flat on my face with fireballs blowing out the back...

[KobraKarl]

Hi guys ..long time no talk.....been doing the divorce thing..

.i AM keeping the Cobra.

any way...I am having some performance trouble with the 427..after running for 15 or 20 minutes it will start popping and missing at 3500 rpm or so.....a bit later it will almost quit running ,and any aggressive use of the throttle will cause a complete "faceplant " and enormous firey explosions out the pipes.

The only other symptom is a general sluggishness to the overall performance. and some increased crackle at throttle letoff

initial timing is 14* at idle.

Thanks in advance for any help, KK

[PatBuckley]

Pop the distributor cap and look in there.

[wilf leek]

I just had a similar problem this weekend.

It was moisture inside the distributor cap, but I don't know if Pat "the subtle and oblique" Buckley means the same thing.

[PatBuckley]

Of course he did.

[Excaliber]

Mine was sticking exhaust valves,,,, or maybe it was that blown head gasket?

[Jahred]

I'm guessing she probably pee'd in the gas tank.

[rbray]

Hope you get your motor fixed. But I think the fire out the side pipes is cool.

[Excaliber]

Yeah I miss those flames out the side pipes! At night that was really cool.

[HI Cobra]

If it isn't a wet distributor cap:

I don't know if you have any kind of computer
controller on your set up but if you do put a wet
rag on it to cool it down after it acts up on you
and see if that makes a difference - if it does - you
need a new one. I was going nuts trying to solve my
electrical situation - if it got warm it would kill the spark
and each time I tried something it seemed to work until
I got stuck at a light or something and things warmed
up in engine bay. I replaced the unit two weeks ago and
it has been running great ever since.
Just one more thing to check but it solved my problem.

Flip

[KobraKarl]

Now i shoulda known better than to post a tech question on a sunday afternoon.....with just my fellow riff/raff holding down the house....




Pat,.....did that, it was all springy twirly ,sparky in there..i popped it back on.

Wilf,......dryer than my joint checking account.

Ernie , I had that same awful thought , but since it comes and goes, i dont know how to confirm..

Jahred....that explains the footprints on either side of the fuel port.

rbray ...yea it would be cool . if i wasnt afraid something was going to get blown clean off.

flip, thanks for the post, but im running a stock 1965 autolite dual point....had it professionally curved and set by the local speed shop less than 500 miles ago.

keep em comin.....KK

[Ron61]

Karl,

If this is only happening after the motor warms up and is under load, it would sound as if you might have an electrical problem along with the above mentiond possibilities. Was it doing it before and is it just under load or will it do it while you are stopped if you rev the engine up? Also does it seem to be out both sides or more on one side? Maybe pulling a couple of plugs and looking at them.

Ernie is an expert now at blown head gaskets and sticking valves. He sould be able to tell you how to test for that.

Ron

[Flyin_Freddie]

Well...the LAST time I was flat on my face with fireballs blowing out behind, I had just gotten home from a Batchelor Party that started out at a Mexican restaurant and bar... ..it was Muy Bien....unless you were behind me or downwind! Needless to say, Mama was less than pleased with both the resonance and aroma...

Karl...give us a little more info. Does it run okay until it gets warm....? I'm thinking maybe your coil's breaking down when it gets heat soaked. If it does the same thing when it's just started, I'd be looking at firing order, or a mis-timed distributor - maybe off one tooth. If you're running a '65 Autolite distributor, it could also be a condensor... Hey, all just ideas for now.

Let us know if it runs okay until it gets warm...could be a key to the source of the problem.

[Hal Copple]

in the winter, with the higher vaporization Reid pressure, my engine will flood, so perhaps you are flooding too, when it gets hot, you might set your floats a bit lower, i run a half inch phenolic spacer under my carb, helps a bit. You might be percoating your carb.

[KobraKarl]

Ron , it only happens when hot ...and the hotter the engine ,the worse it will act..also it will do this without any load on the engine.

Freddie,
it only happens when warm, the coil is also only 6 monthes old ,the overall power does seem down 50 horses or so even when coolor and running ok. hadnt thought of the condenser, that will get replaced today.

Hal ,you may be on to another good possibility, the backfireing sounds like exess fuel igniting in the pipe ,not in the engine .....the engine seems to miss about 12 beats.....then BLAM I just cant figure if its missing on spark then heat igniting in the pipe ,or flooding out and igniting in the pipe or????



???KK

[Ron61]

KK,

The coil and condensor sound like good places to start. Just the fact the coil isn't very old don't mean it isn't breaking down. As for the backfires, you are most likely correct about that being unburnt fuel igniging after the pipes get hot. Easy check for the coil is to just change it with a known good one for a few minutes. I had a similiar problem once except my car would just stop as if I had shut the ignition off. Coast over beside the road and start right up. Finally traced it to the coil as it would start to arc between the high voltage terminaland case when the car got warm. All resistances tested good and I even tested it after it was warm and everything showed good. Switched the coil out and never had another problem. And the fact your'shappens after it gets hot sure sounds as if it is a possible electrical problem. You could pull a couple of spark plugs and see if they are black and wet which would indicate they aren't firing.

Ron

[Todd Hedges]

I had what appeared to be a similar issue.
Found out the distributor gear was shot.
Not a good thing.
I hope it's not that.

The flames out of the exhaust reached almost 4' high.
Cool sight if the car isn't yours.

Good luck.

[Flyin_Freddie]

...even it is IS your car, Todd....! Me likee.... Went to a hot rod cruise in several months ago and there was a gold '49 Merc lead sled there...all slammed on the pavement, chopped top, no door handles, etc,...lake pipes, etc. Waaay cool. Loved it. Everyone took noticed when he pulled in to the Sonic but didn't park....just looped around the building. When he got to the other side, he goosed the throttle and flames about 6 feet long erupted from his tail pipes in the rear. TOOOOOO COOOL! The crowd went nuts...! Standing ovation! He looped around the drive in again and parked it. In a moment or two he was flooded with lookers...

Anyway...back to KK's problems. Karl...I would replace the coil - or at least, swap it with a known good coil as Ron61 suggests. Also...the misfiring is most probably the source of the fuel in the side pipes, and then when it fires...the exhaust torches off the gas fumes ... Awwww, yeah....we're talkin' way cool here, Karl...you'd be a hit at cruise-ins, no doubt..

But, I'd also check everything ignition related....distributor drive gear, too. It's possible you may have sheared off the roll pin that holds the drive gear on the distributor shaft. Not uncommon, and a pretty cheap fix, too. Your problem sounds like your losing fire in one or more of the cylinders, and of course all the valves continue to work to pump the gasoline rich air into the cylinders where it's not burned and then exits through the exhaust valve into your headers and sidepipes. Then, when the plug fires again...BOOM!, one fireball coming up! (Cool...me likee!)

But...I'd investigate everything in your ignition system, from plugs and wires, to distributor cap, condensor(s), dwell angle, coil, etc. etc. Then, if all that checks out and you STILL have the problem, check the distributor drive gear and look for a sheared roll pin.

In fact...I believe I'd check the distrbutor drive gear first....! Don't want that sucker to separate from the distributor and fall down into the crankcase. You may get lucky and have it not get caught in something....and then again.... Well, you get my drift, I'm sure...

Let us know what you find out. I'm thinkin' this is all about your ignition system.