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I did this on my 69 which runs same basic 3 core harrison radiator .
I had the stock 3 core harrison rad recored with a new generation " hi efficiency 4 core " that's designed to fit the original harrison 3 core rad tanks.
Bob Hagerty did my rad resto/conversion from 3 to 4 core hi effciency core whos an expert in radiator resto's with approx 35yrs in the Biz ,he's an honest experienced person to deal with.
Heres the link to hi sit/contact info.
If you call Bob pls tell him S.Wheaton from NY with the 69 chevelle ss 396 rec you to him.
If you dont have a rad Don From Alumnitech can hook you up with a repop harrison rad or a hand mfg'd AL rad that looks a lot like a harrison rad esp if you paint with it blk rad paint.
My rad looked great when done and better yet performs very well,holds at approx 180-182 deg max in 90+ deg temps in traffic and 175-180 deg at cruise in 90+ deg temps too with a mild perf 396.
I run a hd fan clutch Hayden 2747 same as Napa-271303 which provides a little better cooling for bbc then std duty fan clutch/stock gm 7 blade 772 AC-HD cooling option clutch fan/stock shroud/Milodon hi flow water pump for better coolant flow/160 autozone durlast stat/15-16lb stock repop RC15 rad cap/3.31 gear/M20 4spd.
FYI,dont run hi flowhi perf stats mfg'd today/out of USA because many dont work correctly partially opening restricvting coolant flow making the motor heat up when at higher cruise rpm.
I had 2 diff hi flow stats from 2 dif mfgs defective in a row making me chase my tail for a while thnking it cant be 2 bad stats in a row when it was in fact the issue making the motor run hot but not quite overheat either.
These older generation bbcs like to run cooler in 175-180 esp on hot days,but with the 2 defective new 180 deg hi flow stats it ran approx 190-195 at cruise and 200-205+ when in traffic only 3-4 mins.
You could actually see a 1.5-2x increases in coolant flow in the rad with hi flow stat vs std flow 160 deg autozone duralast stat when you had rad cap off, motor hot ,and then bliped the throttle . With the 160 stat the coolant litterally shot out of all 4 rad tubes to other side of rad tanks but with 180 deg hi flow stat coolant would not even go half way across rad tank when i hit throttle to same approx rpms.
Those higher temps on edge of too hot made the motor loose a noticeable amount of power which it regained with the 160 deg duralast stat allowing full/proper coolant flow making the motos temp stabilize at 15-20 deg lower temps in same 90+ deg outside air temps.
Scott
