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Old 06-30-2008, 03:31 PM
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SBC Cooling Saga...can anyone offer a good suggestion I haven't tried yet?

Hello, all!

I notice overheating is a hot topic (bad pun) here, but I wanted to dive in with my woes and see if anyone can figure out what I haven't yet. The history:

1968 Impala Custom, 275/327, TH400, dual exhaust with 'h' pipe. New suspension, engine still stock save for water pump and t'stat. Still gets 15 mpg +/= city, so she's still doing ok there.

BUT, she has a cooling problem from Aitch Eee Double Hockey Sticks I can't figure out or fix. For 2 years, the idiot light came on intermittently, but could find no trouble. Added an Auto Meter gauge with probe inserted in lower center of radiator, but this showed actual NUMBERS that freaked me out...well over 290 degrees, w/o the A/C on!

SO, I did the following, in order (rather, my Goodyear guy did it):
1. Back flushed the coolant;
2. Put in a (tested first) 180 deg. thermostat;
3. Added an Impala Bob's 4-core Desert Cooler radiator, along with auxiliary external coolers for the engine oil and trans fluid;
4. Put dual 16" electric fans on said radiator, mounted 1/8" from the core (no shroud of any kind was provided with the fans..they mount on dual rails that span the radiator left to right).

STILL had high temps as described! Now, I added:

5. 160 degree thermostat;
6. 40 GPM hi-flow water pump;
7. All new hoses inside and out;
8. New heater core (thanks to the water pump);
9. Went broke converting the A/C to the new refrigerant.

And still the problem persists. It takes the car just 15 mins or so to get up to 180 when the ambient temp is 85, but after that it just climbs to about 205-210. If I use the A/C, the temp gauge pegs out and coolant spews out the overflow!

As we all know, the cavernous interior of a '68 Full-Size Chevy takes awhile to cool, but I can't risk using it anymore. I'm fed up and broke, and the only thing I HAVEN'T replaced is the condenser, which seems fine.

What next?
What's the normal op temp for my engine anyway?
Do I need to replace the condenser with something new anyhow?
Should I try to make a shroud of my own out of rubber, etc, to cover the inboard areas of the radiator not covered by the fans?

Please help me...I hate to sound pathetic, but I can't deal with this any more, and need a positive fix!

Chuck
Norman, OK

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  #2 (permalink)  
Old 06-30-2008, 04:21 PM
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Looks like you've pretty much ruled out all of the major components of the cooling system..

A poorly tuned engine can run very hot despite the best endeavors of a good cooling system.. have you checked the timing?

Dunc
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Old 06-30-2008, 04:28 PM
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I'm betting your car came with a shroud, and you should have one on it. Your fan can't be effective in moving air THROUGH the radiator with out one. I agree, also, that you need to check your timing. If your engine is in good condition and good tune, and you install a fan shroud, you'll be in good shape.
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Old 06-30-2008, 04:41 PM
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Cooling woes...

Timing is spot-on as of 2 weeks ago, so I think I've managed to rule that out. As to the shroud, well, the one I have is for the original (shot) clutch-driven fan, so it won't accommodate the twin electrics.

The only thing I can think of is that the fans, though they are so close to the radiator, are mounted side-by-side w/o any gasket or shrouding...they didn't come with any. I've used metal tape to fashion a 'shroud' of sorts to cover the entire exposed radiator area around the fans and force all the air through the fans themselves. I'm sure I've missed a few small parts, but anything larger than 1/4" is taped over for now.

All I can do for now is see what happens, as I can't find any shrouding of any kind for the fans, unless I wanted to go to one big fan in the center of the radiator...

What bugs me is that the mechanics say that the setup I've got (with the fan size and the 160 thermostat) should have me running cool, if anything. @(%&^$*T&! We'll see...! No one can seem to tell me what the normal op temp for my engine/application should be, so I'm unsure of what to look for. I can only hope the 'shroud' I've fabricated will help...

Has anyone had luck in such a situation with replacing what looks like a perfectly good condenser?

Thanks for the heads-up, and I'll keep tabs on timing to see if things are going out of adjustment w/o my knowing. Again, any other ideas you have are welcome!

BTW, Busterwivell, my ol' girl is a former AZ car...lived in Phoenix until 2001, when I bought it.

Chuck

Last edited by cmk59; 06-30-2008 at 04:45 PM. Reason: Incomplete
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Old 06-30-2008, 04:44 PM
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Welcome aboard.

Go with your thoughts about a fan shroud. Your engine set's back too far for use without one. Try to get it between 1 and 1/2" to 2" from thr crank pulley's. Keep in mind a round outlet will swirl the air better than a square one.
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Old 06-30-2008, 04:51 PM
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Shot? Why not just replace the clutch and put the original shroud back on? With your 4 core, I'll bet you'll be happy.
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Old 06-30-2008, 05:16 PM
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Going with the shroud thought...

