Hi, I have posted this last year and have been checking for the vibration but it is still present and seemingly getting worse. 1965 Fury poly 318, 120k miles ,all stock, we replaced water pump, timing gears and chain with double roller in 2022.timing chain was tight on left side, but sloppy loose on the right side as you look at it. vibration started right after that replaced with new vibration dampener seemed to get better but now has become very significant between 14 and 1800 RPMs. seems fine at idle and above 2000 rpms.have disconnected all belts, vibration is still there, checked in park and neutral, vibration still there,new driveline (vibes while parked) fluids all full, runs well.runs elect.ign, rebuilt BBD Carb. Oil pressure is 25 warm idle 48psi warm cruise. Compression is 145-155 ,others suggested torque converter or flexplate. Is loose ?? All ideas appreciated, Davea Lux ?
Poly Motor Vibe
- Thread starter 65GUS
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gyknot
Active Member
It would seen logical that one of the items you replaced is bad. Not sure why your vibration is only at certain rpm's but if it didn't do it before, and now does, something you changed is likely the culprit.
Since the water pump would not spin if the belts were removed, that pretty much leaves either the timing setup or the dampner.
That's my 2 cents worth.
Since the water pump would not spin if the belts were removed, that pretty much leaves either the timing setup or the dampner.
That's my 2 cents worth.
57fury440
Well-Known Member
You said the vibrations started after you replaced the timing chain. That is the first place I would look. Maybe it is defective.
Since all cylinders have good compression, it is unlikely that the engine has an internal issue although stranger things have happened. I would suspect that since the vibration went away with a replacement harmonic balancer that the new unit might be bad. Some things to check first: Pull the cover off of the bell housing and check the flex plate for missing bolts and cracks. Check your exhaust system to be sure it is not wedged against something solid underneath. The 318 poly is internally balanced and should not vibrate. We ran into, very rarely, fractured crankshafts. Usually the engine will come apart all over the street if that is the case and it will make lots of noise before that happens. For your own piece of mind you can check this fairly easily. Line up the timing mark at TDC. Take a screw driver and move the flywheel back and forth about one tooth while helper watches the timing mark. There should be no delay from when the flywheel is moved and the timing mark moves. You should also check the timing chain for excessive slop. Remove the distributor cap. Line up the timing mark to TDC and have a helper rock the crankshaft back and forth. You should have 10 degress or less of free play before the distributor shaft moves. Try these things and report back.
Dave
Dave
1970FuryConv
Old Man with a Hat
These guys have helped me. They can probably answer your question. They give good phone tech advice.
Welcome to Hughes Performance - Hughes Performance
I've been thinking about this problem for the past day. Something from my dim and distant past, and from my experience with @ayilar 's car a few months ago.
Is it an out of balance vibration, which is what the discussion has been thus far? The new balancer didn't solve the problem, but something could be amiss there, for sure. I doubt it's some magically damaged flex plate or crank or whatever. That stuff doesn't just break at little to no load.
Or....is it a dead cylinder (plug, plug wire, cap, valve seat/seal, valve spring, bad rocker) that is okay at idle (check!), bad at 14-1800 revs (check!) and smooths out above 2000 (check!). At idle a dead cylinder is hard to ascertain because there's not enough work being done by the engine to make it shake much. Above 2000, the dead cylinder's shake gets smoothed out by the other seven good cylinder firings. It's that middle zone--depending upon what might have failed to cause a dead hole--where shaking is felt.
Again, this was kinda how Michel's car acted when that pushrod pushed its way through the rocker and mostly killed the Number One cylinder. You would have thought that we would have easily felt that dead-miss, but no. Idle was "okay", cruising was "okay" until things got worse, but mild acceleration below 2K was shaky. As it was, we traveled maybe 70 miles with the damage that @david hill showed us in the Poppy thread.
The OP asked for ideas, so a dead cylinder is my idea to look into if the balancer is ruled out.
Is it an out of balance vibration, which is what the discussion has been thus far? The new balancer didn't solve the problem, but something could be amiss there, for sure. I doubt it's some magically damaged flex plate or crank or whatever. That stuff doesn't just break at little to no load.
Or....is it a dead cylinder (plug, plug wire, cap, valve seat/seal, valve spring, bad rocker) that is okay at idle (check!), bad at 14-1800 revs (check!) and smooths out above 2000 (check!). At idle a dead cylinder is hard to ascertain because there's not enough work being done by the engine to make it shake much. Above 2000, the dead cylinder's shake gets smoothed out by the other seven good cylinder firings. It's that middle zone--depending upon what might have failed to cause a dead hole--where shaking is felt.
Again, this was kinda how Michel's car acted when that pushrod pushed its way through the rocker and mostly killed the Number One cylinder. You would have thought that we would have easily felt that dead-miss, but no. Idle was "okay", cruising was "okay" until things got worse, but mild acceleration below 2K was shaky. As it was, we traveled maybe 70 miles with the damage that @david hill showed us in the Poppy thread.
The OP asked for ideas, so a dead cylinder is my idea to look into if the balancer is ruled out.
57fury440
Well-Known Member
He said he tested the compression and it was good.
Yes, I can read. Are you saying that I'm absolutely wrong about a dead cylinder?
Anything else, other than your comment that the timing chain might be defective?
