Dear TOBS:

That is a very good point about flow problems in the L-head as Packard used longer stroke (4 1/2 vs 4 1/4) in the 359 motor to increase compression.

According to Turnquist the limit on milling is .045, but that is on pre-war cars. Elsewhere I have suggested milling the pistons on cars to reduce detonation problems.

The 359 was an 8.7:1 compression motor and I assume that represents the practical limit as to compression in an L-head.

One big problem here is that when you mill the Packard cylinder head you reduce the sealing surface between cylinders and so higher compression will be more stressful on the gasket. Of course head gasket technology in those days was still developing and the L-head might have done better with plain metal spacers as is modern car practice.

Wow! All these cars having problems.

If there is a car having this problem that also has an electric pump, then how about bypassing the mechanical pump and running the motor via the electric pump?

Way back when I dealt with a high mileage 56 Exec that was having this problem and because it was just an old car we bypassed the fuel pump and ran it on electric. It was a cheap repair that satisfied the owner who just used it as a second car.

However, the root cause is still important. I am sure that these old blocks just don't run as cool as new which creates problems. The prewar cars have bigger radiators and so overheating can be reduced to a manageable level. But I had similar problems with a modern car that was high mileage and always running hot.

For somebody out there interested in an experiment, take a heat gun (or powerful hair drier) and aim it at the fuel line, carburetor, and fuel pump with the motor running. If it stalls then you have isolated a problem area. (I suppose a propane torch would also work! but only on the fuel line)

The insulation block idea is also valid as it concurs with the Packard company service letters which state that vapor locking results in the low pressure carburetor circuits.

Of course stuck heat risers will create big problems in hot weather as well.

I assume in each of these cases valid ignition has already been confirmed. Given today's cell phone infested highways, stalling is a huge safety problem.

Dear Joe:

I think the way to go here is to isolate the problem to either the overdrive relay or the ignition system.

To do that disconnect the ignition interruptor wire at the coil (that is the extra wire that is usually found hanging underhood on original cars).

The overdrive will still work with the exception of kickdown which is no loss.

If your problems persists and you have no wires shorting inside the distributor then there is a short in the breaker plate and you will need to fix that.

The overdrive ignition interrupt is a notorious troublemaker.

These cases of verifiable vapor lock are really interesting.

Obviously the Packard company was able produce problems at the proving grounds because they started putting heat shields around the fuel pump and carburetor.

That one about the filter bowl has me scratching my head because if the motor is starving for fuel then there should be no pressure in the line unless the float is stuck closed. Perhaps the water splashing on the fuel pump released a stuck valve.

Packard cited vapor lock as a cause of poor performance but said nothing further about how to service the problem except for updraft carburetors where they said vapor locking occurs in an idling motor.

One of my suspicions is that there is simply a problem with these old fuel pumps. Maybe the valves don't work right because the castings are getting old and creating problems. They are after all just cheap zinc pot metal. Years ago people were putting electric fuel pumps on cars because they couldn't get parts for the mechanical pump. I remember one Caddy 12 that had the fuel pump gutted and was running on one of those fantastic Stewart-Warner electric pumps. It never broke down so maybe these cars should just be running all electric with a dummy mechanical pump.

Suppose for example that the pump is creating suction internally because of the valves. This reduced pressure will cause gas to boil.

Another possibility is that a restriction in the supply line is causing a low side vacuum. Once I dealt with a Clipper that acted like vapor lock. You could turn the electric pump on and the thing would still be starving for gas at full throttle. The location was terrible so I redid the whole thing and put a Hirsch Airtex unit midway in the line at the lowest point. That fixed it.

The postwar cars are designed to create a syphon action that keeps the fuel pump full when parked. If a filter or fuel pump is higher than the lowest point in the fuel line then that could create a low pressure point where gas boils.

Hey this is a great discussion!

