bad engine vibration

[JBsCamino]

Helping out a buddy. He had a bad engine vibration, bought the car that way. He is pulling the motor and it looks like 4/7 cylinders were never working. Other than plug wires incorrect, what would cause this?

I wouldn't think it would have even ran this way. He said the vibration was pretty constant but would decrease at certain rpms. He already removed all the plug wires, so there is no way now to see if it was wired wrong and engine is about pulled so can't just quick put it together to check.

Any thoughts on what else to check?

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• JBsCamino
• Mar 22, 2016

 

[JBsCamino]

BTW this is a ford 302. He thought maybe the vibration was an incorrect flexplate since the SBF'S had a few different weight flexplates but then found this when pulling the motor.

 

[pontiacgp]

did you check for spark at the plugs and valve lash before it was pulled? Also I have seen the wrong plug being used and depending on the position of the ground strap on the plug it could get hit by the piston. I have also seen a Ford engine that had two plugs that sat too deep from some work done to the heads and they got hit by the piston which killed those plugs

 

[-83MONTESS-]

Check timing? My 496 made had a similiar issue. Turns out it was wayyyy too advanced.

 

[Texas82GP]

I'm not a small block Ford expert by any stretch, but I think I have read they have two different firing orders based on the Era of the cam. I think if for example it is a late Era cam in an early Era motor and vehicle it would be easy to install the plug wires correct for the car (say according to the shop manual), but wrong for the cam and you would have that sort of result. For example if it were a cam that is correct for a 90's Era engine in a 289 in a 65 Mustang and the plug wires are installed correct according to the shop manual for the Mustang but wrong for the firing order for that cam. Or the opposite, an early firing order cam in a late model installation. Hope this helps.

 

[gbondo57]

What he said! Try swapping the 4 and 7 wires, if it smooths out, that is the cams firing order. they make 4/7 firing order swap cams. I'm no ford guy, but heard that too.