BB Idler pulley
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
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From: Forty Fort PA
BB Idler pulley
Hi Guys.
I know this topic may have been addressed before but this may be a slight variation. I have a BB in my 75. I put aluminum pulleys on the crank and water pump along with the idler set-up for the inner belt. The idler hits the pulley with about 2 inches of the adjustment slot left. A 34 5/8 inch belt is too short and a 53 1/8 inch belt is too long because the idler hits. By the way, it is a Merlin block and has P/S and A/C.
Any ideas or a pics of the idler/pulley fit?
THanks
Langg
I know this topic may have been addressed before but this may be a slight variation. I have a BB in my 75. I put aluminum pulleys on the crank and water pump along with the idler set-up for the inner belt. The idler hits the pulley with about 2 inches of the adjustment slot left. A 34 5/8 inch belt is too short and a 53 1/8 inch belt is too long because the idler hits. By the way, it is a Merlin block and has P/S and A/C.
Any ideas or a pics of the idler/pulley fit?
THanks
Langg
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Joined: Oct 2007
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From: Austin Texas
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you have a custom config.
you might specifiy what aluminum pulleys.
Thats like asking how big are my wheels ?
trail and error, in the custom world.
you might specifiy what aluminum pulleys.
Thats like asking how big are my wheels ?
trail and error, in the custom world.
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
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From: Forty Fort PA
Unfortunately, the pulleys are 'no-name' units. The water pump pulley is 6 1/2 inch diameter. I would have to either measure the crank pully in place or remove it. I am getting ready to raise the car for other work. I'll see if i can measure it then.
Langg
Langg
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Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
.
I dont know why you need a idler for the BB anyway...But since you must, Trying to adapt a given belt size to the pulleys will sometimes find problems as you experienced. Do it the other way around. When the pulleys are set, measure with another belt the idler and all pulleys related to the idler even if you have to cut it. Lay it out and tape the measurement. Then buy a belt that length....
I dont know why you need a idler for the BB anyway...But since you must, Trying to adapt a given belt size to the pulleys will sometimes find problems as you experienced. Do it the other way around. When the pulleys are set, measure with another belt the idler and all pulleys related to the idler even if you have to cut it. Lay it out and tape the measurement. Then buy a belt that length....
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
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From: Forty Fort PA
I see there is a typo in my first post.
A 34 5/8 inch belt (p/n 7340) is too short a 35 1/8 inch belt (p/n 7345) is too long. i dont think they make a belt in between. I can't get the 34 5/8 belt on even when I remove the water pump pulley, put the belt on then try to get the pulley back on. I can't get the 35 1/8 belt to tighten even with the idler. The idler hits the pulley when it is moved in the 'tighten belt' direction.
A 34 5/8 inch belt (p/n 7340) is too short a 35 1/8 inch belt (p/n 7345) is too long. i dont think they make a belt in between. I can't get the 34 5/8 belt on even when I remove the water pump pulley, put the belt on then try to get the pulley back on. I can't get the 35 1/8 belt to tighten even with the idler. The idler hits the pulley when it is moved in the 'tighten belt' direction.
Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
I was researching in the 71 Assembly manual a few weeks ago and I was suprised to see that on the BB cars there is a BB idler used. I thought it would be a fixed idler not a spring loaded unit.
Anyway try going to a little wider belt on the one thats too long
Anyway try going to a little wider belt on the one thats too long
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From: Wichita KS
cc
P.S. langg, you need to measure the original water pump pulley and crank pulley and try to find some the same size so the idler doesn't hit. Why would you swap pulleys without making sure they are the same size? Most likely the water pump pulley is all the needs replaced.
Last edited by CCrane65; Feb 6, 2009 at 10:09 PM.
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
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From: Forty Fort PA
The whole engine is a 'custom' setup. The only Chevy parts are the heads and the idler which is an aftermarket repro. I can put 'original' pulleys on. Will that solve my problem? Since the 3 groove water pump pulley is so expensive, I don't want to just buy one to see.
Langg
Langg
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From: Wichita KS
The whole engine is a 'custom' setup. The only Chevy parts are the heads and the idler which is an aftermarket repro. I can put 'original' pulleys on. Will that solve my problem? Since the 3 groove water pump pulley is so expensive, I don't want to just buy one to see.
Langg
Langg
cc
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From: Wichita KS
cc
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
Safety Car
Joined: Apr 2000
Posts: 3,802
Likes: 61
From: Wichita KS
You could try what a po had put on my engine. No crank to water pump belt or idler but rather a large belt over the A/C, crank and water pump. It did not squeal but it did have enough deflection that it was wearing a groove in my lower radiator hose.
That's why I took it back to the original belt configuration.
cc
Check out my reponse in your other post if you are looking for the original configuration of the belts.
That's why I took it back to the original belt configuration.
cc
Check out my reponse in your other post if you are looking for the original configuration of the belts.
Last edited by CCrane65; Feb 8, 2009 at 03:06 PM. Reason: correction RE: pulley vs. belt
