camshaft (Long)
- Thread starter aermotor
- Start date
Got that part mostly right. The rest of the story. The next 4 strokes the exhaust valve for those not familiar with the 8 cycle Aermotor is open due to the cam profile. The cam gear is 4 times the crank gear, (of course in the 4 cycle engine it is 2 times the crank gear) the last 4 cycles - down, up, down, up with the exhaust valve open then back to intake, compression, power and exhaust. Interesting point is that the exhaust exits back toward the exhaust valve cage for more cooling.
John
Patrick L.
Well-known member
I think if I remember correctly we talked about ignition timing quite awhile ago. And I too still kinda think thats the issue.
Patrick L.
Well-known member
Yep, the 8 cycle Aermotor is a strange animal. The intake is atmospheric and the exhaust is mechanical as many engines of the day were. But that big ole cam gear dictating all those exhaust cycles is unique.
Further explanation. The cam gear is 4 times the crank gear for the 8 cycles. Intake, compression, power, exhaust, the next 4 cycles (2 revolutions of the crank) the exhaust valve is open due to cam profile. Then we start over. Interesting fact is that the exhaust exits towards the exhaust cage for cooling. Of course engine is air cooled.
John
Break time over. If the plunger spring is weak or broken the cam will slide forward or they wouldn't be there. Will that make it more or less advanced? To many things apart now to put a timing light on to tell. Talk about over thinking a simple timing problem!!!
Thanks, John
Thanks, John
nkaminar
Well-known member
From the front of the car, the crankshaft rotates clockwise, so the camshaft rotates counter clockwise. The gear teeth on the cam gear are right handed, so as the cam moves forward the cam moves counter clockwise, and thus advances the timing. However, the gear in the center of the camshaft will retard the timing as the cam is moved forward. I don't know which effect dominates or whether they cancel each other out to a net no change.
I suspect that you will find the thrust plunger and spring are OK, or not damaged to the extent that they would cause the problem you are experiencing.
Updraught had a valid point. There may be an advance mechanism somewhere. It would be easy to test this by hand moving the rotor while the distributor is in the car. If it moves more than a small amount there is an advance mechanism somewhere.
I suspect that you will find the thrust plunger and spring are OK, or not damaged to the extent that they would cause the problem you are experiencing.
Updraught had a valid point. There may be an advance mechanism somewhere. It would be easy to test this by hand moving the rotor while the distributor is in the car. If it moves more than a small amount there is an advance mechanism somewhere.
I don't know one way or another about your first paragraph. You may be right about the thrust plunger. The advance mechanism some where has me puzzled, I have the side cover off and everything from the oil pump through the head and I see nothing different from Les A's book or the suppliers catalogs. In post #39 you said "check the plunger in front it is not too hard to do." Loosening the rear mount bolts, blocking up the engine, removing the front mount bolts and the rest of the bolts then reversing the process along
with the front seal, draining and replacing the oil and cost of the parts and oil isn't exactly a easy or cheap 10 minute job. What do you think the problem is?
Thanks, John
Last edited:
Last edited:
If any one still thinks I know nothing about Model A engines, timing, trouble shooting, 4 stroke engines or I am a smart "arse", and feel offended by any one - my previous threads or responses included, I will take my tools, go home and quit the Barn.
John
John
Last edited:
Patrick L.
Well-known member
Seems to me everyone is/was trying to help and be friendly.
nkaminar
Well-known member
Hi John,
Everyone is trying to help and no one thinks you are a smart a@@.
Regarding checking the plunger at the front of the engine. The easiest way to work on the front of the engine is to take the radiator out first. It can be done without doing that but with the radiator out of the way it is much easier. Follow the instructions in Les Andrews' book, Model A Ford Mechanics Handbook, Vol. I for changing the timing gear, page 1-324, but don't change the timing gear, just check the plunger. After getting everything out of the way you just have to remove the timing gear cover. You can re-use the gaskets by cleaning them up and using a small amount of gasket sealer of your choice.
Getting the response you got from the advance lever, I would have just adjusted the distributor cam a little more retarded regardless of where the timing pin dropped into the recess. On a more modern engine you can just rotate the distributor body until the engine runs the best. I wish you could do that on a Model A, and perhaps you could by having the distributor not set in the pin and not tightened down, just to test the timing.
When you get the engine back together let me know and I will drive down to Greenville to help you. I have over 60 years experience with Model A's.
Everyone is trying to help and no one thinks you are a smart a@@.
Regarding checking the plunger at the front of the engine. The easiest way to work on the front of the engine is to take the radiator out first. It can be done without doing that but with the radiator out of the way it is much easier. Follow the instructions in Les Andrews' book, Model A Ford Mechanics Handbook, Vol. I for changing the timing gear, page 1-324, but don't change the timing gear, just check the plunger. After getting everything out of the way you just have to remove the timing gear cover. You can re-use the gaskets by cleaning them up and using a small amount of gasket sealer of your choice.
Getting the response you got from the advance lever, I would have just adjusted the distributor cam a little more retarded regardless of where the timing pin dropped into the recess. On a more modern engine you can just rotate the distributor body until the engine runs the best. I wish you could do that on a Model A, and perhaps you could by having the distributor not set in the pin and not tightened down, just to test the timing.
When you get the engine back together let me know and I will drive down to Greenville to help you. I have over 60 years experience with Model A's.
Tom Wesenberg
Well-known member
I forgot about that pin.
The original was a solid pin, but Bratton's roll pin is a better idea.
Patrick L.
Well-known member
Patrick L.
Well-known member
I didn't think thats what he was talking about. Sorry. Sometimes these posts can get confusing. And I'm usually confused enough already.
Ready for you, I will take care of all expenses. I do want another look - see before that timing cover removal, it's possible I missed something staring me in the eye somewhere. I am all set with TDC etc. but haven't tried to start it yet. 864-316-0496
Many Thanks, John
28PHAETONROY
Member
Aermotor
I’m an amateur at working on A’s but here’s one that happened to a friend and I- the timing linkage was hitting the top of the head when advanced and it would lift the distributor plate out of kilter causing us to chase our tails for awhile. Probably not your problem but it’s very easy to check before pulling the timing cover.
Roy
I’m an amateur at working on A’s but here’s one that happened to a friend and I- the timing linkage was hitting the top of the head when advanced and it would lift the distributor plate out of kilter causing us to chase our tails for awhile. Probably not your problem but it’s very easy to check before pulling the timing cover.
Roy
nkaminar
Well-known member
I drove down the Greenville today, 3 hours each way, and was able to help John sort out his ignition problem. The timing was not correct. John had done everything correctly but not accurately enough. After I adjusted the timing the car started up and ran well. We drove it to a BarBQ place for lunch. It still is popping in the carburetor when backing off, for instance when shifting or coming to a stop. I will have to think about that but it is probably related to the idle adjustment.
John is a real gentleman and it was a pleasure meeting him and being able to help him with his car. He has done a magnificent job restoring his Tudor. His collection of hit and miss engines was a real treat to see.
John is a real gentleman and it was a pleasure meeting him and being able to help him with his car. He has done a magnificent job restoring his Tudor. His collection of hit and miss engines was a real treat to see.