1973 LS4 Water pump belt and Idler Pulley Questions

[Tom K.]

Hello All,

Looking for some more advice regarding my car. This time the questions are about the short belt that runs from the crank pulley to the water pump, and the idler for this belt. First, the belt itself. The one that was on the car had grooves on the outside surface of the belt such that it would allow it to be bent backwards from normal curvature by the idler pulley. Of course I had to buy a new belt so I bought one with the correct markings and date code from one of the typical Corvette Parts suppliers. It seems like the correct size, but no grooves on the back - is this correct for an original belt? See the pix below:

Second question:
I have about .030" play at the rim of my idler pulley - My guess is it aint gonna make it much longer. I do not see anything in my CSM on rebuilding the thing. The replacements are about $150 and look like the have a zinc dichromate (if that is still even used) finish that does not look original to me.
Has anyone replaced the bearing in one of these? I have not been able to find a replacement bearing, but once I get the thing apart I can probably get the bearing. Wondering how to take it apart without ruining it.


As always, thanks for all your help


Tom

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Here are the pix I forgot

[Mark E.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Notched belts came out after your car was built... 1980s? Years ago an auto parts counter guy said the notches help the belt run cooler. Sounds good, but don't know for sure what they do. I do know I don't like how they look and don't use them. Go ahead and use your repro belt. Note it bends each way just fine.

Keep us posted what you do with your idler pulley. I purchased a repro unit which works fine. I use a belt which fits snug without the idler and keep the idler adjusted fairly loose to minimize bearing load (I can turn its pulley by hand when installed).

[Dick W.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

The bearing in the idler is replaceable. I cannot remember where I bought them, but they are/were available.

[Russ S.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

This belt although the only repo available is incorrect. Originals didn't have white lettering. They were black either indented or raised letters. See the judging guide page 75.

Here are the pix I forgot

[Robert R.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

I am sure Russ is correct in that the original belts did not have the white lettering and he is most likely correct about the raised or indented letters. However, I have an NOS belt (Gr. 1.066, #3952336) in the original packaging that was bought over the counter in the mid '70's. It has stamped green lettering. Has anyone else seen belts with stamped lettering?

[Russ S.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Yes Robert, over the counter service replacement belts had the white or green lettering.

I am sure Russ is correct in that the original belts did not have the white lettering and he is most likely correct about the raised or indented letters. However, I have an NOS belt (Gr. 1.066, #3952336) in the original packaging that was bought over the counter in the mid '70's. It has stamped green lettering. Has anyone else seen belts with stamped lettering?

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hello Dick,

Thank you for your reply. Do you know how the idler came apart?
I took mine in to work today and during lunch I tried to drive the center spindle out from the back side of the bearing. I did not hit it very hard as it looked as if the end of the shaft might have been spun or peened over the edge of the bearing to retain it. When I tapped it a few times it was really solid. I also tried a 2-arm puller (the shape of the bracket will not let a 3-arm puller work) to push the bearing loose from the bracket, but that didnt work very well. I will try a pitman arm puller tomorrow as it has wider bearing surfaces and should be more stable than what I had today.
Im pretty sure I can get a new bearing if I can get it apart and measure it. I noticed the outer shell was stamped NDH (New Departure-Hyatt) so it is likely the original bearing.
If I get it the bearing figured out I will post the replacement part number and manufacturer here

Again Thanks


Tom Krause

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hey Mark,

Quite awhile back I was told the grooves were a relief cut into the outer face of the belt to allow it to bend backwards. The wider surface of the VEE stretches when it goes around the outside of a pulley, but it must compress some when it is bent the other way because there is no place for the displaced material to go, they cut the grooves in the outer surface. Not sure of thats totally accurate, but its a pretty good story.
I like your idea of using the tight fitting belt and let the idler put minimal load on the belt - everything will live a bit longer and that belt is redundant anyway as the water pump is also driven by the second belt.

Thanks as always


Tom Krause

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hi Russ,

Yeah I havent bought the J-G yet because I know they are working on a revision.

Hey - I just noticed that I graduated to 'frequent user'!

Probably means I need lots of help!


Tom Krause

[Dick W.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hello Dick,

Thank you for your reply. Do you know how the idler came apart?
I took mine in to work today and during lunch I tried to drive the center spindle out from the back side of the bearing. I did not hit it very hard as it looked as if the end of the shaft might have been spun or peened over the edge of the bearing to retain it. When I tapped it a few times it was really solid. I also tried a 2-arm puller (the shape of the bracket will not let a 3-arm puller work) to push the bearing loose from the bracket, but that didnt work very well. I will try a pitman arm puller tomorrow as it has wider bearing surfaces and should be more stable than what I had today.
Im pretty sure I can get a new bearing if I can get it apart and measure it. I noticed the outer shell was stamped NDH (New Departure-Hyatt) so it is likely the original bearing.
If I get it the bearing figured out I will post the replacement part number and manufacturer here

Again Thanks


Tom Krause

It has been a while since I did one. I remember pressing the bearing in and out.

