How much tension? Drive belt pulley

[J1MMY]

Hello all

Belt was slipping on my '94 Sierra (4.3, ex USAF beater, no a/c) so ordered in new tensioner and belt. Fitted up and there is really not much tension there at all. Offered the new and old belts up and there is no discernible difference. I have spotted that there is a small aftermarket idler pulley. It is 3" diameter. Is this correct?

[mountie]

Would you take a photo of the aftermarket pulley?

[EVRLET]

Even though I don’t own a 4.3, I went through something similar with my 5.7. I own a 1997 Silverado. There are two different alternators. One for a Silverado with all the bells and whistles, and one for other models who don’t need the extra amperage. Because of the two alternators, there are two different belt sizes. The difference in size for the two belts could only be seen when you use an actual belt measurement tool. When I held it up and stretched it in my hands, they looked identical but they were not.

[J1MMY]

Idler pulley....



Interesting to note on the belt....part no. on the new one is RK638.

[mountie]

I can't see the pic. ( It says to update photobucket account)

[J1MMY]

See if this works....

[mountie]

Opps... I was wondering where it was located on the truck...

The outside diameter / width ? But if it's on the spring loaded tensioner, any dealer will tell you the correct size / part

[J1MMY]

Idler pulley sits to the left of the tensioner (when stood at the front of the truck looking in) - presumably where the A/C goes on vehicles that have it.

[Killer Bee]

agree with above, I would call local dealer with vin, eng, make, model, etc. and they should get to the bottom of it for you.. I would also ditch that unknown aftermarket junk and go back with proper factory a/c or non-a/c serpentine set up..

while a non-a/c engine may have an idler where the compressor would be to keep belt route typical, the idler may not be the same diameter as the compressor pulley so two belt lengths may be available..

good luck!

[mountie]

I can't post a photo of a pulley I have. ( I have a frustrating "script blocker" that won't turn off)...

The pully is designed to replace the A/C unit , if removed. Google it.

[Killer Bee]

Originally Posted by mountie

I can't post a photo of a pulley I have. ( I have a frustrating "script blocker" that won't turn off)...

The pully is designed to replace the A/C unit , if removed. Google it.

here ya' go mountie, something like this to run same length belt?

A/C Compressor Bypass Pulley

whole page full popped up with 4.3 chevy search so not sure if this image is accurate but illustrates purpose..

[mountie]

That's correct..... it's for when an A/C compressor is removed. It takes it's place if that's what your old belt ran around.

[J1MMY]

Interesting pic. I'd also be curious to know the diameters of both alternator pulley types.

Going to a dealer isn't an option as they didn't sell these here on my little island. Tbh I would be surprised if this ever had aircon as most of the ex-forces trucks which surface over here are base models. There is also nothing on the heater panel to suggest it. I take it the bracketry on the front of the engine would be the different for a compressor than that for an idler?

[Kudzupatch]

Why not just buy a little shorter belt?

[mountie]

Originally Posted by Kudzupatch

Why not just buy a little shorter belt?

Not as easy as you would think.... I tried that once. ( Then I got the A/C adapter pulley)

[Killer Bee]

Originally Posted by Kudzupatch

Why not just buy a little shorter belt?

without routing the belt correctly, some of the driven accessories may suffer from lack of belt engagement or friction, and slip..

either a factory delete idler with spec'd shorter belt or a compressor pulley size idler with standard belt would be the best solutions..

[LT7A]

J1MMY, if it doesn't seem like you're getting closer to a solution, maybe you can post pictures of all of the relevant aspects of your setup? Not sure how many 4.3ers there are here because of these being full size trucks but I know there are a few around. CapeCodder has one and is a talented guy. Maybe you can ping him and swap some info. I have a 1999 S15 Jimmy with the 4.3 and could take a look at specifics but I don't know if it's the same setup. Not so easy for you to find one local to look at I'd imagine.

[J1MMY]

I should have come back and posted earlier - I had a chance to get to a local parts factor and sorted the issue with a 2330mm belt. About 1/4" deflection in the belt (max) and a squeal-free consistent charge. I have no idea if my alternator or idler pulleys are stock but it works. Very happy.

[Killer Bee]

happy ending

[diveplane]

Originally Posted by J1MMY

Hello all

Belt was slipping on my '94 Sierra (4.3, ex USAF beater, no a/c) so ordered in new tensioner and belt. Fitted up and there is really not much tension there at all. Offered the new and old belts up and there is no discernible difference. I have spotted that there is a small aftermarket idler pulley. It is 3" diameter. Is this correct?

pulley unit is self tension , theres maximum and minimum marks on the pulley tensioner unit.

[diveplane]

Originally Posted by mountie

That's correct..... it's for when an A/C compressor is removed. It takes it's place if that's what your old belt ran around.

yes a locked ac compressor can leave u stranded on the road good to have this bypass pulley in the cab.