Water pump reinforcement

[Michael M.]

My 68 big block L36 has the set up where the water pump pulleys are sandwiched with a two groove pulley behind a single groove pulley.

The two groove pulley is the 3848904 pulley and always appeared to have a welded reinforcement on the inside of the pulley. I just disassembled the cooling system (that's another story on this TDB) and the welded reinforcement has appeared to come loose from the pulley.

Now my question, was this reinforcement ever really welded on to the inside of the pulley or was it just "stuck" there with whatever minor surface rust or crud or whatever may have found its way behind the pulley over the many years. I can reassemble with the reinforcement behind the pulley but it obviously won't be as strong as having it welded to the pulley (if it was ever that way in the first place).

If it was welded on, I guess I should replace the pulley but I'm not sure if any of the repros have this welded reinforcement anyway, so the new one I buy may not be any better than the one I have.

Thanks for any replies.

[Clem Z.]

Re: Water pump reinforcement

My 68 big block L36 has the set up where the water pump pulleys are sandwiched with a two groove pulley behind a single groove pulley.

The two groove pulley is the 3848904 pulley and always appeared to have a welded reinforcement on the inside of the pulley. I just disassembled the cooling system (that's another story on this TDB) and the welded reinforcement has appeared to come loose from the pulley.

Now my question, was this reinforcement ever really welded on to the inside of the pulley or was it just "stuck" there with whatever minor surface rust or crud or whatever may have found its way behind the pulley over the many years. I can reassemble with the reinforcement behind the pulley but it obviously won't be as strong as having it welded to the pulley (if it was ever that way in the first place).

If it was welded on, I guess I should replace the pulley but I'm not sure if any of the repros have this welded reinforcement anyway, so the new one I buy may not be any better than the one I have.

Thanks for any replies.

GM just added them in the field. http://www.thecamaro.com/Vintage-Cam...x=0&pg=dr66-40

[Michael M.]

Re: Water pump reinforcement

Thanks Clem. So I guess my reinforcement was never welded on in the first place. It must have just been stuck or glued on. Interesting because I'll bet I had that pulley apart at least a dozen times over the years and the reinforcement never came off the pulley. I always assumed it was welded on.

[Clem Z.]

Re: Water pump reinforcement

available in the after market. https://www.paragoncorvette.com/p-35...nt-spacer.aspx

[Joe L.]

Re: Water pump reinforcement

My 68 big block L36 has the set up where the water pump pulleys are sandwiched with a two groove pulley behind a single groove pulley.

The two groove pulley is the 3848904 pulley and always appeared to have a welded reinforcement on the inside of the pulley. I just disassembled the cooling system (that's another story on this TDB) and the welded reinforcement has appeared to come loose from the pulley.

Now my question, was this reinforcement ever really welded on to the inside of the pulley or was it just "stuck" there with whatever minor surface rust or crud or whatever may have found its way behind the pulley over the many years. I can reassemble with the reinforcement behind the pulley but it obviously won't be as strong as having it welded to the pulley (if it was ever that way in the first place).

If it was welded on, I guess I should replace the pulley but I'm not sure if any of the repros have this welded reinforcement anyway, so the new one I buy may not be any better than the one I have.

Thanks for any replies.

Michael------


Are you sure that the 3848904 pulley does not have a welded-in reinforcement? My recollection is that it does or, at least, the "updated version" of it used by 1969 did. If it does have the welded-in reinforcement, then the loose reinforcement is either unnecessary or it's being used solely as a spacer to achieve pulley alignment.

The replacement for the 3848904, GM #3995641, definitely has the welded-in reinforcement. It's still available from GM for about 90 bucks, GM list.

By the way, the pulley set-up you have contributes to a hotter running engine. That's because the larger size of the pullies slows down the fan speed compared to the smaller OD 3 groove pulley used for later 1968+. My preference would always be the 5.5" OD 3 groove pulley rather than the sandwiched set with 5.9" OD 2 groove waterpump/fan drive pulley.

[Michael M.]

Re: Water pump reinforcement

Joe, I thought I was certain my pulley had the welded in reinforcement but according to the TSB and other people on this TDB, it was added in the field. It's just that this reinforcement has now come loose and I wasn't sure if it was welded all the while or if it was just "stuck" on there and it hadn't come unstuck until now. I personally think it was welded but the catastrophic contact of my fan blade with the fan shroud and radiator at high rpm may have broken it loose.

The reinforcement on my pulley that has come loose is flat and does not have the curved edges like the ones you see being sold by the Corvette parts vendors and it is thicker also.

Joe, you are recommending going to the three groove pulley but that means I have to buy a new captive belt, correct? And that pulley is quite expensive, I think over $200. I wonder if the 3848904 repros have the welded in reinforcement? I'll have to check. With an aluminum radiator, cooling my engine is no longer an issue, thankfully.

