'73 Westy Increasing Engine Temp

[iwantmybustorun]

This worked a little bit. The temps did not hit 450 but they were still high and I was only doing 50 - 55mph.

Sorry I am late to the party.

Your vacuum advance is not likely to materially affect the CHT readings. As noted, vacuum drops out when load increases.
I just did a Nebraska I-80 westbound-with-headwind at 98* between 65-70 mph playing with the LM-1 and Dakota Digital CHT gauge yesterday.
In the name of science, I successively leaned then richened the mixture.
I am horrified to report that the engine loves "pig rich" and I am damn serious here:
70mph at 14.5:1 ratio, the alarm (440*) went off in no time.
70 at 13.5:1, I was 433*
70 at 12.5:1, I was 420* fuel mileage over 150 miles was 16.6mpg
70 at 11.0:1, I was 406* fuel mileage over 150 miles was 16mpg
70 at 10.8:1, I was 399* fuel mileage over a tank was 16mpg.
these all averaged over ten to twenty miles on level sections. Trucks are your friends, consider them geisha parasols fanning your exhaust valves' dewy brows with the ability to cool your CHTs a good 20* if you draft.

There are many many assumptions getting torpedoed out here, like:
I Don't Know Crap About Air-Cooled Thermodynamics - the engine has its own ideas and is much more internally motivated as far as temperatures.

Please adjust your carburetors a little more rich to see if CHTs settle down. As importantly, pull a couple of plugs from each side of the engine after a good highway run and see if there is any whitishness on the outside perimeter. TOO LEAN, you may need to re-jet, because idle screws do not reach that high up in the performance curve.
ColinMoreExperimentsToday

Have not pulled a plug yet but I did turn the mixture screw almost a full turn. When I pump the brakes it increased my rpms by 200.
Still the temps are right at 450 unless I drop my speeds to 50 mph.
Is it wrong to keep driving at 50 with temps around 430? I really need to find the root of this issue so I know whether to continue on my journey west or if I should head home.
Thanks to all who have chimed in. Your thoughts are much appreciated.

[RSorak 71Westy]

There only 3 ways to increase the fuel going thru that carb, increase the size of the main jet, or 2 raise the float level some if theres room. The 3rd is to run with the choke slightly on. On the road option 2 and 3 are the only ones available unless you have a main jet or fine drill bits with ya.

[Gypsie]

. On the road option 2 and 3 are the only ones available unless you have a main jet or fine drill bits with ya.

And juevos the size of Rhode Island....

[iwantmybustorun]

There only 3 ways to increase the fuel going thru that carb, increase the size of the main jet, or 2 raise the float level some if theres room. The 3rd is to run with the choke slightly on. On the road option 2 and 3 are the only ones available unless you have a main jet or fine drill bits with ya.

Ok, so if the fuel mixture is the number one cause of this temperature increase then I need to do one of the two things you mentioned to get me home without seriously affecting my engine.
Before I head home with my tail between my legs, could there be another cause?
How much driving can I do with my temps this high?
Is there another test that would tell me if my temps are really this high or if it is just my VDO that has given me wrong numbers?

[RSorak 71Westy]

From understanding of a type 4 450 is the limit and ideally you want it less than this. The valve seats are most likely too fall out when the engine is in heat soak just after being turned off after a hiway run, if you let the engine idle for a few minutes after a hiway run before you turn it off, to let some of the heat get away, you lessen the chance of seat coming out.

Fuel mixture and timing both have huge effects on engine temp. You need to find happy numbers for both to have cool running engine.

[Gypsie]

Am I to understand that you have disconnected and plugged the vac advance and are still at the 430-450 range? You hare sure that centrifugal advance is 'all in'?

Have you looked into the possibility of changing the jet sizing? How difficult would it be in your predicament (ie roadside)? Cancel a trip or earn a roadside fixit badge?...


My VDO gauge tested out consistently around 50* high at the boiling point of 212* (ie it showed to be around 260*.
If you have a infrared surface temp reader (http://www.google.com/products/catalog? ... JsBEPMCMAU) Can also be found at most HVAC suppliers, home depot, and flaps
You could double check though finding the proper location to get a read is difficult. (I have pointed it down through the spark plug hole for a read.
Lastly confirm that you do not have any vac leaks.

good luck.

[dtrumbo]

Lastly confirm that you do not have any vac leaks.

When I pump the brakes it increased my rpms by 200.

Isn't this an indication of a vacuum leak?

[Gypsie]

Totally grasping at straws but trying to help a fellow bus pilot out....

give the carb mount bolts and manifold to intake on head a check for snugness. I was just thinking that even though vac leaks aren't as problematic or prevalent with carbs if there is any air getting in under the carbs it could be like having a vac leak making things run a little lean and increasing temps...(right? (scratching head...)).

curiouser and curiouser....

[iwantmybustorun]

Lastly confirm that you do not have any vac leaks.

When I pump the brakes it increased my rpms by 200.

