'67 Fan Clutch Questions

[Michael M.]

I recently had an over-heating problem with my ’67 300HP after having to idle during a local cruise for about 45 minutes. It didn’t boil over but got to the red zone of the gauge (about 250*). I’ve shot the water outlet with an IR gun and it’s pretty accurate so I trust the gauge and know it got hot. My cooling system is new, DeWitts Restoration Radiator and expansion tank, 608 Bill Mock water pump, thermostat, cap, hoses and clamps. I made repairs to the fan shroud and it now fits like new also. The car runs 180-190* as long as it keeps moving. Of course I suspected the fan clutch and replaced it with a Hayden to keep it on the road.

My first question is, I need help identifying the clutch I removed (pics below). At first I thought it was a GM 3916141 (Eaton) service replacement but now I’m not sure. I see the Borg Warner clutches sold by some of the parts houses look just like it. Can anyone tell the difference and is it worth rebuilding?

My second question is, what are people using to replace fan clutches these days if they don’t have an original? The Hayden seems to work although it appears to run hotter at idle – somewhere around 210* - and doesn’t look anything like the original.

I have read that Borg Warner bought the Eaton fan clutch business and wondered if anyone has experience with the BW clutches? Also, can the BW replacement clutch thermostat springs be rotated to run at 180*?

My car is a driver, so I’m looking first for functionality and second for something that looks close to original.

Thanks in advance.

[Timothy B.]

Re: '67 Fan Clutch Questions

Michael,

I can't answer you question except to say that pic looks like the replacement Eaton 141 clutch I own. Is the vacuum advance a #355 and where is you initial timing set, that may help some.

[Ara G.]

Re: '67 Fan Clutch Questions

If your car is a driver, then go with a new service replacement. The picture you posted is of a service replacement as the "ears" flare in. The original "ears" were squared (rectangles). Am sure someone can post a pic faster than I. Originals units were either Schwitzer (horizontal bar on the face) and these units were dated on the flange. The other type of originals were Eaton units and these were no dated. There were different units for big block and small block. Taper on the shaft or straight. Guys can rebuild original units, but if you are driving the car and not judging the car then a replacement unit is probably better and safer. Good luck!. ARA

[Joe L.]

Re: '67 Fan Clutch Questions

Mike-----


I'm virtually certain the fan clutch pictured is a GM #3916141. It's not an original example, though; it's a much more recent SERVICE piece.

[Michael M.]

Re: '67 Fan Clutch Questions

Michael,

I can't answer you question except to say that pic looks like the replacement Eaton 141 clutch I own. Is the vacuum advance a #355 and where is you initial timing set, that may help some.

Sorry, I should have also said it has a new B26 vacuum advance can, 6* initial advance, getting 16* from the can at 16.5" Hg, for a total of 24* at 650 RPM. I'm pretty certain it's an air flow problem at idle. The Hayden clutch I put on cools better but I believe it's calibrated at 200+, runs hotter than I want and doesn't look anything like the original clutch.

If your car is a driver, then go with a new service replacement. The picture you posted is of a service replacement as the "ears" flare in. The original "ears" were squared (rectangles). Am sure someone can post a pic faster than I. Originals units were either Schwitzer (horizontal bar on the face) and these units were dated on the flange. The other type of originals were Eaton units and these were no dated. There were different units for big block and small block. Taper on the shaft or straight. Guys can rebuild original units, but if you are driving the car and not judging the car then a replacement unit is probably better and safer. Good luck!. ARA

I called my local GM dealer and was told they don't list a replacement clutch for the GM #3916141 since Eaton stopped making them a few years ago.

Mike-----


I'm virtually certain the fan clutch pictured is a GM #3916141. It's not an original example, though; it's a much more recent SERVICE piece.

I thought so too until I saw one of the Borg Warner units sold by Paragon, Corvette Central and others. I know the clutch in the pics is at least four years old and I'm not sure how that fits the BW purchase of Eaton clutches timeline? Is the I09J1C on the face a date code? Paragon says BW makes them using the Eaton 3916141 tooling. That's also why I was wondering if anyone had any experience with the BW units available now?

[Edward J.]

Re: '67 Fan Clutch Questions

Mike, It really sounds like you have not missed much on your quest to keep you engine running cool. I only see one question and that is the water pump is a reman. assy. Its nice to have a numbers pump, but my problem is that all pumps are not equal when it comes to reman.s I have nothing bad to say about Bill Mocks pumps its just sometimes the housings erode the impellers also, This will slow the flow down on Water pumps at idle. sometimes the rebuilders use a stamped steel impeller and I am not a big believer that they'll move as much water through the cooling system. I know that there are millions of these types of pumps out there. But the older corvettes have limited air flow as compared to makes and model. this is just food for though. and one other thing is read John H. article on cooling systems there maybe something that will draw your interest. Good luck, Ed

[Tony S.]

Re: '67 Fan Clutch Questions

If you are only interested in driving your car, then abandon the fan clutch altogether and get a direct drive. It runs continuously when your engine is running. I only install a fan clutch when my car is presented for judging.

[Michael M.]

