Does timing affect engine temperature?

[74Orange]

74 pickup, 345 v8, 2210, points distributor.

I recently power-timed The 74 pickup and noticed afterwards that my engine is running cooler. The norm before power timing was my temperature needle being about 1/4 of the way between the "c" on the left and the "h" on the right, after engine was fully heated up and cruising.
Now, after power timing, the needle is much closer to the "c", almost touching the line, at full heat.

Does that sound right, for a timing adjustment to make a difference in engine temperature? I should say that I only retarded the timing during the change (at least I think I was retarding; I turned it a few tiny budges clockwise).

Also, if it matters, I recently had my radiator tank repaired and rodded. Thing is, when I got it back in the truck about a month ago, it went right back to that temperature that it ran at normally (about a 1/4 of the way on the gauge). It was only when I power timed it yesterday that the temperature drastically decreased.

 

[Scoutboy74]

Yes, ignition timing can have an effect on engine temp. But you should also consider the possibility that your gauge May not be an accurate measure of what's going on under the hood. The gauge is old and there aren't any numbers on it. The sender is old too. The wire that runs between the sender and the gauge is old and brittle. The contacts May even be loose and corroded. Lots of opportunity for erratic readout. I suggest you purchase an inexpensive infrared thermometer from harbur fake tulz or the like, and take some readings with it at various points on the engine, thermostat housing, radiator hoses, radiator tanks etc, to get some actual numbers. Record them and post up. Then we will be better able to determine if there is something abnormal going on or not.

Oh, and yes, you retarded the timing by by rotating the way you did. I'm not sure you're clear on the concept of power timing. It generally involves advancing the timing a little at a time, then going for a test drive. Lather, rinse repeat until you notice mild detonation or ping under hard acceleration. That tells you that you've advanced a little too far and now need to retard it back by a couple degrees. Might want to throw a timing light on this thing to establish where you're at now. Most 345's will respond well to about 10 degrees of advance to the timing.

 

[71mtnscout]

Yes it will, but as said the factory gauges are marginal at best.....even when they were new.

Power timing is a fickle thing.....keep advancing little by little while doing fully warm, full load acceleration runs till pinging. Then back it off a degree or 2. I dont like to go much above 10 btdc, the performance of the tune is dependant on the weather also.....the hotter the temp the less advance can be run......its not like these old monsters were great "preformers" to start.

 

[74Orange]

Thanks for the input guys.

Trever, I do intend on taking your advice and spot checking all over with the infrared thermometer. May take a while, as here we are starting another workweek (damn!), but I will post the results.

I hear both of you on the power timing technique. Before I began I read michael mayben's post and realized that, like you said, you're supposed to keep advancing slightly until you hear the pinging. Thing is, I was already pinging all over the place before I started messing with the timing! When I would start from a dead stop and work through gears 2-4 to get up to cruising speed, if I got impatient at all and gave her some real throttle that pinging would start, so I knew from reading the power timing article that I needed to scale back. Hence my backwards looking approach to power timing. I simply rode out on back roads and kept retarding little by little until the pinging disappeared under full load acceleration. Makes sense, right?

 

[71mtnscout]

Yup....that works

 

[Scoutboy74]

thanks for the input guys.

Trever, I do intend on taking your advice and spot checking all over with the infrared thermometer. May take a while, as here we are starting another workweek (damn!), but I will post the results.

I hear both of you on the power timing technique. Before I began I read michael mayben's post and realized that, like you said, you're supposed to keep advancing slightly until you hear the pinging. Thing is, I was already pinging all over the place before I started messing with the timing! When I would start from a dead stop and work through gears 2-4 to get up to cruising speed, if I got impatient at all and gave her some real throttle that pinging would start, so I knew from reading the power timing article that I needed to scale back. Hence my backwards looking approach to power timing. I simply rode out on back roads and kept retarding little by little until the pinging disappeared under full load acceleration. Makes sense, right?

Gotcha. Sounds like someone had it really far advanced to begin with. Does this have breaker points or electronic ignition? I bet you're now probably somewhere between 5 and 10 degrees advanced. It would be nice to know exactly, but I realize not everyone has access to a timing light.

 

[MarkO]

In the late '70's all of our type 'c' conventional buses had loadstar chassis with sv345/5-speeds. All had the 2bbl Holley with vacuum operated/governed throttle plates.

It made for a really good power package in a route bus. Most of the buses were geared for a top speed of 57 and a couple could only see 47 mph. Fuel mileage was consistently in the 6-8 mpg range. Most were the old style points ignition.

When the smogged motors starting showing up with the electronic ignition that was when we started having ignition problems. Coincidently we also started getting the cheap gas.

All of the old buses would run on just about anything with about 5-7* of advance all year long. The amount of advance depended on if the bus was running hills or was running pretty much on the flats.

The new buses hated the cheap gas. But what was odd was they had to run a lot more advance to run right. Even though the factory spe'c was 0* we were running 14*--any more and they would ping on acceleration and wouldn't stop when you turned off the key. Anything less than about 10* and the buses didn't have any power and really ate up the gas.

With the huge cooling system of a school bus running that much advance really didn't risk overheating the engine but we did have to back off the advance in the warm months to keep from pinging.

The oddest problem was the two 1978 vintage buses we had. To all intents and purposes they were identical on the LST to the '77 and the '79 buses. But when the weather conditions were just right (or wrong, depending on your perspective) the '78's would freeze up the carbs. We never did figure out what was different and we never did get it to stop--we just learned to live with it.

 

[74Orange]

Okay gentlemen, I got an infrared thermometer and shot up the engine compartment at various spots. I did this a few minutes after coming home from a 2 hour drive, so I'm pretty sure she was at full operating temperature!

Oh and by the way, that temperature gauge has fluctuated since I posted, from the low end of right by the "c", to the high end of a quarter of the way to the "h". And these different results are coming after it is at full operating temperature, so the gauge is confirmed erratic. It's a damn shame, I'd really like a way of knowing at a glance of my instrument panel what my engine temperature is. Too bad no one seems to make new gauges for the pickups.

Anyway, here are the results:

202 driver side water pipe
180 pass side water pipe
160 upper radiator hose, near radiator
184 upper radiator hose, near thermostat housing
154 lower radiator hose, near radiator
152 lower radiator hose, near water pump
185 bypass hose
198 thermostat housing
190 pass side radiator tank, top
150 pass side radiator tank, bottom
175 driver side radiator tank, top
160 driver side radiator tank, bottom
185 engine heads (both about the same)
200 intake manifold
185 engine block

as always, input from anyone on what I should take from these results is welcome and appreciated.

Also, a related question, and I realize this is getting into material that should be in another subforum, but which thermostat should I be getting to replace my current one when the time comes? There's 3 different temperature options from IHPA.
-chris

 

[Scoutboy74]

None of those readings appear that abnormal to me. I say go with the 195 thermo, but the 180 is also a fine choice. I'd investigate your stock temp sender, wiring, and terminations before throwing in the towel on the gauge.