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Old 06-24-2010, 04:33 PM
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350 sbc running hot on highway

I have a 350 in a '32 Chevy sedan with a th-350 tran. behind it. 3:55 rearend. Runs 180-185 in town, stop and go w/o air on, runs 190 with air in same situation. Go out on the highway and after 15 or so miles at 60-65 mph, the engine temp starts to go up and seems to run about 225 or so. Gets hotter if a semi gets in front of me. I have a hayden elec. fan on it. Don't know what the cam is but the engine is a 1969 vintage with Edelbrock manifold and 500cfm carb on it. Stock distributor with pertronix flame thrower II conversion in it and high voltage coil. How can I tell if it's timing (too retarded), to lean, air flow, or radiator? This is a real stumper for me. Where to go from here as I've done all the basic testing. I did back the timing off a bit after it was running hot and causing ping when accelerating.

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Old 06-24-2010, 04:47 PM
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Are you still running the hood sides?? Might try removing them temporarily to see if it is and airflow/air escape problem. If the hot air can't get out of the engine compartment after it goes through the radiator it is as bad as not having enough airflow or enough radiator size.
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Old 06-24-2010, 04:56 PM
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DITTO with ericnova72, it's a air flow problem thru the radiator.

What do you have for cooling system?

I also recommend Royal Purple Ice or Red Line added to the coolant, it does work.
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Old 06-24-2010, 05:13 PM
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Running hot

Running a brass/copper radiator, cannot tell brand. I believe it was not the original. It has tranny cooler in bottom. I have an aftermarket chrome water pump, again no brand or model #. (I bought this car and it had been in storage at least 5 years or more, old build) As I said elec. fan thermostat in bottom of radiator tank.

Yes the hood is on, but not stock it is louvered top and sides extensively, but still could cause a flow problem. Good suggestion, I'll try it without the hood and see what happens.
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Old 06-24-2010, 05:17 PM
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I'm thinking that this electric fan is blocking flow through the rad.
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Old 06-24-2010, 05:23 PM
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My car would do something similiar to this. After checking over the whole system and finding nothing, I went back to what I started with, the T-stat. It was a new 180 degree unit. In town, ran 190, get on the interstate and do 70 the temp would climb to 230 which made me uncomfortable. I checked the stat in boiling water, opening temp great, closing temp off, after the water cooled down past 150 the T stat was still wide open, down to 120 still wide open. Got a new one, tested it before I installed it, it too was bad, next checked out good so I used it. I`ve found over the years the quality of T stats has really went down, I even tried the high dollar 6 bucks a piece jobs to find they too were bad right out of the package. Check your T stat, it may save you a lot of work.
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Old 06-24-2010, 07:50 PM
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Is there a fan shroud covering what the electric don't?

How much of the rad is open on the motor side ?

Check what DV said also.

Plus put a 1/8" hole in the thermostat it helps any cavitation & air pockets.
Any pics ?
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Old 06-24-2010, 08:49 PM
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Retarding the timing will make it run hotter. Maybe try advancing for max vacuum?

Could also be a too small radiator.
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Old 06-25-2010, 09:05 AM
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Advance for max vacuum

I can wire anything, but it's been many years since playing with sbc's. Can you help a timing rookie on advance for max vacuum?
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Old 06-25-2010, 09:17 AM
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Fan / radiator answers

Quote:
Originally Posted by 1BAD80
Is there a fan shroud covering what the electric don't?
No, there is no shroud
How much of the rad is open on the motor side ?
Basically the whole back side is open to the engine. The fan is there set up as a puller.

Check what DV said also.

Plus put a 1/8" hole in the thermostat it helps any cavitation & air pockets.
Any pics ?
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Old 06-25-2010, 09:27 AM
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I would guess 1 of 4 issues listed in order of probability

1, Too little air flow through radiator or it is undersized.
2, Internal cooling system pressure holding thermostat closed.
3, Radiator hose sucking shut at highway speed.
4, Ignition timing retarded
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Old 06-25-2010, 09:46 AM
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Thanks for suggestions

Quote:
Originally Posted by T-bucket23
I would guess 1 of 4 issues listed in order of probability

1, Too little air flow through radiator or it is undersized. Possible

2, Internal cooling system pressure holding thermostat closed.
Running a 7-8 lb cap and it does not blow off through the overflow. If I watch the temp guage, as it goes over 180 to around 190, the temp then will drop back to 180 in about 30 seconds, so I think it is opening.
3, Radiator hose sucking shut at highway speed.
Brand new hoses for top/bottom/heater core.
4, Ignition timing retarded
This is where I'm going right now. Also, checking lean and vacuum stuff. Then to #1 with hood off trial at highway speed.

Thanks again.
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Old 06-25-2010, 10:14 AM
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I see green mold outside the radiator. That radiator needs to be either replaced or boiled out. Some of the tubes may be clogged from letting it sit around. I wonder if tubes in the radiator are more efficient horizontally then vertically. I read an article a while back it's more efficient running the tubes horizontally. I do not know of that is true.
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Old 06-25-2010, 10:22 AM
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Quote:
Originally Posted by Jim7231
This is where I'm going right now. Also, checking lean and vacuum stuff. Then to #1 with hood off trial at highway speed.

Thanks again.
I will be surprised if the hood make a difference at highway speed if you are not having issues in the city. A water cooled engine does not rely very much if at all on block surface cooling from ambient air.
I have seen several vehicles that don't have the heater connected and the block plugged that the internal pressure keeps the thermostat from opening.
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Old 06-25-2010, 02:22 PM
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green stuff

Quote:
Originally Posted by lg1969
I see green mold outside the radiator. That radiator needs to be either replaced or boiled out. Some of the tubes may be clogged from letting it sit around. I wonder if tubes in the radiator are more efficient horizontally then vertically. I read an article a while back it's more efficient running the tubes horizontally. I do not know of that is true.
I'll check it, but I did spill antifreeze when I put in the thermostat and again when I put new hoses on it and may not have gotten that area washed off. I will look closely to make sure it's not mole or something alive. It could have stuff in it since it was in storage so long. I did have all the fluids changed, but I'm sure they didn't flush it let along boil it out. Thanks.
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