Trouble with vibration....

[Mikey]

I'm having trouble with vibration with my "new" 70 truck with a 302 three-speed. I did a compression check; all checked out at 120 - 130. Retimed the engine and re-gapped the points. I checked firing order and put an induction light on each wire and revved to check if the plugs were firing. All is good. The vibration occurs in neutral and feels like an out-of-balance situation though all rpm range. I'm thinking a bad plug wire or bad flywheel....maybe even the wrong flywheel. I took the belt off to eliminate the alternator and water pump but still there. Idle feels great but very slight vibration.

Any ideas????
Thanks,
Mikey

[GT-Racer]

what year is the 302? Might check to see if you have the right flywheel. Some were 50 ounce balance and some were 28 ounce. May be a bad motor mount? Just guesses here though.

[Mikey]

It's a stone stock 1970.

I was wondering about motor mounts but it shakes on steady revving.

Guess I'll try again next weekend....
Thanks,
Mikey

[flyboy2610]

I agree. My first thought was bad motor mounts, also.

[Docholiday72tx]

A vacume leak may also cause the motor to run rough and vibrate. Spray something like WD40 around the intake and carberator. If the vibration stops, you found the leak.
Also check your vacume lines and make sure their up to speed.
Double check idle speed, wires and plugs.
Check out all the little things before trying to replace a fly wheel.
If it ends up being a motor mount follow Rjewke's advice and go ahead and replace both sides.
Doc

[rjewkes]

See thats why there is more than just one person on this site. I completely forgot about vacuum/intake leaks and plugs and what not. Thanks Doc And Flyboy.

[Docholiday72tx]

I've been there...and that's why I'm here. LOL.
It makes my day if I can help another old truck lover.
Doc


I just remembered something....I had a 302 several years ago that had a bad vibration. I searched for days to find the root of this evil.
I finnaly located a huge vacume leak....It was the rubber diaphram inside the vacume advance on the distributor. So if spraying something around the intake and carberator doesn't find a leak, try this.
Un hook the vacume line that goes to the vacume advance, and hold your thumb over the hose. If the engine levels off you have located the culprit....If not...look some where else.
D.

[Mikey]

Hey, do you guys think it could be the timing chain skipped a tooth? It's supposed to be the original chain with over 200k miles?

[Mikey]

Oh....engine seems to be held in pretty good by the mounts. You feel the vibration more than see it. It is in the engine, though. It feels exactly like someone swapped a couple of plug wires.

[rjewkes]

probably so. the 302,351C/351W,360,390 AFAIK wire as follows 1-5-4-2-6-3-7-8. Counter clockwise. Not sure but you may allready know it. And if you didn't you do now.


--Back
4------8
3------7
2------6
1------5
--front

[flyboy2610]

Are you getting a lot of static on your AM radio?
If so you may have a cracked distributor cap. It could also cause misfiring.
Check that and your timing.
Good luck.

[Mikey]

I checked the firing order already. All OK. I checked the vacuum diaphram...both of them...all OK. I changed out the plug wires with an old set I had, no change. I checked timing. No radio so can't check that. I have a couple of old spare caps so I can try that.

Is there any easy way to check the flywheel? Any inspection plates?

Anyone think my timing chain jumped a tooth?

[FORDification]

I doubt it's your timing chain....if it jumped a tooth it would be a lot worse than a slight vibration. If it ran at all it would be VERY rough. However, if the chain and sprocket are both worn, and with 200K+ it's very probable, it could conceiveably cause a constant timing variation as the chain tightens up and loosens again. You said the vibration occurs at all RPMs, but does it seem to remain fairly constant or is it slightly intermittent?

What transmission do you have? It's a manual, correct? How does it shift? Do you have any problems getting it into or out of gear? Depending on the transmission, there should be an tin access cover on the lower front. I'd check the condition of the flywheel, make sure it's tight and not warped.

[Mikey]

Shifting is a problem. It seems to not transfer power and feel like it's slipping. Then, you can smell burnt asbestos. This problem is intermittent.

I did check the timing and watched the mark carefully...the mark is very steady. Granted...the chain will have to be changed but I must at least find the vibration or there is a good chance I'd give the truck back and he would take it to the junk yard. If I can isolate the problem and evaluate the time and $$ to fix, then I can probably convince my wife that it's OK to have eight cars between the two of us!

Vibration is pretty severe and constant throughout all the rpm range. The engine itself, if you look at it, doesn't move much but when you sit in the cab, it vibrates pretty bad. Feel just like two plug wires are reversed.

Will the transmission need to be removed to diagnose a flywheel?

Thanks everyone for your help.!!!!
Mikey

[FORDification]

Well, that depends on what you find when you remove the inspection cover. I know I'm grasping at straws here, but the reason I was asking you about how it shifted was that I was thinking if the flywheel was loose or slightly warped, it would cause that vibration, and would cause clutch engagement problems. How does the clutch pedal feel when releasing it? Any pulsing sensations?