460 overheating

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Nov 20, 2001 | 03:23 PM

yellowrosefarm

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460 overheating

My recently purchased '78 F250 4x4 w/auto and 460 will nearly peg the temp guage when idling. The previous owner rebuilt the engine about 5k ago and said he put in a larger cam, new pistons, etc. I pulled the radiator and had it checked and they said it flowed fine. I replaced the 195 thermostat that was in it with a 180. The fan shroud is in place, belts are tight, water flows steadily when warmed up. I'm wondering if the stock 3 core radiator is up to cooling the slightly "warmed" 460. Any ideas?

Nov 20, 2001 | 03:27 PM

Franklin2

Moderator

Joined: Jan 2001

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From: Virginia

460 overheating

Does it overheat sitting or going down the highway? If going down the highway, I wonder if the lower radiator hose has the spring inside?

Nov 20, 2001 | 04:09 PM

weldman

Fleet Mechanic

Joined: Feb 2001

Posts: 1,290

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From: Toronto, Canada

460 overheating

[updated:LAST EDITED ON 20-Nov-01 AT 05:12 PM (EST)]First of all, are you sure that it is overheating?

I've been chasing this same problem and have determined that the truck is not overheating, although the gauge says it is running on the 'M' instead of the 'O' it normally reads on. I took it to a rad shop and had them use their ambient temperature gauge to determine that the temp at the top of the rad was around 190.

I would check the sending unit, the voltage regulator on the back of the instrument panel and finally the gauge.

I replaced the sending unit and have a new 'used' gauge in hand.
Also, when I replaced my sending unit, I used teflon tape to seal it, and have since seen on this board that maybe wasn't a good idea as the sending unit might not be grounding properly.

Good luck!
Matt

Nov 21, 2001 | 05:33 PM

therigwelder

Tuned

Joined: Mar 2001

Posts: 491

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From: MS.

460 overheating

had the same identical problem with my 79 460 i replaced everything in the entire cooling system. finally took the cylinder heads off had them die checked low and behold heads were cracked put a diffrent set of heads on and it cured the problem and beleive you me i scrathed my head for 6 months trying to figure what was wrong

Nov 21, 2001 | 10:21 PM

classic79

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Joined: Jun 2001

Posts: 480

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From: Alabama

460 overheating

Well check the obvious stuff first. If it only overheats at idle sitting still, I would look towards not enough airflow i.e. fan clutch going bad? It does have a clutch right?

Definately put a after market temp guage on there to get a true reading. As someone said above its not unheard of for the guages to just do what they want.

Chris

79 F-150 Lariat: Long-bed, 2wd, 460 (intake, headers, cam, early heads), C-6 (shift kit)
79 Mustang: 460 swap under way, balanced rotating assembly, forged pistons, truck rods, c-8 heads ported, Lunati solid lifter cam, more stuff...
98 Chevy Silverado ext. cab 4x4 (work truck)
95 Lexus SC300 (wife's baby)

Nov 22, 2001 | 08:44 PM

yellowrosefarm

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460 overheating

No fan clutch, just a spacer. Today, I installed a high flow 180 thermostat from Mr Gasket and a Perma cool 17" flex fan. I also discovered that the vacuum advance was hooked up to a non vacuum port on the carb so the engine was running way retarded at idle (only 8 degrees btc, now is more like 28)These 3 things have brought the temp down from pegging the guage and boiling to between the "M" and the "A" on the guage after idling for about 15 minutes. I'll try it again tomorrow when I have more time to let it run and see if it stays steady or gets to climbing again. Thanks for all the advice. Now on to the brakes and maybe I can get this beast on the road.