[C2] Idler pulley purpose
05-24-2017, 09:32 PM
#1
Racer
Thread Starter
Idler pulley purpose
I do not know the purpose or reason for the idler pulley that was original equipment on my original 340 HP engine. I still run an idler pulley on my current power so having the reason would be an interesting bit of information. I did find them on 409’s in the junk yard back in the day. Thanks in advance and safe driving to all.
Steve Stone (original owner ’63 triple black convertible, 550,000 miles)
Steve Stone (original owner ’63 triple black convertible, 550,000 miles)
05-24-2017, 09:47 PM
#2
Safety Car
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Hi Steve,
I admire your use of your midyear! Someone once said it ain't the destination, it's the journey
Kudoos to you and yours! To your question, I believe all the solid lifter small blocks had the idler pulley because of their higher revving capabilities. The pulley was deep grooved to aid in keeping the belts from spinning off at those higher r's. Others will chime in on this.
Regards,
Jim
In God We Trust!
I admire your use of your midyear! Someone once said it ain't the destination, it's the journey
Kudoos to you and yours! To your question, I believe all the solid lifter small blocks had the idler pulley because of their higher revving capabilities. The pulley was deep grooved to aid in keeping the belts from spinning off at those higher r's. Others will chime in on this.Regards,
Jim
In God We Trust!
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Steve Stone (05-24-2017)
05-24-2017, 10:59 PM
#3
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Hi Steve,
I admire your use of your midyear! Someone once said it ain't the destination, it's the journey Kudoos to you and yours! To your question, I believe all the solid lifter small blocks had the idler pulley because of their higher revving capabilities. The pulley was deep grooved to aid in keeping the belts from spinning off at those higher r's. Others will chime in on this.
Regards,
Jim
In God We Trust!
I admire your use of your midyear! Someone once said it ain't the destination, it's the journey
Kudoos to you and yours! To your question, I believe all the solid lifter small blocks had the idler pulley because of their higher revving capabilities. The pulley was deep grooved to aid in keeping the belts from spinning off at those higher r's. Others will chime in on this.Regards,
Jim
In God We Trust!
Jim, I agree with you, you got it right.
Dave
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6T5RUSH (05-25-2017)
05-24-2017, 11:40 PM
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St. Jude Donor '07
you can eliminate the idler pulley and use the 'right length' belt that just fits between/around the crank pulley and the water pump pulleys.
Bill
Bill
Last edited by wmf62; 05-25-2017 at 07:36 AM.
05-25-2017, 05:54 AM
#5
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The idler pulley was added to keep the water pump spinning in the event of throwing the alternator belt in competition.
You can run without an alternator and fan but you won't get far without a pump.
You can run without an alternator and fan but you won't get far without a pump.
Last edited by MikeM; 05-25-2017 at 05:55 AM.
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PeteVS (05-25-2017)
05-25-2017, 10:38 AM
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Hi Bill, That's exactly how I'm running mine.
MikeM, you are right on about the result of throwing belts ar high r's,. Having the idler in place DOES keep that water pump running.
Jim
In God We Trust!
MikeM, you are right on about the result of throwing belts ar high r's,. Having the idler in place DOES keep that water pump running.
Jim
In God We Trust!
05-25-2017, 11:07 AM
#7
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The idler pulley is the belt tensioning element. The moveable gen/alt is the tensioning element for the other belt. As stated, some later dual pulley setups used a "captured" belt that has no tensioning element, but changing it requires removal of the water pump pulley, and it can be a real pain getting it reinstalled against the new belt tension.
BTW the sealed bearing in the idler pulley can be replaced if it goes bad - just like a water pump bearing. Give the number stamped on the bearing to a bearing supply house and they should be able to come up with a current replacement.
Duke
BTW the sealed bearing in the idler pulley can be replaced if it goes bad - just like a water pump bearing. Give the number stamped on the bearing to a bearing supply house and they should be able to come up with a current replacement.
Duke
05-25-2017, 11:28 AM
#8
Safety Car
Correctamundo...............threw 3 alternator belts and the idler kept the pump spinning.
There were some 1965 L79s without power steering that used a "captured belt" between the crank pulley and the pump pulley with no tensioner. It was a stopgap that filled the same purpose as the idler or the power steering pump.
There were some 1965 L79s without power steering that used a "captured belt" between the crank pulley and the pump pulley with no tensioner. It was a stopgap that filled the same purpose as the idler or the power steering pump.