[Old Goat 67]

Chalk up one more for the cast impeller.

https://forums.maxperformanceinc.com...d.php?t=411256

FINALLY, a correct water pump
https://forums.maxperformanceinc.com...d.php?t=752911

[allenga]

Radiator out. Since I am taking it all apart, I will put in a high flow pump and new backing plate. Anyone know which aftermarket pump has the best clearance with the backing plate. Edelbrock, Milodon, Flowcooler.

[Old Goat 67]

Word of advise.
Don't buy into smoke & mirrors bull.

An once of prevention is worth a pond of cure!

Get a PONTIAC CORRECT pump with a CORRECT UNCUT IMPELLER.

[allenga]

Originally Posted by Old Goat 67

Word of advise.
Don't buy into smoke & mirrors bull.

An once of prevention is worth a pond of cure!

Get a PONTIAC CORRECT pump with a CORRECT UNCUT IMPELLER.

Ames has this one.

FN258 1970-79 Water Pump w/Gasket, 11-Bolt,
Pontiac V8, Exc. 301 (RP) ............................ 49.00/ea.
Cast impeller. FN257L-FN258 are new, not remanufactured, water pumps. These carry a 90-day warranty.

[Old Goat 67]

Sure can't tell much about that???

Is it made to fit the plate? I don't know.
Maybe an educated call to them?
Must do your homework and/or order one to find out?

[allenga]

Ok, water pump out. I don't see any blockage. There is a gap between the impeller and backing plate. Is this enough to cause the motor to run so hot. The pump is a cast iron Gates.

[allenga]

More photos

[Old Goat 67]

From what I can see in your photos, seems that pump may be the major cause of overheating.

Gap pretty large. Results in cavitation (air bubbles do not pump well).



Only about half of vanes in the chamber. Volume moved = not much.





Anyone have a picture of an original pump and plate for this car??

[allenga]

I called Butler Performance Pontiac tech line and asked what pump they use on their builds. They use the Flowkooler. Put one on, clearanced the plate a little.

My ranged dropped from 200-234 F to 190-212 F with the AC on. Range is 5-10 lower with the AC off.

Also, put a heavy duty clutch on too.

Thx.

[Old Goat 67]

That pump looks very different from the flowkoolers seen before.
Where is the clearance to the rear plate? How much clearance?

[allenga]

Originally Posted by Old Goat 67

That pump looks very different from the flowkoolers seen before.
Where is the clearance to the rear plate? How much clearance?

The clearance on the plate was pretty good out of box. I massaged a bit. I did not measure. I just made it way better than with my Gates pump.

[autobahn]

Just curious how many of you that are reading high temps have installed a new sensor? When I rebuilt my 400 2 years ago I installed a new sensor, it indicated very hot pegged,infared showed normal temps on the pump,radiator,ordered another sensor same thing, reinstalled original back to normal gauge and infared agreed, so I'm thinking the sensors was the problem

[Peter Serio]

As far a coolant temperature sender goes (this would be on GM cars with factory in dash gauges) there are no moving parts inside of one of these senders. So there is nothing that can ever "wear out" or go bad. If you have the original AC delco sender (the one that was in the car when it came from the Pontiac dealer) I see no reason that you would ever need to replace that . The aftermarket & replacement senders available today are not made the same as the original senders as far as accurate gauge readings in 1960s and 1970s GM cars. Inside of the sender is a thermister All of the senders to GM cars with factory gauges are made as a sealed unit and the sender is not adjustable. A thermister reacts to changes in temperature. With the engine running the gauge circuit in the car feeds a very small amount of current into the sender (via a dark green wire) looking for a change in resistance. When one of those senders is cold it will have very high resistance (around 600 to 800 ohms) as you warm the coolant the temperature rise causes the sender's resistance to decrease; thereby telling your gauge to show pointer movement as a rise in temperature. The relationship between the gauge and the sender is critical if you expect an accurate gauge reading. Since the car was made by GM and AC delco was the supplier of all part electrical to these cars. It only makes sense (if you are able) to use an original Delco sender.

Other replacement senders claim to give true readings however sometimes gauges can fail. So replacing just the sender will not solve that problem.

I test the senders that I sell with the car customer's gauge so I know ahead of time that we have a "matched set." There are many new senders listed in computers that will thread into the intake which are not made properly for the year or the car it is sold for. In many cases when a modern replacement aftermarket (non-delco) sender is put into an older 1960s or 1970s GM car that gauge (if working properly) will display a false reading on the dash at a temperature greater than true. In many cases this will be an error of around 20 to 30 degrees higher than actual.

You have to have both the gauge & the sender on a test bench to determine if the pair are working as a matched set. I use boiling water, a thermometer and a 12 volt DC battery (with a bunch of jumper wires) to test gauges.


The parts makers simply do not have data on how these gauges work and GM blueprints are not available unless you buy into their special reproduction parts program. There are licensing fees involved and there is also paperwork to fill out. + GM demands up front payment on anticipated sales.


Makers just sell what they sell but I doubt they actually test their senders in older GM cars.

[DOC]

Didnt see it mentioned above but check your timing and vacuum advance as well as your jetting.. If it is slightly retarded or slightly lean it can cause similar symptoms. If easy check the temps on your exhaust manifolds/headers and make sure they are all somewhat close as well. How do your plugs look?