[redbird68]

Hi guys
I am chasing down a belt squeal and I believe I have incorrect pulleys.
My goat...AC, PS car, has a single groove water pump pulley. Not a pulley expert, but I believe this would be for a manual steering car?

I believe the squeal is most likely caused by incorrect belt widths....current belts are Gates 7490 for alt and Gates 7480 for PS. You can see they ride at different heights in the crank pulley, and manual shows should be 3/8" belt for alt and 15/32" for PS....not same width for both (they are both 0.41", or 13/32" wide).

I will try to find correct width belts or as close as i can and hopefully squeal will be gone.

What I am wondering about is if the single groove water pump pulley is causing me problems. not much belt contact on the pulley, less than 90 degrees. Car does not overheat though. OE fan with clutch. I do not use the AC, but might in the future.

I have a 6-1/2" (AC car) water pump pulley, 2 groove, from a 68 motor, 978886 XT that I believe is in usable shape. Do you recommend i install it and then run a PS belt correctly? Or just replace belts and not worry about it?

[400 Lemans]

I would definitely use the 2 groove pulley with the correct wider PS belt. As it is right now its just using the crank and PS pullies. So adding the water pump pulley gives you that 3rd pulley that be help with the squealing, adding a little more friction. It will also be factory correct.

[redbird68]

Thanks 400L, and I agree with you.
The engine is actually a 1968 400 with 8 bolt timing cover so the 9788886 XT pulley I believe is correct in terms of belt alignment. Visually it appears to be.

I need to clean it up and paint it. Reading old threads I see that some guys recommend not painting in the grooves of the pulley to reduce chances of belts slipping. I have always painted in grooves and not had problems, but always looking to learn. The paint I typically use is POR15 flat black. I will clean pulley with blast cabinet, 80 grit.

Thoughts on painting in grooves?

[ZeGermanHam]

I agree with the need for a 2-groove water pump pulley. As it is currently, the belt squeal is probably coming from the water pump which doesn't have a lot of belt contact at the moment. If it had a second belt which also had more contact around the radius of the pulley to spin the PS pump, the belt squeal will almost certainly go away. Look at how much more traction the WP pulley will have with two belts:

[Joe's Garage]

You alternator belt is a 15/32" wide belt, which is what the factory originally used.

The power steering belt needs to be a 17/32" wide belt or it will ride on the bottom of the pulleys rather than the sides. That is probably what is happening now.

I agree that the water pump would be better served with a 2-groove pulley, so long as the depth is correct for your water pump length.

With that said, I'd speculate that YOUR squeal is due to the thinner belt being used on the power steering.

You could verify this by simply removing the power steering belt and seeing if the squeal goes away. Won't cost anything except your time.

We've always glass-beaded pulleys and repainted with a semigloss black paint. As long as the correct width belts were used and the tension was right, they haven't slipped or squealed afterwards.

Good luck!

[vertigto]

I'm also fighting belt squeal on my 70 400 under moderate acceleration and assume it is the PS belt (hydroboost setup). Not sure what the shop put on, but it appears to be 16/32" and sits a tad higher in the groove than the other belts...which seems odd if 17/32" is factory.

Which manufacturer/length have you had good results with 17/32" belts??

[redbird68]

No more squeal! I can rev the motor without gritting my teeth.
I installed the 2-groove pulley, after blasting and painting, masked off the grooves so they received no paint.
Measured with a cloth tape and ordered new belts from O'Reilly, so I could easily exchange if needed different lengths.
Ended up with Gates XL belts, about $30/each.

Alternator 7490
Power Steering 9525
AC 9590

All went on ok, but PS and Alt belt were a struggle to get on, a little longer might have been better. I assume they stretch a little so maybe ok, but either way I will retighten after a little driving.

Bought Krikit gauge off Amazon for $20 or so, seems to work well.
I tightened the belts more than I would have if I did not have the gauge and went by feel only.

Service Manual specs for belt tension:
New belt Used belt
Alternator 120 lbs 70 lbs
Power Steering 145 105
AC 145 105

I was not able to get numbers that high for new belts but got close. Much tighter than I am used to running.

Belts fit the pulleys much better now.

Thank you all for your help. Very nice to eliminate the squeal.

[Joe's Garage]

Congratulations on getting rid of that annoying squealing !

It's always nice when a project goes the way you planned.

I'm amazed that so many sources (like RockAuto) specify skinny 15/32" belts for the power steering. They NEVER work right because the grooves in the pulley are just the right width and depth for them to ride lightly on the sides and tighten against the bottom of the pulley. Squeal city!

And, yes, the new belts will loosen up slightly after some driving, but now you know the drill to correctly tighten them right back up.

Have fun!