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Overheating issues with Big Blocks are frequently, vacuum advance still plugged into ported vacuum or disconnected altogether, or Insufficient initial timing. A worn out fan clutch can also be at issue. When hot the fan blade should only spin about one revolution when spun by hand after the engine is shut down. Also there are lots of issues with reproduction sending units and gage reading accuracy. Have you actually checked the running engine temperatures with an IR gun to verify it's as hot as the gage indicates? If you are concerned about your shrouding it would probably help to post some photos of the fan/shrouding as installed on your car.
Read that first link in my post. The second one is good if you think you have ignition problems causing your problem. Your fan should be half in and half out of your fan shroud.
To answer the OP's original questions, the fan shroud doesn't completely surround the fan. The bottom quarter or so exposes part of the fan, even though the shroud makes a complete circle. The frame cross member fills in the open part of the shroud. For an L72, the correct fan has 5 blades. Dan's pic shows what belongs there.
Thank You..this shroud appears to be an air conditioned car shroud. My shroud (non air car) does not have the lower portion. My understanding is non a/c BB 425 hp cars did not have a full shroud ( top and bottom piece). I an going to install an a/c car shroud in my none a/c BB. This will definitely help.
Thank You..this shroud appears to be an air conditioned car shroud. My shroud (non air car) does not have the lower portion. My understanding is non a/c BB 425 hp cars did not have a full shroud ( top and bottom piece). I an going to install an a/c car shroud in my none a/c BB. This will definitely help.
AC cars used the same shroud. only difference was AC cars used a add on inch or so wide part at the bottom and had rubber seals around the shroud
Last edited by Nowhere Man; 11-13-2018 at 08:50 PM.
Years ago incorrect fan shrouds were sold as replacements for these C2 BB cars - I think they were C3 pieces. You could have one of those. Or you could have an original that had part of the lower section broken off and missing.
You are correct... my lower piece is missing... most likely broken off. I emailed DeWitt this morning asking if they recommend a shroud because I switched to a De Witt Alum. radiator. Thanks again.My car is running real strong in these cooler temps.
Thank You..this shroud appears to be an air conditioned car shroud. My shroud (non air car) does not have the lower portion. My understanding is non a/c BB 425 hp cars did not have a full shroud ( top and bottom piece). I an going to install an a/c car shroud in my none a/c BB. This will definitely help.
AC was not available on 425 HP cars, but it was on the 390.
11-13-2018, 05:07 PM
