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Hey Chris !! have you ever thought of trying a vacuum gauge on the inlet manifold ?, these were magic on the older engine, I found a chart of the different readings but wasn't able to save to my desktop, I will keep trying though.

As soon as I get this, I will attach to your post.
 

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Discussion Starter · #26 ·
Recently, I converted back to points & condenser. Same problem. I guess to check vacuum, I would need to drill & tap a hole in the center of the manifold? Then, I guess if the gauge goes crazy when it pops, I've got a floating valve issue?
 

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Discussion Starter · #28 ·
Drop the exhaust pipe so the exhaust is coming right out of the manifold. That will narrow down where the 'popcorn miss', isn't!
I did take the exhaust pipe off and substituted a 3 foot bent pipe without muffler. No change, so I took the manifold off, cleaned everything up, (didn't look that bad) and put back with new gasket and Permatex ultra copper sealant. No change in popcorn.
 

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Discussion Starter · #29 ·
Well, it still does it. Not all the time. My neighbor said most of them (early Fords) do it.

I'm wondering if it could be from not using leaded gas. About 20 engine hours ago I installed new valves & guides, and lapped the seats. Compression is fine on all cylinders. I wonder if I should buy some "100 low lead" (has more lead than car gas used to) from the airport and run it on that for a while. I have heard that valve stems may get sticky without any lead.
 

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Well, a popcorn miss sounds to be electrical connections loose or bad somewhere. I had the same symptom and it was the brand new coil. The Stainless Steel inside contact (not the spring) in the front, that contacts the distributor cap below was not good. That curved Stainless Steel strip wasn't making a good contact so a little creative bending, scraping the slight pitting in the Stainless steel contact strip and light sanding of the distrib cap contact (followed with a tiny bit of Dielectric grease just on those contact points) fixed the problem.
- Joe -







0
 

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For what it's worth, I have a 49 8n and finally had to replace the exhaust as the various bandaids
finally got to me. After I put on a tailpipe and muffler combo bought on the internet, my tractor started making a sound very similar to yours shortly thereafter. Still does. I did nothing else but replace the exhaust. Just a thought...maybe disconnect your exhaust and see if it still "pops"? Might be your new exhaust.
 

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Might also be a change in back pressure from the 'similar but not exact' new exhaust system, too. If you try removing the exhaust system that, in itself, changes back pressure.

Of course, spending some time around idling big Harleys will make the teenie, weenie popping seem to be just gentle purring.

OH, maybe substituting spark plugs, one at a time, would help remove a random plug wire short or intermittent short in a plug. Inside of the distrib cap squeeky clean? I've had carbon trails ("Lightning Bolts") create intermittent internal shorts for just one plug before.

- Joe -
 

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Discussion Starter · #34 ·
Well, before it got cold, I tried a few more things - and now I've tried just about everything that seems possible. When it warms a bit I'm going to buy some aviation 100LL gas (which has tons of lead) and run it a bunch on that. It just about has to be intermittent valve sticking.
 

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Chris,

I spent 5 years refueling aircraft of all types from 747s through home built ones and from that hands-on experience I actually know something about Aircraft fuel designations - including "Avgas" 100LL.

100LL is a designation of two primary characteristics in this fuel - simply 100 from it's Octane level (the same Octane rating as on gas station pumps) and the lead content ---Low Lead--- . NOT high lead but rather LOW lead compounds directly affecting the octane. Read paragraph 5 here: EPA Takes Final Step in Phaseout of Leaded Gasoline | About EPA | US EPA

If you think that the valves are sticking, REALLY think that, then either you or someone else is just going to have to pull the head and check them out. If they're sticking it could be old, bad fuel used in the past, poorly adjusted carb in the past or even something like a damaged push rod or even a poorly seating valve.

Hoping that pouring something in the gas tank is your answer (if it is a sticking valve or such) is a bit over hopeful. I find it helpful to work from a position of specific knowlede instead of just hope.

All the best to you.

