<VV> Aluminum Pulley - or idler assembly?

Sethracer at aol.com Sethracer at aol.com
Sat Jul 17 15:33:59 EDT 2010

In a message dated 7/17/2010 12:05:33 P.M. Pacific Daylight Time,  
rtruss65 at yahoo.com writes:

I've  tried the aluminum underground idler pulley. Dazaling perhaps, 
however, I  
think it's a bolt-on fix for the other "real" problems that cause the  belt 
toss. In addition, the underground "car show"  pulley actually causes the 
belt to 
kick off occasionally upon  shut-down of my engine. After replacing my 
(with correct  pulley), getting rid of the goofy idler pulley assembly and 
sure I had a true Corvair fan belt I've had no problems loosing belts  at 
I've driven over 35,000 miles with no problems. I've replaced the  belt 
since then and have thrown none at all. I have a short  stroke engine and 
it to 5,000 RPM's is not uncommon for me. I  drive my Corvair every day.
basically, the underground pulley's greatest  advantage to me was being 
able to 
change the belt without tools. However,  I've found it's preferrable to run 
factory GM-designed setup and not  have to change belts at all. My old 
underground  pulley resides in a landfill now.

R. Truss
Sunland,  CA

I have never run the aluminum idler pulley. The Underground idler, as  
usually supplied, uses the stock stamped steel pulley. If you were running a  
different pulley on the alternator as well as an aluminum pulley on the idler, 
 you, indeed may have ended up with a bad combination. The complaints I 
have  heard about the aluminum pulley was poor wear characteristics. 
It may not be generic to Aluminum pulleys, either. On my current  
race/autocross car, I am using the underground spring-loaded idler, with  the LeVair 
half-speed fan kit. This system replaces the drive pulley/balancer,  with a 
smaller, aluminum pulley, replaces the driven pulley on the fan with  a 
larger, aluminum pulley, and modifies the generator/oil filter adapter on  both 
sides to re-align the alternator and the idler to correctly accept and  
direct the fan belt. No belts lost since the system was installed. I also spray  
a silicone lube on to help retain the belt. And I wind the crap out of it!
This system is not recommended for street usage since it would likely not  
provide enough air at lower engine speeds - such as street cruise speeds.
I do know that Underground made a few changes to their idler kit after the  
first run of units, some time ago. If the one you have doesn't seen to be  
working properly - like tossing belts on a regular basis, I would contact 
Lon  and see if there is an update available. 
I agree that it is disconcerting to watch the belt at idle, at least on my  
installation. The idler jumps around a bit. But the belt stays on!
Seth  Emerson

C's the Day! - Corvair,  Camaro, Corvette

San Jose, CA

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