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engine vibe source? 120-130

posted by someone claiming to be Erik on Tue Apr 27 09:07 CST 2004 [RELATED]

Ok, ever since the new engine was installed (b20e overbored to 2.2 with torque cam)there has been a slight vibration at high rpms. The engine was balanced to a half gram by a professional race car engine builder.
Thought it may be from the driveline. When the M41 was installed we had the driveshaft balanced, and all the bearings/bushings/u joints replaced.
still have the vibe. The vibe is enough at high rpms (4,000+) to cause things to become loose, vibrated the starter solenoid screws right out after a spirited cross-state run on the highway.

The engine will be pulled this summer when the body and paint are done and i am wondering where to look next? The only wild card is that the bearings were measured by the guy who overbored the engine (thought he would be better than my inexperienced self). Could slightly off bearings cause a vibration?
Could it also be the cause of the modern (ipd upgrade) rear main seal failure too?
It would be easier to check with the measuring paste while it is on the stand.

Any other areas to look?

expert head scratching greatly appreciated.

-Erik

65 pv 544, 66 220, 66 1800s so many cars so little time.

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engine vibe source? 120-130

posted by Bennie on Tue Apr 27 21:01 CST 2004
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last visit: Wed Nov 28 03:03 CST 2007

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Erik, vibrations suck. Not of any help, but just to cheer you up�

I have weird vibrations/humming when driving at speeds higher then 60mph. It also started after I put in an other engine (which ran fine before), although the vibrations I�m getting are not directly rpm-related nor are they speed-related, seems to be a harmonic-resonance problem. Till now I have not been able to figure it out.

I have swapped the following parts:
2 flywheels (also tried fitting them on in other position)
3 presure and friction plates (also tried fitting them on in other position)
5 gearboxes (2xM41, 2xM47, 1xM46)
4 drive shafts / supportbearings
2 rear axles
3 camshafts
2 timing gear sets
2 sets of tires/wheels

Till this day I have not been able to figure it out. I�ve finished a B20B just this week which I will be putting in soon, hoping for some more power and hopefully get rid of those #@*!#-vibes�

Does that help?...
Cheers Ben
--
Daily driver: P130, '65, B18+M47. In the proces of restoring: P131, '69, B20+AW71L. (www.knutselsmurf.web1000.com)

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engine vibe source? 120-130

posted by someone claiming to be JimL on Tue Apr 27 11:31 CST 2004 [RELATED]

Your engine balancer may simply have not done the job properly and missed something. Did he say if he had to add or remove any significant amounts of weight? Weight changes should be very minor unless something is out of whack.

Very doubtful that bearing clearances contribute at all to the vibration problem. Race engines run looser clearances than stock engines. If your oil pressure is ok, then unlikely you have a bearing problem.

Usually it's not necessary to align bore the main caps on a 4-cyl unless there is an unusual problem, but then the block is probably no good either.

Variables introduced are heavier pistons, different cam, balanced driveline. I assume you changed the motor and transmission mounts? What about compression ratio and ignition timing? Increasing the bore size increases the compression ratio. The "torque" cam can also increase the cylinder pressures (effective compression ratio). Are you possibly getting detonation? Maybe you can experiment with some other (retarded) ignition settings and see if things smooth out.

Otherwise it sounds like the balancing will have to be double-checked when the engine is next out of the car.

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engine vibe source? 120-130

posted by someone claiming to be erik on Tue Apr 27 11:44 CST 2004 [RELATED]

Would detonation be so consistant and not cause damage over time?
Would the addition of the larger pistons make an impact with the crank being intended for lighter pistons? This was the standard ipd overbore kit, does anyone else with an overbore have this problem?

sounds like either way i am going to get dirty and have to take things apart.
If I double check the bearings and they are good then it should be the balancing to redo? As for the balancing he did take off some of the connecting rods but no more than a few grams, less than the factory specs for wiggle room.
I was hoping for something easier, but alas...

thanks for your opinions and help.

-erik

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engine vibe source? 120-130

posted by Phil S. on Tue Apr 27 09:35 CST 2004
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last visit: Fri Oct 24 13:18 CST 2014

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No easy answers to this one, just questions...

Were the flywheel and clutch pressure plate balanced as a unit?

Were the rods checked for straightness and matched length?

Is the crank straight, and was an accurate align hone/bore done on the main bearings?

