Engine shakes under acceleration

[standup303]

360LA the engine seems to shake under acceleration. It’s a hard vibration almost. As soon as it hits about 2,000 rpm and about 1/3 throttle it starts. Do you guys have any tips?

 

[Inertia]

Missed any shifts or over-reved it lately ?

 

[standup303]

Missed any shifts or over-reved it lately ?

I have not.

 

[RustyRatRod]

If it does it in park or neutral, it's very likely an imbalance of some sort. The 360 is externally balanced from the factory. I would look for maybe evidence the balancer has slipped. Maybe get a good picture of the balancer and post it.

 

[bcschief]

Possibility of mismatched torque converter or flywheel?

 

[Bewy]

Is it smooth at idle & then rough at 2000? If so, I agree with above.
If rough everywhere, I would looking at anything that causes a variation between cyls: fouled spark plug, burned valves, wiped lifter/lobes, etc

 

[AJ/FormS]

360LA the engine seems to shake under acceleration. It’s a hard vibration almost. As soon as it hits about 2,000 rpm and about 1/3 throttle it starts. Do you guys have any tips?

Is that stall rpm?
Is it better when cold?
Is it worse with more throttle?
if yes times 3, then check your firing order, and separate numbers 5 and 7 wires. If those are ok, then disconnect the Vcan and roadtest again. If still bad, check the Power-timing beginning at whatever rpm it starts . Make sure TDC of the piston is TDC on the balancer.
Pre-Ignition going to detonation, can feel like that. Detonation must be Eliminated.

 

[teringer]

Was it right and now has a problem. Also see if dist loose and turned

 

[RustyRatRod]

Was it right and now has a problem. Also see if dist loose and turned

That's why I mentioned the balancer slipping.

 

[4mulas]

Check plug wire at the cap and plug gif being on tight.

 

[moparlvr166]

Under heavy load as if hard acceleration? possible something is loose causing engine, trans, exhaust contacting body or frame causing vibration? Possible engine misfire under load? try lightly power braking engine slowly up to stall speed or 2,000 rpms and see if you can feel the miss, just don't overheat the trans fluid.

 

[Charrlie_S]

What transmission? If a lock up , could be converter clutch shudder. Does it do it in all gears or only in 3rd?

 

[Dave999]

cracked flexplate ?

 

[TrailBeast]

Lots of guessing with near zero information.

 

[Woodys_Cuda]

Crickets.... after so many people trying to help out...

 

[RustyRatRod]

Lots of guessing with near zero information.

So typical for this place.

 

[RustyRatRod]

Crickets.... after so many people trying to help out...

Nobody's times is worth anything. Dontchya know?

 

[standup303]

If it does it in park or neutral, it's very likely an imbalance of some sort. The 360 is externally balanced from the factory. I would look for maybe evidence the balancer has slipped. Maybe get a good picture of the balancer and post it.

If parked and I Rev to 2k I can feel it. But not at idle. I checked the balancer to see if it felt loose at all and seems good. I can’t get a good eye on whether it slipped or not. I’ll have to dig in more this weekend.

 

[standup303]

What transmission? If a lock up , could be converter clutch shudder. Does it do it in all gears or only in 3rd?

It’s a 727. It will shake in all gears.

 

[standup303]

Under heavy load as if hard acceleration? possible something is loose causing engine, trans, exhaust contacting body or frame causing vibration? Possible engine misfire under load? try lightly power braking engine slowly up to stall speed or 2,000 rpms and see if you can feel the miss, just don't overheat the trans fluid.

I will give this a try. Thank you.

 

[standup303]

Is it smooth at idle & then rough at 2000? If so, I agree with above.
If rough everywhere, I would looking at anything that causes a variation between cyls: fouled spark plug, burned valves, wiped lifter/lobes, etc

Yes smooth at idle.

 

[standup303]

Is that stall rpm?
Is it better when cold?
Is it worse with more throttle?
if yes times 3, then check your firing order, and separate numbers 5 and 7 wires. If those are ok, then disconnect the Vcan and roadtest again. If still bad, check the Power-timing beginning at whatever rpm it starts . Make sure TDC of the piston is TDC on the balancer.
Pre-Ignition going to detonation, can feel like that. Detonation must be Eliminated.

I’m not sure on stall. The car is new to me. The shake comes around whether cold or warm. Definitely gets worse with more throttle. I’ll try this out this weekend.

 

[RustyRatRod]

If parked and I Rev to 2k I can feel it. But not at idle. I checked the balancer to see if it felt loose at all and seems good. I can’t get a good eye on whether it slipped or not. I’ll have to dig in more this weekend.

Put a timing light on it. You'll spot it real quick if you cannot see the timing mark on the balances, or if the mark is WAY off the pointer.

 

[RustyRatRod]

If parked and I Rev to 2k I can feel it. But not at idle. I checked the balancer to see if it felt loose at all and seems good. I can’t get a good eye on whether it slipped or not. I’ll have to dig in more this weekend.

Yup. Classic imbalance vibration.

 

[Woodys_Cuda]

Mr dramatic. Busy work week.

Mr dramatic, not really. Was expecting another post and run, others were thinking the same after a week...it only takes a couple of seconds to say "Thanks, I'll get back to you guys". *sigh* Anyways, good luck.