383 overheating

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tom340

tom340

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Ughh, my buddy Gregg's '70 Chally. A car he sold 20 years ago and found again last summer..Undergone a Complete restoration, fresh motor thats making 502hp at the crank. Car has been back on the road for just a few short weeks again. A few details: factory style 26" rad., Block was bored .060 over and machined/balanced by a reputable engine builder. Compression ratio is just UNDER 10.0:1, no pinging or anything like that. Matter of fact just had a chassis dyno tune and picked up almost 50 more HP. Motor truly seems to run great. Gregg had noticed the engine temp stays cool at idle, even if it idles for some time. {Clutch fan works perfect.} Take it for a ride and the engine temp will rise sharply , pinning the temp gauge. My brother had found last Friday the engine had trapped an air pocket, and he flushed the system and wound up adding nearly a gallon and 1/2 additional fluid. Also he changed to a heavy duty water pump and a high flow thermostat for him. Again restarted the car, idled for an hour and shut it down to cool without overheating. Restart and idle/drive around the lot a bit and no more overheating. Then today Gregg again takes the car out for a ride. All seems Ok for a while and then the engine temp rises really fast. While the car overheating, there is no smell of antifreeze, and no plume of smoke from the exhaust. Also, there is NO sign of water on the oil dipstick and no film of oil in the radiator fluids. The engine builder who is VERY particular with his work has extreme doubts its the head gaskets. My brother & I both tend to agree with him as well.
I have a gut feeling the problem may lie with the radiator. Its @ 22 or 23 years " new". When it was new, sure a 3 core /cross flow was the bom but the car sat for 19 years and accumulated a total of 62 miles until gregg repurchased it. It hasnt been flow checked, I feel its not an efficient 3 core radiator and may be clogged with all kinds of ****. I bet the innerds of the radiator are pretty f'd up by now. Now hes got a healthy 383 with much thinner water jackets and when you stress the cooling system while driving the radiator just cant handle it.
I'm open for suggestions to pass along to him. My brother & I want Gregg to really explore every option before yanking the motor and handing this to the engine builder.
 
A quick test for hydrocarbons in the antifreeze will tell you if combustion gasses are leaking in to the antifreeze. No hydorcarbons will mean no headgasket leaks.
 
Pull the rad and either flush it yourself to see how it flows or bring it to a rad shop and have it rodded out. The quick way that rad shops check em is to block the lower bung with their hand while filling it thru the top bung and when it's completely full releasing the lower one to see how fast it can empty. If it doesn't dump out in a few seconds then it's plugged. You can try and back flush it but it's only temporary for the most part. If that's the case then you can have it rodded out or recored/replaced/upgraded.
 
I gave Greg the # for Valley radiators in Canton yesterday-he called me today says the rad is out of the car and he started flushing it out. He says he can hear all the crap inside slushing around when he tips the unit back & forth, and was able to coax some of the thick sludge out. This stuff was aweful, like from the bottom of a septic tank. He told me he was able to see some of the passages are completely blocked off as well. He'll be bringing it to the shop Monday 1st thing , I think the problem is solved here .
I kinda hope he goes for a new 3 or 4 core and a better quality core.
 
tom340 said:
I gave Greg the # for Valley radiators in Canton yesterday-he called me today says the rad is out of the car and he started flushing it out. He says he can hear all the crap inside slushing around when he tips the unit back & forth, and was able to coax some of the thick sludge out. This stuff was aweful, like from the bottom of a septic tank. He told me he was able to see some of the passages are completely blocked off as well. He'll be bringing it to the shop Monday 1st thing , I think the problem is solved here .
I kinda hope he goes for a new 3 or 4 core and a better quality core.

I bought a 2 core from be cool and that sucker is almost 4 in. thick. saw the same one in a 550hp 427 at a car show last week so the new 2 cores cool fantastic compared to the older stuff. It was only 229 canadian. good luck
Click to expand...
 
Hopefully problem is solved. And just to be certain we talked him into replacing the heater core as well. Radiator shop boiled it out, was pretty badly blocked up. Turns out the core he has was actually a pretty damn good crossflow unit and the shop owner suggested to reuse it if he was able to get it cleaned up.
If it still overheats after all of this, then he's got a serious problem with the motor.
 
May seem like a silly question but... what gauge are you reading ?
Wild needle swings in factory gauges are electrical faults not actual engine temp swings.
 
Two more things to check Tom, make sure that there is a coil spring inside the lower rad hose it keeps the hose from collapsing under high flow condition. You'll really see it with a high flow pump. Also, I just installed a high flow pump and Mr Gasket 4367 high flow thermostat on my 383. After a couple days the thermstat failed to open. This kind of thermostat will pass enough glycol to keep it cool idling (it doesn't completely shut off flow) but out on the street she'll heat up fast. I replaced it with another and works fine. Besides it sounds like you may have found the problem.

Terry
 
Fortunately it was not an engine problem. Whew! Radiator back in, Gregg took for a nice test drive and all is fine. Heater core was also plugged solid. Thats been replaced as well. Rad shop owner says he has only seen 2 other used radiators that had been this bad or worse in all his years.
Gregg has found out the hard way that time is an enemy for a car sitting idle for 19 years. His brake lines were plugged solid as well-found that out last week. The line from the master cyl to dist. block was plugged and the stuff inside looked like broken glass.
 
Crystalized brake fluid from a shot of moisture. Been there before with the brake line problem. You should of seen the lines from a parts car that I had, the car sat in one spot since 73 till 04.
 
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