VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 Loss of power on hill

A friend is getting his 34 master back on the road and it runs very well on flat ground but will lose power to the point of almost stalling on a hill. Gas tank has been removed and cleaned, fuel pump rebuilt, and a later (41) carb rebuilt and installed. Float is set to the 41 spec, seems like it was 3/8 but I don't remember.

The ignition system has been gone through with new components and the timing set to spec. The advance is working.

Any thoughts on where to start?

Thanks

Dave

I would start with the ignition system. I understand that new components were installed but that does not guarantee they are all working well. As an example most new point sets I have installed have an insulating coating on the point contacts. It is necessary to clean them with a crisp dollar bill or ? to get a hot spark. I have not used a timing light in probably 30 years as timing by ear is better given each engine has its own "sweet" spot.

I'd be tempted to connect a vacuum gauge and see what it shows before and during the hill. It may run well with a light load but if the engine has problems, it just won't be able to keep up with the heavier load of hill climbing. Things that come to mind right away are fresh fuel, valve lash, weak condenser, clean even brand new points, plugs/wires, generator output/battery condition and just general engine wear so it's weak. New parts are not necessarily good parts thus mentioning the condenser.

Does he know the overall health or history of the engine? When you said the timing is "set to spec", is that the original spec or has it been properly advanced (more than OEM spec) to work best with today's fuels?

See Chipper's post as he clicked "post" a split second before me...

Ignition is generally the first place to check.

If the ignition tests good, then I would look at the fuel delivery system (the engine is going to require more fuel on the hill).

Start with removing the gas tank cap for a driving test. This will check to see if the tank vent is working, and that you are not pulling a vacuum on the fuel tank.

If this tests good, then check the condition of the fuel filter.

And finally, there are aftermarket carburetor fuel valves that use two glass balls (a small one and a large one) as a means of fuel control. We have had numerous customers with these and fuel delivery issues, that removed this valve and replaced with a normal plunger type fuel valve and solved the issue.

Jon.

Thanks for all of the responses.

I will keep you posted.

Dave

Does it have a miss when losing power or just runs smooth? Does it have good compression? You say the advance is working but is it fully advancing and retarding properly? I agree that a vacuum gauge will tell a volume of info.

I had the same exact issue. The truck was losing compression going uphill. Everything was checked over and was in order. I got a New head and heavy duty lifers and the truck is riding like a tank. The new set up is a 235 head with the last casting numbers being 848 that gives me over 9:1 compression in the block. Good luck

These were my compression specs before changing

Exhaust intake
.225-.216 .210-.201 ACCEPTABLE RANGE IN SHOP MANUAL
0.190 0.203 #1
0.224 0.203 #2
0.217 0.202 #3
0.222 0.175 #4 repeted intake, got .175. This is worst out of spec
0.219 0.198 #5
0.208 0.206 #6

He says no miss, just smoothly coming to a stop . He is going to try some of the tests recommended and I will go by on Saturday with some test equipment.

Thanks again

Dave

We did some tests running it up the hill and at idle. The vacuum is 15 with very slight but rapid fluctuation between 14.8 and 15.2 approx. at idle. The gas cap test did not make a difference.

It does have the original starterator system on it and seems the trouble may be in that adjustment since we did make it up the hill using the hand throttle but that may have been coincidence.

Next session we will check the timing.

Dave

It should be easy to check the throttle movement from an idle but much more difficult when the vacuum drops as the throttle plate is opened. I had not thought about that being the cause of the hill climbing problem. With the description it is NO. 1 on my list. If the linkage moves back toward the starting position it can limit the travel of the accelerator pedal and cause the slowing to a stop going up a hill.

I think he has a manual for the 34 but any ideas on how to correct or adjust? It seems a very complicated system and from what I remember reading on here often replaced.

Dave

No luck yesterday, getting full throttle shaft movement and the starterator adjustment points are 1/8 as required but a lot of play and lost movement in the system.

It has new radio suppression wires so we may try swapping these out to see if it helps. The timing is where it should be but I am going to try with a vacuum gauge to see what we can get that way.

Dave

Hi Dave,

If you are like me you enjoy these work sessions to help others. They can be frustrating but I manage that by limiting how much time and effort we out into each session. Plus the between session breaks give us time to think about solutions.

I have to wonder if you are simply dealing with a "tired" engine. 15" vacuum sure seems low to me. You have never mentioned miles on the engine and if any major work has ever been done on it. Any indications of excessive oil consumption?

I would definitely consider a compression test as part of the next session. A key point to remember is that you might get reasonable or even high compression numbers due to lots of carbon build-up.

Keep us updated.

The points seemed to be gapped a little tight so we adjusted those and advanced the timing as suggested above and it made it up the hill in fine form without replacing any parts. My vac gauge is 50 + years old so I replaced it and the gauge reads 17 with some very slight fluctuation. It might pay to go back and double check all the basics at some point soon but for now he is motoring.

Thanks for the help and suggestions

Dave