Many of us have/had overheating problems. Well I discovered an issue with Fan Clutches and that is that many are set to lock up after 210 deg. Early ones locked up much sooner. A simple adjustment on some result in them locking up at 170 or so deg. I did mine this AM and it dropped the engine temp to a stable 175 with a 160 stat in 75 deg temps.
Dean helped and posted the PDF article here:
Adjust fan clutch
Hope it might help some who are struggling with temp creep.
Is your 175 deg with temp sender in the head!
If so thats very good!
But if the temp senders in the intake then be aware the 175 deg intake temp = approx 190-195deg in head temp in warmer summer temps and if thats a cruise temp then when you hit moderate traffic your motor will see 200-205+ deg .
Just to clarify something here, the HD fan clutch /HD Hayden thermostatic 2747 I rec using on 69-72 chevelles isnt set to lock up at the higher 210 deg mark you mentioned. It locks up at a much cooler temp than that and doesn't need any tweaking unless your motor needs more cooling then the HD fan clutch provides with its thermostatic spring in stock factory position as recieved from Hayden.
The Hd fan clutches generally lock up a bit tighter for more fan rpm = more air being pulled thru the rad and they also should be set to lock up at a slightly lower temp too both of which is why the HD thermal fan clutch I rec cools significantly better then the std thermal fan clutch that came on these cars.
But this is great info to know if someone used a fan clutch thats meant for newer app on a chevelle or if their fan clutches lock up temp was adj too high from factory so you can tweak it to lock up at a lower temp.
Thanks for posting it!!!!
BTW,since we are talking cooling my mild perf bbc in my 69 in 90+ deg outside temps (runs cooler in 75 deg outside temps!) with temp sender in head runs 178ish at cruise & 180-185 sitting in moderate stop/go trafffic never hitting 190 deg .
I get those great engine temps in hot 90+ weather with temp sender in head using a basically stock GM clutch fan cooling system setup (that i tweak to run cooler esp in hot 90+ deg temps) is a std flow 160 stat w-bypass drilled (vs stock 195 or 180)/hayden hd fan clutch (vs less effective stock std duty fan clutch)/stock gm 772 clutch fan and matching stock fan shroud/stock type 4 row rad(vs 2-3 core rad with less cooling efficnecy)/milodon stock repl hi flow pump (vs stock pump likely running newer less effective stamped steel impeller)/ 30% anti frz-70%dist water coolant mix(better heat transfer)/and of course also proper tuning of motor when it comes to timing(esp base with aftermarket non gm perf cam!)-proper fuel calibration in carb & running vac adv on full int vacuum for additonal timing at idle .
The 4 row rad/hi flow pump/hd therm fan clutch/std flow 160 stat/30-70 coolant mix/vac adv on full int vac & proper engine tuning COLLECTIVELY reduced overall stabilized cooling system-engine temps a lot as compaired to the stock gm clutch fan setup.
I have found this cooling system setup to consistantly be the key to reducing engine temps in hot weather they are a stock bbc or sbc to a pretty hot 496-502-540cid /550-600+hp bbc . This simple fairly inexpensive yet reliable effective cooling system setup satisfies them all from my many yrs of 1st hand exp dealing with & correcting running hot issues on stock for fairly hot street muscle cars running old school 35-40 yr old bbc/sbc motors these cars came with & not newer efi/ emmissions motors that are a diff story!