PY Online Forums - Bringing the Pontiac Hobby Together - View Single Post - 5-blade flex fan vs. 7-blade clutch fan for better cooling and possible HP gains

tremo · 08:17 PM

Quote:

Originally Posted by GTOLou

David Freiberger did a episode on engine masters - pretty sure the clutch fan was okay, but the flex fans were...horrific - but don't quote me! Find the episode..

Quote:

Originally Posted by lust4speed

Only problem I see is that a shroud for the 5-blade 19" fan is going to be a little large when you drop down to the 18" fan. Think you can flip a coil on whether the 7-blade potential for moving more air will be offset with the poor fit in the shroud.

I had the H.O. fan with the proper shroud and it worked well supplying cooling for my added AC system except at very low speeds. I converted to the 19.5" 7-blade AC fan, proper shroud, and SD clutch and it will idle forever with the air on without the temp climbing.

Quote:

Originally Posted by nUcLeArEnVoY

How's your water pump? Is it clearanced properly? Coolant flow affects all avenues of cooling; hi and low speeds.

Thanks for the replies, all!

Yeah, I forgot to mention that the water pump is a FlowKooler Hi-Flow #1649 from Summit with the accompanying divider plate (see attachments). I replaced the stock pump back in March 2018 and I vaguely recall doing a cursory check for clearance while also ASSuming the newer divider plate from FlowKooler would have it clearanced properly?!

The engine has never overheated, but it does get to ~210-215 degrees in traffic on hot 90+ degree days with the 19" flex fan along with the original/stock fan shroud used on the 350ci (no A/C, so it had a 4-blade fan) which I replaced with the 400ci. My goal is to reduce the operating temp so that the engine is not so heat soaked after an hour+ drive to the track.

Thanks for the pointer, I will search for that Engine Masters episode!

I now have the 18" 7-blade fan and clutch from Ames (#P154GA, #P154G 1964-76). The catalog did not offer a 19" clutch fan, so I went with what was available. I just need to find time to install it. I will provide some empirical testing feedback once I get it installed. However, now that the weather is cooler, the real test will be next summer...

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