[68lemans462]

I've never had a problem with belts in the past. I had the same belts on for at least the last 15 years until last winter when I rebuilt my PS pump. I decided to throw some new belts on. I used the DAYCO Top Cog belts which seem to be complete JUNK.

At the dragstrip I will usually remove the PS belt its good for about a tenth in ET and I need all the help I can get.. The car has PS/AC (unhooked). The last 2 times out I've either broken or almost broken the ALT belt. I realize that hooking up the PS belt would likely fix/eliminate this problem and I may just start running the PS. At this stage I'm mostly removing the belt for consistency. My last 40 or so passes have been with no PS and I'm pretty closely monitoring timeslips.

At the dragstrip parts store they had this NAPA belt which is wider/deeper and way beefier. I bought it after breaking the first belt at the strip to get home. This is the only belt that continues to survive.

Despite the belt problems the car is running faster than ever. I had a new best time of 12.84 at 105.5 MPH last week in 9,000DA air at THUNDER MOUNTAIN.

Any suggestions appreciated. Thanks.

[PunchT37]

I`m just the opposite. The Top Cog`s are the only ones that will stay on mine. Seems they have more surface contact inside the vee. If I run cogged belts inside the pulley, off they go.

[form74]

I use the Dayco, lawn tractor belts, just need to match up the length, I have good luck with them.

[steve25]

If there's a Gates dealer near you, or a well stocked good size lawn mower / power tool repair shop see if they stock the Gates green series of belts in the size that you need, as this will cure your issue.

[lust4speed]

You need to take a really good look at the alignment of the alternator pulley in relationship to the crank and water pump pulleys. Just a slight misalignment will have the belt climbing up on the wall of the grove until it flips.

Are the bolts for the PS unit fully tighten back down when the PS belt is removed? The PS unit still provides additional support for the Alternator and any play in the mount would magnify problems.

I don't know whether you still have the stock '68 pulleys on the car or not, but my '68 that I sold had the wider 25-9520 belt on the PS and the narrower 25-7490 belt on the Alternator. The 9 series is a size larger than the 7 and would sit pretty high in the alternator pulley. Pontiac used different pulleys with different accessory combinations so the belts on my 68 might not have any correlation to the correct belts on yours.

[68lemans462]

Thanks for the info! I ended up finding both the Gates XL and Dayco green stripe XL belts. I found a nice Gates chart showing the different belt sizes. I ended up going with the Gates XL 9500 and 9510. Amazon Prime had the best price, just under $30 shipped for the pair. If they dont fit I'll just send 'em back.

[Formulajones]

I've pretty much had the same experiences over the years you've had. My Chevelle for a long time was horrible. I used to carry spares in the trunk.

It pretty much never liked the Dayco cogged belts, and honestly I never liked their appearance anyway. Tried some other cheaper belts with no success. Gates always seemed to be the belt of choice for this car. As they got harder to find over the years, I started using Napa Premium belts like you have pictured and those have also worked perfectly fine. I have those on just about everything nowadays with no issues on any of the cars.

Congrats on the new best time. Keep chippin away at it.. With that DA and those times, it's an easy mid 11 second car at probably 115+

I feel for ya on those DA's. It's constantly over 8000 feet here during the summer time.

[Half-Inch Stud]

ditch the full mech fan for a whimpy plastic "racer" fan, and rely on electric fan(s).

Alt should have the slightly larger Driven Pulley. 60s SD was a much bigger dia.

crank pulley ought be 6" not 8"

these things i know, except for the plastic "racer" fan is just an idea. I gots no mech fan.

[Formulajones]

I love my trusty mechanical clutch fans. I tried the electric fan route and while it looks clean and frees up a bit of HP, I learned they just don't do as good of a job cooling the engine. I went back to mechanical, I'm willing to sacrifice a little power in the sake of cooler temps and reliability.

[Gary H]

Do you have the hockey stick shaped reinforcement bracket that goes from the alternator bolts down to the power steering bolts? It has two bolt holes at the top and one at the bottom. This bracket strengthens the alternator where it's attached so it can't flex. It's also listed in the Ames catalog. If you don't know, take a picture of the front of your alternator and PS setup so we can see.

[Half-Inch Stud]

...I removed those brackets "all the time teens-30s". NOW since all me Manifolds are cut, i'd like 1 Bracket back.

I'd love to put a Mech Fan back on for the Super-assured Cooling at idle and Stoplights. My "combo" is 95% just fine. That last 5% is concern for Cooling Margin for the Starter.

Either the Driver Header goes to Round Port Manifold, or a Mech Fan of soome sort, or Both.

[68lemans462]

Originally Posted by Gary H

Do you have the hockey stick shaped reinforcement bracket that goes from the alternator bolts down to the power steering bolts? It has two bolt holes at the top and one at the bottom. This bracket strengthens the alternator where it's attached so it can't flex. It's also listed in the Ames catalog. If you don't know, take a picture of the front of your alternator and PS setup so we can see.

Yes I do have this piece and my brackets are 100% complete and original. And the belt is TIGHT

[Jay S]

You might try speeding the engine up and watch the belts too see if they start to whip at higher rpms. If the belts run steady it is more than likely an alignment issue. If the belts whip it is more of a balance issue. Usually the crank dampener or one of the driven accessories causing the whip. Combining a harmonic frequency with the load the belts will break. We had an engine we kept installing new belts because we thought we had a alignment issue, spend a ton of time on alignment. It turned out the dampener was going bad. It does not take out of balance much to make belts whip.