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engine vibe source? 120-130

posted by someone claiming to be Erik on Tue Apr 27 09:38 CST 2004 [RELATED]

Were the flywheel and clutch pressure plate balanced as a unit?
-yes

Were the rods checked for straightness and matched length?
-yes
Is the crank straight, and was an accurate align hone/bore done on the main bearings? The crank was was honed where the bearing go (not sure the technical name of this).
Are you asking if the new bearings were honed or the place on the block that they fit into?

Thanks for your expertise phil.

-erik

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engine vibe source? 120-130

posted by someone claiming to be mjamgb on Tue Apr 27 11:41 CST 2004 [RELATED]

If the crank wasn't checked for straightness and if it wasn't "normalized" after grinding it could be the trouble. Were the bearings that came out of the engine prior to the rebuild all evenly worn in the same amount?
Seems silly, but are the motor and transmission mounts all OK?
Pre-ignition (ping) at sub-audible levels can also cause a vigration from harmonics being set up in the crank. Are you flirting with large advance or compression? Are the carbs accurately balanced and adjusted (better a little rich than lean).
Hmmmm.
Are all your belt driven accessories in good condition?
Plasti-gauging journals is one of my little quirks as I will always do it if possible (doubles time of engine builds) so of course I recommend it.
The only other things rotating are the transmission and camshaft (OK, the dizzy and oil pump too).
Does vibration reduce/go away when the clutch is dis-engaged?
I suppose it is possible that a cam blank from an aftermarket producer could be off-center and introduce a vibration.
Wears me out!

Mike!

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engine vibe source? 120-130

posted by someone claiming to be Erik on Tue Apr 27 12:49 CST 2004 [RELATED]

If the crank wasn't checked for straightness and if it wasn't "normalized" after grinding it could be the trouble. Were the bearings that came out of the engine prior to the rebuild all evenly worn in the same amount?
--nothing looked unusual to me or a real machanic.
Seems silly, but are the motor and transmission mounts all OK?
--all new
Pre-ignition (ping) at sub-audible levels can also cause a vigration from harmonics being set up in the crank. Are you flirting with large advance or compression? Are the carbs accurately balanced and adjusted (better a little rich than lean).
--switching new carbs made no difference and running them rich enough to start in cold weather without a choke (as rich as you can get without stalling) made no difference.
It is an E head and was bored to 2.2 liters compression is high but never calculated it out. It has the stock coil with pointless electronic distributer.

Hmmmm.
Are all your belt driven accessories in good condition?
--spose i could take off the belt and rev it up to see if it goes away, would be a good first try as it is easy.

Plasti-gauging journals is one of my little quirks as I will always do it if possible (doubles time of engine builds) so of course I recommend it.
The only other things rotating are the transmission and camshaft (OK, the dizzy and oil pump too). --new distributer and oil pump. ..
Does vibration reduce/go away when the clutch is dis-engaged?
--it appears to be related to rpm's with or without gears engaged.
I suppose it is possible that a cam blank from an aftermarket producer could be off-center and introduce a vibration.
Is it possible that the timing gear could be off? new timing stock not steel,and crank gear installed with engine.

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engine vibe source? 120-130

posted by Phil S. on Tue Apr 27 10:00 CST 2004
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last visit: Fri Oct 24 13:18 CST 2014

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Normally you'd hone the block so 1) the bearings were all perfectly in line, and that line was perfectly perpendicular to the cylinder bores, and 2) the clearance between the bearings and the crank journals (that's the term) was to spec.

I imagine this was done correctly -- just grasping at straws for lack of a good idea.

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engine vibe source? 120-130

posted by someone claiming to be erik on Tue Apr 27 11:27 CST 2004 [RELATED]

Do you think it would be worth the effort with engine out to just measure the bearing clearances to rule a mismeasurement out?
hate to pull the engine out any more than needed.
thanks,
-erik

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engine vibe source? 120-130

posted by iadr on Thu Apr 29 11:03 CST 2004
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last visit: Wed Jan 1 18:39 CST 2014

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erik,

IMO chances are extremely slim that the source is in the "major hard parts".

- check throttle lever alignment (firewall, engine side) in case there is extra vibration reaching you that way

- check the motor mounts- 140 ones seem to help reduce vibration on my car but raise engine (see above)

- meticulously check ignition and fuel flow. eg. my 544 had mismatched needles for at least several years when my dad had it

- acessories- eg. alt conversion vibrating was a problem in my case

- greater the power/displacement, the greater the vibration. There is no harmonic dampener, and no balance shafts. What you feel may be normal. There is a certain threshold at which just a few % more vibration over stock begins to pass through to you as a major increase.

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