57fury440
Well-Known Member
I didn't say you were wrong, but wouldn't good compression rule that out? I still think it is related to one of the changes he made. Maybe the cam is off the mark.
Good compression could also mean a wiped exhaust cam lobe, i.e. dead cylinder. Unlikely yes, but other than the balancer, something else "changed" to cause this vibe. It's possible the cam was off the mark, but the compression psi wouldn't likely be in the 150 range. We don't know what else happened during this timing chain work. Did the plug wires go back to the correct plugs? Or back at the cap? If you mix up 5 and 7, it runs just fine....for the most part. 1-8-4-3-6-5-7-2 Easy mistake to miss because it's not farting back through the carb if these two are mixed, but it'll shake with a few revs above idle.
The crank didn't break, the flexplate didn't break, the converter didn't throw a weight, the chain isn't unbalanced, the carb is fine, the air in the tires is fine, the windshield wipers work, and it's very likely that the OP got the timing marks aligned correctly because it runs and has 150 psi. So what else could cause this vibe that might not be a vibe?
So...before I would buy a crate hemi to solve this problem, I'd make sure it's firing on all eight in the proper sequence. That's all I'm saying.
I'll now step out of this conversation and watch from the sidelines, hoping that the OP can find the problem.
The crank didn't break, the flexplate didn't break, the converter didn't throw a weight, the chain isn't unbalanced, the carb is fine, the air in the tires is fine, the windshield wipers work, and it's very likely that the OP got the timing marks aligned correctly because it runs and has 150 psi. So what else could cause this vibe that might not be a vibe?
So...before I would buy a crate hemi to solve this problem, I'd make sure it's firing on all eight in the proper sequence. That's all I'm saying.
I'll now step out of this conversation and watch from the sidelines, hoping that the OP can find the problem.
Last edited:
KennatMurphy
New Member
Hi Dave,
Based on the information you provided, it sounds like the vibration you are experiencing may be related to the drivetrain or engine. Since you have already disconnected all belts and checked in park and neutral, it is less likely to be caused by accessories or the transmission.
A loose torque converter or flexplate can certainly cause vibrations in the drivetrain. The torque converter is the component that connects the engine to the transmission, and the flexplate is the component that connects the torque converter to the engine. A worn or damaged torque converter or flexplate can cause imbalance and vibration, especially at lower RPMs.
Another possibility is that the engine itself is causing the vibration. You mentioned that the timing chain was loose on the right side, which could indicate wear or damage to the camshaft or cam bearings. This can cause a "lopey" idle and vibration at certain RPM ranges.
Since you mentioned that the vibration has gotten worse over time, it may be a good idea to have a professional mechanic inspect the drivetrain and engine components for any signs of wear or damage. They can also perform a vibration analysis to help pinpoint the source of the vibration.
I hope this helps, and good luck with diagnosing and resolving the issue!
Based on the information you provided, it sounds like the vibration you are experiencing may be related to the drivetrain or engine. Since you have already disconnected all belts and checked in park and neutral, it is less likely to be caused by accessories or the transmission.
A loose torque converter or flexplate can certainly cause vibrations in the drivetrain. The torque converter is the component that connects the engine to the transmission, and the flexplate is the component that connects the torque converter to the engine. A worn or damaged torque converter or flexplate can cause imbalance and vibration, especially at lower RPMs.
Another possibility is that the engine itself is causing the vibration. You mentioned that the timing chain was loose on the right side, which could indicate wear or damage to the camshaft or cam bearings. This can cause a "lopey" idle and vibration at certain RPM ranges.
Since you mentioned that the vibration has gotten worse over time, it may be a good idea to have a professional mechanic inspect the drivetrain and engine components for any signs of wear or damage. They can also perform a vibration analysis to help pinpoint the source of the vibration.
I hope this helps, and good luck with diagnosing and resolving the issue!
I'm really with @Trace 300 Hurst on this one.
I'll even throw another possibility in the mix. I've seen plug wires, especially the 5 and 7, have a cross fire (don't know what to call it) where the two wires run parallel with each other and will "leak" making both cylinders fire at once. The solution is to cross the wires at right angles and use good plug wires. It doesn't cause a miss, but it does cause some issues that may mimic a vibration.
No cost and easy to reroute these 2 plug wires to try it. If it helps, buy some good wires and route accordingly.
IIRC, This was addressed in another thread recently... I can't find it though.
Did you get the vibration issue fixed?
Dave
Dave
Hi Dave and everyone at FCBO. been away from the site all summer but i see more replies and info to my vibration problem. its still going on , latest things ive done or checked are, had the original harmonic balancer sent to Cali and rebuilt. installed a month ago, no change. double checked condition of motor mounts, they are fine. just double checked firing order again, it is correct. #5 & #7 are not mixed up. all ignition systems have been checked, timing, cap, rotor, wires, plugs etc... they are good. it has dropped 3 psi oil pressure at highway speed over the summer. from 49 to 46 psi. mechanic friends tell me the vibe is not that bad & just drive it and watch it. if the new cam and crank gears were not set up correctly, they said dot to dot, i dont think that would cause a vibration in motor , would it ? i checked the vibe at appx. 1400-1800 rpms. im kinda thinking maybe cam bearings getting worn out. im going to drive it another summer and just watch and see what it does. Thanks for all help and suggestions.
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