Hot Rods 8ba overheats on hi way

Been chasing this problem since the truck was first put together and was hoping for some input. Set up is 8ba with aluminum heads and two 94carbs. Bubba Chevy distributer with pertronix. T5 trans. In 1950 f1 with stock rad,electric fan and 160 thermostats.At anything over 60mph truck will get up to 230degrees on a hot day. But around town it never gets over 180. Truck starts and runs great so I really don't think it is a timing issue. Could it be a back radiator even though it looks clean inside? Any suggestions would be great.

Thanks
Mike

 

Check your lower rad hose,,,sounds like sucking shut,,

 

Stock radiator, but is it a new repro or the original? If it's the original it could be restricted from years of rust and shit that u do not see looking down it's throat. Is the motor rebuilt or old? Same could apply there. Is the fan a push or pull? Push fan could be causing air restriction at highway speeds. If the carbs are running rich that could also contribute to it running hot. Would that cause it to run hot only at highway speeds? I do not know. Lower radiator hose closing at higher rpm?

 

Mechanical fan, Speedway sells a good fan, go with the largest dia. that fits (leave the elec. fan/trigger with a 194 to 200 sender), 180 or higher thermostat (you need to keep water in block longer), after market radiator that looks right and fits the hole. Not an expert, just saying.

 

Are the water pumps new?

 

Rear end gear was the culprit with mine going over 55 mph. The temp climbs a bit until I go back down to 50-55 mph. Timing on mine is 2 degrees stock plus 6 = 8 degrees top dead center with the Bubba dizzy. You may want to look at the carbs as well they tend to run very lean at highway speeds. Hope this helped.

 

Keeping the water in the block longer would just heat it to a higher temperature. That's an old wives tale. I had my water pumps rebuilt by Skip Haney in Punta Gorda Florida. The new pumps move twice as much water as the stock originals. I don't run thermostats and have an electric fan (puller type). This is on a full race 8-BA 286 CI. No overheating problems. If your overheating at 60 MPH with a T-5 something else is wrong as you are probably running at less than 2000 RPM's at that speed. Do you have a shroud on your radiator? Where is your fan mounted? In front or back of radiator? Let us know.

 

Have the radiator flow checked or at least get a laser temp probe and check different areas of the radiator to see if they are equal.

 

My flatty does that too. I think that the water is moving too fast through the engine and doesn't have time to cool off. As soon as I push the clutch in and let it idle as I am coasting down the highway the temperature drops rapidly. I have not found a solution yet.

CN

 

Good idea, never thought of that. I have one of those laser temp things, when my gauge reads 230 the heads are only about 200. I have checked the gauge and the thermometer against boiling water and they both are accurate so I don't know why the difference unless that's how much heat the water is carrying away. Gauge sender is right at the head.

 

Thanks for the replies. Few more points I should have mentioned. Radiator is original. Water pumps are speedway.(same issue with stock pumps) motor was rebuild years ago but have very low mileage. Maybe 5000miles if that. Electric fan is is a sucker fan. Truck is channeled so radiator has to sit 6 inches lower then stock height. This prevents me from running a mechanical fan. I have never thought about carbs possibly leaning out at hi way speeds. Rear end in truck is the original. I have been thinking about maybe changing it to go to a different gear ratio.

 

As someone mentioned earlier ; do you have a shroud around the fan? I have found that containing/controlling radiator air flow is usually very beneficial in dealing with heating problems. Another area : sheet metal in FRONT of the radiator ; does it partially 'block', or does it(hopefully) direct, or 'channel', through the radiator? If all these are positive, then Definitely look into 'high speed lean' with the carbs!

 

If you decide to replace your radiator, I use a U.S. Radiator brass/copper, 4 row, triple pass because I was adding A/C to my car. Turns out, my distributor was frozen in full retard and was running hot on the freeway. Swapped distributors and that cured my problem on a sbc. She ran at 210. Now she runs at 140 and 180 if I use the A/C. U.S. Radiator also makes my radiator in aluminum.

 

I have the same problem in my 36 pickup with a stock 8cm. Except I have spring in the lower hoses and a new Grifin Radiator , New 8RT pumps . I run the advance at about 14 degree ( elev 5000 ft) run good. But the engine has 0 tolerance for overheating. I run high flow thermostats, water with soluble oil ( max heat transfer ) I too would like some good input been fighting this problem for years. Thank you in advance 36fordguy

 

Make sure it's not running lean at freeway speeds, that the dist is advancing. Might need a more efficient radiator since 6" of the bottom is covered and not getting airflow. My '47 has a stock radiator and doesn't like the freeways rpms (no o/d). You can live without a fan or shroud with enough airflow at speed (both of those are for traffic). Also if the passages in the motor are slightly clogged (rust, old freeze plugs, deposits) it will be ok at low speeds but higher speeds the water can't flow through enough.

 

23 degree advance @ 2500 rpm , Holly 390 cfm carbureator with 13.8 afr and its still marginal at overheating

 

Zirgo 3000 cfm puller 12 v electric fan . The grill is 100% open to road airflow with baffels to direct air into the radiator but when it gets hot here northern nevada (95 to 100 degree ) it over heats

 

I can almost guarantee it's not a radiator issue. I'm running a stock rad with 160 degree thermostats with 6- 1/8" holes drilled out on stats for flow( learned from a old time rodder) I too have Speedway water pumps and radiator sitting 4" lower than stock, with a Spal electric fan( spelling?) If it's running in town at normal temps most will find it's the low gearing or carbs leaning out at hi way speeds as said before.

 

One more thing to add. I run Water wetter with distilled water and Rotella T oil in mine.

 

At 60 enough air should be blowing through the radiator you could throw your fan away. If you are sure your radiator is good, unless your gearing is so high (doubtful with a stock truck ratio) the engine isn't spinning fast enough in 5th to pump sufficient water then timing, fuel mixture, or collapsing hoses are your probable culprit.

 

Fan clutch?

 

When I took truck to Austin for lsru it ran awesome and no cooling issues, I kind assumed it was just better fuel then we get up here. Must have more to do with the carbs then I would have thought.