Cooling Issues

[Devil Pup]

How would i check the cap to make sure it is working?

[Devil Pup]

I had a quick thought when i was gettin ready this morning. . we were talking about possible air flow issues and it dawned on me, when my truck gets hot and im sittin at a light at idle, i put it into natural and bring the rpm's up and the temp falls a bit. does that change anything?

[Stocker]

That's normal, because the coolant will circulate faster, but mainly because the fan will move more air...

[Devil Pup]

ok but does that mean i have an air flow problem?

[69 longhorn]

Originally Posted by Devil Pup

ok but does that mean i have an air flow problem?

It sounds like an airflow problem to me.....but if that is so, it should run cooler @ highway speeds, than it does in town. If it were mine, I would install a smaller waterpump pulley(1-1 1/2" smaller), & see what happens. You could also have other issues ,as in timing,or lean carburation. I like to set the total timing @34 degrees @ 3000 rpms(vac can unhooked & plugged on a pump fuel smallblock). on an HEI dist, this will relate to approx 12-14 degrees intial @ idle with the vac unhooked. I would address those 2 things 1st, & move on from there. another thought.....what carb are you running,& how much vacumn does the engine pull @ idle?(possible air leak?) Is the waterpump brand spankin new? crazyAl

[Stocker]

Originally Posted by Devil Pup

ok but does that mean i have an air flow problem?

Maybe -- but not necessarily. I have owned new or near-new vehicles, with everything in top condition, do the same thing -- probably just as a result of very high ambient temps and cooling system designs that were perhaps not quite up to extreme heat.

Since yours cools down a bit at higher RPM, air is being pulled through the radiator by the fan.

Did you ever check the gap between the fan shroud and the radiator? If so, I missed it...

[Olden Days]

lot of good suggestions here already. I will throw some more possibilities out.
You say same engine that was overheating was rebuilt? Was it hot tanked and thoroughly cleaned checked for cracks? bored over? Cylinder walls too thin? Were new heads checked for cracks? Have you looked into the radiator with the cap off and the engine running? If not do so and see if there are any bubbles in the water.

[Devil Pup]

Yes i checked the gap it was pretty much non existant.
i have looked into the rad when it was running and no bubbles just the flow of coolant.

i really dont know if they checked everything for leaks or too thin of side walls, alls i know is the motor ran at a great op temp when i had it built in cali and then when i came to az it started over heating constantly.

and crazy al i am running a edelbrock 600cfm and the water pump is about 2-3 years old now.

[mclairmo]

Originally Posted by Devil Pup

I had a quick thought when i was gettin ready this morning. . we were talking about possible air flow issues and it dawned on me, when my truck gets hot and im sittin at a light at idle, i put it into natural and bring the rpm's up and the temp falls a bit. does that change anything?

As the rpms go up, so does the rotation of the water pump and the flow of water through the engine. Airflow is not the issue as you still overheat at speed. Clearly, you have a water flow issue as evidenced by the fact hthat temps drop when you raise rpms. Your 1 to 1 ratio pulleys are underdriving the water pump which means that the water pump is spinning too slow as compared to stock oem. I would switch to a smaller water pump pulley (less than 6 inches) and a larger crank pulley (more than 7 inches). While this may not be your only problem, I think it will help. I would also run a hi flow T-Stat. Also, your block (which I assume was re-used in the rebuild) may have some casting slag in the coolant passages blocking coolant flow. Did the rebuilder check for that? Also, check timing for too retarded and carb for being too lean. Make sure vacuum advance is hooked up.

[69 longhorn]

Did you get her sorted out? crazy Al

[Devil Pup]

No unfortunately, i ended up having some crazy things go on and had to move out on a one day notice, spent every dime i had to cover the new apartment so i gotta wait until i have even $10 to try the T-stat lol.

[69 longhorn]

Let us know how it goes..... crazy Al

[lovnthe70]

did you ever figure anything out? i have a fairly similar issue i am working on now.