- Joe -
 

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Discussion Starter · #36 ·
Chris,

I spent 5 years refueling aircraft of all types from 747s through home built ones and from that hands-on experience I actually know something about Aircraft fuel designations - including "Avgas" 100LL.

100LL is a designation of two primary characteristics in this fuel - simply 100 from it's Octane level (the same Octane rating as on gas station pumps) and the lead content ---Low Lead--- . NOT high lead but rather LOW lead compounds directly affecting the octane. Read paragraph 5 here: EPA Takes Final Step in Phaseout of Leaded Gasoline | About EPA | US EPA

If you think that the valves are sticking, REALLY think that, then either you or someone else is just going to have to pull the head and check them out. If they're sticking it could be old, bad fuel used in the past, poorly adjusted carb in the past or even something like a damaged push rod or even a poorly seating valve.

Hoping that pouring something in the gas tank is your answer (if it is a sticking valve or such) is a bit over hopeful. I find it helpful to work from a position of specific knowlede instead of just hope.

All the best to you.

- Joe -
Have they changed 100LL in the last 20 years? Used to be that it actually had lots of lead and when you pulled the plugs it would adhere to the elements - had to regularly sandblast them.
You're right that it's best to have real evidence, but I've done everything short of pulling the head off. I did a valve job (new parts and lapped) 18 engine hours ago, and the compression remains perfect on all four cylinders.
 

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Chris,

I'm not (ABSOLUTELY NOT) an organic chemist, but as I understand it, Tetraethyl Lead was added to gasoline, starting in the 20s, to raise octane - and from that change knocking was reduced / eliminated in the engines of the day. It was added in diminishing amounts up until the mid 90s when it was completely phased out. That is why the gasoline at the pumps in the 50s was labeled as "Tetra Ethylene Added", then it went to "Low Lead" and now, today, is called "Lead-Free" (and now replaced with Ethanol Alcohol, giving us the catchy name "BIO FUEL"). :mad:

I think the talking point here is the quantity of lead and the resulting lead deposits after burning. What, how, why and other specifics concerning the lead deposits are all a bit beyond me. In the past things I've heard all sorts of things about TEL's effects on engines but, ahhh, all that was 'unconfirmed' at best. There was a consistent rumor that the lead deposits somehow had something to do with the valves seating (or alternately, burning) - but ... blah, blah, blah ... I don't know much beyond just gossip.

Just as a question - do you use gasohol or non-ethanol gas in your '52 N? Gasohol that sits in seasonal storage scrubs water from the air migration in/out of the fuel tanks every day. I know it's sort-a grasping at straws, but even though early engine designers and engineers ALMOST decided to run those new Internal Combustion Engines on alcohol (instead of that new fangled gasoline) it finally was decided to run them on gasoline only. That's the way "things" stood in '52 and then up until the politicians got their unknowing hands into the works and screwed things up. Here is something just to know on "Good for You - NOT!" additives: MTBE controversy - Wikipedia

One other thought - in re-reading and thinking about your first and latest posts, you had mentioned that 16 - 18 hours ago you (or someone else) put in (among other things) new valves and guides. 16 - 18 hours of normal use COULD have been just enough time for those valves to have 'worn-in' and maybe, could, possibly should be re-checked anyway. Just a guess, but that's pretty much the minimum time interval for a break-in period and good 'go back and check' interval on those new valves. Good compression after a rebuild is a good thing to have but going back and checking for OMGs comes in there as well. As a bare minimum I (the only person I can speak for) would throw a compression check to see if the numbers have stayed about the same as right after the rebuild.

Anyone else have some thoughts? Better thoughts than mine, at least?

- Joe -
 

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Discussion Starter · #38 ·
I started this thread 12/19 and have tried many things to effect a cure. Well, I FINALLY found it - I used an oscilloscope to look at the points side of the coil, and could see that every now and then the pulses were irregular. The points looked good, so I suspected that the grounding of the points mounting plate was intermittent. I ran a ground wire to the points hold-down screw, and voila! problem cured.
 
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