Engine Miss

I have a problem that I hav'nt figured out yet...and thought maybe I might see if any of you might have any suggestions. At the Drags on Sunday I developed aa engine miss on the drivers side. Its a random miss and kinda sounds like a vaccum leak. I figure that since its random it pretty much rules out and burnt valve or a bent valve. I've changed cap& rotor, plugs and wires...but its still there. Funny thing is..it hasn't hurt power at all...still runs about dead on for ET and MPH at the track...but it runs rough at highway speeds(3400rpm). Any ideas or suggestions would be really appreciated. Thanks in advance..

 

Highway speeds of 3400 rpms??? What kind of gears are you running...4.11s?

Check for mice eating at your plug wires, causing a short at the shock towers (this is kind of in jest, but also sorta serious, since I have an outdoor rat problem at the current time!)

 

Maybe an air bleed problem? some little bit of junk stuck in one of the circuits in the carburetor? If it's on the main or transition circuit somewhere, maybe it wouldn't affect wide open throttle operation?

 

"Highway speeds of 3400 rpms??? What kind of gears are you running...4.11s?"
Yup 4.11 gears..and I've changed the wires and no diff.
"Maybe an air bleed problem? some little bit of junk stuck in one of the circuits in the carburetor? If it's on the main or transition circuit somewhere, maybe it wouldn't affect wide open throttle operation"
Almost seems like a carb problem...except it's only doing it on one side of the engine. But I will swap carbs and see if it goes away...

 

Aren't you running a dual plane intake? My mistake if not.

 

Yup..a dual plane but I have a 1" open spacer and the center divider is cut down about an inch.

 

hmm. okay. well if the carb swap doesn't pan out maybe a lifter starting to get a bit gummed up? I can see how that might come and go a bit.

 

a freind was having a miss....kinda like the psark stops for a split second.... then starts again.... he though the volt regulator was suspect ...or the coil.... i havent asked him lately if he fixed it.... but i will check when i see him next

 

What ignition system are you running? Maybe the timming is too far advanced for cruzing.

 

sticky valve gets my vote.

Since I said that, its gotta be ignition.

 

Timing is at 16 deg intial and 36 total with no vac advance. On Wednesday I'm going to run a oil flush..although I use Mobil one with a Napa Gold filter and change the oil once a year(I only put maybe 2000miles on it per year) Carb made no diff...but it did seem to run better when I put my first carb back on. It still misses at low rpm but seems fine now at speed. Thanks for all the replys..this one has got me stumped. On Thursday I will readajust all the valves.. and maybe check for a broken valvespring. Hopfull it will be history soon!

 

with the car running, spray some carb cleaner around the intake manifold. If the car starts to sputter you will know you have a leak. Sounds just like the problem I had with my truck. Spits and farts at low RPM, but once its up and running it ran great.
Just a thought.