P/N 3859826 Date I or L 192. What was this P/N used for? Corvette specific?
Thanks Brian
Thanks Brian
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Re: Water Pump I.D.
Brian-----
I think that you'll find that this pump casting number is 3859326. This is an external bypass type water pump which was used on many Corvette small blocks with aluminum intake manifolds which all utilized the external bypass system. The years of use for this casting was 1965 to 1967 and it may also have been used for 64, but I don't recall for sure at the moment.
This water pump has a large drilled and tapped boss on the upper portion of the casting which is the external bypass provision. Early examples of the casting were drilled and tapped for 1/2" NPT fittings; later versions were drilled and tapped for 3/4" NPT fittings.
While this casting was used mostly for Corvettes, it was also used on other Chevrolet car lines that had, basically, Corvette engines with aluminum manifolds. This included the 325 and 350 hp 327 engines used in Chevelles and Chevy IIs. The external bypass casting was also used on some trucks.
After about 1969, this casting was the one utilized for most all 55-70 SERVICE water pumps from GM. These were sold under GM PART #3998206 and a few other numbers. The GM #3998206 is still available, but it no longer uses a GM-sourced pump casting. The 3998206 pump unit was supplied with a 3/4" NPT pipe plug and a 3/8" dowel plug. For external bypass applications, the dowel plug is installed in the internal bypass hole in the left side "leg". For internal bypass applications, the 3/4" NPT pipe plug is installed in the top fitting.
The GM #3859326 casting is NOT rare, by any means. Due to its widespread use in SERVICE, it's a VERY common casting.In Appreciation of John Hinckley -
Re: Water Pump I.D.
Brian-----
I think that you'll find that this pump casting number is 3859326. This is an external bypass type water pump which was used on many Corvette small blocks with aluminum intake manifolds which all utilized the external bypass system. The years of use for this casting was 1965 to 1967 and it may also have been used for 64, but I don't recall for sure at the moment.
This water pump has a large drilled and tapped boss on the upper portion of the casting which is the external bypass provision. Early examples of the casting were drilled and tapped for 1/2" NPT fittings; later versions were drilled and tapped for 3/4" NPT fittings.
While this casting was used mostly for Corvettes, it was also used on other Chevrolet car lines that had, basically, Corvette engines with aluminum manifolds. This included the 325 and 350 hp 327 engines used in Chevelles and Chevy IIs. The external bypass casting was also used on some trucks.
After about 1969, this casting was the one utilized for most all 55-70 SERVICE water pumps from GM. These were sold under GM PART #3998206 and a few other numbers. The GM #3998206 is still available, but it no longer uses a GM-sourced pump casting. The 3998206 pump unit was supplied with a 3/4" NPT pipe plug and a 3/8" dowel plug. For external bypass applications, the dowel plug is installed in the internal bypass hole in the left side "leg". For internal bypass applications, the 3/4" NPT pipe plug is installed in the top fitting.
The GM #3859326 casting is NOT rare, by any means. Due to its widespread use in SERVICE, it's a VERY common casting.In Appreciation of John HinckleyComment
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More....
The '326 casting may also have come from Tonawanda, but from the date code sequence given (single digit year) I suspect the one here is a Saginaw/Flint casting. The difference will also lie in presense/absence of a 'floating' "T" in/around the GM + cast number along with thick reinforcing ribs on the LH side of the casting. These '326 pumps would be considered incorrect for Corvette use....
I both agree and disagree with Joe on the availability of '326 pumps. I agree they're 'relatively' common, but disagree that finding one in a correct/original Corvette configuration is easy. In the last 10-years of walking scrap yards and scrounging through water pump core bins, I've been able to come up with a whooping FOUR units!
Here's the boogie.... The '326 body casting had a nice thick upper boss (like its predecessor the '609 casting). Secondary operations (drill/tap upper boss for external bypass, install impeller/shaft/fan hub) is what turned the the '326 casting into a particular GM P/N water pump configuring it for a given host engine application.
When these pumps wore out and went through the hands of local water pump rebuilders, an 'inspiration' took place! If the upper boss were tapped and drilled out WIDE (3/4-inch NPT hole), and the rebuilder stuffed the box with a 3/4-inch blind plug as well as a reducing sleeve (3/4-inch NPT thread on the OD and 1/2-inch NPT thread on the ID), he made a "one-part-fits-all" Chevy SB water pump.
