Timing notch

[rickf]

Ok, Mike, I will try to explain a little about timing vs. fuel/air mixture and RPM. I am not a teacher so this may or not make sense. I see you are in Poland so I am going to have a tough time relating to vehicles you are familiar with but when this type of situation comes up I always refer to the Ford Model A. Basically to get the best vacuum your timing and fuel mixture have to be just right for THAT particular RPM.. So when you set the best idle mixture according to the vacuum gauge that is fine and it is how it has been done for 70 or more years. Then you adjust the timing to get an even better vacuum. This is where it gets sticky. That timing is only best at THAT exact RPM. As soon as you start to accelerate the timing is no longer the best, you have a variable situation instead of a dynamic one. Now, as soon as you hit a certain RPM, and I don't remember off the top of my head what it is but not very high, the centrifugal advance starts advancing the timing even more. So now you are ahead of the optimum timing for the RPM you are at and basically you need a richer mixture to compensate for that. As the RPM starts to get up near road speed it is at full advance and you are now in detonation territory. With the low compression and noisy conditions of a mutt you may not hear it but you can damage things like break rings. You are also losing power because the spark is happening too far before TDC and this is in effect trying to push the piston back down. This is why the initial timing is set at 6 degrees. It is a little retarded at idle which will give you around 18 inches of vacuum but as soon as the rpm starts coming up and the advance starts working things come in line.

The Model A. On the Model A you had a lever on the steering column to control the timing. I am not even going to go over the starting procedure as this was a chore in itself. But once running you set the timing advanced when cold to warm it up but then had to back it down some so it did not detonate and buck when starting out. Once on the highway you advanced the timing to get the best power without detonation. So you were always playing with the timing to keep it running smooth. This is a good example of how much timing matters. I hope that gives you a little insight into how it works. I can tell you that the M151 engine is very picky when it comes to the settings. Now, with all of that said, if you drive it down the highway and you feel a flat spot at 45-50 mph like it really has nothing left, then back out the idle mixture screw 1/4 turn. This will usually richen it up enough to eliminate the flat spot. Does the gas over there have alcohol in it? That is a big problem over here. It gives you a higher octane rating but it also runs less effectienly since alcohol does not have the btu output of gasoline. Hence, you need to run richer.

[mike]

Rick, thank you for the wonderful explanation. You may not be a teacher but Im sure you could be as it does make perfect sense to me. I am familiar with the Model A manual ignition advance principle (sadly I have never had a chance to drive it although there is one parked nearby my place). I will go through all the adjustments again step by step (valves, points gap, timing and then carburetor) however this will have to wait for now as we have snow again over here and I dont feel like taking the Mutt out for a test drive through all that salt on the roads. As for the gas up until 31st of Dec we had regular 95 Octane gas (equal to 87 in the United States I believe) with 5 % of ethanol but due to EU regulations as of 1st of Jan it now contains 10 % ethanol (we still have premium 98 with 5 % ethanol which is a lot more expensive unfortunately). Thank you again for all the great help!

[rickf]

Ah, So basically you have the same crap we have! You may have to back out the idle screw a bit more than a quarter turn. Just listen to the idle, you do not want it chugging. So adjust for best idle and then back the screw out in 1/4 turn increments until it runs better but not enough to idle too rich. It is a balancing act. Most people will say you need to change the main jet but if it has the #30 main jet that is more than enough. The design of the exhaust manifold is such that it will not let the engine breath well enough to even come close to fully utilizing the main jet. Another question, what altitude are you at? If you are above 5,000 ft then it might want to run a bit too rich and then, and only then with that gas, a little more timing may help. That is going to be an experimental thing. You are aware that you will need a sacrificial spark plug wire from a regular car for your timing light aren't you?

[mccoop72]

IMG_3237.jpeg

That all escalated quickly.

Went ahead and went through my engine. Bored it .020 new pistons, rods, bearings and had the head reworked. Also new clutch and seals.

[rickf]

Funny how that happens. Whenever I take an engine apart with the intention of just resealing it I have to check the bearings while I have the pan off and if they are questionable then the pistons come out and usually it ends up the same way.

What year is your 151? I notice the old style bell housing with the cover plate for the manual starter control.

[mccoop72]

Funny how that happens. Whenever I take an engine apart with the intention of just resealing it I have to check the bearings while I have the pan off and if they are questionable then the pistons come out and usually it ends up the same way.

What year is your 151? I notice the old style bell housing with the cover plate for the manual starter control.

Yeah, compression was in the low 80’s when I checked earlier last year… did a leak down test after I pulled the pack and was blowing out all around the rings. So, I pulled the head and the cylinder walls were polished…. Measured and found they were all egg shaped too.

Rick, it’s an Aug 68 manuf.

[rickf]

That means the bell housing, and probably the entire powerpak, was from an earlier vehicle. They used that bell housing on the straight 151 but I do not know for sure when they stopped using it.

[mccoop72]

That means the bell housing, and probably the entire powerpak, was from an earlier vehicle. They used that bell housing on the straight 151 but I do not know for sure when they stopped using it.

Yeah, I think the data plate was a 64-66 contract date.