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**HO455** · 09-10-2020, 07:42 PM

No need to apologize for posting lots of information on a problem. You have done a great job troubleshooting this problem.
A couple of thoughts. I am guessing that the motor has a fair amount of miles on it from your report on how dirty the water was. Tired engines can run hot.
I had overheating problems on an old 236 Chevrolet 6 that was cured by removing the water pump and physically rodding the rusty clay that had collected in the bottom third of the water passages around the cylinders. You may have a similar situation. However it's nowhere as easy to access the passages on a BBC as it is on a 235.
And as FlyNavy says ignition timing can be a big factor. Do you have access to a distributor machine?
Have you tried disconnecting and plugging the vacuum advance hose to the distributor to see if that helps?
Pusher fans are really more of an air flow reducer and should not be used unless there is on option for a puller fan.
And it is hard to tell from the photos, how much of the fan blade sticks out past the rear edge of the shroud? You should have about 1/3 of the fan blade past the back edge of the shroud. This link may help.

http://67-72chevytrucks.com/vboard/s...d.php?t=582331

09-10-2020, 07:42 PM	#29
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,810	Re: ???Coolant Temperature Sending Unit??? No need to apologize for posting lots of information on a problem. You have done a great job troubleshooting this problem. A couple of thoughts. I am guessing that the motor has a fair amount of miles on it from your report on how dirty the water was. Tired engines can run hot. I had overheating problems on an old 236 Chevrolet 6 that was cured by removing the water pump and physically rodding the rusty clay that had collected in the bottom third of the water passages around the cylinders. You may have a similar situation. However it's nowhere as easy to access the passages on a BBC as it is on a 235. And as FlyNavy says ignition timing can be a big factor. Do you have access to a distributor machine? Have you tried disconnecting and plugging the vacuum advance hose to the distributor to see if that helps? Pusher fans are really more of an air flow reducer and should not be used unless there is on option for a puller fan. And it is hard to tell from the photos, how much of the fan blade sticks out past the rear edge of the shroud? You should have about 1/3 of the fan blade past the back edge of the shroud. This link may help. http://67-72chevytrucks.com/vboard/s...d.php?t=582331 __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 Last edited by HO455; 09-10-2020 at 09:21 PM.