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Hoping someone can help with question about fan blades on 1975 stock L48.with 7 blade fan - I have searched numerous threads and can find that there are a number of questions about the spacing between the blades but looking to find out if the pitch of the blades should all be the same or they vary. In picture below the blade in the foreground is about 0.5 in further from the shroud then the one behind it. I have had the fan off and laid on a flat surface and note that all of the blades differ in pitch so it is not just an illusion created by the shroud. There doesn't appear to be any damage to the blades and when fitted and running I do not observe any vibration issues. Is the pitch change just a feature of the design or is there a problem with the blades? Don't want to see it come flying through the hood one day!
Didn't the small block engines have a shroud extension?
Yes. It looks like the car is missing the shroud extension piece, #331870, that attaches with the drilled holes in your existing shroud.
Here's a pic that was posted a few years back from the NCRS judging guide: (Note the main shroud is 339175, extension is 331870.)
Thanks for the responses - I will order the extension shroud (car didn’t have one when I got it). If the blades are all supposed to have the same pitch I may need to get a replacement . Should I just get a blade and do away with the clutch - car is in Florida so basically fan would be running all the time anyway
Thanks for the responses - I will order the extension shroud (car didn’t have one when I got it). If the blades are all supposed to have the same pitch I may need to get a replacement . Should I just get a blade and do away with the clutch - car is in Florida so basically fan would be running all the time anyway
No, do Not get rid of the clutch. Also consider a 180 or even a 160 thermostat.
Thanks for the responses - I will order the extension shroud (car didn’t have one when I got it). If the blades are all supposed to have the same pitch I may need to get a replacement . Should I just get a blade and do away with the clutch - car is in Florida so basically fan would be running all the time anyway
Originally Posted by MelWff
No, do Not get rid of the clutch. Also consider a 180 or even a 160 thermostat.
I agree: keep the clutch. They work and work well.
The blades I have had experience with are all in the same plane. (Not to a high degree of accuracy, but in a general sense.) Have you tried to slightly tweak the blades that are out of plane with the majority? I seem to recall being able to shift one or two of mine to be in better alignment. (Easier to do when it's mounted on the engine.)
Didn't the small block engines have a shroud extension?
My 76 small block has a different shroud/fan and radiator mounting brackets. there is no provision for a shroud extension could 75 and earlier that requires the extension.
Make sure you have the little foam strip on top of the core too. It's a very important part. My motor dropped ten degrees when I replaced it on my car.
Thanks for the responses - I will order the extension shroud (car didn’t have one when I got it). If the blades are all supposed to have the same pitch I may need to get a replacement . Should I just get a blade and do away with the clutch - car is in Florida so basically fan would be running all the time anyway
You should get a proper electric fan solution, especially if you live in Florida.
That way, it can run when it needs to (stuck at a light, or in traffic, yay Florida), and it doesn't run at all when you are blasting down the highway.
Unless you really need to keep it stock for some reason, there's a reason the C4 and every Corvette since has had an electric fan or fans.
Thanks for the suggestion about the electric fan - I just rewired the car and it did include wiring for an electric fan but then I got to thinking of when do I stop spending money. While looking at the fan I thought while I have it off might be a good time to replace the water pump as it looked original and then if I was doing that I might as well change the harmonic balancer as I had previously expressed some concern with it and then thought might as well look at the timing chain. This did prove to be a good choice as it was way too slack. Getting the timing cover back on was not fun. Having just finished replacing a lot of the interior trim and installing a vintage air system I am now considering upgrading the brakes and putting on headers and maybe a top end upgrade, ok you convinced me an electric fan it is but when does it stop, the wife was not impressed when I bought her some new tools for her birthday
Thanks for the suggestion about the electric fan - I just rewired the car and it did include wiring for an electric fan but then I got to thinking of when do I stop spending money. While looking at the fan I thought while I have it off might be a good time to replace the water pump as it looked original and then if I was doing that I might as well change the harmonic balancer as I had previously expressed some concern with it and then thought might as well look at the timing chain. This did prove to be a good choice as it was way too slack. Getting the timing cover back on was not fun. Having just finished replacing a lot of the interior trim and installing a vintage air system I am now considering upgrading the brakes and putting on headers and maybe a top end upgrade, ok you convinced me an electric fan it is but when does it stop, the wife was not impressed when I bought her some new tools for her birthday
I think you'll find the electric fan solution is best for your situation. If you've already planned ahead with an alternator and wiring upgrade, you may just need an inexpensive solution, like the C5 fan which should fit with some trimming of the plastic. Ask for help if you need (perhaps in a new thread), but there are a lot of examples on this Forum (and lots of counter-examples, too, which is perhaps how electric fans sometimes get a bad rap, based poor results from an improper install).
As for keeping your wife happy, make sure she has, at all times, a running, driving Corvette of her own!
Fan Blade Question
