Help!! Engine Miss

[Ben Kallies]

Kirk,

No new relays installed with the new switches, only what was already there for the fuel pump, electric fan, and water pump. I've never heard of your method for checking for a draw. Thanks for sharing.

-Ben

[junior barns]

Hey Ben, ever get your miss figured out?

[Ben Kallies]

Junior,

I just finally fired up the car last weekend after making a number of positive changes to the ground circuits including isolating and adding grounds along the way. I also replaced the negative battery cable, just to be sure, as well as the water pump and electric fan relays, just because. I also performed a lot of continuity and resistance checks along the way, as well as checking voltage to all areas. I've been reevaluating and checking every aspect of the vehicles wiring, and I haven't found any smoking gun. Everything checks out ok. Needless to say, problem persists.

I plan on performing a leakdown test next weekend (after I buy a leakdown tester). If that checks out OK, I'm not sure what my next move will be. My dad and I have been tossing around the idea of installing another engine that he's got, to know for certain if it's the car or not. Of course, that's a big task, and free time's been hard to come by lately.

As always, I'm open to thoughts and suggestions. Thanks for checking in.

-Ben

[FED 387]

had a gremlin we chased for 1/2 a season--we solved ours this way-----look into the distributor itself any wires in there??? we insulated/shielded them by wrapping them with alum foil--- it worked in our situation --not saying it will in yours but it seems we were picking up signals?? or interference?? of some sort when we got to higher RPMs from electrical wiring passing in the area of the distributor--look into it might just be it---Comp

[Joe Martens]

Ben, check the gear on the distributor. Had a situation where the edges of the gear were worn almost razor sharp which was causing a miss. Replaced the gear and problem solved. Hope you find the problem.

[Ben Kallies]

Joe,

Thanks for your thoughts. My distributor gear looks great. I've actually had 3 different distributors (all new) in the car since the problem began, so I think it's safe to rule out a bad distributor.

-Ben

[buzzinhalfdozen]

Ben, hate to hear you're still chasing this problem. After reading all the posts here, looks like every avenue has been explored. The post about the carb. being set up for W.O.T. seems like it could have some merit, that would be easy to check, simply install a "normal" carb and test, sure it's not a race set up but under no real load it should quickly tell you if that's the issue.Broken valve springs could be an issue however I'd expect you would only encounter the misfire at a higher RPM range, unless of course they're "really" bad. When the engine starts to "break up" does it have smoke out the headers?Black or dark grey smoke would indicate 1 of 2 things, insufficient ignition events or being overly fueled.AS I've posted before, borrow or buy an MSD ign. tester ( this is an invaluable tool) put the spark tester on the coil and spin the system up to redline, paying close attention to the "look" of the spark.IF you can trigger the system to redline with no loss of spark you know your box and coil are up to the task.I don't believe I've been to a race in the last 4-5 years that I haven't had my MSD tester on my own or someone elses car. A leak down or at least a compression test would be in order, a cheap valve spring pressure tester would be nice to verify at least that all springs are close.Moroso makes an inexpensive one , not sure how accurate it is but it would show a weak spring I'm sure. Flat lobe on cam should be easy to recognize with valve covers off, spinning engine while observing each rocker 1 at a time. While this problem does seem to be very odd, the only SURE way of resolving it is with proper inspection and testing, of course we can always hope to stumble upon the answer, but that requires much more time and effort. Please consider some of the pinpoint tests provided as I've found them to be invaluable tools in diagnosing issues such as the one you're experiencing. Joe 1 other thing that caught my eye, you posted your batt. neg. cable goes to the frame near the batt. and your engine is grounded near the front on the frame, this is correct? Using the frame as ground is not advisable, Running a dedicated ground cable for all your electronics, electrical loads is far better to insure proper function. I've got a #4 ground run from the battery neg. postto the front of my car going to a buss strip, you can ground everything to this strip knowing it's all directly grounded to the battery.Thought of 1 other thing, have you ever had a timing lite on the engine and reved engine to the issue RPM range? If so what happens, does the timing move, do you notice the lite starts to quit flashing?

[tony wood]

Ben unplug the tach. Will probably fix your miss. Good luck.

[larrylomascolo]

Ben is any of the factory wire being used in the car or relays ,regulators,check for the green corrosion,im just thinking here ,hope you get this fixed

[Terry Cain]

Originally Posted by tony wood

Ben unplug the tach. Will probably fix your miss. Good luck.

You might have something there. I remember yrs back a car I was working on did the same thing and the tach was the problem.