Re: 1941 One Eighty - curious engine problem

Posted by Victor On 2011/1/13 23:05:58

We rechecked on almost everything we could think of, including carburator, points, distributor, fuel pump, etc., just to make sure everything was ok. Here it is, our findings, the good and the bad:

Good:

- Spark plugs look great, with a dry orange color, apparently giving good combustion

- From the very little that can be seen of the combustion chambers, everything looks bright clean, no carbon deposits.

- Carb is clean and looks great. We took it appart again and everything seems to be fine, including choke.

- One running, there is no noticeable smoke, nor gray nor black.

- Fuel pump delivers 6 lbs constant pressure. We forgot to note the mechanical pump pressure but it is working reasonably well when cool, but misses when hot, even though it has a fresh Max Merrit kit. This last thing is a small problem, but nothing compared to the next finding.


The Bad:

My mechanic, still with his failing valve theory, decided to check on compression, and the findings are terrible. Difficult to explain how the engine works so fine when hot, but that's the fact. Compression, measured without plugs, with the carburator wide open, and on 3 full engine turns, reads as follows:

1. 0... yes cero... ouch... though because of the color of the spark plug my mechanic thinks that at higher revs somehow the cylinder does work.
2. 60
3. 20
4. 40
5. 60
6. 60
7. 55
8. 60

I don't know what compression is to be expected from the cylinders, but I do know that it should be about the same in all of them. So, my mechanic still thinks that we have some valve lifter problems. He will come back next wednesday and he is going to check with air to determine losses and use and old analyzer we have. What he thinks is that some of the valves are not closing completely, so either they were not seated properly when the engine was rebuilt or perhaps there is some kind of problem with the valve lifters in that they are a little high and don't allow some of the valves to completely shut against their seat.

Once the engine is working fine, after about 4 or 5 minutes (once with some temperature, of course) Cylinder no. 1 gives us an almost contstant small miss in the engine in an otherwise very smooth running and silent engine. I know... things sound strange. How can an engine with such lowsy compression readings and expected valve problems be so silent and smooth. I guess the nine mains and Packard high standards have to do with it.

So, next week, and after the inspections he want's to do we might have to start taking the fenders off to take a look at the lifters, and most probably take the head off also... I don't like the idea much, but I guess everything is pointing in this direction.

Any ideas?

Victor