Looking for some details around the 284 big block water pump. Judging Manual says the back plate is flat. I have seen both the flat and the "dished" type. What's the story? Is one orignal and one on rebuilds, or did GM change the plate after some date? Also JM says the early ones used slotted cap screws to hold the plate on, but I think I read somewhere that the later ones went to hex head bolts. If bolts, what head markings? Should the 284 on my '66 be configured the same as the one on my '69? How late were 284 pumps used on big blocks? Thanks for any inputs guys.
-
-
Re: 284 Water Pump
Everett-----
Although I can't answer the main points of your questions at the moment, I'll be able to this evening provide you with a definitive answer to part of the information which you seek. You see, it so happens that I happen to have an NOS '284' casting number water pump in my collection with a late 1966 cast date. So, I can certainly provide some definitive information regarding what the manufacturing characteristics were at that time. This piece is a real "time warp". It is in the GM original box and is virtually rust free after all of these years.
My recollection is that the '284' pump was used from 1965 until sometime in the late 1969 model year.In Appreciation of John Hinckley -
Re: 284 Water Pump
Thanks Joe, the information will be appreciated. It will be interesting to compare the configuration of your '66 dated pump with my March '66 pump as far as back plate type and screw/bolt type.Comment
-
Re: 284 Water Pump
Everett --- According to Colvin, Joe is close on the last use of the # 3856284 big block water pump; used from the introduction of the Mark IV in '65 to early '69 (Corvettes only in '69).
I have one dated A 12 8; it has slotted pan head screws with serrated washers. The back plate is flat except for a ring depression (inward) of about 4.25" dia.
Hopefully others will respond with late '68 / early '69 info., and, of course, Joe will respond with his NOS '66 configuration.Comment
-
Re: 284 Water Pump
Thanks Wayne. Your back plate sounds like the one I am wondering about. I have compared two '66 pumps, one has the completely flat back plate, and the other has the "dish" shaped plate, with sort of a raised outer edge. Both use hex head bolts.
I am wondering about '66 configurations and early '69 configurations, for both of my cars. The '69 has a beautiful aluminum GM water pump on it, but when I eventually restore the car, I suppose I will need to put on a 284 and would like to do the correct configuration.Comment
-
Re: 284 Water Pump
Hi Everett ~
I believe it should have the flat plate with slotted screws. The problem occurs when the pump is installed. According to a Senior NCRS '67 judge the recessed head bolts strike the timing cover due to the close tolerance...
Bob P NCRS #21991Comment
-
Re: 284 Water Pump
Everett-----
Well, I checked the NOS '284' pump that I have in my collection. It has the rear plate with the "turned up" edges and the circular "depression" of about 3" diameter. Also, it has slotted, pan head screws. It is dated "K 22 6".
Based upon a little research that I did, it appears that 1965 was the only unique year for Corvette big block water pump rear plate. For 1965 only, the plate was GM #3724990. I expect, but am by no means certain, that this is the "flat" plate. For 1966 through 1970 the plate was GM #3878262. I expect that this is probably the plate with the "turned up" edges.In Appreciation of John HinckleyComment
-
Re: 284 Water Pump
Thanks to all for the information. I wonder if the '66 Judging Manual statement about the flat back plate is based on '65 style plates? Based on Joe's information regarding the part numbers for the back plates, it would seem that only '65, and maybe some early '66 pumps used flat, and everything from then on used the raised edge style of plate. Now, all I need to do is locate some of the correct slot head cap screws - wonder if they are available from GM, or from a fastener supply house...Comment
Comment