the plugs, do you notice any type of drag at any one cylinder?

There are many things to consider while troubleshooting, but hopefully this helps you. Let me know what you find and I'll try to help more if I can.

 

[kiltedrunner]

Thank you for your input.

I should have marked that my engine has an electric waterpump and electric fans - so that isn't it. I know the crank pulley / alternator / power steering are true too. There's no question that there's something very unusual about number 1 cylinder - lots of cylinder pressure compared to the others. All others are at 180 (ish) while number 1 is at 220.

I hadn't considered these other options to try -so I'll give them a go and report back.

 

[kiltedrunner]

Found the likely problem... my new Comp Cams hydraulic roller lifter is bleeding down immediately after I shut off the engine. The lifter was actuating the exhaust valve on cylinder 1 - so that would severely bump up my cylinder pressure if the valve is closed while starting the engine.

Time for a new lifter.... with only about 30 minutes on the engine running.

 

[TetanusShot]

I don't see how the lifter/cylinder pressure issue is related to the intermittent vibration. First thing that comes to my mind is a mix of internally balanced and externally balanced rotating assembly parts. Is it a forged 440 crank with factory 400 flex plate and damper?
Or maybe the other way around, cast 440 crank with internally balanced damper and/or flex plate. Good luck, hope you resolve your issue, cool car.

 

[727]

I built a 440 cast crank engine once and it did the same thing. Turned out to be the wrong weights on the torque converter

 

[snakeoil24]

Found the likely problem... my new Comp Cams hydraulic roller lifter is bleeding down immediately after I shut off the engine. The lifter was actuating the exhaust valve on cylinder 1 - so that would severely bump up my cylinder pressure if the valve is closed while starting the engine.

Time for a new lifter.... with only about 30 minutes on the engine running.

If your having issues with brand new Comp roller lifters call them and send them back for a new set!

 

[kiltedrunner]

I don't see how the lifter/cylinder pressure issue is related to the intermittent vibration. First thing that comes to my mind is a mix of internally balanced and externally balanced rotating assembly parts. Is it a forged 440 crank with factory 400 flex plate and damper?
Or maybe the other way around, cast 440 crank with internally balanced damper and/or flex plate. Good luck, hope you resolve your issue, cool car.

I guess I was hopeful that it's the lifters that are causing my vibration issues, but the more I think about it you're right, it has to be a rotational imbalance issue. It has to be the converter or the crank, rods & pistons out of balance.

The crank is a forged 440 piece that should be internally balanced with the rods and pistons.

The flexplate is a thin plate that came off a 383 - but those engines are internally balanced too - so nothing that can be out of balance there.

The converter was built as if the crank is internally balanced... though it is a possible culprit.

 

[racin-jj]

You may want to double check your crank/flexplate. I can not say the same for ALL of the B/RB motors (because I don't want to mislead you), but I learned with my 440 that my cast crank was a external balance. When I went with a steel crank it was internally balanced and I needed to purchase a new flexplate and harmonic balancer (my converter was already a neutral balance).

You mention your 440 is a forged piece, but where did it come from? Was it pulled from another motor? Did you purchase from a retailer (scat, etc?) Retailers normally sell cranks for internal and externally balanced. You may want to check. Just because a flexplate didn't vibrate on one assembly, doesn't mean it can't on another. Though flexplates and crank "dampners" are made to balance the engine (through set weighted locations), it is always possible for the weights to be off or the part damaged. Just a thought. I always balance all of my engines, even when I buy new components, only because I'm always afraid of an imbalance issue.

On another note, the lifter bleeding down can cause an issue as it may not be staying pumped up during the engine running, but this would cause the engine to run poor above a given rpm and not just in a certain rpm area. I find it hard to believe it would cause the "intermittent" vibration, but definitely look into fixing it. It can cause a vibration issue if the valve isn't opening (or barely opening) during operation. Its definitely something you don't need causing you problems.

I wish you luck, please take my suggestions as just that... I have built a few of these and the unfortunate fact of an imbalance is that it is hard to trace once apart.

 

[kiltedrunner]

Finally providing an update to this thread.

The issue turned out to be that my used motor wasn't exactly what it was supposed to be. The crank was ground down to lighten it - and match a set of rods and pistons... unfortunately those rods and pistons didn't stay with the crank when I got it. The new rods and pistons were MUCH heavier than the cranks reciprocating weight. After adding nearly a pound of weight to the counterweights I now have a balanced engine!

It's in the car now and out performs the old build!

 

[Garys1969RR]

Glad you got it fixed! My 451 had the same issue, the crank grinder took too much metal off the counterweights. When it went to the balancer, he had to add some Mallory Metal to some of the counterweights as they were too light. Boy, that thing runs strong now! Luckily we didn't have to take it apart to fix it.

 

[MOPOWER871]

OUCH, GLAD YOU GOT IT FIGURED OUT .ENJOY THE SUMMER.