How many v groves on LS5 crank pulley?

[Jeff Y.]

I have a 72 LS 5, PS no air conditioning and am trying it figure out belt routing. I'm looking at the AIM and it seems to show a 2 groove pulley on the crank. When I took the car apart it had a 2 groove pulley and a 1 groove pulley bolted to the balancer. What pulley should be on the balancer? Any one have the part number?

Thanks

Jeff

[Paul O.]

Re: How many v groves on LS5 crank pulley?

Jeff

Do not know if this will help but on a 1971 AIM UPC N40 Sheet A8 for a LS5 with PS shows a belt from the crank to water pump then a belt from crank to Water pump to PS pump and then a belt from PS pump to Alternator. It shows only a pulley with 2 groves at the crank shaft, water pump and power steering pump and a single at the alternator . Hope this helps.

[Jeff Y.]

Re: How many v groves on LS5 crank pulley?

Thanks Paul, 72 AIM shows the same. Just can't figure out why someone would have added a pulley.

[Joe L.]

Re: How many v groves on LS5 crank pulley?

I have a 72 LS 5, PS no air conditioning and am trying it figure out belt routing. I'm looking at the AIM and it seems to show a 2 grove pulley on the crank. When I took the car apart it had a 2 grove pulley and a 1 grove pulley bolted to the balancer. What pulley should be on the balancer? Any one have the part number?

Thanks


Jeff

Jeff-----

You should have a 2 groove pulley of GM #3921923 (in fact, it's still available from GM). No Corvette big block ever originally used a 3 groove or 2+1 groove crankshaft pulley configuration.

[Jeff Y.]

Re: How many v groves on LS5 crank pulley?

Thanks Joe, exactly what I was looking for. Can't figure out why someone would have added the extra pulley.

[Joe L.]

Re: How many v groves on LS5 crank pulley?

Thanks Joe, exactly what I was looking for. Can't figure out why someone would have added the extra pulley.

Jeff-----


Is there a GM part number on the added-on pulley or is it some sort of aftermarket piece?

If it's aftermarket, it could be that it was part of an aftermarket air conditioning system once installed on the car.

[Jimmy G.]

Re: How many v groves on LS5 crank pulley?

I have had a 72 BB A/C car since the 70's. Being an engineer, I removed the smog system and added a 3 belt pulley to the crank to run the A/C and tied it into the third groove on the water pump pulley. A/C has worked well for 30 years with no issues. That is a possible answer

[Jeff Y.]

Re: How many v groves on LS5 crank pulley?

The car was missing the air pump but does not have A/C. Joe I plan to take it off tomorrow. I'll post if it has a part number on it.

[Jeff Y.]

Re: How many v groves on LS5 crank pulley?

Joe,

I didn't find a 3921923 pulley. So I ordered one from the local Chevy dealer, $50 new. I did find a 3850838 2 groove pulley and a 3751232 single groove pulley. Someone for some reason took the original off in the past and installed this set. Guess I'll never know why but thanks for the part number for the correct one.

Jeff

[Joe L.]

Re: How many v groves on LS5 crank pulley?

Joe,

I didn't find a 3921923 pulley. So I ordered one from the local Chevy dealer, $50 new. I did find a 3850838 2 groove pulley and a 3751232 single groove pulley. Someone for some reason took the original off in the past and installed this set. Guess I'll never know why but thanks for the part number for the correct one.

Jeff

Jeff------


The two pullies you found are small block pullies, never originally used on a big block. The 3850838 is a non deep groove crankshaft pulley used for many 1965-70 lower horsepower applications (i.e. 250 and 300 HP). The 3751232 is an add-on crankshaft pulley used for the power steering pump driver for these same applications.

[Jeff Y.]

Re: How many v groves on LS5 crank pulley?

I got the correct pulley today and see that it is a smaller diameter than the small block part I took off. I'm wondering if someone put this larger pulley on to try and spin the fan faster in an attempt move more air and keep the car cooler? Anyway, installed the 3921923 to put it all back to stock.