6T5RUSH

Boy, you sure can tell it's summer. Lot's of threads on overheating and what to do.

My issue is my '5 tends to climb in temp (210 +) when she's in slow traffic. The temp gauge has been confirmed reading correct by use of an IR gun. This temp climbing is taking place without the Classic Auto Air being on (added a year ago). I've double checked how deep the fan blades are into the shroud (roughly 1/3 into the shroud...thinking this is normal). I've also sealed off the rad support and shroud with the factory piece for air cars across the top utilizing the self sticking foam around the sides of the shroud.

Everything in the engine compartment is fresh relative to the cooling system.

What I've done in the past 2 years:

Rebuilt the original 300 horse to 365 horse (LT1 cam, lifters and intake)

New Dewitt's rad.

Replacement 7-blade fan

Upper and lower hoses were new 2 years (spring is in lower hose)

New heavy duty water pump last year

Replaced the original fan clutch (still have) with a Delco 15-1431 which according to the tag says it replaces the 3814560, 3916129 & 1482705 and not the 3916141 (didn't know better).

180 thermostat

Fresh 50/50 mix of DEXCOOL (I know, got to go to G05)

What I don't know on this replacement fan clutch is what it's # is.

So, my question to you is: Can these fan clutches be adjusted to kick in sooner? Let's say the replacement fan is set to kick in at 195 degrees. Can this be adjusted to kick in at 180 degrees? I seem to recall a site that majicv8 posted way back when where it gave you a "how to do it" on this.

I'm reluctant to replace the fan clutch with what I've read recently is the correct fan clutch for this '5...the 3916141. Short of adjusting these, that's what I'll end up springing for.

Getting ready for a road trip to St. Ignace, MI.

Here's to staying cool.

Thanks in advance!

Regards,

Jim

ctjackster

Jim - I put the GM Fan Clutch you id in your post in my 65 at the beginning of the 2004 season, I understand it locks up at a slightly higher temp than the oem unit from back in the day, but never had any probs, a steady 180 on the hottest of days (of course, the cooling system WAS the big issue with the car when I got it, so EVERYTHING in that system has been updated - checked - replaced - refreshed, including one of Tom's restoration rads)

From my GMPD order history page:



Order Detail

---------------------------------------------------------------------
Order Number 69472
Order Date Feb 9, 2004
Customer Number
Customer Name Jack
Order Total $130.31
Order Status


Complete

Invoice Number:
159344



Order Detail:


Tracking Number(s)

54412098974

Quantity 1
PART NO. 3916141
DESCRIPTION CLUTCH
PRICE $108.59
EXT. PRICE $108.59
CORE $0.00
TOTAL $108.59
STATUS Shipped DHL
Tracking #


Taxes: $0.00

Handling and Shipping: $21.72

Donny Brass

Jim, my clutch and fan are off the car right now, if you would like to try them out on your car, let me know.

pdorazio1

Has your heater core ever been replaced?

vark_wso

Jim

I am not familiar with your Delco p/n fan clutch, but if it is an "Eaton" type design similar to xxx6141 (that is, contains the coil-type bimetal spring, NOT the flat bar), then it can likely be adjusted to run at it's maximum friction at all times. Assuming you've got the clutch off and in your hand ...



Lift up the thermostatic coil's tang on the spring's OD from the 'factory' slot, and rotate it 180 degrees to the opposite slot/fitting. I'm not sure of the direction of rotation -- just watch the valve turn at the center as you rotate. If the valve doesn't turn as you move the spring's tang, go the other way. You want to see the valve turn -- about 1/4 turn authority, as I recall.

You'll have more fan roar since it will be manually set at maximum friction at all times(instead of having the underhood temp turn the valve via the bimetal coil spring). I'm not suggesting this will solve any problem, but yes, you can "fool" the clutch in this manner.

macdarren

I think if you have done the clutch and the Radiator, then I might suspect the water pump. If it is really old there is some chance it is not pumping like it should, also be sure the belts are not slipping. Since you say the problem is in traffic the following is probably not your problem but I thought I would relate that my car tended to climb in warm weather too, and after chaging everything it still did it, but mine wanted to heat when running say on the Freeway.....of all weird things, changing springs helped. I think the car tended to nose up such that not enough air was forced into the radiator. Again I don' think that is your problem in traffic but it just goes to show that overheating can be the result of some odd things.

6T5RUSH

ct: Yup, thinking that buying the 3916141 will probably cure this but ya' think the unit I did buy, the Delco unit, would have also cured this. I don't seem to have a cooling issue at speed, hovers right around 190. It's just sitting at idle for any length of time.

Donnny: Thanks for the offer but I'm going to try vark_wso's suggestion (think I do have the coiled spring in this DELCO unit on the car now). If that doesn't change the cooling behavior, then before springing for the 3916141, I'm puttiing the original I had on the car to begin with and see what happens to the cooling at idle.

pdorazio1: Heater core was replaced 8 years ago. Car, since assembly, has about 8K miles on her.

macdarren: Water pump was replaced last year.