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hello All,

The pitman arm puller worked out ok - I rigged it up it like so:




it was a lot of work, but it came apart. It got pretty crooked at the end before the bearing finally cam out of the housing, but no damage to the housing or the stamped flange.


and...
Here is whats inside the little so-and-so's



The problem I had was I went to the arbor press right after I got it apart and tried to press the center shaft out of the bearing thinking that it was separate from the bearing - it isnt - the center shaft actually has two inner races for the ball bearings machined into it. I have not seen that construction before. So when I pushed on the end of the shaft, it went down until the outer bearing race touched the idler wheel. Then the thing loaded up until I split the outer race in two. The shaft pressed the rest of the way out of the assembly, but the bearing is toast.
Fortunately I have been buying bearings in the machine tool industry for quite a while and I know 'the guy'. He will be at the office on Monday and if the thing is still made most anywhere he will be able to get it. If not, I gotta go to plan 'B' and make something.

Anyway, there was an NDH logo and MADE IN THE USA stamped on the end of the outer race, but no P/N that I could find anywhere.
The description of the bearing is:
5/8" dia shaft (also the inner race) and the outer race is 1 3/16" OD the shaft continues through the idler wheel and extends out about 1/8". The bearing was not sealed, but it was shielded on both ends. There were two rows of ball bearings spaced pretty far apart with plenty of room for some grease.

Anyone have an opinion on what to do assuming this little beauty is no longer available?

Right now Im thinking make a new shaft, press on the idler wheel, press on a bearing with 1 3/16 od make a spacer and press on a second bearing to get a similar length. OR maybe make a new shaft and something from a sintered steel bearing. It would then be a plain bearing instead of a ball, but would that matter?
I gotta noodle on it a bit...


Tom

[Harmon C.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

I had a 73 454 that had no idler pulley. Was judged to Duntov with no deductions for no idler pulley. 454 -4 speed

[Joe L.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hello All,

The pitman arm puller worked out ok - I rigged it up it like so:




it was a lot of work, but it came apart. It got pretty crooked at the end before the bearing finally cam out of the housing, but no damage to the housing or the stamped flange.


and...
Here is whats inside the little so-and-so's



The problem I had was I went to the arbor press right after I got it apart and tried to press the center shaft out of the bearing thinking that it was separate from the bearing - it isnt - the center shaft actually has two inner races for the ball bearings machined into it. I have not seen that construction before. So when I pushed on the end of the shaft, it went down until the outer bearing race touched the idler wheel. Then the thing loaded up until I split the outer race in two. The shaft pressed the rest of the way out of the assembly, but the bearing is toast.
Fortunately I have been buying bearings in the machine tool industry for quite a while and I know 'the guy'. He will be at the office on Monday and if the thing is still made most anywhere he will be able to get it. If not, I gotta go to plan 'B' and make something.

Anyway, there was an NDH logo and MADE IN THE USA stamped on the end of the outer race, but no P/N that I could find anywhere.
The description of the bearing is:
5/8" dia shaft (also the inner race) and the outer race is 1 3/16" OD the shaft continues through the idler wheel and extends out about 1/8". The bearing was not sealed, but it was shielded on both ends. There were two rows of ball bearings spaced pretty far apart with plenty of room for some grease.

Anyone have an opinion on what to do assuming this little beauty is no longer available?

Right now Im thinking make a new shaft, press on the idler wheel, press on a bearing with 1 3/16 od make a spacer and press on a second bearing to get a similar length. OR maybe make a new shaft and something from a sintered steel bearing. It would then be a plain bearing instead of a ball, but would that matter?
I gotta noodle on it a bit...


Tom

Tom-----


As you have discovered, you cannot press on the shaft of these bearings (same for waterpump bearings). Of course, destructive effect on removal is not a problem if the bearing is to be replaced.

The bearing was once available from GM under GM #908076. It's discontinued, though. So, what you need is an aftermarket bearing (SKF, etc.) equivalent to a GM #908076.

By the way, the above bearing was also used for 1968-74 big block idler pulleys.

[Tom K.]

Re: 1973 LS4 Water pump belt and Idler Pulley Questions

Hello Joe,

Thank you for the P/N!
I was able to order a replacement from Corvette Specialty (SKU 108345). I havent found it anywhere else yet, but it must be out there. I think there is also a marine application for it because i found the same P/N comes up as an OMC number as well and the picture looks the same. Of course, as its a marine application, the price nearly doubled.
Anyway, I should be on track to put the thing back together.


Thanks again to all


Tom Krause