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I have a 1976 K-10 pickup. Just installed a 350, .030 over, appx 9 to 1 compression, around 300hp that a friend (and I) built and put in his truck, put on about 500 miles, then put in my truck. All is fine when running around town. Runs at 185 deg and stays there well. Yesterday I went down the freeway for about 20 miles and it slowly and gradually got hotter and hotter (up to 220 deg) and started to run ****ty till I got off the freeway. Then it went back down within a few miles to 185 deg. and was OK. Same thing on the way back home. I know these are good: thermostat, gauge (mech), cap, radiator is clear, new 50/50 mix coolant. I have a stock 2 row radiator and with the other engine I had (about 200hp, 8 to 1 comp 350) it ran hotter as well (up to about 195-200) on the freeway. All the guys I know with 4 rows have no problem. Should I try one with 4 rows or could this be something else?
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i had that problem in my camaro so i throw 2 big eletric fans this should help. or if you dont need the heat take out the thermistate.
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Yes on the 4 row but check that Tstat again and make sure it's opening.
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160 thermostat instead. Also, use a good 3 row or 4 row.
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OK, I was wrong about one thing. The rad in it is a 3 row, not a 2 row and it looks perfectly clean and flows good. I boiled the thermostat and it started opening at 175 and was fully open at just over 180. I forgot to mention I also have a new fan clutch as well.
Is 1 more row on the radiator really going to make that much of a difference? I can't believe that it would make that much of a difference that it runs perfect at 185 everywhere then gradually goes that high on the freeway. I don't have the money to keep throwing at this and need it fixed.
Thanks If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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You have the right shroud on it right? Is the fan at least 3 inches from the radiator? The lower radiator hose might be collasping at higher speeds. Is there a spring in the hose? The three core should be good for your small block.Heck I have a three core in one of my big block trucks no problems.
Steve
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I had the same problem as you, my suburban temp was fine around town but as soon as i got on the highway the temp would rise to 220+. i replaced the radiator thinking that it was clogged and replaced the thermostat and that didn`t help. a friend suggested that i change the water pump. without any other good explanation why it was running hot i changed the water pump and that was the problem.
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The lower hose doesn't have a spring in it. I guess I'll try a water pump, lower hose, and new thermostat. Thanks
If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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Well, now I have a new t-stat, t-stat housing, upper and lower hoses, heater core and hoses, water pump, and I tried my neighbors 4 row radiator. Still doing the same thing. I tried a 160, 180, and a 195 t-stat - nothing. No matter what I do, no fix. WHAT NOW????????????
If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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You mention that this is a new motor. Are they the correct head gaskets, intake gaskets? Just a thought.
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How is the tune-up on the carb? Running lean on the highway will heat it up. How is the fuel pump, filter, lines? You might have a fuel delivery issue which is leaning out the carb during long driving periods on the highway causing it to heat up as well.
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All gaskets good. Carb is rebuilt (Carter AFB). I put a clear fuel filter that I can see between the gap of the hood to make sure I was getting proper fuel - stays full (Carter universal electric 5-7psi, 72gph pump).
Here's what I found today. I noticed that it had a slight (barely even noticable) miss/stumble at idle so I reved to 2k rpm and got worse and at 3k (where it is at 75mph) it was a really bad miss/stumble. I disconnected my vac. adv. and it went away at higher rpm so I checked my timing and it was up around 24 for some reason. I think my balancer ring may have spun. Anyway, I retarded it to 8 and it stumbled all over the place. After playing around a bit, with it set at about 15 deg. and the vac adv disconnected, it runs good through the RPM range (idle to 3500) So I tried it out on the highway and it still got hot but not as bad. About 8 miles got to 210deg. Also it sat at 195 for about 4 miles and then heated up more.
But when I pulled off the highway, I got out fast to see if there was anything was weird. Well, the cap must have vented and ran out the overflow. It's a new cap (330deg, 16psi) so I tried another one and the same thing. Why would it be venting?? And could this be the problem?? If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
Edited by: warlok1469 
at: 3/7/07 7:53 pm
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Ok you tried everything. I have a suggestion though,
If your catalytic converter, if you have one, gets clogged with carbon rust whatever, the back pressure of the exhaust will create serious heating issues.