We can all agree on one thing: The Packard script Cover (as they call it) was 1940 only and 1940 could have either script or block letters according to the parts book, but 1941 taxi should have script, and 1941 120 ambulance could have script or Block letters.

Now there is only one part number for Block letter Six and since the data book says the cover has the model number I assume then it says Packard 110.

So I assume Block Letter Packard means no model number and the other part number for the Business cars say Packard 120.

Now things get interesting because in the 1941 Packard sales brochure the cars clearly say Packard 120 and Packard 110 on the hubcaps.

So I think the only way to figure this out is to get mint originals with the part numbers on the back. But beware, I was looking at a set of mint original hubcaps once and they featured a part number that wasn't in any Packard parts book.

Dear Tobs:

I didn't think about backing into the residual volume until later. It would be interesting to see how accurate the calculation is given the compression ratio is accurate to one significant digit. And an adjustment also needs to be made for the spark plug insulator.

Anything over 8:1 will have to be monitored for carbon build up in the quench area.

I've seen carbon knock cases even on the pre-war motors with the HC cylinder head and they were well under 8:1. 6.85 to one on the Clipper for example.

Dear TOBS:

I don't understand "marks from the old head gasket" The only reason to cut the head is if the deck is not flat or if the surface is damaged. So I assume he is talking about an area where the gasket was leaking.

Anyway, I think your compression ratio calculation requires some revision. You need to take a graduated cylinder, and with a piston at TDC, pour gasoline into the cylinder to determine the residual volume R. For accuracy using the weight will eliminate false measures.

Now do the math for the displacement V = PI * ((Bore/2)^2) * stroke.

The compression ratio is now (V + R) / R.

A rule of thumb I've heard is milling .060 raises the compression by one.

Long stroke L head motors are very susceptible to piston noise and carbon so I would avoid to high a compression ratio.

Hope this helps.

Since everybody is trying to scare poor Dan how about checking it for bedbugs? Bedbugs and body lice transmit typhus and the bacteria can hang around for awhile.

When I was overseas I had a very mild case of typhoid fever. It lasted several weeks and was like the flu except that you woke up feeling okay and as the day progressed you got sicker and sicker. Finally one day I collapsed and had to lay perfectly still in darkness for 48 hours.

Now there's something to be afraid of.

Don't put urea in the gas tank. It is an amonia type molecule that requires a catalytic converter to function.

The present emissions situation regarding diesels is insane and stupid. The cost of building a urea plant, production, packaging and shipping; produces far more pollution than the urea reduces. And the systems render the diesel far less fuel efficient. Thus, valuable fuel is being wasted and CO2 emmissions are increased so high that truckers are rebuilding old trucks rather than buying new ones (the only environmentally beneficial aspect of the EPA standard).

If you think you have a fuel problem, first check the ignition system when the motor is acting up. If that is good, make sure the fuel system doesn't have an air leak (some will suck air but not leak gasoline). Then pull a plug when the motor is stalling to check for a lean mxture.

Hope this helps.

Cadillac had the same set up on the Hydramatic only it was on the right hand side and had an access cover. The fluid drive Chryslers had only a plug in the fluid coupling which was also accessed via a floorboard cover and plug.

Given Packard dealers relied very heavily on service for revenue it is fitting that the Ultramaitc would require trained personnel for even routine maintenance. Thus, the location of the dipstick. After trade in the Ultramatic could be very troublesome given it would then end up running low on fluid if leaking.

If the pan is leaking use Mopar ATF-RTV and let the sealer sit for twenty four hours before filling (and use a torque wrench). If the trans is throwing oil out the vent, there is a service bulletin as regards the speedometer gear. If it is installed backwards that will cause problems. I have been told as well that if the filler cap is not vented it will throw oil.

After that there is the front pump seal, TV, tail shaft housing, and shifter.

I have taken care of leaking Ultramatics and had the cars sitting for weeks without a drop of leakage. So they will hold oil.

Today, they are omitting transmission dipsticks altogether.

Hope this helps.