Sudden (relatively) overheating

69 B Roadster - New 160 degree thermostat and new water pump (QH brand) and has been working like a charm, even on hot days in the high 80's in traffic. Took it out on a 90 degree day before I went away for the holidays and it overheated to slightly more than halfway between normal and hottest possible reading and started mis-firing. I am REALLY disappointed as I thought all of that was behind me. The timing is set at about 17 Degrees BTDC as one book says 14, another source says 20 and the 17 seems to work better than the 14 in terms of starting car, etc. Thanks for any thoughts/guidance.

JTB

John,
Not sure what to say about the misfiring, but temperature-wise I think you're ok -- I wouldn't call it "overheating" until it started spewing water. I run a 195 deg stat in my '69, and the temp needle stays between just a smidgen right of "N" and about half-way to "H." (Lately our highs have been in the upper 90s, which probably puts the air temp in triple digits sitting in traffic...) Just out of curiosity, I stuck a thermometer in the radiator when the needle was in the latter position, and the thermometer said 190 exactly.

Smokey Yunick said that it's possible to overcool an engine, and I tend to believe him. His argument is that the energy you're draining out of the engine by trying to keep it down at 160-180 could be better spent turning the crankshaft....

So I don't think that it running warmer than you're used to caused your problem, but rather an effect of something else. Does it still misfire, or have the symptoms abated now that the car has rested?

Ron,
When car is cool it runs fine. This has happened several times on a lesser scale. Hadn't gotten to the carbs yet but that wouldn't seem to be it, I don't think. The 160 thermostat just seems to hold it at normal a bit better than a 180 or 190 thermostat does and it runs fine when first cranked.
At low humidity here (20-40%), things don't cool off as fast as there is very little moisture to help evap process. Feels good on people but not sure it helps engines. Given that a thermostat takes 20 degrees of temp to open fully, I felt that give low humidity and difficult evaporation it might just be balancing that out.

My thought was that if I am on edge of being over advanced, wouldn't slight overheating cause ignition in advance of planned causing mis-fire?

JTB

My 71B on a 80 plus degree day always runs between low and normal with a 160 degree thermostat. However, when it gets up over 100 degrees everyday in the summer here in the California desert, the B will run right at normal or slightly above. This is when I can tell the car is getting hotter then a two dollar pistol. But really that wouldn't mean much of anything to you other then a comparison of gauges that may have totally different calibrations. Have you had your radiator checked by a shop lately? It may need a rod out from deposits. Hopefully you still have your orginal radiator and don't have to concern yourself with one of the aftermarket radiators?

Jim, ;-)

I guess it depends on what you mean by misfire. If you're at the hairy edge of overadvanced and your engine for whatever reason starts running hotter, I'd expect it to just start pinging. Misfire to me is when a cylinder fails to fire. If that's what you've got, then it could be something like a marginal coil that starts failing as the underhood temp climbs....

HTH!

Uh-uh. Starts to miss at lower rpms and generally lose power. Not ping. Relatively new coil from Moss. Year old or so...maybe two. Can they just go suddenly? Really just starting to think of getting new dizzy and at least eliminate one problem so I can focus on the next. But would like to figure it out and not spend money where I don't have to. Hardheaded, I guess.

John

Rob,
Guess I could spell you're name right...not like I don't know it. Sorry.

Tom,
I will check my thermostat and gauge tonight with a meat thermo. Gauge might be reading a little high right now if it is like it was previously....it always read a bit high. If so , the approximate corrected read should tally with your experience. Radiator is aftermarket replacement one I got 4 years ago (was even more ignorant then) and it has generally worked reasonably well......not to say you're not correct that I would do better with a re-cored one but seems like I shouldn't have to do that. Very clean system. If anyone knows how to test whether it's working properly or not, let me know.

John,
No problem -- I get "Ron" all the time! Probably something to do with the 'b' and 'n' keys being side by side on the keyboard... :-)

Sounds like you've got a tough one to diagnose -- especially tough to do long-distance. Here's how I'd probably attack it, though (and if you've already thought of this, forgive me repeating it....) Start with a full tune-up, or at least inspect all the aspects of a tune-up. Check the valve clearances, pull & inspect the plugs, inspect the wires (& check them for resistance), inspect the distributor cap & rotor for problems like carbon arcing, check the points gap & condition, inspect the distributor mechanism to make sure it's working freely & properly and not excessively worn, confirm the timing, check for vacuum leaks, check all the emissions plumbing & gear, check the carb balance, check the fuel flow, check fuel mixture. Checking the cooling temp & cooling system condition is a good thing too. Once you've established a baseline, you're on better ground to start diagnosing.... Do all this before you start throwing parts at it (unless you've got spares around, in which case you can use the time-honored diagnosis method of "Replace with known good part" -- perfectly fine techique as long as you don't have to shell out cash for the test parts!)

Wish I could say more, but without being there....

DID YOU BACK FLUSH THE HEATER?

DID YOU BACK FLUSH THE HEATER? ever?

Sometimes when Jerry yells, he stutters and repeats himself!! :o) I don't think he smacks himself in the head, but he may!!!

Don't know why flushing the heater core should matter here....I'm pretty sure he's got the heater valve closed in this kind of weather. Even if it was plugged solid, it wouldn't cause the engine to overheat...

You are right there Joe!! Jerry was just being 'Jerry'!! :o)

Yeah.....but he didn't tell him a Weber would solve his problems :-)

Weber....arrrrghhh....and yes the heater was back flushed along with the whole system early on a number of times but as Joe points out, it's closed anyhoo. So no magic bullets, eh? Have to do it the hard way and actually know what I am doing by taking the "Ron" Edwards approach. Sometimes I hate it when I have to learn the next thing and ain't in the mood. Car doesn't care about my mood however so I will have at it. Just thought I had it there and didn't want to spend time on the next system. Well, gotta get through them all sometime.

Thought Jerry had gotten his rabies shot. Oh well, we'll just have to shoot him.

Me too!! I hate that sh!t!!!

John,

any luck with the cooling problem yet?

Dan