How much travel is too much for my timing belt pulleys?

[RobertwFiat124]

Both my intake and exhaust pulley shimmy just slightly but they don't seem terrible and don't make noise. What could this be and how serious is it?

[SteinOnkel]

Given that Fiat did not mess around with the engineering on their excellent twin cam engines, I would say the tolerance for play in the cam sprockets is between "zero" and "none at all".

On a different car, I've broken them off before. It doesn't take much.

I wouldn't run your engine until you get to the bottom of it.

[RobertwFiat124]

I have no idea if it may be an illusion with my pulleys just being dirty. When I did the timing belt they seemed firm as hell and didn't move or wobble in the slightest when pulled on and tested.

[18Fiatsandcounting]

Robert with Fiat 124, can you describe "shimmy"? There is a metal lip on the outer circumference of each pulley, towards the engine on the intake cam pulley and away from the engine on the exhaust cam pulley. These lips often get slightly deformed, and I guess that could give the appearance of the pulley shimmy-ing as it rotates. The lips are there to prevent the belt from sliding off the pulleys.

Does the body of the pulley (where the belt rides) move in and out as the engine runs? If it's just the lip (not uncommon), you can take off the pulley and lay it on a flat surface, and gently pound the lip so it's true again.

-Bryan

[RRoller123]

+1, we just had this with one of the adjustable pulleys here in Frankenstein's Laboratory. The lip was bent during shipping, looked like the wheel was bent, but it was only the lip. Easily straightened.

If you can get a dial indicator on the body of the wheel and check it, that will tell the story. Either a 38 mm socket or a 1.5" socket up front will turn the engine by hand.