Check out your exhaust??? SgtDel
aka "Andy"
www.delbridge.net
1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
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nope no cat. exhaust is free.
If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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You might have to go diggin back into that motor if you've tried and checked everything thrice!! Be absolutly sure everything is the way it is supposed to be.
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What could be pressurizing the system to make the cap vent? If it was a head gasket or a cracked head, wouldn't it do it at lower rpms too? I mean it's the difference of fine at 2800rpm and screwed at 3200 rpm. I'm really finding it hard to believe its a head or gasket. It just runs soooo good!!
If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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Have you changed the oil since the rebuld?
Don St.Clair
Culleoka Tn
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If it is lifting the 16lb spring off of the cap and venting you are building up too much pressure in the cooling system. Check for the presence of hydrocarbons at the radiator with a gas analyzer. Any decent shop will have one. Run the engine with the radiator cap off and if you are seeing HC's or Co's aboove the radiator neck you are leaking compression into the cooling system. This means bad headgasket sealing, or cracked combustion chamber etc. When you built the engine did you check your cylinder head mating surfaces with a precision straight edge? Edited by: VileZambonie
at: 3/10/07 8:48 am
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I hoped you were wrong but I'm afraid you may be right. That is really the only way I can think of that it would pressurize like that. The oil has been changed since the rebuild and no water in it. When we rebuilt it, The block was decked and the heads were resurfaced and rebuilt with new parts. I'm hoping it's only a head gasket. I noticed that the new coolant looks kind of dirty (pretty quick too
). Ummmm.... @#%$!!!!!! If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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Maybe try a coolant/rad flush first. Pressure test the coolant system.
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Let us know the results.
SgtDel
aka "Andy"
www.delbridge.net
1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4
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Well........ Yesterday, I looked in my radiator and found a nice film of oil on top of the water and a nice coat of gunk (looked like green oil) on the walls. Kind of cemented the head gasket theory. So I flushed the cooling system (wow that worked great, spotless!!) and got to tearing down today. Found no obvious problem with the gasket. No cracks breaks etc. The only thing that is weird is one side looks blue and solid like the Fel Pro Permatorque and the other looks like perforated metal with flaky crap imbedded, kind of like an exhaust gasket if you know what I mean. No breaks but looks kind of junky. I cleaned up the surface and will puit new Fel pro's and hope all is well.
I'll post up after I test it out tomorrow. If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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Make sure the heads are not warped. If you don't have a precision straight edge run them to a machine shop and they'll check em for free for you.
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OK.............. Here's what I found. The head gaskets had NO signs of any cracks or anything abnormal except they were 2 different styles. One was steel and blue like Fel Pro PT and one was an impregnated perforated core style. But no damage and both looked like they were sealing. No visual cracks/problems with the heads so I went to have the heads checked for cracks, turns out that they are 1.72 heads. (wonderful!!). So instead, I have a set of 1.94 heads that only have about 5K since rebuild so I brought them to make sure they are OK. Nope, int. valves on one are sucked into seats and sharp as a razor. So now, do I put the crap (but rebuilt and in good condition) 1.72's on and waste all the lost power, or do I sit and wait for my account (and wife) to agree on a rebuilt set of 1.94's for $300? Not to mention, I still don't know what was causing the overheating on the highway!!!
If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!
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Did you use non-retorque gaskets and sealant on the head bolts? Torqued to 75ish? intake not warped? Finally, did you have the heads magged?
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Yes to all. The heads and block were mag'd, surfaced, torqued to 65'#. I'm kind of thinking the problem was one gasket was fel pro permatorque (no re-torque) and one was a impregnated perforated steel type that should have been retorqued and probably never was. However..........
This is hopefully all a moot point now. I traded a guitar and amp for a 2000 model 285hp crate 350 complete pan to intake from another friend. I know it ran perfect and I'm dropping it in tomorrow or wed. Hopefully no problems....... there's mud to be slung and rocks to crawl!!!! If you kill a man, you're a murderer.....kill many, and you're a conquerer..... kill them all,..... YOU'RE A God!!