Isn't this an indication of a vacuum leak?

This was a trick Colin showed me. If you pump the brakes the rpms should go up by about 50rpms or so if it is rich and drop by the same amount if it is lean. When I was messing with the mixture I richened up the mixture so much that I saw a jump of almost 200 rpms.

- I tested for vacuum leaks today and found none.
- I stuck my head all the way in the engine compartment so I could peek in the spark plug holes in the tin to see if I had any nests of any sort (damn mice!) and found nothing. Moved the cooling flaps around and got a good look at the oil cooler, that looked clean too. Stuck a coat hanger up in there and fished around, again nothing. I did see one little piece of paper towel, about the size of the "O" on your keyboard, back by the number 1 spark plug. Not a trace more anywhere.
- Checked to make sure the thermostat was working and it is, opens all the way.
- I have pinched off the vacuum hose going to the canister on the distributor and that gave me cooler temps by 5-10 degrees but I was also going a little slower. (Do I need to adjust the timing at all if I chose to leave the vacuum hose plugged. My advance will be stopped at 28* when doing anything above 3200 rpms. Is that ok?)

I am at a rest stop now, waiting for the engine to cool a bit and I will go out to pull a couple spark plugs as Colin suggested.

I can't thank you all enough for ALL of your thoughts. I'm looking for anything short of getting a new carb right now.

[Gypsie]

When I was messing with the mixture I richened up the mixture so much that I saw a jump of almost 200 rpms.

How does one enrich the mix at operating speeds (ie 2500rpms and above) without changing jets? I am getting the inkling that you are describing enriching the "idle mix" and not the "operating mix". I think someone was suggesting a few posts back that you will only be able to adjust mix ("operating mix") with new jets, drilling your current jets to a larger size (a brave act on the road with family in tow IMHO) or adjusting float levels. I am curious about the float level adjustment. Perhaps someone could elaborate.

(Do I need to adjust the timing at all if I chose to leave the vacuum hose plugged. My advance will be stopped at 28* when doing anything above 3200 rpms. Is that ok?)

Just for clarity, you are saying that, (with the vac advance pinched off) when the engine reaches 3200 you are at 28* and it will not advance any further with an increase of rpms above 3200 rpms?

I would not be surprised if, at hiway speeds, your engine is near 4000 rpms. maybe I am wrong, but if this is the case then you want to know what your timing is at these rpms. in another thread there seems to be some discussion about the advance curve maxing out above 3200 rpms. Just want to be sure that you are checking for 'full advance' no matter where that is on the rpm scale. It should be somewhere between 3200 and 4000 rpms. You want max advance (with no vac) at 28*.

[RSorak 71Westy]

A new carb will not solve anything as it will have the same stock main jet. You need to learn about your carb and how to rebuild it. It's not hard at all. The main jet is a small brass orifice that screws into the carb body in the float bowl. You need to remove yours and read the number off the side and find-buy one with a larger orifice.
My bus was running hotter than usual when one of it carbs inlet tubes was getting clogged with rust, shortly before the inlet tube clogged enough that that side of the engine started to miss at speed. I assume your fuel filter is of known age?

[Gypsie]

It's not hard at all. The main jet is a small brass orifice that screws into the carb body in the float bowl. You need to remove yours and read the number off the side and find-buy one with a larger orifice.
My bus was running hotter than usual when one of it carbs inlet tubes was getting clogged with rust, shortly before the inlet tube clogged enough that that side of the engine started to miss at speed. I assume your fuel filter is of known age?

Dat's what I'm talkin' about. Roadside Repair Badge in the works.

The way I understand it is that this can be done with the carb in place.

Considering that this issue "just started" the 'bit of crud in the jet is a distinct possibility. and perhaps could be cleared (ie remove jet, spritz out with gumout, reinstall...)thereby eliminating the need for any changes (ceptin' maybe a fuel filter...).

You may be near some towns that might carry this kind of thing if you wanted to find a new jet to try.

How far have you gotten (miles and investigatin' the issue...)as of now?...

[IFBwax]

How clean is your engine? Including the bottom cooling fins?

[iwantmybustorun]

You need to learn about your carb

YES, exactly. I will take a look at removing that main jet tomorrow morning.
My fuel filter is brand new. I just replaced it before I left CT. In fact, I also changed the fuel hose before the fuel filter. Colin had mentioned that the hose I had from my gas tank to the pump had diameter that was too large. Could that have changed the amount of fuel getting to my carb or wll the pump still push the same about of fuel?

I am getting the inkling that you are describing enriching the "idle mix" and not the "operating mix".

Yes I was talking about enriching the idle mix. I thought that was what Colin said to do in his post. So I gave it a shot.

Just for clarity, you are saying that, (with the vac advance pinched off) when the engine reaches 3200 you are at 28* and it will not advance any further with an increase of rpms above 3200 rpms?

