Hot Rods SBC overheating...yes I've tried almost everything!

Will I need to add some type of overflow or could I leave it plugged indefinitely?


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unless its boiling over nope ... I few foreign cars I have worked on run this hot for emissions reasons , thye do not use a gauge just a idiot needle . thats another thing did you reference your gauge ??? ( check it in hot water ) some cheaper ones are known to run way off scale , and if its electric is the sender compatable with the gauge as some have different ohm settings .

 

It's not boiling over but it does puke out of the overflow nipple. I need to reference my gauge as I have not done this. It is the mechanical style with the copper line sending system. I bought it new and put it straight on the 55. I just assumed it was accurate. But I suppose a cheap gauge from Advance could be wrong.


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The ignition timing...maybe you are not real familiar with how ignition timing affects engine temperature? If the timing is retarded, it can make the engine run hot (it reduces the efficiency of the engine, so more heat goes into the cooling system, instead of being used to make power).

That's why I suggest you check the timing. You can have it retarded 10 degrees and it will start fine and run ok, but be a bit low on power, and cause the engine to run hot

 

Can you hold a cloth in front of the radiator with the fan hold the cloth in place? HRP

 

I have not done this, just felt the engine side of the fan to see if there is air flow. I will do this and see.


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Thank you for the explanation. I am not familiar with the timing and how it affects cooling. So would should the idling degree of timing be and what should it be above 3000 rpm? 34 degrees right?


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Cooling system pressure test will assure the system is good or no good in that dept.
I say change the water pump.........ask me how I came up with that idea.

Most air in the system will work it's way out by driving it, except an early reverse flow LT motor which you don't have.

When we redid my oldest boys Camaro while in High School we had a overheating issue with town driving only (35 and below) everything was new radiator, water pump etc. Long story short the water pump impeller was not pressed on far enough, and was cavitateing making bubbles, not moving the coolant. Pressed it on about another 3/16" to 55 Chevy Chiltons standards (all I had on rebuilding water pumps) and never another problem.

Pull the thermostat completely out leave the cap off and have someone start the engine and observe the coolant flow, that's what sent my sniffer to the water pump even though it was new.

 

Could there be a vacuum leak after switching manifold and carb? Or running really lean?

 

install a proper overflow , the cap is just for data, if you burp it, cap it and it stops overheating, you have your answer as to where the air is coming from.

 

and I hope your radiator isn't like this beauty I pulled from a customers truck ( 95 5.0 efi) , truck was overheating for another reason , but look what the blown headgasket from a super stretched out chain (trying to run at 15* retarded ) did .http://s102.photobucket.com/user/stimpy1966/library/Radiator

 

I don't notice any leaks from the intake and just had the carb rebuilt. I have the air/fuel adjustments out to 1 1/3 turns from stock on the edelbrock. If anything, it smells like it may be running slightly rich.


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I would put a 17 or 18 pound cap back on it (I run 18 on everything I have) verify gauge works properly. Is it overheating or just overflowing into puke tank.

 

It's not overheating to the point it can't be driven, but every time I drive it more than 10 miles or so the temp is up around 235 and I go home and shut it off. It does start puking around this temp. I will change the cap to a higher rating.


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These are my back yard checks.
I would check your timing @ idle and total timing. "By ear" isn't the best way
even if it sounds right. Also, by timing light you can tell if the chain is stretched by the marks not staying steady (jumping). For vacuum leaks, take the air cleaner off and put your hand over the throat of the carb. to suffocate it while the engine is running. If the engine starts dying then shouldn't be any leaks, if it still runs, then you have a leak.

 

I will do this and see how it turns out. Will have to get my hands on a timing light. What should the timing be?


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Replace the radiator and your problem will go away. I'll bet theres a reason that Griffin radiator was sold in a swap meet. I've had a couple of Griifins and was never impressed.

Gary

 

I had a mildly built 327 in an OT car at one time; the engine was rebuilt, new radiator, and all new hoses (everything was several months old). Then one day, it started overheating to the point it would't spin the motor over, due to heat sink to the starter motor, when it was hot, and it was losing coolant out the radiator overflow; BUT, it would't do that ALL the time. I had gone through EVERYTHING trying to find/figure out out why, several times. It had a points distributor, and when I removed the rotor to replace it (I was replacing everything/doing everything, including a new tune up it did't really need), BINGO, busted centrifugal advance spring; it had been running way advanced! Replaced it, and no more getting hot. A simple, tiny little part, was causing all the problems! BAD part of this story; I was on I-405 trying to "blow carbon out of the cylinders", thinking maybe it was carboned up (trying everything, remember?), and I had't found the broken advance spring yet. I went through a Washington State Patrol's "traffic enhancement zone" (radar trap) at the top of 2nd gear, and was about to shift into 3rd. It would pull 90 MPH in second gear (TH350 trans and 3.08 gears). The trooper knew me from my work, and let me "go", after a good talking too. He had a V-8 Vega himself, so I think he kind of understood the car guy thing. It was a couple of days later, I found the busted spring. Start with the basics, before throwing money at the problem; I had't yet learned that! I am Butch/56sedandelivery.

 

By the way, I have a 99 chevy pick up that for some reason the distributor hold down got loose. Only way to time it is by scanner. I did the "ear" thing since I don't have a scanner. It starts and sounds right, but it gets hot when idling. It never got hot until now. I need to get a scanner to set the cam retard right.

 

What do you have on it for an exhaust system? A partially plugged exhaust will cause it to overheat. Some Y pipes have issues of closing off one side when they get old and rusty. Does it have a heat riser valve on the exhaust manifold? If so is it stuck or is it free to open? If it is stuck closed it would cause the engine to run hot.

 

It has the old style cast iron manifolds with straight exhaust run to two individual mufflers that are all new as of today actually. So I shouldn't have a problem with a clogged exhaust. Thanks for the suggestion though!


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The distributor I had laying around from an old build. I will pull the cap off and check the cap and rotor button as well as the spring. Thanks for the idea!


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Do you know what degree I should be at idle and at total timing?


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That I couldn't tell you, you would have to look it up to your year motor. All I know for my '99 (which won't help you), -/+ 2 degrees @ 1000 rpm.
I threw in a 305 in a high mileaged van and used the old radiator. A brainless install and everything ran fine. I guess I got lucky having - what do I have to lose? attitude.

 

there are marks on the dampner ( 95 was the last year you could manully adjust the distributor for timing ) , should be about 34-36 total at 3000 ( your going to have to put a timing tape on the dampner for this ) and around 12 btdc at idle , basically its a egr 1979 truck motor now without the computer stuff .

 

i set my timing by ear=i am an idiot.

 

I sent you a Pm on this so it don't hijack the thread

 

The thing about timing at idle, is that there are a lot of different distributors, with different amounts of advance. The total advance is more critical than the advance at idle, so I generally set the timing at higher rpm, then let it idle and see what the timing is at idle, and make a note of it. If it's way too much or too little, I'll change the advance curve in the distributor to get it to run good at idle and off idle.

 

Two thoughts come to mind every time I hear about overheating.
1. Vacuum leaks. This could be a leaking intake gasket, bad power brake reservoir, loose and cracked hoses, anything.
2. Retarded ignition timing. Today's fuel likes 14 BTDC at idle, plus vacuum advance in some instances (especially larger displacement engines or those with a heavy reciprocating assembly.).
If you use an infrared thermometer, you can check coolant temps in and out of the radiator to see if it and the cooling fan are working. 40 degrees is about the largest temp drop you can expect.

What distributor did you install? Replacing bad with bad = bad.


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