Rebuilt Engine Trouble

[Axlman]

Need your expert advice.
Rebuilt the 350 and installed.
Now have a wobble when it is in idle and running.
Shakes and wobbles badly.
Tried everything, new wires, new carb, adjusted timing, new plugs, and it stays the same.
I am thinking that the flexplate got bent but it was never at riskof any damage.
Also started to think maybe an issue because the flex-plate seems to have a counterweight and I think it shouldn't. But the trans and engine and flexplate are the same as before. No changes.
I am stumped.
Any thoughts or similar experiences?

[Mike S]

 When you say "wobble" are you referring to an engine balance/shake issue?
What work was with the engine rebuild? My initial hunch, if wobble is engine shake/balance, is to check the vibration damper to make sure the rubber is not damaged causing the outer weight to slip on the inner shaft bolted to the crank.

Mike

[CNorton]

350 short blocks are internally balanced.  Neither the damper nor the flex plate should have a counterweight.

c

[RonA]

Hi.  I assume that your 350 is a older one [ 2 piece rear main] then as stated it should not have any counterweights.  If by chance it is a newer one piece seal the balancing is different and the flex plate may be in the wrong position.

[69pace]

I assume you are noticing a rpm hit so you think its internal to the block, or is this an exterior vibration and maybe you have a loose or broken mount, crossmember, or something else free in the drivetrain  and or loose subframe bushings?

[Charley]

Have you triple checked that you don't have any plug wires mixed up ?

[miket1]

Did you install a different flex plate from previous,

[ko-lek-tor]

Did you install a different flex plate from previous,

"Also started to think maybe an issue because the flex-plate seems to have a counterweight and I think it shouldn't. But the trans and engine and flexplate are the same as before. No changes."

[Axlman]

Same flexplate.
Drove it on a trip and it ran terribly, used 7 tanks of gas and sputtered.
But it didnt shake and wobble really bad.
Now it is wobbling. Seems to be at the flexplate in my opinion.
you can see it shake and wobble at idle and it gets bad and is loud at high rpm.
But I have checked wires and plugs numerous times.
Going to try another new set of plugs today and see though.

[janobyte]

Let's see, ruled out plugs (one fouled plug will do it), wires( correctly routed/firing order), cap (hairline cracks, moisture), and rotor. Ignition.


Carb "sucking air" through the gaskets, base plate ? Vacuum leak: hose cracked, unattached, intake ports ?

Running rich? float level, needle and seats bad, o rings allowing fuel passage when closed?  Any recent backfires through the carb?

[KurtS]

Please explain what is wobbling.

[ss jim]

If it was a rather short trip and used 7 tanks of gas I would be looking at a bad needle and seat or choke partially closed. Don't ask how I know about the choke. Jim

[Axlman]

The wobble feels like it is at the flex plate and torque converter. It actually sounds like it is loose and shaking there between the seats while driving(all bolts are tight). (maybe torque converter is in wrong?)
I am going to try to change plugs today in about an hour. If there are no improvements after that I will pull tranny and flex plate maybe and see if it is cracked or warped maybe.
Could be running rich but i have put a Carter carb on as well as the rebuilt Rochester Quadrajet. Wobbles and shakes with both and when they are adjusted.

[BULLITT65]

May sound dumb, but firing order could be re-checked. What about drive shaft out of balance?
I understand most of the items are the same that came out of the car but stuff happens sometimes, and it is just a matter of tracking it down through a process of elimination.

[ko-lek-tor]

May sound dumb, but firing order could be re-checked. What about drive shaft out of balance?
I understand most of the items are the same that came out of the car but stuff happens sometimes, and it is just a matter of tracking it down through a process of elimination.

I kind of ruled out the drive shaft as OP said it was occurring at idle and the D. shaft would not be turning. Might want to check the pushrods and do a compression check before tearing into the trans. area to rule out the engine being sick. I am confident I could diagnose and repair if I were there. Hard to do so far away though.