I would not be surprised if, at hiway speeds, your engine is near 4000 rpms. maybe I am wrong, but if this is the case then you want to know what your timing is at these rpms. in another thread there seems to be some discussion about the advance curve maxing out above 3200 rpms. Just want to be sure that you are checking for 'full advance' no matter where that is on the rpm scale. It should be somewhere between 3200 and 4000 rpms. You want max advance (with no vac) at 28*.

My rpms are below 4000 on the highway if I stay below 70-75 mph, which is usually the case. When I checked the timing I did bring the rpms up past 3400 with no vacuum.

If you have a infrared surface temp reader (http://www.google.com/products/catalog? ... JsBEPMCMAU) Can also be found at most HVAC suppliers, home depot, and flaps
You could double check though finding the proper location to get a read is difficult. (I have pointed it down through the spark plug hole for a read.

good luck.

I just bought a "cheap" one of these for $40. I drove it down the road and by the time I could pull over, shut the engine down and run back there to pull the spark plug wire on #3 the temps read 350 on my VDO and the infrared gun read 352 as a MAX temp it found while pointed in the spark plug hole. I will try and test that again tomorrow as well as look for another main jet for my carb.

I can't thank you guys enough for sticking with this. Your feedback is sooo greatly appreciated.

[Amskeptic]

You need to learn about your carb

YES, exactly. I will take a look at removing that main jet tomorrow morning.
My fuel filter is brand new. I just replaced it before I left CT. In fact, I also changed the fuel hose before the fuel filter. Colin had mentioned that the hose I had from my gas tank to the pump had diameter that was too large. Could that have changed the amount of fuel getting to my carb or wll the pump still push the same about of fuel?

I am getting the inkling that you are describing enriching the "idle mix" and not the "operating mix".

Yes I was talking about enriching the idle mix. I thought that was what Colin said to do in his post. So I gave it a shot.

Just for clarity, you are saying that, (with the vac advance pinched off) when the engine reaches 3200 you are at 28* and it will not advance any further with an increase of rpms above 3200 rpms?

I would not be surprised if, at hiway speeds, your engine is near 4000 rpms. maybe I am wrong, but if this is the case then you want to know what your timing is at these rpms. in another thread there seems to be some discussion about the advance curve maxing out above 3200 rpms. Just want to be sure that you are checking for 'full advance' no matter where that is on the rpm scale. It should be somewhere between 3200 and 4000 rpms. You want max advance (with no vac) at 28*.

My rpms are below 4000 on the highway if I stay below 70-75 mph, which is usually the case. When I checked the timing I did bring the rpms up past 3400 with no vacuum.

If you have a infrared surface temp reader (http://www.google.com/products/catalog? ... JsBEPMCMAU) Can also be found at most HVAC suppliers, home depot, and flaps
You could double check though finding the proper location to get a read is difficult. (I have pointed it down through the spark plug hole for a read.

good luck.

I just bought a "cheap" one of these for $40. I drove it down the road and by the time I could pull over, shut the engine down and run back there to pull the spark plug wire on #3 the temps read 350 on my VDO and the infrared gun read 352 as a MAX temp it found while pointed in the spark plug hole. I will try and test that again tomorrow as well as look for another main jet for my carb.

I can't thank you guys enough for sticking with this. Your feedback is sooo greatly appreciated.

I say rip the damn gauge out.

Go get the engine "horribly hot" again. Pull over. Smell the engine compartment. Check the dipstick temperature. Check your valve adjustments cold, and pull all the plugs to look at their color in the morning. If your senses do not find a problem, if your feeler blades do not find a problem, if your plugs are black on the outside ring and grey/tan/ a little white is OK on the porcelain, I say you don't have a problem. Most importantly, if your plugs are not dusted white on the outside perimeter, particularly if they are still black, and if the porcelain insulator is not bleached white, drive! drive! enjoy the day! to hell with the VDO gauge!

Note too, that if the ring terminal on your CHT plug allows any blowby whatsoever, the temp will skyrocket, it is like the difference between a shuttle reentering the atmosphere with hot ceramic tiles and a shuttle reentering the atmosphere missing a hot ceramic tile. Any black soot past the ring terminal or on the side of the plug outside of the combustion chamber, and you have a little combustion air leak that is blasting the terminal. Is #3 plug a different color than the others?

I ran 460* with RandyInMaine's VDO gauge in the Road Warrior from San Marcos to El Centro CA and couldn't care less! I knew my engine! It was happy! Dipstick was easy to touch! Rocker boxes smelled like good clean hot oil, no burnt stench. Valve adjustments never changed! My laser thermometer read 750*-900* on the exhaust pipes after I climbed out of Death Valley in the 125* ambient.

Just make sure that your timing is correct at 3,000-4,000 rpm, your mixture is decent (plug color at shell), your oil level is good and the dipstick is not branding your finger with a stripe of burnt flesh, and use your senses to ask the engine how it is enjoying the day. P.S. IS IT HOT OUT? If it is 90*-100*, your engine will run hotter.
ColinStupidGaugesRuinEverything