6T5RUSH

Guys,

I am convinced after driving this summer and having done all that I have to address running cool in traffic that my fan clutch is just not engaging at a low enough temp. Here's my background story...kinda' long but I guess you can't give too much info in order to zero in on a fix.

I have a fan clutch which I had removed ‘cause of not functioning. My car is a ’65 327/300 converted to visually look like a 365 horse version. I changed the hydraulics, using a 70 LT1 cam, lifters and service replacement intake. Along the way I’ve also added Classic Auto Air’s Perfect Fit system. In this conversion, I specifically addressed the cooling of this new motor. I’ve replaced the rad with a DeWitt’s, added the factory sealing on top of the rad as well as sealed off all gaps in the sides and bottom. The original 5-blade fan was replaced with a service replacement 7-blade fan (for air cars). I’m running with a 180 degree ‘stat. In addition, the correct Holley 2818-1 list carb and the correct vacuum can is in place. Further, both upper and lower hoses have springs inside and were new at the time of this rebuild. Finally, I addressed the ignition by mapping her out. Initial is @ 10 degrees (I’m using the 300 horse distributor that has been recurved and shimmed up), all in by 2600 r’s for a total of 36 degrees.

This original fan clutch has a rectangular metal tab across it’s face. When you spin the clutch, it seems lumpy. Could be the silicone fluid has leaked out of her over the years. My reason for replacing her.

The current fan clutch is a DELCO replacement I purchased 2 years ago. From what I’ve read the replacement fan clutches are designed to not engage until the air temps immediately behind the rad (in front of the clutch) reaches well over 200 degrees. I have an IR gun and have confirmed the temps read at the thermostat housing are the same as the factory gauge. This DELCO clutch will not engage until the temps are in the 220 degree range. The car will not puke its guts but it certainly is unsettling to watch the gauge climb to 220 degrees and hang there. This only happens when I’m in traffic over a 10-12 minute time frame. On the highway she runs at 185…with the air on. The Classic system came with 2 Spal fans which currently only kick on when the compressor is on. Oh, the high temps occur in bumper to bumper are with the air off.

I do plan on adding a switch and wiring this to the Spal fans so that I can manually and independently turn those fans on when needed, but first, I am focusing on this fan clutch to do its job a lot sooner then 220degrees.

Which brings me to my questions:

1. Can these original fan clutches be recalibrated to kick in at 185-190 degrees?

2. If so, who would you recommend doing this?

I jumped over to the NCRS board (not a member, but the board is open to search their archives for rebulding fan clutches. Fred Oliva is the recommended person to do these. Unfortunately, Fred has a very good thing going and is totally backed up. I'm not so interested in correct finishes as I am functionality.

Again, sorry for another cooling thread but everything points to this fan clutch just not engaging early enough.

Thanks guys!

Jim

wmf62

try a flex-fan...
Bill

6T5RUSH

wmf62,

Thanks for responding Bill, but b/4 I go that route I want to exhaust the possibility of recalibrating the factory fan clutch.

Jim

ctjackster

Jim - which fan clutch (you advise "DELCO") do you have in there now?

Is it pn 3916141? That works very well for me, at idle, even though I have heard that it, like all "modern day" fan clutches, engage at a higher temp than the FC that was originally installed on the 65

Black_Magic

Here is a PDF file on adjusting clutch.

**** It's about 1.8 meg *****

Click here to download

George

6T5RUSH

Black_Magic,

THANK YOU, THANK YOU, THANK YOU!!! Excellent and to the point article. Ya' know, I've seen this posted over the years but didn't copy/save. I'm definitely going to try this.

THANKS AGAIN Black_Magic!!!

Jim

6T5RUSH

Yo Jackster,

I checked my records and the current fan clutch on the '5 was purchased from fleabay. It's #15-1431 and is listed as fitting Chevy Corvettes. Showing as replacing GM #s3916139 and 3814560. This has the spring on its nose. I'm sure it's calibrated to not kick in till upwards of 210-220 degrees.

That article to adjust these clutches applies to both the flat metal bar as well as the spring type.

Wish me luck!

Jim

Jack60

Thank you, George I put a new clutch fan on my 60 and though it still wasn't right, this should work. Thanks again.

Hitch

He wants to cool his car not sound like it's an airplane... Jim you are on the right track to adjust the fan clutch. That is exactly what I was going to post but Black Magic beat me to it. I had a similar problem that I corrected by making my clutch engage at the temperature that we need it to. Good luck. I think this will help you considerably. Dave