Thx for the feedback! The radiator (even though a 4-core 'desert cooler') sits about 8" from the pulley. The fans are mounted side-by-side across the radiator from left to right, overlapping the sides of the radiator by about 1/2" on each side, and only project about 1 1/2" from the rear face of the radiator.I've tried to cover over this overlap, with marginal success.

The gap in between the fans (kind of like two triangles sitting point-to-point above and below the two fans) has been plugged with the 'shroud' made of the aforementioned speed tape layered over a thin piece of wood and secured above and below them. I intentionally made this to fit tightly between the fans, and nothing SHOULD get through this area now.

The 2" gap between the top of the fans and the expansion tank of the radiator has also been blocked by several layered strips of speed tape. I figure 90% of the air now has nowhere to go but through the fans themselves.

It just remains now to see if this works. If not, all I can think of is to change the two 15" fans for slightly smaller ones with an integral shroud and/or replace the A/C condenser and hope one or both work...everything else has been checked and replaced.

Chuck
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Old 06-30-2008, 05:18 PM
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The electric fans will do nicely without a shroud, as cmk59 described the install @item #4 of post #1.

I would pull the block drain plugs and verify that no gunk is left in the block from the flush. Many shops "flush" engines but really don't do anything meaningful. Assuming ignition and cam timing is right and the plug range is right, it should cool fine as long as the block is clear, meaning as long as enough water is actually able to flow enough to cool it.
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Old 06-30-2008, 05:28 PM
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Thanks, Bluesman!

Quote:
Originally Posted by bluesman2333
The electric fans will do nicely without a shroud, as cmk59 described the install @item #4 of post #1.

I would pull the block drain plugs and verify that no gunk is left in the block from the flush. Many shops "flush" engines but really don't do anything meaningful. Assuming ignition and cam timing is right and the plug range is right, it should cool fine as long as the block is clear, meaning as long as enough water is actually able to flow enough to cool it.
I guess that's another chunk o' change I'll have to cough up. Can't physically do it myself anymore, but it's about the only thing I haven't thought of!

Thanks again, and I appreciate the help, even if it IS going to cost me...!

Chuck

Chuck
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Old 06-30-2008, 05:42 PM
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The only reason I even thought of it is that once I pulled apart a motor and was amazed at finding the cooling passages completely full of brown sludge. I guess it was originally from someone putting stop leak in it.

*Something else, make absolutely sure the cooling system holds pressure with a pump and gage. If it doesn't, it will never cool.

Last edited by bluesman2333; 06-30-2008 at 05:50 PM.
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Old 06-30-2008, 05:56 PM
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My Avatar picture is a 1973 Corvette. It has a 3# alumimum radiator, along with a single 18" electric fan. It ran 230-240 prior to the addition of a fan shroud. Now it runs at 205-210 on hundred degree days.
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Old 06-30-2008, 06:50 PM
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Can you get a pic of your fans and shroud setup?
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Old 06-30-2008, 07:23 PM
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Shrouds and overheating...

Fan relay fuse blew ... think there's a short in the fuse holder ... the fans were pulling hot air out great guns, but temp was still at 220, regardless. I touched the fuse (literally) to the fan relay, and it blew. Geez......

Anyway, it's now off to the mechanic, and probably more of my stereo equipment off to the pawn shop to pay for it! ***grrrr*** And did I mention that it's not only our 7th wedding anniversary today, but the plastic radiator in her '88 Chevy truck blew yesterday? HOW MUCH FUN CAN ONE COUPLE HAVE, I TELL YOU??????? :
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Last edited by cmk59; 06-30-2008 at 07:26 PM. Reason: Incomplete
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Old 06-30-2008, 07:50 PM
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I'm going to chime in.....

I would check the radiator CAP. I know you replaced the radiator, but did you replace the cap also?

what is "spot on" on the timing?
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Old 06-30-2008, 07:56 PM
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Radiator Cap...

Yep, radiator cap was replaced with a brand-new cap (16 psi) and checked before installation. Timing was literally right on the mark where it was supposed to be according to the Chilton's book (don't remember right now, but I remember being tickled that it didn't require any adjustment!). That having been said, I'm having my mechanic pick it up in the morning and re-re-check the timing AND ignition, as well as pop the freeze plugs and flush the block as was suggested earlier.

Am also strongly leaning toward the suggestion of removing the electric fans and putting a flex fan on with the OE shroud...maybe, just maybe leaving one of the electric fans on the condenser as a pusher, wired to the AC relay...

Chuck
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