Horray! Parts dealer inventory was reduced and everyone benefited--the pump was built the way GM 'should have' done it in the first place (in the eyes of many). BUT, the process has systematically WIPPED OUT original/untouched Corvette water pumps making them artificially scarce.
Judges are told (mid-year JG books) to look CLOSELY at the upper boss on these pumps for evidence of over-bore. Is there a visible reducing sleeve there? Is there evidence of 'tampering' on the upper boss's natural cast texture surrounding the bypass nipple?
Several of these untouched/original 326 water pumps have traded into the $200-300 range on eBay based on their scarcity. That doesn't mean you won't get 'lucky' here/there. But, it's my opinion based on walking/looking that finding a 'vigin' pump body that's NOT a Tonawanda casting, NOT been overbored on the upper boss and is dated to match your car (dating of the 326 casting at Saginaw/Flint is currently thought to have began 11/65) is a LOT harder than most think! Plus, when you look at the catalog houses that advertize these pumps for sale, you do NOT see them guarantee their offerings are Flint/Saginaw castings nor do they tell you the upper boss is Corvette-virgin, drilled/tapped for 1/2-inch NPT bypass nipple installation....Comment
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More....
The '326 casting may also have come from Tonawanda, but from the date code sequence given (single digit year) I suspect the one here is a Saginaw/Flint casting. The difference will also lie in presense/absence of a 'floating' "T" in/around the GM + cast number along with thick reinforcing ribs on the LH side of the casting. These '326 pumps would be considered incorrect for Corvette use....
I both agree and disagree with Joe on the availability of '326 pumps. I agree they're 'relatively' common, but disagree that finding one in a correct/original Corvette configuration is easy. In the last 10-years of walking scrap yards and scrounging through water pump core bins, I've been able to come up with a whooping FOUR units!
Here's the boogie.... The '326 body casting had a nice thick upper boss (like its predecessor the '609 casting). Secondary operations (drill/tap upper boss for external bypass, install impeller/shaft/fan hub) is what turned the the '326 casting into a particular GM P/N water pump configuring it for a given host engine application.
When these pumps wore out and went through the hands of local water pump rebuilders, an 'inspiration' took place! If the upper boss were tapped and drilled out WIDE (3/4-inch NPT hole), and the rebuilder stuffed the box with a 3/4-inch blind plug as well as a reducing sleeve (3/4-inch NPT thread on the OD and 1/2-inch NPT thread on the ID), he made a "one-part-fits-all" Chevy SB water pump.
Horray! Parts dealer inventory was reduced and everyone benefited--the pump was built the way GM 'should have' done it in the first place (in the eyes of many). BUT, the process has systematically WIPPED OUT original/untouched Corvette water pumps making them artificially scarce.
Judges are told (mid-year JG books) to look CLOSELY at the upper boss on these pumps for evidence of over-bore. Is there a visible reducing sleeve there? Is there evidence of 'tampering' on the upper boss's natural cast texture surrounding the bypass nipple?
Several of these untouched/original 326 water pumps have traded into the $200-300 range on eBay based on their scarcity. That doesn't mean you won't get 'lucky' here/there. But, it's my opinion based on walking/looking that finding a 'vigin' pump body that's NOT a Tonawanda casting, NOT been overbored on the upper boss and is dated to match your car (dating of the 326 casting at Saginaw/Flint is currently thought to have began 11/65) is a LOT harder than most think! Plus, when you look at the catalog houses that advertize these pumps for sale, you do NOT see them guarantee their offerings are Flint/Saginaw castings nor do they tell you the upper boss is Corvette-virgin, drilled/tapped for 1/2-inch NPT bypass nipple installation....Comment
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Re: More....
Jack-----
Please note the following:
1) In my post, I said that the GM #3859326 water pump casting is NOT rare. I DID NOT SAY that finding one with a 1/2" NPT was not difficult and I DID NOT SAY that finding one correctly dated for a particular car might not be difficult. I just said that the 3859326 casting is NOT rare. And, a GM #3859326 casting IS NOT rare.
