Projects Kookie Kar engine missing

Problem solved. Now runs smooth up to 6 grand. Afraid to go higher

Went through all four 97s again. Removed and cleaned the emulsion tubes. Thanks Bruce your method for removing them works great!
Started it up after last carb. rebuild. Ran better. Still small miss about 4 grand. A backfire or two from the exhaust. Changed fuel filter. Better yet no backfire. Closed the points to a tight .018.
Now like I said it runs smooth right up to 6 grand.
Thanks everybody for the advice.

Want to run this by all the experts before I start tearing into 97s. Okay here is the problem. Engine runs great at idle and up to about 3000 rpm then starts missing and backfiring through the exhaust. Just checked plugs. All are firing white, except the two left middle which are black porcelain and brown tip.
Engine is pretty stock (flat top pistons)except for a mild to medium Iski. roller cam. It will idle below 1000 rpm.

I did go through the old 97s but didn't change any shafts. I would think leaky shafts would be more of an idle problem though.

I've moved the timing all around but it doesn't seem to make too much difference.

Think I'll clean those two plugs and see if it makes any difference. In the meantime any thoughts will be appreciated

 

Bad coil?

 

Carb location and runner design do not lend themselves to problems at those cylinders, IMHO...I'd lash up the plug wires there way separate and see what happens. Betcha crossfire or ground firing is fubaring things in there.

 

"Kookie Kar engine missing" Psst, it is behind the radiator.

Seriously, though, I'd check the manifold gaskets for leaks at the head, and manifold bolt torque.

Black with a brown tip is more what you'd like to see, if a bit rich, on all of the cylinders. To me, it sounds like the others are a bit lean.

I had an SBC that was doing this on two adjacent cylinders, and it turned out to be a leaking gasket, at the bottom of the port. It was pulling air from the lifter valley.

I had several bald spots before that was sorted out.

 

Hey Gary... It's nice to see you're up and running.... The leaky gasket theory sounds reasonable but I'd probably go through the ignition system first. Doesn't really sound like carb trouble to me, but*****ing air is a definite possibility.

Rich

PS. Are you gonna go to Jerry's BBQ this year??

 

I was thinking it had gotten ripped off ,

as in

Missing in the dark of night!

Glad thats not the case....

 

Look at the manifold geography. Looks like any real gasket leak should affect pairs at the end...middle pair are pretty far fromboth runners and carbs.

 

If it idles well then I don't think you have a vacuum leak. It acts like it is starting to go lean hence the back fire out the exhaust. The plugs being dark in color hmmmm are they sooty? If not sooty then possibly a bad wire or two not getting enough pulse to fire the plug as the mixture increases.
When you are accelerating is it at WOT or are you easing it out??

 

check the rotor for cracks and make sure the carbon piece is in the cap is there yet. happened to me before.

 

Yeah, the more I think about it, the more I lean toward ignition.

Check the wires. Both for burn through and resistance.

 

Think you might have a point. Looked at them and they have some burn bumps. Think I'll put some new ones on and see how it runs.
I have some new 8mm I bought for my '85 truck. Not retro but good for testing.
Thanks

 

Well any updates?

 

I had a Jeep with a flathead four that acted just like that, new coil fixed it.

 

I had a SBC acting like that...it had a flat lobe on the cam...

 

Wow I hope not. Won't be much trouble to pull the valve covers and make sure all valves are moving. No time on the engine though. It's brand new.

Thinking of sending the dist. back to Joe Panec (kool name) to check it out.

 

I had a similar problem mine turned out to be a condenser wire that when you put your foot in it the points plate advances and the wire in the condenser would slide out, let off and it would go back in, you could drive all day long at low speeds but step on it and thats when the***** started check it out be sure to try and move the condenser wire because if you just look at it every thing looks OK........................

 

Yup. Valve springs will drive you crazy chasing a missfire !! >>>>.

 

Thanks folks! I'll be pulling the valve covers as soon as the weather cools down up here. Never thought of a bad valve spring.
Keep them coming though I'm pulling my hair out.
I've already changed the condenser, coil, points, plug wires. I still think it's electrical but I'll check the valve springs.

 

I too am wondering about valve spring (or the coil as the simple answer). does the roller cam have enough lift to get into coil bind problems? Also, are the spring being used up to the ramps on a roller cam? Just me wondering out loud. I would think if it was the coil it would show up on the plugs of ALL cylinders, not just the two. Carbs would, I think, affect cylinders on both side of the engine, not two side by side. some else is going on. Might also be a worn shaft bearing in the distributor or bent shaft allowing a dwell change that would maybe affect the two cylinders in question. Or not.

 

Changed coil. No difference.

The cam is pretty mild only .420" lift. Although that might be pretty tall for a 50 Cad. Just noticed the specks call for .014 valve clearance. I just checked and a .025 will slide in.

What do you mean "are the springs being used up on the ramp"?
I have noticed the exhaust valves have spacer washers under them and not the intake. Not sure why the builder did that and he's not around to ask.

Bent shaft on dist. Dist. is new. I did install the offset dog drive backwards when I first started it. Saw it flexing and changed it right away. Thinking of sending it back to Joe Panec (kool Name) for a check.

Those two cylinders seem to be burning fine now.

Keep throwing***** out something will stick.

 

Did you get to the bottom of this?

I'm having the same problem with my nailhead and I've taken all the same steps you did and no dice. So many things it could be.

Pete

 

btt