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View Full Version : Belt Size? Under drives / Stock Alt Pulley



Dahoopd
10-10-2008, 01:34 PM
Anyone have the correct belt size for running under drives, w/AC and the stock alternator pulley.

mywhite89
10-10-2008, 03:12 PM
As far as I know You can run the stock belt with underdrives. I guess since you plan to run the stock alternator pulley, you may need a a belt that is 1/2 to 1" shorter then stock possibly. I know I am able to use the stock belt using just the underdrive alternator pulley.

Dahoopd
10-27-2008, 08:40 PM
Anyone have any help on this. I have tried 5 belts and cant get it right.

CaifanSC
10-27-2008, 11:54 PM
if by 'cant get it right' u mean the belt aaaaalmost touches between the water pump pulley and the top idler...then thats fine...tons of people are running like that without issues. I've ran the UD's in 3 of my sc's like that w/o probs.

Dahoopd
10-28-2008, 07:00 AM
if by 'cant get it right' u mean the belt aaaaalmost touches between the water pump pulley and the top idler...then thats fine...tons of people are running like that without issues. I've ran the UD's in 3 of my sc's like that w/o probs.


Yes, and that doesn't look safe to me. What happens when the ragged out tensioner spring decides its just not ragged out enough and gives in to that little 1/8 inch gap.

There has got to be a belt that works.

Mike Puckett
10-28-2008, 09:40 AM
I put the smaller diameter sc tensioner pulley up on the tensioner by the alternator. It gives me a little more clearance above the water pump pulley. When you rev the motor, notice that the tensioner pulley moves away from the water pump pulley and the space gets bigger not smaller. I used to worry about this too but I've never heard of anyone having a problem.

ricardoa1
10-28-2008, 10:32 AM
Yep, people at the Shootout kept asking me if that was a problem and I told them I never had issues.

Dahoopd
10-31-2008, 08:33 PM
There must be some other issues. I have the K080893 belt with the under drive alternator pulley to take up the slack and the belts still touch.


I will try my 6th and final belt from Napa. After that its 5 rolls of electrical tape wrapped all the way around the pulleys. I think the old saying is.......6 times a charm.

Dahoopd
11-10-2008, 10:56 PM
Well it must be a problem with the configuration of the pulleys I used. I assume the the diameter differences have made the issue. I have the AC delete pulley, the aluminum tensioner pulleys from spinning wheels, underdrives and the belt is too long. If I get a belt one step shorter, its too short for the underdrive alt pulley and too long with the stock alt pulley on.

I cant find an in between. The only option I have left is to get an SC tensioner and try that. Its always the stupid ~~~~ causing a problem.

SC Spyder
11-11-2008, 10:59 AM
While my experience is unique (read that as custom SC engine in a none SC chassis) you might find the information helpful.

I removed the pwr steering pump, A.C. compressor and added a 5% Jackshaft pulley, this required me to hand select all the new belts.

If you go on line to the Gates & Gaterback sights you can find a listing of all the belts that are available listed by the number of ribs and length. If you have the part number for the belt that is too long, you only need to see what is available in the next size down. Every part store I have dealt with has allowed me to take a handful of belts with me to try and as long as I have not damage the belt or soiled the packaging, allowed me to return the unused belts. I the case where I removed the power steering pump, I ended up reversing the idler spring by cutting off the stop tab and winding it the other direction and re clocking ( rotating the idler assembly and drilling a new locater pin hole).

In one case, for the crank to jackshaft pulley, a 7 rib pulley was not available so I used a 6 rib pulley. The only problem I have had is when one of the belts stretched and began to slip and replacing it with the next size smaller took care of that problem.

Hope this helps.

Dahoopd
11-11-2008, 10:17 PM
Does anyone see any problems using a 6 rib belt for the main belt. I found one that works until I find an 8 and it has about 1/2 inch space. I am glad because it was rubbing itself pretty bad.

Dahoopd
11-11-2008, 10:18 PM
I used a 6 rib pulley.

Just caught that :o

David Neibert
11-12-2008, 01:18 AM
Yes, and that doesn't look safe to me. What happens when the ragged out tensioner spring decides its just not ragged out enough and gives in to that little 1/8 inch gap.

There has got to be a belt that works.

1/8" is plenty of clearance...I drove mine for years that way and Kurt K's was even closer, with barely enough space to slip a matchbook cover between the belts.

David

PS: 6 rib belt will work fine.

Dahoopd
11-12-2008, 08:35 AM
1/8" is plenty of clearance...I drove mine for years that way and Kurt K's was even closer, with barely enough space to slip a matchbook cover between the belts.

David

PS: 6 rib belt will work fine.

Dave,

I used the K080897 (Nappa) belt instead of the K080893 (Autozone) and it stretched to the point of rubbing itself on the water pump. I got the K060883 from Nappa and its 7/8 shorter. Its only a 6 rib but it gave me about 3/4 quarter of an inch gap. I have to special order the 8 rib K080885HD

SC Spyder
11-12-2008, 12:00 PM
Dahoopd - I ment to say that I used a 6 rib belt (not pulley) because a 7 rib belt is not available in the size I need. At any rate, it is not slipping.

Do verify how much tension is bing applied to the belt, If you have clocked the idler, you could have enough clearance but not enough tension.

Sorry for the brain fade

David Neibert
11-12-2008, 05:24 PM
Dave,

I used the K080897 (Nappa) belt instead of the K080893 (Autozone) and it stretched to the point of rubbing itself on the water pump. I got the K060883 from Nappa and its 7/8 shorter. Its only a 6 rib but it gave me about 3/4 quarter of an inch gap. I have to special order the 8 rib K080885HD

If that doesn't work out you can always do this style AC delete belt routing and tensioner.

http://i251.photobucket.com/albums/gg286/wzenheimer/enginepicsandvids002.jpg

http://i251.photobucket.com/albums/gg286/wzenheimer/enginepicsandvids003.jpg


For part numbers on the same setup with an 8 rib belt see this post.

http://www.sccoa.com/forums/showpost.php?p=778594&postcount=67

David