Re: '67 Fan Clutch Questions

Mike, It really sounds like you have not missed much on your quest to keep you engine running cool. I only see one question and that is the water pump is a reman. assy. Its nice to have a numbers pump, but my problem is that all pumps are not equal when it comes to reman.s I have nothing bad to say about Bill Mocks pumps its just sometimes the housings erode the impellers also, This will slow the flow down on Water pumps at idle. sometimes the rebuilders use a stamped steel impeller and I am not a big believer that they'll move as much water through the cooling system. I know that there are millions of these types of pumps out there. But the older corvettes have limited air flow as compared to makes and model. this is just food for though. and one other thing is read John H. article on cooling systems there maybe something that will draw your interest. Good luck, Ed

[Gerard F.]

Re: '67 Fan Clutch Questions

Mike,

Hate to send you off on a tangent, but take a look at the carburetor.

Seems like you are running too rich at idle. If the fuel is dripping into the air horn, especially after a hot run, it is a carb problem.

Had a similar problem with my 67/300 after I put on a restored 3810 (restored by myself) and was testing it out with some hot runs up a grade and back.
Found that during the end of the run and then stopped in traffic at a light, the temperature would always go way up, stalling but short of overheating and puking.

With a little tightening of the carb to manifold bolts and a little adjustment to the mixture settings, the problem went away.

With the equipment you have on the cooling system, I don't think that's the problem. You seem to have the timing correct.
But the 3810 carb can always give you problems.

It is normal that after a hot run, that the temp goes up, but it shouldn't stall at a light. And with a little cruising after the temp should go down.

Just my two cents.

[David L.]

Re: '67 Fan Clutch Questions

"CK" = GM # 3916141
"I09J1C" is some kind of "modern" date code

Dave

[Michael M.]

Re: '67 Fan Clutch Questions

"CK" = GM # 3916141
"I09J1C" is some kind of "modern" date code

Dave

https://www.paragoncorvette.com/p-35...utch-unit.aspx

Does anyone have any experience with the Borg Warner clutches currently available from Paragon?

[Joe R.]

Re: '67 Fan Clutch Questions

Mike,

You have done nothing wrong and changing anything you have mentioned will help the cooling problem. When caught in traffic, parades etc. your Corvette is going to get in the 250 range.
You can help the problem by adding an additional fan on the front of the radiator that will be moving more AIR thru the radiator at low speeds. Dewitt also has a set-up to add the fans to the rear of the radiator including a shroud.
Age old problem but you can help out as your Corvette is a driver.

JR

JR

[David L.]

Re: '67 Fan Clutch Questions

GM # 3916141 appears in my 1967 Chevrolet Parts Catalog (Apr. 1967) for only the following:
67 PASS. (Air Cond., fan drive)(6 cyl.)
67 PASS. (396)(427)

GM # 3916141 replaced GM # 3857530 in Jan. 1968.
GM # 3916141 replaced GM # 3938944 (stamped "CS") in Mar. 1973.
GM # 3916141 replaced GM # 3814560 in May 1973.
GM # 3916141 replaced GM # 3857531 (stamped "CT") sometime between May 1980 & Dec. 1981.
GM # 3916141 replaced GM # 3916139 (stamped "CJ") in Jan. 1974.

GM # 3916141 sold for $177.61 list/ $133.20/ $106.56 in Nov. 2001.

Dave

[Jack H.]

Re: '67 Fan Clutch Questions

What Joe says is spot on. Idling the engine on a classic Corvette for 45-minutes in the middle of the summer is a REAL thermal stress that you'd like to avoid if/when possible. But, you might find there's nothing wrong with your car that can't be cured by a little driver-ed. What?

Later cars with more elaborate emissions controls and lower compression ratios, had generally higher under-hood temperature profiles. They dealt with the threat of over heating in summer stop/go, grid lock, traffic by giving the car two curb idle settings. The 'switching' function was accomplished by a solenoid.

This is a 'feature' of my 1971. The control electronics monitor engine coolant levels and when temp climbs too high (the trigger point is around 230F), the solenoid is switched on to bump the carb's idle setting up a notch (about 200 RPM). That doesn't sound like much but here's my experience...

I was in a club July 4th parade. The ambient was pushing 90F and after 30 minutes of stop/go, the temperature began to climb. I sat and watched (without panic) and when she hit about 233F, there was an under-hood CLICK as the CEC solenoid energized. The engine RPM climbed by about 200 revs and SLOWLY but SURELY, the coolant temp began to fall!

When she hit about 195F, another CLICK and the solenoid released allowing engine idle to fall back 200 revs. Shortly after, the temp gauge began to climb again. I watched this process cycle 3-4 times for the next 40 minutes, while other classic Corvettes in the parade either did nothing or did the WRONG thing by shutting their engines OFF periodically. I saw three cars overheat and blow their rad caps with coolant spewing joyfully!

But, those who simply put their foot on the pedal to rev 'er up a bit, got through without a hiccup!

[Dale M.]

Re: '67 Fan Clutch Questions

I have been watching this thread. I wondered if there is any method to test the clutch on the fan? My clutch fan seems to always spin freely, just a little resistance. Even when the engine and air temps are high. Thanks