The Stovebolt Site Forums The Shop Area Engine Shop Sreaming fan belt

On to the next problem. About 2500 rpm, my 235 fan belt starts to scream like a stuck pig. The belt is new, and the alignment appears to be fine. I tried some belt dressing, but it gave little benefit. Any suggestions?

I didn't think they were prone to squeal at higher RPM's. Is the alternator tight enough?
If so, I would say that it's something more than just the belt.

I looked back at the picture, and it looks like you are about out of space for adjustment.
Maybe a sorter belt might help? (Just a thought)

Belts scream for various reasons. Although new to you it may be old stock. The belt being too narrow.. it seams to be going rather deep in your crank pulley. Belt being too loose or too much load. Is your battery discharged so that your alternator is really working? Once a belt has slipped a lot and gets shiny, it will scream no matter what you do. Possibly a little wider belt would help. The numbering denotes the length and width of the belt. I usually tighten a belt until it deflects about 3/4" at the longest span and then recheck it after it has run for a while.

I have had new cheap belts do that....Joe

crenwelge - You're right, the belt rides fairly deep on the harmonic balancer. The belt is 1/2-inch wide and "V-shaped", so maybe a slightly wider and shorter belt would help? The battery is new and charged, so that shouldn't be a problem. Will a wider belt still fit the water pump and alternator?

If its not as deep in alt, and water pump your dampener pulley may simply be worn out allowing belt to bottom out

From your picture it appears that the belt has a "roll" on the bottom of the alternator pulley.....the belt should be tensioned so that there is only a 1/2" up and 1/2" down flex from the centerpoint between the pump and the alternator.

Looks to me like 54 TOW is correct in you needing a slightly shorter belt so you can snug it down a tad more. You can't go wrong with the Goodyear Gatorbacks. Also, on the belt dressing......if a belt needs dressing you need a new belt. Your belt just needs to be properly tensioned.

Dave

Same thing here Dave, first thing I see when I look at the picture is a sag at the bottom of the belt from the balancer to the alternator, much to loose, gonna screech like a "stuck pig".
DG

Dave,when i first built my engine,i couldn't get the belt tight enough.Wrenchbender from this site looked at it,and told me i had the tension bracket on the wrong bolt hole of the water pump.I changed it like he said,problem solved.Maybe this could be your problem also,looks like you are all the way tight on the bracket.

Looks like he did run out of hole on the tensioner. I don't think there is another hole that would give more length. He might just have to get a longer tension bracket to make up for the difference between a gen and an alt.

Or a smaller diameter belt.

Could the harmonic balancer be for a 5/8" belt ?
I know my 1954 261 runs a 5/8" belt.My water pump and the pulley i bought for the alternator is 5/8" .

What year is your 235 ?

Problem solved! Based on all of the good advice above, I installed a new fan belt. This belt is the same length as the last belt, but is slightly wider. The wider width causes it to ride higher on all three pulleys, and pulls the alternator toward the engine. I also increased the tension on the belt. Several test drives and not a whisper from the belt. Thanks, guys!

FYI - the engine is a '59 235. The old belt size was a 15385 and the new belt is a 17385. The guy behind the counter at my FLAPS tried to convince me that the first two digits on the belt number are the width of the belt in millimeters, and the last 3 digits are the diameter in millimeters. However, this can't be right, because the new belt measures exactly 1/2-inch wide. A 17-mm belt would be 0.67 inches wide (there are 25.4 millimeters in an inch).

Anybody know how fan belts are measured?

That looks right,glad you got it fixed.

Hello, saw this chat and thought I would throw in my 2cents worth. I had been fighting a squeal on my 56 265V8 when reving up and put new belts on a couple times too. Finally decided to go with a wider belt, and found out that my harmonic balancer pulley is for the narrow belt, and my water pump and alt are made for the wide belt. So at some time somebody swapped in a different balancer that was not the right size. So now I'll need to find one, but I know I'm on the right track now.