Overheating problem finally solved!

[Don L.]

Re: Overheating problem finally solved!

Interesting indeed, Patrick. I had the distributor in my '72 L48 rebuilt last year when I found that there was substantial play between the lower bushing and shaft. Upon re-install, I found the car liked the initial timing @ either 12* or 13* most (can't remember which), giving me 36*ish on high throttle. As you know, I have the TCS installed and it's functional to NCRS Ops requirements.

My engine temp is good, exceeding 200* only when it's hot outside and when I'm driving at parade speeds (think Woodward Dream Cruise). As soon as I move, the temp falls back to 180* or so.

I was told that these cars no longer like their original tune up specs because of today's fuel. Has anyone else heard this?

[Patrick H.]

Re: Overheating problem finally solved!

But Patrick, thousands of these engines ran trouble free with ported vacuum and timing set at factory specifications. Something else is wrong and you are treating the symptom. Could the timing chain have skipped a tooth? Those nylon gears don't like to be without oil for a long time (or so I was told by a Powertrain Engineer).

Yah, I'm well aware of that. As noted, one of them lives in my garage.
I suspect anything is possible, but since the car will be much closer to you the next 5 months you're welcome to have a hand at fixing it.

I have absolutely no clue how one could ever determine it's a timing chain tooth (which I've never really believed in - how do you skip one tooth when they're all made of crummy nylon?) but open to suggestions.

[Patrick H.]

Re: Overheating problem finally solved!

Patrick------


The timing change might be "compensating" for the real cause of the overheating.

See comment to Terry above.
It very well may be, but I sure can't figure out what the real cause might be - unless it's a crack that occurred as it sat in an unheated Michigan barn for 15+ years. THAT has crossed my mind many times too.

[Monte M.]

Re: Overheating problem finally solved!

Patrick,

can dig up another TCS switch for judging. I would still like to have one on the car for every day. My concern was how the car runs the best for every day driving. My car only has 39K miles on it, but by the time my kid gets it, I hope it is turning 100K. So, I plan on driving it, but want it to look correct and more importantly, run great.

Monte

[Timothy B.]

Re: Overheating problem finally solved!

Patrick,

If there is any crack in the engine the coolant system will pressurize with combustion or the exhaust will have water vapor smoke beyond normal. If the timing chain tooth has skipped, timing at TDC will move the distributor to a position that's not normal as the book shows so IMO, the distributor cap will not be in a normal position.

Did you change the water pump, I am thinking about the internal bypass and if it's plugged. Not sure but would this keep coolant from circulating with the thermostat closed.

One thing you DO know is the exhaust is getting so hot that the parts around are melting. Heat riser installed correctly, exhaust open without blockage after sitting all these years. Consider all the simple things also..

[Terry M.]

Re: Overheating problem finally solved!

Yah, I'm well aware of that. As noted, one of them lives in my garage.
I suspect anything is possible, but since the car will be much closer to you the next 5 months you're welcome to have a hand at fixing it.

I have absolutely no clue how one could ever determine it's a timing chain tooth (which I've never really believed in - how do you skip one tooth when they're all made of crummy nylon?) but open to suggestions.

The one I had that did that skipped a whole bunch of teeth and that nylon gear was shot. Of course it didn't run at all. I have never had one skip just one tooth, and even if it did I doubt it would run at all well -- but we always hear about that as a potential issue. I think checking the mark on the damper against the position of the distributor rotor is the way to check the position of the timing chain as well as everything else between the crank and the rotor. My wrenching days are getting short. I will let you young 'uns do that.

[Paul O.]

Re: Overheating problem finally solved!

Yah, I'm well aware of that. As noted, one of them lives in my garage.
I suspect anything is possible, but since the car will be much closer to you the next 5 months you're welcome to have a hand at fixing it.

I have absolutely no clue how one could ever determine it's a timing chain tooth (which I've never really believed in - how do you skip one tooth when they're all made of crummy nylon?) but open to suggestions.

