3947867 Hose For '69 3x2 L68 Tri Power???

[Michael B.]

Re: 3947867 Hose For '69 3x2 L68 Tri Power???

There has been a lot of discussion on the topic. I have seen many early 69s with pumps that have the relief valve. Several with the proper date code too. There is a theory though that since the 68 pumps with the relief valves are forward compatable with 69 and later, but not the otherway around, that pump rebuilders of the era routinely added relief valves to reduce part numbers and stocking inventory. If you go down to the parts house and buy a rebuilt pump you are likely to get one with the relief valve. That pump on my car has a date code from 1973. Seems like a big job retrofitting all those pumps to be compatable with 1968 and the few L88s. Why would a 73 have a relief valve though?

The correct answer? ... I don't know for sure but I have seen more early 69s with the relief valve. You have to remember that in the late 60s and early 70s there were no smog check programs and the AIR system was the "most obvious thing that was reducing horsepower" so off it came. Now days it is costing us more than a engine overhaul to restore it back to stock. And whether they are the right configuration is debatable.

[David S.]

Re: 3947867 Hose For '69 3x2 L68 Tri Power???

Mine is dated 01081Y (10th day of 1968) which is outside of the six month rule.

[Joe L.]

Re: 3947867 Hose For '69 3x2 L68 Tri Power???

There has been a lot of discussion on the topic. I have seen many early 69s with pumps that have the relief valve. Several with the proper date code too. There is a theory though that since the 68 pumps with the relief valves are forward compatable with 69 and later, but not the otherway around, that pump rebuilders of the era routinely added relief valves to reduce part numbers and stocking inventory. If you go down to the parts house and buy a rebuilt pump you are likely to get one with the relief valve. That pump on my car has a date code from 1973. Seems like a big job retrofitting all those pumps to be compatable with 1968 and the few L88s. Why would a 73 have a relief valve though?

The correct answer? ... I don't know for sure but I have seen more early 69s with the relief valve. You have to remember that in the late 60s and early 70s there were no smog check programs and the AIR system was the "most obvious thing that was reducing horsepower" so off it came. Now days it is costing us more than a engine overhaul to restore it back to stock. And whether they are the right configuration is debatable.

Michael-----

The GM-cataloged SERVICE pump for 1969 applications has always been a pump with an external relief valve (GM #7806686) even though the original non relief valve pump (GM #7803948) was available in SERVICE until the mid-70's. So, it's very possible that the SERVICE "route" is how the pump got on your car. In any event, though, I have rarely seen the 69-75 style pump available as a rebuilt pump. So, I have always presumed that the 69-75 style pumps were converted by the rebuilders to the external relief valve type. I don't know that this happened; it's pretty much speculation on my part.

As far as early 1969's using the 1968 style pump, I suppose it's possible. However, I can't find anything to support that. There's nothing in the AIM to indicate a change from one part number pump to another. Also, I've never seen a known-original early 1969 with the 68 style pump (except L-88, of course). But, this definitely does not mean that it didn't occur.

Anyone out there with a known-original, early 1969 with an AIR pump with external relief valve?

[Grant W.]

Re: 3947867 Hose For '69 3x2 L68 Tri Power???

I have a slightly off topic question. I noticed Michael Brown's engine picture has a smog pump with the built in pressure release valve. I also have an early built (Nov 4th, 1968) L68 with the same style smog pump but was informed only the L88's in 69 had this style off smog pump. Can anyone shed some light on this topic.

Hi David
Regarding the smog pump with a relief valve. It is mostly a 68 item. From all the smog pumps that I have and with its date codes. An early 69 car should have the non relief valve but the smog pump dated late 68. Unless someone had the very first made 69 corvette vin 1 to 100 then it could possibly having the style of the 68 relief valve. The non relief valve is a new style version for 69's.
The non relief valve smog pump that Jamie has is correct for his 69. I don't know the date of his smog pump but so far looks good.
Grant

[Jamie F.]

Re: 3947867 Hose For '69 3x2 L68 Tri Power???

Grant,
My pump is dated 2809S1 for the 280th day of '69 which is Oct. 7, 1969. The trim tag date of my car is Nov. 20, 1969.