67 Big Block running a fever

[Craig]

I recently purchased a 1967 390HP roadster. I know the 435HP cars historically run hot and have overheating problems. I wanted a car I can drive, that is why I chose the 390 over the 435.


In cool weather, my car runs at about 190 for 20 minutes and then ramps-up to 215. If I have to make any stops it can run-up to 225 or 230. I flushed the radiator and changed the thermosat and still have the exact same behavior.


My questions are:


1. What is an acceptable (or typical) running temp?


2. Should I boil the radiator or what would be my next process?


Thank you for the help. I'm not an experienced mechanic.


Craig

[Joe L.]

Re: 67 Big Block running a fever

Craig------


A few comments-----


1) Make ABSOLUTELY SURE that your radiator seals(fan shroud to radiator support)are in good condition, properly installed and all there.


2) Replace your fan clutch with a new HIGH QUALITY, THERMAL-TYPE, unit. The GM fan clutch is still available and is GM #3916141. This unit is manufactured by Eaton and is very similar to the original configuration used on your car. A better bet, but one which would require some adaptation would be to use the 74-75 W/AC fan clutch, currently GM #12529342. To use this clutch you will need to use a 71-74 configuration big block water pump shaft and hub, a 71-74 water pump pulley, and a 71+ fan blade assembly. Also, this clutch is configured considerably differently that the original. But, IT WILL COOL. This is THE ONE that will be on my "ZL-1". You can be sure of that.

[John M.]

Re: 67 Big Block running a fever

I have a 69 435 car and the previous owner said that it ran hot. The fan clutch was shot and it had a restrictor plate in the thermostat housing. I installed a TRW $50 fan clutch,(the GM service replacement is $150) a Robertshaw 165 thermostat and a Flowcooler water pump. I now worry that it runs too cold. If you can't locate the waterpump that Joe recommends the flowcooler is a good alternative. By the way, I made these changes based on an article in the restorer by Steve Cataldo.

[Wayne W.]

Re: 67 Big Block running a fever

Probably will need a radiator or recoreing.

[Robert C.]

Re: 67 Big Block running a fever

Craig. 1. Check to see if you have an aluminum radiator or a replacement copper/brass. The correct alum. radiator will cool at approx.30% more efficiantly than the copper/brass repl. one. If you have the alum. one,you might want to have it checked out by a proffesional. If you need a new one, I would recomend DeWitts model #3155316 ($695) 2. Has the enjine been overhauled? If so, expect it to run 10 degrees hotter. 3. Make sure your coolent is 60/40 anti-fr.to water.(ie. higher boiling point) 4. If your system is tight(no leaks)and you have a tested radiator 15lb. cap, I wouldn't worry about opperating temp's of 220-230. 5. Test your temp. gauge for false readings. I bought a separate gauge at a parts store. Install the gauge to test against your inst.pannel original.There are several ways of doing this. 6. Try a 160d. thermo.( Before installing test thermo in a pan of water heated on the stove to make sure it opens. You can use that new remote temp. gauge to test what temp the thermo opens at) I Hope this helps with your problem- Bob

[Richard S.]

Re: 67 Big Block running a fever

Craig, if you are running the original fan clutch or if that is what you would like to run, contact Fred Oliva in Florida. His work is excellent and he is very helpful with any questions you may have. You may find that different clutches turn on at different times and Fred knows all of this information. He is an NCRS member and is one of the best resources available on this subject. Of course, previous threads on overheating can be found in the archives and boy are there a ton of possible causes discussed there. Good luck.