Old school Chebbie guy assembling first Olds. Have had trouble on other threads, now it's a water leak. Engine is in and all hooked up - I always do a straight water fill for the initial start just in case of an issue (coolant is soo much messier right?) I don't even get a full gallon in and already hear it hitting the floor. The leak is big and is along the bottom of the water pump in 3 lines. Pouring out like the pump isn't touching the timing cover. See pics. Dont know how this is possible, all bolts in and tight, the little ones aren't stripped out, all surfaces were super clean, pump was working fine before tear down...did I miss something obvious?

 

Are you sure you used the correct gasket? Every gasket set I have bought had 3 different water pump gaskets. One is very close but the area around bypass hole is slightly different.

 

I will check - I do have the other 2 gasket saved that were in the kit. I just slid a .003 feeler gauge in there very easily. Confirmed it is not touching along the bottom for some reason grrrrr

 

^^^^^^^

 

Also be very careful with those self-tapping 1/4-20 fasteners. They only thread into the sheet metal front cover and are very easy to strip. Use the factory recommended torques.

 

There are two gaskets that are close but one doesn't cover one corner at the bottom. What brand water pump? I had the old riveted cover on an open impeller Flowkooler pump hit the timing cover but still didn't leak. Remove the pump and check both the pump and cover for fatness. I have never seen a warped timing cover water pump but you never know.

 

So these 2 gaskets are very similar - only diff is this slot. Which one works better? I haven't cleaned up the pump surface but both gaskets line up nicely.

 

The one with the slot is for this bleed hole on your water pump. Just fit it up and be sure it completely covers the sealing surface. I'm not sure it does.

 

Did you use any type of sealer ? I use Permatex Aviation Form a Gasket on those gaskets. Also, make sure the bolts are not bottoming out in the block.

https://www.permatex.com/products/ga...-liquid-16-oz/

 

Ok so on close inspection BOTH of these gaskets are wrong. Each has 2 small places where the paper drifts off the pump casting. (Like suggested above) perhaps my pump is wrong for my car? Casting 412265 and my car does have AC

 

Likely this.. 😉

 

When I did the 307 in my Wifes car a few years ago I had to go through 3 different pumps from different manufacturers to get one that matched the original. I ended up with a GMB and it has been fine. And if I remember correctly I had problems with the gasket matching also. Especially around the bypass area.

 

So this is the same pump on the engine before the rebuild, and it didn’t leak then, so there is a gasket that fits.

 

I'm the least expert person here, but just to let you know I tapped my big block timing cover screw holes long ago with the next larger size because someone before me had stripped them.

Also, when doing gaskets, a surgically clean flat metal surface on either side of the gasket is where to aim. So, sandpaper, dremel, whatever you can do to ensure a flat even surface for the gasket to seal.

Not sure what current advice is on silicone or no, but I've always used either the gray stuff (in high temperature spots) or orange stuff as a thin coat (not goobered up) on both sides of the gasket.

I let it tack up (aka dry) a bit then assemble the parts to torque spec working in a star pattern, not sequential one by one.

I finish up this job with a prayer dance & ritual offering of silicone on an alter to the gasket gods to improve the odds on a seal.

Cheers
Chris

 

Previous owner installed the pump with great stuff and no gasket material. BTW I noticed the lower rad hose is too big for the pump outlet and had 2 clamps and sealant when I tore it down

 

And HERE's the issue. 1970-older pumps use a 2.0" inlet (and a 1.75" outlet at the bottom of the radiator). 1971-up pumps use a 1.75" inlet (with a 1.5" outlet on the radiator). Obviously you have the late style pump and an early hose. Try VICTOR REINZ 711397400.





And to fix the half-fast hose attachment, use a 2.0" to 1.75" reducer bushing. Gates P/N 26392.

 

I think the first thing I would do is see if a correct new water pump is available. I checked GMB but they only show non AC. Carquest shows one for AC but says to call for availability.

 

The 5.6" pumps with the 2.0" inlet are pretty much non-existent in the replacement market. You're pretty much stuck using the later pump with the bushing. Ironically, most replacement radiators for these cars also use the later small outlet, so sometimes two wrongs DO make a right, since you can just use the 1971 lower radiator hose in that case.

 

Can I use the $200 Thornton reproduction?

 

Sure, or use a $15 gasket...

 

The 404847 pump would solve a couple of other issues, like the mismatch lower hose size and the pulley alignment. Turns out my current pump has a 6.0" height and I need the 5.6. Has anyone had a good experience with the reproduction pump?

 

I can't recall the part number, but I have been using FlowKooler pumps for at least 25 years to good effect.

I've got the impression that in a world of cheap rebuilds they decided to do it right even to the point of putting a plate behind the pump vanes that improves flow. Hence FlowKooler, I think.

Hope that helps.
Chris

 

It makes me wonder why the factory used the larger outlet then shrunk it down. I find the gasket pictured us always the right one but I only have the 6" long A/C pumps in standard rotation, probably have 5 of them. One is a factory closed impeller cast iron pump. I have one of the riveted plate on open impeller Flowkooler aluminum pumps, does nothing positive for cooling but has not failed in 15 years. I bought the second to last Flowkooler reverse rotation V6 diesel water pump with their billet closed impeller, very nice, probably helps. It fits much tighter than the smaller open impeller. With a 455, I would go closed impeller, since they tend to run on the warm side.