[Clem Z.]

Re: Water pump reinforcement

Joe, I thought I was certain my pulley had the welded in reinforcement but according to the TSB and other people on this TDB, it was added in the field. It's just that this reinforcement has now come loose and I wasn't sure if it was welded all the while or if it was just "stuck" on there and it hadn't come unstuck until now. I personally think it was welded but the catastrophic contact of my fan blade with the fan shroud and radiator at high rpm may have broken it loose.

The reinforcement on my pulley that has come loose is flat and does not have the curved edges like the ones you see being sold by the Corvette parts vendors and it is thicker also.

Joe, you are recommending going to the three groove pulley but that means I have to buy a new captive belt, correct? And that pulley is quite expensive, I think over $200. I wonder if the 3848904 repros have the welded in reinforcement? I'll have to check. With an aluminum radiator, cooling my engine is no longer an issue, thankfully.

the curved part is what make it a reinforcement a flat one would just be a spacer

[Michael M.]

Re: Water pump reinforcement

Thanks Clem. In the terminology then, I guess I had a welded on spacer inside the hub of the pulley.

[Joe L.]

Re: Water pump reinforcement

Joe, I thought I was certain my pulley had the welded in reinforcement but according to the TSB and other people on this TDB, it was added in the field. It's just that this reinforcement has now come loose and I wasn't sure if it was welded all the while or if it was just "stuck" on there and it hadn't come unstuck until now. I personally think it was welded but the catastrophic contact of my fan blade with the fan shroud and radiator at high rpm may have broken it loose.

The reinforcement on my pulley that has come loose is flat and does not have the curved edges like the ones you see being sold by the Corvette parts vendors and it is thicker also.

Joe, you are recommending going to the three groove pulley but that means I have to buy a new captive belt, correct? And that pulley is quite expensive, I think over $200. I wonder if the 3848904 repros have the welded in reinforcement? I'll have to check. With an aluminum radiator, cooling my engine is no longer an issue, thankfully.

Michael-----

The GM reinforcements, either welded-in or separate, have a curved periphery. As clem mentions, the flat pieces are spacers only. GM used to have available such spacers but they have not been available for a VERY, VERY long time. They are easily available in the aftermarket, though, and have been so for many years. Moroso and Mr. Gasket are among the manufacturers. The curved GM reinforcements are sometimes used as spacers.

Look at the rear side of your pulley into the snout area. If you see any welding, at all, in there, then there is a welded-in reinforcement. There should be no welding in the snout area of the pulley if no reinforcement was part of the pulley.

As I mentioned, the GM #3995641, which is the replacement for the original pulley, definitely has the welded-in reinforcement and it's still available from GM.

Yes, if you were to go to the 3 groove pulley you would have to use another captive belt (which is a special size and ONLY available as a reproduction belt). And, yes, the reproduction 3 groove pulley is expensive.

[Michael M.]

Re: Water pump reinforcement

Thanks Joe and Clem. I am traveling right now, but I'll check the pulley when I get home. I believe I just had a spacer and it must have just been stuck there over these many years. Definitely not a curved reinforcement. I went onto eBay and saw an original 3848904 pulley and the picture of the inside of the pulley did not appear to show a welded in reinforcement.

Great information and when I reassemble, I'll make sure to verify the pulley alignment between crank, water pump and alternator. Any tricks to verifying pulley alignment?

[Clem Z.]

Re: Water pump reinforcement

Thanks Joe and Clem. I am traveling right now, but I'll check the pulley when I get home. I believe I just had a spacer and it must have just been stuck there over these many years. Definitely not a curved reinforcement. I went onto eBay and saw an original 3848904 pulley and the picture of the inside of the pulley did not appear to show a welded in reinforcement.

Great information and when I reassemble, I'll make sure to verify the pulley alignment between crank, water pump and alternator. Any tricks to verifying pulley alignment?

i have posted how to use a 1/4" diameter steel rod to check alignment. someone better than me with a computer can find it quick and re post it.

[Michael M.]

Re: Water pump reinforcement

This one Clem?

"A quick way to check pulley alignment is to take a piece of 1/4"-5/16" diameter steel rod about 18" long and 6" from the end bend the rod 90 degrees. lay the 90 degree bend in one pulley groove and allow the other end to point towards the other pulley and if in alignment that end will lay in the center of the other pulley."

[Clem Z.]

Re: Water pump reinforcement

This one Clem?

"A quick way to check pulley alignment is to take a piece of 1/4"-5/16" diameter steel rod about 18" long and 6" from the end bend the rod 90 degrees. lay the 90 degree bend in one pulley groove and allow the other end to point towards the other pulley and if in alignment that end will lay in the center of the other pulley."

that is it !!