1931 plymouth 30U coupe vibration

acebopper · November 09, 2012, 06:10:35 AM

I will check the graval pans. Took the rear mounts off and they don't seem to be that bad, the only thing I found with them is that they had sagged a bit and may have been resting on the chassis. I turned them up the other way before reenstalling them but because of the weather here in the UK I have not taken it out for a test drive.
I can buy replacements from the US but with the exchange rates, the postage ,import tax and custons handling charge they work out very expensive only to find that that is not the problem.

SD Glenn · November 06, 2012, 11:43:50 AM

Looks like everything has been covered. How about the front pully/Vibration damper? How about the flywheel/clutch area? Sounds like that is about all that is left.Good luck and have a nice "Election Day", don't forgrt to vote. Sure will be interesting to find out what you find.
SDGlenn

plym_46 · November 06, 2012, 01:36:44 AM

Long stroke 4 cylinder large displacement (yep 199 cu in is large) engines are inherently out of balance, modern ones usually ran some sort of counter rotating balance shaft inside the block. I believe ther should be some rubber isolation pads between the rear mounts and the frame as well as at the front, but I could be wrong. but if you can fabricate and mount some sort of isolating pads at the rear mounts you may decrease the jitters.

GWR · November 05, 2012, 07:19:06 PM

Sorry for the tardy post. Just found this thread.

Acebopper, I was going to tell you about rear mounts, but guess you found them.

I have a 30U with the same problem. Been working on this problem for years. Vibrates like crazy from engine RPM. You get the vibration by just reving the engine at a stop in the garage. Have tried everything including replaced front and rear engine mounts, had distributor rebuilt, had flywheel and clutch balanced, and had water pump rebuilt and balanced.

What I am going to do now is pull the engine. I built an engine stand so I can mount it on there and run it out of the car. This will tell me if it is the engine or the mounts. I think maybe that when they put new rubber in my rear mounts they may have let the mounting bolts touch inside the mount. This would allow a sympathitic vibration from the engin to the frame.

Also check the gravel pans on either side of the engine. Mine had them attached to both the engine and the frame. Fixed that, but didn't solve my problem.

Gary R - Happy Motoring

acebopper · October 08, 2012, 11:13:25 AM

Oh, May have solved the problem. There are two rubber mountings at the end of the bellhousing but they can't be seen very easily as they are tucked inside the open chassis, you can only feel them. my two are very hard and perished so will order some new ones, may as well replace the front one while I am at it. many thanks for all the replies, will let you know if this cures the problem.

John Maddocks. UK

acebopper · October 08, 2012, 05:16:30 AM

No, this model does not have the floating power, that only came in in 1932 with the PA model, mine only has one front engine rubber mount, the rear is fixed directly to the chassis rails.

TodFitch · October 07, 2012, 01:14:22 PM

Quote from: elmo on October 07, 2012, 02:30:32 AM
acebopper, i would say thay your problem is the front engine mount , they were rubber ,vulcanised (heat treated)onto the steel mount , after a lot of years they are inclined to fail . they used the same system right through to the end of the flat heads , i have several , looking at them, they look perfect, but after putting them under a bit of stress , they fail. Rex

Might be, but I thought the PA was the first model with "Floating Power". I guess I should check the literature.

Don't rule out the accessories (water pump, fan, generator) as having an issue. Fan balance might act like that...

elmo · October 07, 2012, 02:30:32 AM

acebopper, i would say thay your problem is the front engine mount , they were rubber ,vulcanised (heat treated)onto the steel mount , after a lot of years they are inclined to fail . they used the same system right through to the end of the flat heads , i have several , looking at them, they look perfect, but after putting them under a bit of stress , they fail. Rex

acebopper · October 06, 2012, 01:56:13 PM

Update, thought I would start with the engine its self. Put sparkplug testers on all 4 flugs, fired her up and she is firing on all 4 and running very smooth with no missing or vibration. Let her warm up for a while then sitting inside slowly aplied pressure to the throttle, ok to start with but the more thottle I gave her the vibration started and by about half throttle the vibration was being transmitted thoughout the car.
As far as I cane tell there is only one rubber mounting for the engine, this being at the front, bottom of the engine which seems to be in very good condition, the rear engine mount is fitted to the chassis via the bell housing with is ridged. ie no rubber mounts, when I blip the throttle the engine remains ridged and does not flex at all . took her out for a test run, got her up to 50mph, vibrating very badly, take her out of gear at that speed and she is as smooth as silk.

SD Glenn · October 06, 2012, 12:12:21 PM

If it was a problem with the wheel brgs you should hear that. My SWAG would be the drive line. Check your u-joints or Web joints. I do not know which you have. You could jack up the rear end, puts some stands under the axle and run the car in high gear, you shouldn't have to rev very much to find a vibration in the drive line. Was this a problem that just now developed? or is this the first time you drove the car?
Take care
SDGlenn

acebopper · October 06, 2012, 06:13:32 AM

Hi,no the vibration is not in the steering wheel but the whole car vibrates.

SD Glenn · October 05, 2012, 04:33:28 PM

Is the vibration in the drive line, or can you feel it in the steering wheel, front tires wobbling?
SDGlenn

acebopper · October 05, 2012, 01:32:26 PM

My 31 plymouth is very smooth up to 35mph but after that the vibration increases and at 45mph it is undrivable, any idears,