Engine vibration

T

Trident team

New member
I have just completed a complete engine overhaul and the initial
running of the engine there has been a 'noticeable' vibration
felt through the car.
It happens on start up and continues when driving in any gear, I replaced only the harmonic balancer pulley and the clutch plate at overhaul along with the pistons and rings. Everything else is original.
The pistons were the only items that were balanced as they were
'checked' just to be sure.
The fly wheel was surface ground just to 'clean it up'.
The engine mounts incl. the gear box mount were all replaced with new items and feel very hard compared to the originals.
Any ideas or suggestions would be gratefully received.
Cheers :?
 
I'm no real engine guru but I suspect that the answer is down to the last thing on your list. Brand new mounts will transmit quite a lot of vibration to the chassis until bedded in and even then, if the old ones were worn out, you will notice a difference I suspect.

Did you line up the propshaft as it was? Sometimes there is a harmonic with the rest of the transmission that needs to be tuned out. I found this out in about 1971 after a clutch change. Rotating the prop shaft mountings 180 degrees made a huge difference.

I suppose there could have been an imbalance introduced into the flywheel if it wasn't checked while it was cleaned up.

Finally, is the this throughout the rev range? If so, it's probably not an engine problem. Assuming all cylinders are firing, dodgy carburation could cause low speed vibrations but that should disappear with revs.
 
To the 83man
Thank you for your interest in my 'problem' I didn't consider the
tailshaft as contributing to the problem even though it may.
The vibration actually starts as soon as the engine is started and
continues through the rev. range whilst the car is stationery.
When I select a gear and drive off it is still there and can be felt through the steering wheel, there are no unusual noises other than a little timing chain 'rattle' which I will adjust when the cam cover comes off when I check torque the head bolts in about 350 miles.
Compressions are pretty good #1, 151 #2, 150 #3, 150 #4, 151.
The flywheel was just 'skimmed' I was told to clean it up only.
Carby tuning is something I must admit I am still working on
I just hope that's all it is.
Regards and thanks again I will keep you posted.
 
You could try slacking of the engine mounts to see if the vibration changes , the exhaust could be worth a look at.
Neil
 
Your suggestion re engine mounts is on my list.
Actually I intend to lift the engine ever so carefully with my floor/trolley jack to relieve the weight and see what happens.
I'll let you know the result
Cheers Neil
 
Is the engine, gearbox or exhaust making contact with something on the body or crossmembers for some reason? Know it sounds funny but I've found blocks of wood & all sorts wedged between crossmembers & sumps etc over the years! Also for some reason I think the gearbox mount has a front & rear side, don't know if I dream it tho so don't quote me on it but Im sure some one will tell us if Im wrong! Hope you find the cause soon.
 
Did you have the flywheel balanced, after the skim?
I once found an oil absorbent granule, squashed between the flywheel and crankshaft, on a car that had just been fitted with a new clutch and dual mass f/w. The vibration was startling.
Also, as you've fitted new mounts, check the lay of the exhaust, as it may be grounding somewhere along its length. If it's a Mk1, check it at the steering idler, it runs pretty close there.
Good luck
Scott
 
Hi ozzy
The car has been completely rebuilt ie., every mechanical part, steering, suspension, diff., rear axle bearings, new exhaust system incl., mount
rubbers, the only items not replaced, were the universal joints, but they were checked and considered serviceable, and the gearbox which was in good condition before the engine overhaul so strip and reconditioning was not required. I did all the work and am sure every part was fitted properly [no blocks of wood or rubbing parts at all.]
To your comment relating to the gearbox mount I found interesting as
I examined this new mount prior to installation I did wonder which way around it went as it did appear to be slightly ''thicker'' on one side than the other and not being able to get any detail on correct positioning I fitted it with ''thicker '' section to the rear.
Thanks for your interest
 
Hi Scott
I will check exhaust routing again
No, the engine guys that did all the machining didn't believe that such a light skim off the flywheel should require a balance and as they said ''you can lose a couple of teeth off the ring gear and it won't throw the engine out of balance'', so I took their word for it.
Still checking , will keep all you good interested people posted.
If anyone has any more comment I would love to hear it.
 
Hi,

Looks like you are already looking at the mounts thing - but:
I ran very stiff mounts on a race car I had some years back. It felt like I was sitting in a cocktail shaker until flat out. These mounts were also shorter in length - to improve weight distribution I guess. Given I wanted to put the car back to road spec, I replaced them with stock mounts and refitted the spilt prop etc and the problem was fixed.

Good luck with it.

Cheers,

Andy
 
Hi Trident Team,
Would have said engine mounts every time as the vibration is there whilst standing still!
I had a GT and it gave the same Vibration when I fitted a new engine back in 76. I left my brother incharge whilst I went to get some more parts and his idea of a torque wrench settings etc was forget the book everything must be FT!!
I took it too a friend who said first thing to do is check the engine mounts are'nt too tight. After slackening them off a couple of turns the vibration disappeared. I have never overtightened mounts since!
Andy M
 
I am very appreciative of all the constructive comment regarding this
''problem'' on Thursday she is going out for a drive and hopefully after all my adjustments I will be able to give a good report.
Thanks again
 
Well
The test drive on Thursday was great fun but that pesky vibration is still evident...
next step is to put the original engine mounts back.
That should eliminate them from calculations.
If I get a result from doing that it will prove that the rubber material used on new mounts is too hard, if not I dread pulling the engine out and dismantling it again.
All I want to do is drive and enjoy without the worry :(
 
Well
The test drive on Thursday was great fun but that pesky vibration is still evident...
next step is to put the original engine mounts back.
That should eliminate them from calculations.
If I get a result from doing that it will prove that the rubber material used on new mounts is too hard, if not I dread pulling the engine out and dismantling it again.
All I want to do is drive and enjoy without the worry :(
 
Having followed your problem with interest it reminds me of a similar problem I had myself way back in '67 when I had with a frog eye sprite. On replacing the engine following a rebuild I managed to put a slight crack in one of the arms of the diaphragm spring in the clutch assembly. This caused a bit of a vibration all the time the engine was running which became progressively worse until the clutch finaly exploded leaving me with a 100 mile trip with no clutch & the car stuck in 4th gear.
I'll stop there as it's too distressing to carry on.
Since then my motto has been 'If in doubt, check it out'.

Regards

Dave B
 
I replaced only the harmonic balancer pulley
Click to expand...

Can you explain what this part is? as you are having vibration and its not linked to the drive chain it points to the engine itself.
 
This is an interesting discussion and this is my view. If the vibration is evident when the car is stationery, then you can discount the prop shaft and transmission. Before you start stripping the engine, I suggest you drop the gearbox off and check the flywheel. Make sure that it's properly seated on the locating peg on the end of the crankshaft (as Scott suggests) and that all the bolts are present, torqued correctly and the lock-tab washer is OK. Rig up a datum pointer that runs close to the rim of the flywheel and rotate it by hand to see that it's running true. Check the ring gear too as it's a shrink fit and can be displaced it it's taken a heavy knock whilst being off the car. If all is OK then take the clutch assembly off and check it over. Taking the engine apart must surely be the last resort! Good luck old mate............. I watch with interest!
 
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