Patrick

I agree with Terry that your timing adjustment has just cover up the real cause of the problem. A retarded engine timing will cause an engine to overheat due to the loss of fuel/air burn efficiency after top dead center. Also would increase fuel usage for power needed thus also increasing engine heating.

As others have said check the dampener for slippage, timing of your valve train at top dead center is correct, timing chain and gear for wear and chain looseness. The chain most likely has not skipped a tooth but the chain could be stretched. Also if the gear and chain set has been replaced at some earlier date it could be indexed incorrectly off by one tooth one just never knows what others may have done in the past.

Just remembered 1 tooth misaligned on the cam gear to crank gear is about 16 degrees of timing which is about what you have added. That is if I remember correctly you know age.

[Robert K.]

Re: Overheating problem finally solved!

I had a similiar problems years ago. It liked alot of advance at idle, but was hard starting when hot. I always felt that it had something to do with having the cam degreed in. The problem disapeared after replacing the cam.

[Timothy B.]

Re: Overheating problem finally solved!

Robert,

That's a very good point, if the camshaft was changed or someone advanced or retarded it relative to the crankshaft the engine timing can change. With what Patrick reported about the hot exhaust manifold melting hoses, the mixture could be burning when the exhaust valve opens.

[Patrick H.]

Re: Overheating problem finally solved!

Patrick,

If there is any crack in the engine the coolant system will pressurize with combustion or the exhaust will have water vapor smoke beyond normal. If the timing chain tooth has skipped, timing at TDC will move the distributor to a position that's not normal as the book shows so IMO, the distributor cap will not be in a normal position.

Did you change the water pump, I am thinking about the internal bypass and if it's plugged. Not sure but would this keep coolant from circulating with the thermostat closed.

One thing you DO know is the exhaust is getting so hot that the parts around are melting. Heat riser installed correctly, exhaust open without blockage after sitting all these years. Consider all the simple things also..

No vapor smoke, no oil consumption (to speak of). Water pump replaced in course of getting the car back on the road.
New exhaust, heat riser has the blockoff removed and previous to that was wired open.
Distributor is exactly where it should be; in fact, I got within a couple of degrees by eye when I reinstalled it. And, the trick of matching the distributor to the mark on the intake would have previously shown any issues when I confirmed them previously with a timing light.

As noted, just with the 2 changes in the timing system the overheating is gone. I'd expect a major systemic failure (crack in block or head) would have continued to overheat the car, and it's not.
I'm interested in seeing how backing the timing off to 14 or less degrees affects the temps.

Patrick

[Patrick H.]

Re: Overheating problem finally solved!

Patrick,

can dig up another TCS switch for judging. I would still like to have one on the car for every day. My concern was how the car runs the best for every day driving. My car only has 39K miles on it, but by the time my kid gets it, I hope it is turning 100K. So, I plan on driving it, but want it to look correct and more importantly, run great.

Monte

If it's just for day-to-day then forget about the TCS solenoid and run a direct line from the carb to the distributor. No sense messing around with the solenoid then.

[William P.]

Re: Overheating problem finally solved!

I don't think the engine would run as well as you describe if the cam had slipped a cog .

Bill

[Robert K.]

Re: Overheating problem finally solved!

I don't think the engine would run as well as you describe if the cam had slipped a cog .

Bill

That's true! If it jumps one tooth you can adjust the timing and get 90% of the performance back. Jump another after about 2 weeks maybe 60% jump another after another week and I barely made it home. This all occurred over a period of about 3 weeks.

[William F.]

Re: Overheating problem finally solved!

Sounds like something else going on. 20* initial is a lot. Surprised it'll even start without "kicking back."

[Michael G.]

Re: Overheating problem finally solved!

The "melt-down" of plastic items in the engine compartment is what worries me. I don't know how much of the heat can affect the nylon on timing gears but if they were week before, then they are probably shot by now.