63 engine overheat or not?

[Anthony P.]

I 'm working on a 63 327/300hp 4 speed, idle temps will climb steadily to 230 degrees, (confirmed with temp gun) it has a 180 t-stat in it now. Driving temps at 20-40 mph reach as high as 240 and climlbing we shut it down not to damage! Highway speeds maintains 180 but if temps reach 230-240 at lower speeds it will not recover at hight speeds List of known good parts that have been switched for testing reasons, new fan clutch, 5 and 7 blade replacement fan blades, 160-180 and no t-stat, Original flow tested aluminum rad, and a replacement 4 row brass rad. Dist timing is set to factory specs, with a new vacuam advance! seems like low air flow at idle.

Any oddball things we may have overlooked! any and all suggestions please!

[William C.]

Re: 63 engine overheat or not?

Checked vacuum advance for function? (Hooked to manifold vacuum, not ported or other source) Checked TDC actual using a piston stop to verify the centering of the marker on the damper? (have been known to slip/move)

[Anthony P.]

Re: 63 engine overheat or not?

William It is hooked to a ported vacuam source on a none original carb! you are saying it needs to have manifold vacuam at all times? that could explain it! will check the dampner next week.

[William C.]

Re: 63 engine overheat or not?

Yes on full time vacuum on an early midyear and do check the damper!

[Anthony P.]

Re: 63 engine overheat or not?

ok! good news Thank you! In your opinnion what should the temp drop be across the rad. on a 80-90 degree day at criuse speed rpm?

[Edward J.]

Re: 63 engine overheat or not?

Tony, I few thoughts for you, I would be thinking that you may want to check water pump,(impeller problem) not enough flow. also a easy check make sure the fan belt is not glazed and slipping, Causing the water pump not to spin fast enough.

Running with out a themostat is not a good idea. you need to give the radiator a chance to do its job cooling the anti freeze down before entering the engine .

You also want to be sure the anti freeze mix is close to 50/50 this is important also.this helps with proper cooling effect as coolant flows through radiator and proper boiling point for protecting the engine when they do overheat or run hot.

[Michael W.]

Re: 63 engine overheat or not?

Make sure the lower radiator hose is not getting drawn closed. Possibly swap the pump for a known good one.

[Anthony P.]

Re: 63 engine overheat or not?

We know the water pump is pumping good and the belt is tight, we will check the coolant mixture next week Thank you.

[Timothy B.]

Re: 63 engine overheat or not?

Anthony,

Another thing to think about is the proper fluid level. Fill the overflow tank almost full and let the pressure push some out when the engine is hot. These cars can be difficult to get the full load of coolant because the high point of the expansion tank is not really high to allow air purging.

Make sure the radiator cap is holding the correct 13psi pressure.

What does original flow tested aluminum radiator mean. If it's the original radiator that is your problem.

[John H.]

Re: 63 engine overheat or not?

What does original flow tested aluminum radiator mean. If it's the original radiator that is your problem.

Anthony -

If you indeed have the original radiator, there's no way it's going to cool adequately; it has almost 50 years' worth of accumulated scale in it, acting as an insulator between the coolant and the air. Failure to "recover" to 180* is the key symptom here.

You might try this link for a better understanding of how your Corvette cooling system works:

http://www.lbfun.com/warehouse/tech_info/cooling%20system/cooling.pdf

Note the item near the end on "Ignition Timing".

[Anthony P.]

Re: 63 engine overheat or not?

well thanks to all for the suggestions, at this point I can see that there are two things for sure that must me corrected just to start, 1st the vacuam advance is now being souced by a ported feed, I will change that to manifold source and install the correct 180 degree Robertshaw t-stat. We used and infar-red temp gauge and the dash gauge is right on. I will report back next week after completing the two most obvoius conditions. John the artical link was very informative!! thanks to all.

Merry Christmas to all