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drolston · 07-13-2019, 05:03 PM

Road test #1: Full advance on the distributor adjustment and reset vacuum brake to contact plus two turns. Outside temp 94. Still overheats beyond the hot mark for only a few minutes in traffic. At 60 - 65 mph the temp crept past the hot mark. Got pretty noticeable spark knock (pinging) on hard acceleration. Conclusion: retarded spark is not the overheat problem.

Road test #2: Removed the 170 degree high flow (Subaru) thermostats. Gave the vacuum brake an additional full turn in. Spark knock much less but still a bit more than I am willing to risk. Slower to overheat in slow moving traffic, but still pegged hot sitting at idle for three minutes. Outside temp 95. Did not get to 60 mph, but at 50 mph the temp went just over the 3/4 mark. Observation: With speed, baffles and shroud, airflow through the radiator is still not enough to cool the flathead under load (60+ mph). With Dennis Carpenter high flow water pumps and no flow restricting thermostats, it still overheats too quickly in traffic. Conclusion: That pretty little Champion aluminum radiator just does not have the heat transfer capacity or efficiency to do the job.

The same engine (pre bore and stroke) did not overheat with the '41 truck radiator that was wedged in there. And the block was thoroughly cleaned during the rebuild. I will have that radiator re-cored (ouch!) and put it back in.

The .047 jets came today. We will see if it runs any cooler at highway speed, and if that helps the problem of stalling at stoplights.

07-13-2019, 05:03 PM	#13
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Running too Lean? Road test #1: Full advance on the distributor adjustment and reset vacuum brake to contact plus two turns. Outside temp 94. Still overheats beyond the hot mark for only a few minutes in traffic. At 60 - 65 mph the temp crept past the hot mark. Got pretty noticeable spark knock (pinging) on hard acceleration. Conclusion: retarded spark is not the overheat problem. Road test #2: Removed the 170 degree high flow (Subaru) thermostats. Gave the vacuum brake an additional full turn in. Spark knock much less but still a bit more than I am willing to risk. Slower to overheat in slow moving traffic, but still pegged hot sitting at idle for three minutes. Outside temp 95. Did not get to 60 mph, but at 50 mph the temp went just over the 3/4 mark. Observation: With speed, baffles and shroud, airflow through the radiator is still not enough to cool the flathead under load (60+ mph). With Dennis Carpenter high flow water pumps and no flow restricting thermostats, it still overheats too quickly in traffic. Conclusion: That pretty little Champion aluminum radiator just does not have the heat transfer capacity or efficiency to do the job. The same engine (pre bore and stroke) did not overheat with the '41 truck radiator that was wedged in there. And the block was thoroughly cleaned during the rebuild. I will have that radiator re-cored (ouch!) and put it back in. The .047 jets came today. We will see if it runs any cooler at highway speed, and if that helps the problem of stalling at stoplights.