[Nathaniel1234]

I have 1962 421 SD In a 55 Chieftain and am having some Cooling issues. I am running Hilborn fuel injection. Had some drive ability issues that seemed like it might have been vapor lock. Installed a water temp gauge and saw was pushing 210 degrees and counting. Yes, the issues of erratic rpms not relating to the amount of throttle returned once I saw temp climb. I felt the radiator and it was not even hot! Upper radiator hose was not even hot. I replaced the thermostat with a new 180 degree unit And new 13 lb radiator cap- did not help. Drained coolant from radiator ( it is the original 1955 Chieftain type) and ran a hose to top and watched water flow freely out the now open bottom of radiator... Seemed to flow through fine. The radiator externally appears good and even seems to have been recored at some point. Threw the thermostat in a pot of boiling water with a thermometer and it opened at 180. There is a hose going to heater core with a return. Yanked the water pump and shaft turned and stamped steel impeller blades are intact. I should mention that with the Hilborn injection there is some custom pipe work with a later style thermostat housing. What do you guys think the issue might be? Think it could help to eliminate coolant to heater core box? This is a hot rod kind of car and I am not concerned about functional cabin heat. Any other thoughts? Glad to take radiator to radiator shop to check/clean/pressure test...

[Nathaniel1234]

[Nathaniel1234]

Pic

[Nathaniel1234]

Pic 2

[Bill Hanlon]

The 4 bolt water pump and associated timing cover are not notorious for improper spacing between the impeller of the pump and the cover like later pumps that used a divider plate. However, I'd use some modeling clay to measure the clearance between the impeller and the big opening in the back of the cavity that it spins in. I don't know what the measurement should be, but on later style pumps 0.030" or so is desirable. Don't forget to use a gasket when you make the measurement.

Just curious, where did the temp sensor plug into the engine at?

Someone will probably chime in soon with the "reverse rotation direction" pump old wife's tale.

[Nathaniel1234]

Thanks Bill, yes I have clearanced the plates closer to the impeller on 65 and up water pump assemblies by modifying the plate insert. Can I modify that piece in the back of the cavity?

There is a female thread in that custom piping which housed the factory 1955 water temp gauge sensor, I just threaded in a autometer sensor in exact same place.

The 421 SD (it is a 61 actually, not a 62 like I said below) is not a reverse flow cooling engine like what came originally in 55. I did wonder if maybe the 55 radiator might operate differently as part of a reverse flow system, but didn't really think so.

[Bill Hanlon]

Assuming the radiator has the capacity to cool the 421, the reverse flow through the heads on the 55 engine vs. the 421's "normal" flow shouldn't make any difference at the radiator. Besides that, you said the radiator was cold while the engine was hot.

More thoughts on "clearancing" the 4 bolt pump: Bolt the pump into the housing WITHOUT the gasket. Turn the pump by hand. If blades hit the casting, pull the pump and install it again WITH the gasket. If it no longer hits, then the clearance in less than the thickness of the gasket. If it didn't hit WITHOUT the gasket, then the clearance is more than the thickness of the gasket.

Clearance testing is a lot easier with the later pumps that use a divider plate. You can check them with the pump removed from the engine.

[Jack Gifford]

Originally Posted by Nathaniel1234

... it is a 61 actually, not a 62 like I said below...

That confuses me, since the '61 SD (or "heavy duty" as Pontiac called them back then) stuff was actually based on 1960 parts. For instance, my '61 SD aluminum Tri-Power manifold is an exact fit on '55-60 heads. Is there possibly some question about hot coolant finding its way out through that weird water manifold?

[Nathaniel1234]

Thanks Jack, well it has a 1961 date code... Looks like a "G" I think, which would make it July...

I will look closely at the manifold... I hope not!

[Nathaniel1234]

Not leaking into valley pan area...

[Teej]

You can also leave the radiator cap off and run the engine till it gets up to temp, or at least above the thermostat value, according to your gauge. I'd think that you should be able to see the point where water begins to really flow when the thermostat opens up. That would also give you an idea how much water the pump is moving.

[Bill Eveland]

I suspect there may be air trapped in the back of the engine in the coolant circuit, I ran into this when I first put my 455 together. I know at least on my newer engine I ran coolant out the back of each head to the water crossover and no problems to date. I know there used to be aftermarket manifolds that had 2 holes on the crossover and depending on early or late heads 55-64 would require soft plugs to plug up one set of holes, but since this is a custom crossover that shouldn't be an issue.

[tom s]

Get a lazer temp gun and see where the hot spots are on the engine.You can point it at the Xover,the area of water going into and out of the block and radiator.Cheap tool for doing exactly what your looking for.Tom

[61-63]

I once had a cooling problem on a setup I was flow testing on my test stand engine and the problem turned out to be a blob of casting sand that had never come out of the water neck. The problem drove me crazy until I took the water neck off and tried to look through it and saw the blockage. Of course digging and banging the sand blockage out solved that problem pronto. You might look inside your water neck, intake manifold, and every other water passage and see of you have something like that going on.

[BruceWilkie]

Its possible someone added water holes to block deck. (made it like 55-59 deck). This would allow a great bit of water to shortcut to the crossover and right back to the radiator. Water in radiator or crossover would be significantly cooler than water in rest of block.

Its also possible something else is allowing too much water to shortcut back to radiator.

Study this link showing differences in 55-59 reverse cool system vs the 1960(and up) "conventional" cooling. Includes plenty of good pics and info showing differences.

http://www.pontiacsafari.com/EngineCooling/index.htm

[flat-bill]

Have you tried to actually verify that the pump is moving water? flatbill

[Bill Hanlon]

Something doesn't make sense here Nathaniel. I've isolated 4 statements from you below.

Originally Posted by Nathaniel1234

Installed a water temp gauge and saw was pushing 210 degrees

Originally Posted by Nathaniel1234

There is a female thread in that custom piping which housed the factory 1955 water temp gauge sensor, I just threaded in a autometer sensor in exact same place.

Originally Posted by Nathaniel1234

I felt the radiator and it was not even hot! Upper radiator hose was not even hot.

Originally Posted by Nathaniel1234

I replaced the thermostat with a new 180 degree unit And new 13 lb radiator cap- did not help.

If the temp sensor which is just downstream from the thermostat is seeing 210 degrees and
If the thermostat is working and
If the upper hose is cold and
If the coolant is flowing through the upper hose
... the where is the heat going?

By the way, I assume the autometer sensor is feeding an autometer temp gauge. If it is feeding the 55 Pontiac gauge it is most likely reading wrong.

[rompn63]

Just a thought, is your engine running lean?

[Nathaniel1234]

Thanks all for your responses!

Yes, it's a new auto meter gauge.

It may have been running lean- last time I had it running, the exhaust was burning my eyes- gotta read the plugs.

The car has other issues which we are working on that I won't go into here right now.

I think the most credible theory is that there have been air bubbles in cooling system. I am going to drill a 1/8" hole in the thermostat to allow for a little better water flow and to "burp" air bubbles, especially just beneath the thermostat (the thinking being that hot water was touching the gauge sensor, but not the thermostat whereby it was not opening.

[Nathaniel1234]

Then will run with cap off to see water is flowing. Inspected water pump and it seems good. Is there a plate in this vintage water pump housing?