Guys, thanks for the tips/suggestions/offers. Will post back after my trials.

Regards,

Jim

ctjackster

then your current fan clutch, which tightens up at 195-ish, might not be the culprit, unless it is defective. (My point is that the situtation you describe, engine temp pushing past 210 at idle, would mean your current fan clutch is or should be tight during that incident, and the cause must lie elsewhere.)

ro.co3

First let me say I feel your pain. When I first got my 65 I had overheating problems. Mine is a base engine with factory air. I tried a lot of different things like new flex fan, different thermostats and so on. But finally hears what worked , I flushed the radiator, installed insulation around the radiator support top sides and bottom, put in a Robert Shaw thermostat (160*),installed the original fan (7 blade) and new fan clutch, removed the two plugs in the bottom sides of the block and flushed the the engine. After that the car now stays at 180* except on really hot 95* days it might go to 190*. When I first had the a/c worked on the tech talked me into having a double electric fan put in front of the radiator, after all the work described I've disconnected them, don't need them. If your not running a Robert Shaw thermostat I'd change it. By the way my car came with a copper aftermarket radiator, at first I thought that was the culprit but now realize if everything is working properly even a piece of crap like that can keep these cars cool. Also it wouldn't hurt to pull your thermostat and see what happens to the temp. Good luck.

Donny Brass

Jim, have you checked the timing and the vacuum advance ?

toms silver 60

Ditto on pulling the side drains and seeing what comes out. Night and day difference on mine.

6T5RUSH

As a follow up to this issue, I've flushed the engine and radiator and replaced with G05 (50/50 mix). I've monitored her with an IR gun. Doing this after I went back and mapped out my timing.

Sure enough i had 4 degrees too much. Initial read 12 degrees. Rubberbanded the advance weights to confirm this. Then, after removing the bands I checked the "all in" which was 40 degrees at 2,500 r's. Backed off the distributor the 4 degrees too much to get her all in at 36 degrees. Readjusted the idle then threw a vacuum gauge on her to fine tune that. She now runs at a 900/950 at idle and a test drive confirms a sharper response and a smoother transition from idle to off idle when starting off. Temps were in the 90's yesterday and she stayed at 185 to 190 for the test. Still need to test the clutch fan engagement. I do like vark_wso's suggestion to adjust the clutch fan. We'll see how she performs this week in this heat with the air on.

Thanks to JohnZ's article on Timing 101 and Mapping your Curve as well as Barry's rendition of same!

Stay tuned!

Regards,

Jim

Kensmith

I had the same problem but my car ran at 200-210 in traffic and on the road. Have a Dewitts aluminum radiator so thought maybe fan clutch. Put on a Eaton type and didn't make much difference. So emptied the radiator, checked the thermostat to find out it had a 195* stat. Put in a heavy duty 170 stat. Runs at 175 to 180 constant. Check your stat?

BarryK

and that's all mine is - mostly paraphasing John's paper, and as stated in that sticky post I gave all credit where due. As you all know I'm just learning this stuff myself but I figured ity might help others that wouldn't read the proper referenced articles out of laziness.
I'm glad if it helped you, but give all the credit to John for the info!

BTW, if the motor is rebuilt as a L76 365hp, than the curve should allow for an intial timing of 12º with the total at 36º. If I read your post correctly you had 12º initial but than ended up with 40º total. That means your mechanical advance is too long and you need to shorten it a bit because by turning it back to bring the total to 36º your initial is now only 8º - that's pretty low for a L76 although I really can't answer if having the LT1 cam vs the stock 30-30 cam would make any difference in that.
You may want to look at having the distributor recurved to shorten the mechanical advance. Maybe a larger diameter bushing on the stop or weld in a bit of the slot and than file it down to get the advance amount you need. A Sun Machine would make this pretty easy to set up if you have access to one or have someone that does.
Than again, if it's running fine now and you are happy with it, it runs good, throttle response is good, idle quality is good, etc than hell, just leave it alone and drive it!

6T5RUSH

Yeh Barry, I know it's not per the 30/30 specs of 12 degrees initial and I believe that is because when I converted my 300 horse to where she is now, I used the original 300 horse distributor. Think the '65 base timing of the 300 horse motor is the same as the '67 300 horse...8 degrees of initial timing.

Gonna' drive her for a while set up as is and see how she behaves with the air on as well. As I said my initial test drive had me smiling a bit. She just seemed sharper on the gas and more civilized (if that's a word you can use on her) around town in stop and go.

Kensmith, I'm running with a 180 degree stat and read somewhere that's where the motor should be warmed to. Do understand the thinking on your approach but I've also read that the stat is opening at that temp and, once opened, has no affect on operating temp.

We'll see. Thanks again!

Regards,

Jim