2) I really doubt that many 3859326 castings originally drilled and tapped for 1/2" NPT fittings were subsequently drilled and tapped for 3/4" NPT fittings by rebuilders. First of all, there were never a whole lot of the 1/2" NPT fitted castings to begin with due to their limited application. Secondly, I doubt that rebuilders would spend the time necessary to re-drill and re-tap the castings. The labor cost of the operations would exceed the value of the castings. I expect that they would simply discard the 1/2" NPT if they only wanted to inventory the 3/4". However, more likely, I think that they just rebuilt them and sent them out with the 1/2" NPT, just like they receved them.
3) I would defy any judge to discern the installation of a reducing bushing if the bushing was carefully and cleverly installed and if the water pump was subsequently painted as all of these water pumps originally were when installed on the engine.In Appreciation of John HinckleyComment
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Re: More....
Jack-----
Please note the following:
1) In my post, I said that the GM #3859326 water pump casting is NOT rare. I DID NOT SAY that finding one with a 1/2" NPT was not difficult and I DID NOT SAY that finding one correctly dated for a particular car might not be difficult. I just said that the 3859326 casting is NOT rare. And, a GM #3859326 casting IS NOT rare.
2) I really doubt that many 3859326 castings originally drilled and tapped for 1/2" NPT fittings were subsequently drilled and tapped for 3/4" NPT fittings by rebuilders. First of all, there were never a whole lot of the 1/2" NPT fitted castings to begin with due to their limited application. Secondly, I doubt that rebuilders would spend the time necessary to re-drill and re-tap the castings. The labor cost of the operations would exceed the value of the castings. I expect that they would simply discard the 1/2" NPT if they only wanted to inventory the 3/4". However, more likely, I think that they just rebuilt them and sent them out with the 1/2" NPT, just like they receved them.
3) I would defy any judge to discern the installation of a reducing bushing if the bushing was carefully and cleverly installed and if the water pump was subsequently painted as all of these water pumps originally were when installed on the engine.In Appreciation of John HinckleyComment
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Re: More....
Thanks guy's. I will put this one into stock for now. May come in handy some day. Regards BrianComment
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Re: More....
Thanks guy's. I will put this one into stock for now. May come in handy some day. Regards BrianComment
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Re: More....
Brian-----
As it turns out, I've confirmed that the GM #3859326 was used for Corvette applications in 1964 and also 1963. However, dates on these pumps didn't begin until late 1965. So, the pump that you have must have been cast in either 1972, 1982, or, possibly, even 1992. That being the case, it had to have started its life as a SERVICE water pump inasmuch as this casting was not being used for any PRODUCTION applications as late as 1972. As I mentioned previously, MANY of the 3959326 castings started life as SERVICE water pumps.In Appreciation of John HinckleyComment
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Re: More....
Brian-----
As it turns out, I've confirmed that the GM #3859326 was used for Corvette applications in 1964 and also 1963. However, dates on these pumps didn't begin until late 1965. So, the pump that you have must have been cast in either 1972, 1982, or, possibly, even 1992. That being the case, it had to have started its life as a SERVICE water pump inasmuch as this casting was not being used for any PRODUCTION applications as late as 1972. As I mentioned previously, MANY of the 3959326 castings started life as SERVICE water pumps.In Appreciation of John HinckleyComment
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1/2" NPT; don't be fooled by a 3/4" ID hole
After reading this thread yesterday I dragged out the 326 water pump I bought last year as part of the restoration of my of my 66 L79. I was dismayed to
find that the top hole on my pump is about 3/4" in diameter. This morning Joe Lucia straightend me out when he told me that a 1/2" NPT fitting has an OD at the top of the taper of 0.840" and screws into a hole that looks like it has an ID of about 3/4". I thought I would add this information to the thread so that others don't panic if they see a hole at the top of their 326 water pump that has about a 3/4" ID making them think they have the incorrect pump.
GaryComment
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1/2" NPT; don't be fooled by a 3/4" ID hole
After reading this thread yesterday I dragged out the 326 water pump I bought last year as part of the restoration of my of my 66 L79. I was dismayed to
find that the top hole on my pump is about 3/4" in diameter. This morning Joe Lucia straightend me out when he told me that a 1/2" NPT fitting has an OD at the top of the taper of 0.840" and screws into a hole that looks like it has an ID of about 3/4". I thought I would add this information to the thread so that others don't panic if they see a hole at the top of their 326 water pump that has about a 3/4" ID making them think they have the incorrect pump.
GaryComment
Comment