I am changing out the water pump on the car 66 427/425. Bought rebuild dated 284 pump. I cant stop the backing plate from leaking. I have tried silicone both on the pump and the plate and of course on the screws. I am also using the gasket. I need help with this. I have had the pump on and off twice now. My next try is to turn the backing plate around and bolt it up that way. The plate is held on by 6 slotted screws and I torqued them to 12 ft lbs. Any suggestions would be appreciated -- maybe a different sealant. I am using permatex orange silicone. Maybe I am not letting it cure long enough -- I am stumped.
-
-
Re: 66 BB Water Pump Back Plate Leaking
John-----
I know of exactly the problem that you're talking about. It occurs with BOTH big block and small block waterpumps.
I believe the main factor in this is the configuration of the waterpump backing plate. Early waterpumps, both small and big block, used a FLAT backing plate. Later, this was modified to include "curled" edges which greatly increased the stiffness of the plate. Later yet, there were ridges or "indentions" formed into the plate between bolt holes. The latter configuration is the only configuration that I've found that will reliably seal. With the others, it's "hit-or-miss"----sometimes it works out, sometimes it doesn't.
I've done some tests in the past on a small block waterpump using all 3 types of plates. I sealed each on the same waterpump casting using a stock-type gasket PLUS Permatex Ultra Copper, the best RTV I've ever found. With the flat plate and the non-indented "curled" plate, the highest water pressure that I could get the pump to withstand was about 10 PSI. When I increased the pressure beyond that, the pump started leaking from the plate.
With the "curled" plate with "indentions", I could get the pump to hold pressure at 15 PSI. However, at about 20 PSI, even that would start leaking. Of course, all you need to hold is 15 PSI, because that's where the radiator pressure cap, if it's working properly, will relieve and limit the system pressure.
So, I would suggest that you look for a pump with a "curled" edge backing plate with the "indentions" between holes. Remove the plate from that pump, clean it thoroughly and install on your pump. Yes, it won't be original but it will seal properly and RELIABLY. In my opinion, FUNCTIONALITY is ALWAYS more important than ORIGINALITY (except for "museum pieces" where functionality is irrelevent).
Also, make sure that both sealing surfaces are absolutely clean, use a stock-type gasket, and seal with Permatex Ultra Copper. Let the RTV cure for, at least, 12 hours and, preferably, longer. Remember to let the RTV "skin over" (about 5-10 minutes) before you assemble the parts, too.In Appreciation of John Hinckley -
Re: 66 BB Water Pump Back Plate Leaking
Joe -- thank you for the response. The old pump I removed appears to be a replacement pump and maybe that backing plate will work. I will give it a try. I am also having a heck of a time getting the bypass hose to stop leaking at the pump side. I now wonder if the pressed in pipe is the problem. I wonder how guys like Art Gould or Bill Mock solve this challenge.Comment
-
Re: 66 BB Water Pump Back Plate Leaking
John
I assume you put silicone sealant on the bypass hose ?? This would normally do the trick re leak issue.
PeterComment
-
way back when i used to modify BBC water pumps
by grinding off every other vane on the impellers to cut down on high RPM cavatation i would use permatex part # 80019 aviation formagasket on the plate gasket and never had a leak. it is a much stronger bond than RTV. JMHO. the impeller vane to pump body gap should be .015Comment
-
Re: 66 BB Water Pump Back Plate Leaking
Peter - it is the bypass pipe that is pressed into the water pump housing that is actually leaking -- not the hose. I didnt think silicone would hold so I just finished sealing it another way. Another thing that may be of interest to you -- I bought this dated rebuilt pump (Nov 65) back in 2001/2002 after the car was judged. Good thing I did because I am currently looking for another Sept through Nov 1965 284 pump to put on the shelf and cant find one anywhere.Comment
-
Re: way back when i used to modify BBC water pumps
Clem -- any idea where I can find this aviation sealant ??? Did you used to coat both pieces -- the pump and the plate ??Comment
-
Re: way back when i used to modify BBC water pumps
any good autoparts should carry it. it comes in a white plastic container with a brush in the top. yes i did the plate,both sides of the gasket and the pump body and i would wait till it sets up before using the pump. check the plate for flatness alsoComment
-
Re: way back when i used to modify BBC water pumps
John and clem-----
I agree that the Permatex aviation form-a-gasket would be a good thing to try. In the old days, I used to always use Indian Head (a product similar to the aforementioned) and it always worked perfectly for me. I still use it for certain applications. The only problem with both of these sealers is getting it off when you disassemble the unit. As far as sealing ability, I don't think that anything works better.In Appreciation of John HinckleyComment
-
Re: way back when i used to modify BBC water pumps
Wow -- Indian Head Sealer -- I used that when I was much younger (59 in Dec) as well - That is a brand I have not heard about in a long time. We used it on all gaskets.Comment
-
i remember "indian head" shellac
the hardened up like glassComment
-
the "indian head" name is still used by
permatexComment
-
Re: the "indian head" name is still used by
5JComment
-
Re: i remember "indian head" shellac
John and clem-----
Yes, Indian Head shellac, now a Permatex-branded product, is still available in some auto parts stores. The one that I use carries it. I've used it for years and still do for a few, limited applications, for which I still prefer it. It is definitely a "hardening-type" product; no doubt about that.
While it's still available, it's definitely been "eclipsed" by modern sealers. It's still my "sentimental favorite", though, and I refuse to give it up completely.In Appreciation of John HinckleyComment
Comment