my 46 flathea has a skip at midrange rpm's.I replaced the coil,resistor,condenser,coil wire,plugs,cap,rotor,checked the points,replaced wire from coil to dizzy and from resistor to coil,removed mu metal wire looms but still have had no luck.i'm running reproduction 39 style wires.ran the car in the dark and i don't see any spark jumping.engine has strong spark and plugs are properly gapped.help!
plugs are golden brown.two strombergs on thickstun pm-7 intake.40 main jets 65 power valves.navarro heads.stock cam.
Make sure your coil is mounted vertically. I had a similar problem and changed everything including jet sizes. As soon as I remounted the coil, no more miss. Hope this helps Hack
^^^I think this has to due with the fact it's an oil-filled coil and causes problems with heat when not submerged, coil gets too hot causes all kinds of funky misfire issues.
Do you have any plug wires running in parallel with each other. If so, then you can be picking up some 'induction firing' on one or more cylinders. Recently experienced this on a Bonneville built Flattie where the wires were routed through the tunnel ram to make for a clean look. Ended up separating the wires to fix the misfiring that was taking place.
Can you make it skip when it is in your garage and reving it at that rpm? If you can, then spray some intake air cleaner or carb cleaner or propane down the carbs while that is happening, if it clears up and the rpm rise then it is too lean. I would then spray around the base or the carbs and the intake and see if you have an intake leak. If this has only just started to happen then chances are its not a jetting issue unless you got some dirt in the carbs that is causing a restriction. If that doesnt help then you may have an ignition miss, I agree with the comments on the ign coil. I have seen lots of failures on coils mointed upside down. If that isnt it, best advise I have would be to have someone who knows how to use an ignition scope and can read a firing line, they should have an answer for you in minutes. A small diagnostic fee could save you a lot of headaches. My 0.02 Good luck
Try a sparkplug and wire tester. One of those lights that fit on. It will give you a specific location. Then go from there. Don't forget to test your compression on that cylinder when you find it.
.40 is too lean. Below midrange you are still pulling fuel from off-idle circuit, above mid you are getting help from power valve, at mid range you are just too lean with .040...assuming these are 97's, normal jetting would be about 045 and you don't want to get very far below that.
I went through this too - #45 jets fixed it - 2x Stromberg 97's on a 59a Flattie. I'm now running adjustable main jets - now that's a trick to tune nice!
PS...a quick diagnostic: If you suspect a lean condition, drive the car at the speed that has the problem and slowly pull out the choke. If the engine starts to run better, it wants more gas; if it runs worse, you need to think some more!
When it comes to jeting for a street car I use a vacuum gauge and a flat level road. Drive 60mph and take a reading change jets to leaner if the reading does not drop do it again and keep going until the reading drops. Them go back one step.
changed the main jets to # 45.still had skip.changed the power valves to #69.still has a skip and faint "ping."motor runs best with low test gas and retarded timing.much stronger power and less exhaust fumes.with proper timing ,exhaust at idle is so strong my eyes well up.distributor was rebuilt by bubba's. any guesses?plugs are golden brown with lite carbon.some plugs seem to be slightly cleaner(hotter) than others.
Have you located where this miss is located yet with a spark plug/wire tester? As mentioned before...find the miss location first.
will get a tester and try to locate it but I can hear it out of both exhaust pipes so it is multiple cylinders.
Check to make sure your carbs are still in sync, I had this problem once and the carbs were out of sync. Also, how is your coil mounted? If it is a chevy coil it needs to stand up. if you have it laying down some Olds were designed to lay down. this can affect how a coil performs as the oil moves and does not cool.
Maybe. But this will isolate the problem. Don't forget to hook that tester right onto your distributor too, along with the wires. This will definitely tell you if its electrical. From there you will have to go towards gas and then lastly internal problems. I don't believe you mentioned what type of distributor you are using...
engine has a stock crab distributor with 12v condenser.carbs were in sync but I will recheck that.i don't think the problem is fuel related now that I have it set up so fat.
fixed the skip!turned out the distributor i had rebuilt had too small a point gap at one set.through on a back up dizzy and re synced the carbs and it runs like a top.thanks everyone.
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