Hey guys, I am having a problem with my 59AB. I rebuilt it 2 years ago, and it has always ran very well. It has a 4" stroke, Navarro heads and a high rise 2x2 intake. Late last summer I won a set of new Stomberg 97's in a contest. I installed them, hearing nothing but good reviews. They have the same jets as my old carbs (.042) Since installing the carbs, I occasionaly foul #8 plug (drivers side very rear). It is gas fouling. I cannot figure out why, I have tried a little smaller jet size, re-synk'd the carbs, even different brand plugs along with a new distributor/cap/rotor/wires wondering if I had an ignition issue. I had an idea that my old carbs had small leaks and pulled more air...making the new carbs run more rich. But the sizing down in jets did not do much. It runs great, and when #8 fouls I put a new plug in and it runs great again. I just do not understand what is going on. I do not understand how it can foul the same hole. I put my old carbs on, seeing if it was an issue with the new carbs, but it was so late in the year I do not have any drive time on it. A couple guys have told me maybe fuel is "pooling" in the intake and running to #8, fouling that hole. However all the plugs are a light brown, not near as dark as if it was running that rich. I'm not super great at diagnosing tuning issues- does anyone have any ideas or other theories on what I have going on? It did not start until I put the new carbs on and I would love to run them still if I can figure out what is going on.
Yer plugs are fouling. A fowl is a chicken. Sorry for being a spelling nazi, but sometimes you can't help it
Chris When you run the engine and look down the throut of the carbs do you see them dripping? Take a look at idle and through a gradual throtle sweep. If theyre dripping your gonna have problems. Have you tryed swaping the carbs around from front to back? If it was a carb problem you would think the problem would move to a different hole by moving the carbs. That would also tell you what carb it was. Have you got a nice strong blue spark to #8? Good Luck Brad
one of my customers had trouble with his flatheads fouling plugs, i put a new set of idle jets in the 97 and it seemed to fix it, this was on a tri power, so only one carb used the idle circuit. Im pretty sure its the smaller the hole in the idle jet the richer it runs and large is leaner but i cant remember for sure, i think one of my customers looked smushed so it would idle richer, so get 2 extra pairs of idle jets and drill em out one size and see if it helps. jeff
Don't worry about that. Sounds like you're taking a logical and analytical approach to figuring this out so you're already a couple steps ahead of the game. Flatnasty's got some good advice to get you started. Keep swapping parts till something changes. And check the things you normally wouldn't expect like compression and manifold vacuum.
Hard to believe it would always be pooling into just one cylinder... I would forget the carbs for a minute and look at only things that are related to that one cylinder... Ya dig? Like... say, a weak or inconsistent spark caused by a high resistance plug wire or a damaged/cracked/corroded distributor terminal/cap...
Do what Flatnastys has advised. The if no change, replace that plug and re check. If no change swap the plug wire. And re check. Then dist cap. Etc.... No dice? Then check the rear carb. I always do the easy stuff first. After that Im screwed hahaha
I am thinking a bad plug wire or something like that. Maybe a little weaker compression on that cylinder. I know you said it was a new overhaul but things happen. Valves out of adjustment? Correct me if I am wrong but a carb too rich would foul more than just #8 cylinder. Neal
If the engine has a bit of angle back and to one side it could explain the one cylinder fouling if u have a drip.
Easiest thing to check first, see if there is strong spark at that plug. If yes, then I'd try switching the carbs around. But this seems odd, because there is more than one cylinder fed by that runner. What other cylinder is fed the same as #8? How does that cylinder's plug look? Are you sure the fouling (fowling) is because of gas? Maybe there is oil in the cylinder because of a bad intake valve seal or broken ring?
Yes, and that is where my question comes in. Why only one hole? I did swap distributors/cap and new wires. It still had fouling problems. I am hoping it is nothing internal, I need to borrow/buy a compression tester and make sure #8 is close to the rest. It's super cold here now, and I do not have any heat in the garage, so this will probably not happen until it warms up a little but it's been bugging me since I put the car away. I've scratched my head a lot, figured maybe someone would think of something I have not... Thanks a lot to the guys that help...spelling and grammer will not foul plugs.
Chris, seems like you have done most of the standard diagnosis. As others have said, check your compression, check for oil. as this happened when you changed carbs I would definitely change them back to the old ones as you have already done to see if the problem continues. my stock 97's leak like crazy and I have a stock model A tank so it gravity feeds right into the motor. I have to have a shutoff inline to prevent the crankcase literally filling up with gas..... I've still never had a plug foul...
I think it would be hard to foul just one...it seems like a fueling problem, but the process would be hard to explain! I would look around first, before going nuts there. Crossfire of some sort springs to mind, that plug either firing at a peculiarly bad time or simply erratically losing its spark to somewhere else. Could be happening within distributor cap, too... Examine all of that, try separating wires as much as possible for a test, perhaps swap in parts you replaced at last tuneup. Run the thing in the dark, too, looking for sparks... Swapping front and rear carbs would quickly rule some things out. Or in.
97's are very fuel pressure sensitive. I believe they work best at 2 psi or they will seep fuel passed the needle valve and seat. You must run a regulator. I have a suspicion your plug wire may be stating to go bad. Typically you will foul more than one plug if the Carbs are rich/leaking fuel.
seems like you guys aren't reading his post?? problem started after new carbs he already did an ignition tune up... new cap rotor plugs and wires it now has the old carbs back on it. I say just wait until you can test it with the old carbs again. if the problem is solved and you are happy with the way the old carbs run, I'd sell the new carbs and be on my merry way....
Yes, thats about where I am at. Like I mentioned before, I can tune a car fine, but diagnosing is not a hot area for me (nor spelling/grammer apparently). Just seeing if anyone saw something obvious that I did not notice... "You gotta hit the refresh button before starting it" Thanks everyone for the help, I'm sure I will figure it out once it warms up a little and I can actually get it started LOL
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