Water pump question

[dzbowtie]

Currently working on initial start up of a 638 1-piece rear seal block, oe roller cam set up. Upon the initial start up, my temperature gauge read hot (230-240) I just wanted to make sure that this block did not require a certain flow water pump. I installed a standard long style water pump, pic attached. Heads are aftermarket vortecs set up to run with the roller cam. The temperature sending unit is attached to the driver side head, which I also replaced (I’m wondering if it is compatible with the original equuis gauge I have in the cab).

The temperature was read prior to dialing in new carburetor and distributor timing. When I saw the gauge I turned the engine off.

When it first fired up, the only coolant I had was in the radiator, 50/50 mixture. Once it cooled down enough to remove the radiator cap, I had to add more to top it off. It appears that what was originally in the radiator has cycled into the engine.

I appreciate any information I may be missing.

[geezer#99]

What rpm did you run it at on first start up?
Why didn’t you fill it right up with coolant before starting?
Did you hook up a bypass hose from the water pump to the intake?
Instead of relying on your maybe working gauge you should use a heat gun.
What’s the timing like?

[dzbowtie]

When it first fired up, I’d say idle - 1200ish rpm. I initially filled the radiator prior to start up and it was pulled into the engine. I verified my sending unit, it is compatible with the same brand gauge so I’m sure it was reading correctly. I’m guessing it read the head temp without coolant making it up there at that point. The heater hose has been hooked up to the water pump and intake, prior to starting. The timing has not been set yet as I shut the engine off once I read the gauge. I was thinking the cooling system needed to purge the air out.

[geezer#99]

No matter what motor, roller cam or not, it’s good idea to run them at 2000 rpm for 20 minutes. Cam and lifters get their lubrication from oil splash.
You’ll need to keep an eye on the coolant level as the motor burps the air out.

[Accelo]

If you leave the top heater hose off till water runs out of it and then connect it you will fill the block and avoid the burps.

2000 RPM makes a lot of heat. Extra fans help.

If the motor gets hot I shut it down and restart and continue after it cools down. Lectric Limited sells correctly calibrated sensors for the early vehicles. Over the counter (i.e. imports) temp. sensors are junk avoid them at all costs.
Cheers

[dzbowtie]

Thank you all for the help. It is greatly appreciated!

[dzbowtie]

Is there any reason to think that the long style traditional water pump would not flow correctly for the later model block? The block is a 638 casting and had provisions for oe roller set up. I assume it originally has a serpentine set up, but it has the v belt set up now.

[dzbowtie]

Update: the issue was not the water pump. Long story short, the issue ended up being the temperature sending unit and adapter bushing used to mount in the cylinder head. I used a steel bushing that was longer than the original brass bushing in my old engine. I never paid attention to the length, but the sending unit was recessed and shrouded in the bushing. I put the old unit in the head and temperature read at 180.
Thank you all for the help, it is an issue I’ll pay attention to next time for sure!

[53burb]

thx for the follow up....not everybody does that and we're left wondering....