y5mgisi
1 ton status
So that 77 i just picked up has a stock 350 and an M15 manual in it. The thing is, at higher rpm like above 2500, it has a moderate to severe vibration. Could it just be a miss? Or is the clutch/flywheel off balance?
CK5
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Engine vibration?
- Thread starter y5mgisi
- Start date
I'll go with something is off balance. A miss would be felt most at lower RPM.
trukker
1/2 ton status
Harmonic balancer or flywheel would be my two choices
y5mgisi
1 ton status
The balancer LOOKS good. but who knows? Could the last guy have used a flywheel for a 400? or would that be an all out no go? Any ideas on how to go about diagnosing it?
Someone could have installed either a harmonic balancer or flywheel from a 400SB and then it will vibrate. It would be noticable at idle and the faster the engine spins the worse it will get.
y5mgisi
1 ton status
Balls. Its going to take me a while to figure it out im affraid...
Either remove the harmonic balancer and take some pics of the back side of it or if you can take some pics with it still on the engine but you'll have to rotate the engine a few times and take pics so I can see the entire back side and I can tell you if it is a 400SB or not. You can do the same with the flywheel, take pics of the engine side of the flywheel and post them here.
y5mgisi
1 ton status
Ok. Can i see the flywheel from the oil pan side?
djtejas
1/2 ton status
If it is a 400 balancer, it will have an area of the O.D. that looks like it's missing...like a depression. You may not be able to see it from the front, but can from the side if you rotate it around.
Yeah, a 400 balancer isn't smooth all the way around. You can see the flywheel if you remove the tin inspection cover (if it still has one).
gotblazers
1/2 ton status
Gettin back to basics: What about motor mounts?
y5mgisi
1 ton status
hmm i dont know what shape the motor mounts are in actually. I'll give that a look see. Was also wondering if a bad cooling fan could cause it. It has one of those hard mounted four blade, non clutch fans on it that i suppose could have been installed incorrectly or something. I'll check it out soon as i can depending on the weather...
You'd have severe vibrations if you had a 400 SB balancer or flex plate on any other small block--one I bought that way felt like the motor was shaking off the mounts above 2000 rpms...
Bent fan blades can cause vibrations,so can warped flex plates..I've seen a torque converter wobble enough to cause one too...motor mounts that have the rubber worn down can cause a rumbly vibration....I had one engine that had a weird vibration at certain speeds,after a few years it finally started knocking--I found 3 main bearings had been spinning in the block for a long time!--weird thing was it was a low mileage crate motor with only 10K on it,that had been installed by a previous owner...
I'd take all the belts off and start it up,to ensure its not a water pump or altenator,P/S pump,noise first off---then check for the wrong balancer or flex plate..if you have a manual tranny the pressure plate & disc can cause vibration if they are warped or unbalanced too..
Bent fan blades can cause vibrations,so can warped flex plates..I've seen a torque converter wobble enough to cause one too...motor mounts that have the rubber worn down can cause a rumbly vibration....I had one engine that had a weird vibration at certain speeds,after a few years it finally started knocking--I found 3 main bearings had been spinning in the block for a long time!--weird thing was it was a low mileage crate motor with only 10K on it,that had been installed by a previous owner...
I'd take all the belts off and start it up,to ensure its not a water pump or altenator,P/S pump,noise first off---then check for the wrong balancer or flex plate..if you have a manual tranny the pressure plate & disc can cause vibration if they are warped or unbalanced too..
y5mgisi
1 ton status
I checked out the balancer today and its all just a big circle. No reliefs. So in other words it did NOT look like this one,
It DID look like this one,
Tomorrow im going to start it for a couple seconds with the fan belt off, and try peaking at the flywheel.
It DID look like this one,
Tomorrow im going to start it for a couple seconds with the fan belt off, and try peaking at the flywheel.
bailey9r
1/2 ton status
2500 is not so high so first put it in neutral and rev it to 2500 and see if its the same level of vibration, then do the same with the clutch in to eliminate the drive train out of the equation. Depending on how severe it is you could remove the belts to remove the chance of it being one of the accessories as well, then concentrate on the motor if it stays the same. If it doesn't change from that I'm betting on an engine bearing.
An exhaust pipe pinned against the chassis or body can cause a very annoying vibration/grinding sound too.....so can the engine or trans if the mounts are broken and the rubber no longer insulates the two metal peices,or they rub against a chassis or body part...
I had one truck someone used an old connecting rod as a tailpipe hanger--it looked cool,but the darn truck sounded like a buzz saw,everything vibrated so bad !..soon as I unbolted it,it was golden silence..
I had one truck someone used an old connecting rod as a tailpipe hanger--it looked cool,but the darn truck sounded like a buzz saw,everything vibrated so bad !..soon as I unbolted it,it was golden silence..
COCHEV
1/2 ton status
When my dad bought his 77 vette it had a bad vibration that was worse at certain rpms and it turned out someone put the wrong flywheel on when they put the ritchmond trans in. Hope thats not the case, but it sounds like it. The trans thats in there isn't all that big tho, right? not like a 465 at least
y5mgisi
1 ton status
Yea the trans is just a little guy. It would be quick and easy to pull it down. I just replaced a u joint in the rear that was shot and topped off the trans oil which was very low. I'll try and do more investigating today but now something is wrong with the car so I gotta deal with that first...
