Puzzling ignition issue

When are car stays hooked it revs to 4500 and then starts to babble and wont rev any higher. If it spins it will still babble between 4500-5000 then clears up and pull clean to 7000 rpm. Msd digital box 7535 with there hvc coil. 540 hemi with f3 procharger. Have changed cap rotor and coil looking at box or wires next. Any input would be greatly appreciated.

Are you carb or injected.... if injected what does the
O2 tell you.. whats the plug gap

If you're sure it's ignition, I would check rotor phasing. I know I sound like a broken record on that point, but with small caps, boost referenced timing and high cylinder pressure, you have to get phasing correct. Phasing at peak cylinder fill when cylinder pressure is the highest(peak TQ) is a must.

Plug gap is at .018, its a carburated deal. Will have to check rotor phasing the weird part is once it clears up it pulls clean the rest of the way and we are going thru the end at almost 33 pounds of boost which in my mind would put more stress on the spark. Is it possible we are pulling too much timing too quick? Its set at 35* then at 3 pounds it pulls 17* out.

Why the big step in the timing? Are you running a map, or pressure sensor? I would think you would get a much more even timing curve with load based timing. Maybe I'm not understanding what your set up is.

This is a generalization, but I would pull about .8 degrees pr lb of boost. That was with 93 ethanol pump gas.
So, set up the timing curve like you would a N/A engine and remove timing in direct relation to boost pressure. If the timing at atmospheric pressure is 35, then at 3 lbs of boost the timing would be 32.6.

I'll ask ...if the timing drop is at the same rpm..
in other words.. is that rpm when you hit 3 psi and
drops timing... that is a big drop

The only reason i can give for the big drop is its a 35 for driving around on the street and 18* was a safe tune on the dyno. We have the msd map sensor on it.

Mr P i think i get where you are going here, right now its set up to go straight to 18* once the boost starts. But maybe a more gradual curve of timing versus boost?

It's the tune up. The difference in hooking or not, is because it changes the load on the motor. The fuel curve through that area, with the timing that low is not right............sounds rich to me

thats my thinking... have it follow the boost... is
the point where it babbles at the timing drop

You should have the 3 bar map on it. All your timing should be load/rpm based. Cruising around will want more than 35 degrees in certain situations, and less in others. Smooth transitions in the whole table. I believe msd allows for a 45 degree sweep.

Appreciate all the input, Mr Smith do you think being more aggressive timing curve this by increasing the load on the motor?

Mr P I would think the timing drop is right before the babble starts. We do have the 45 sensor on. And double checked the box had the right sensor entered just in case.

This is a sample of a decent timing curve for a 2 bar/ sbc. Get the timing curve corrected, then get after the fuel. It is only here to show the smoothness of the timing, and the range at different loads. Don't use these specific numbers as they are not intended for any motor but the one they were wrote for.
If your engine rpm wont increase, it's because the engine load is higher than the engine power. You have a big blown hemi, you should have enough power, so your tune up has to be WAY off. Your timing curve is way out of wack, and most likely, the carb has a hard time transitioning from low boost to high boost. You are likely flooding, and retarding the engine at that part of the engines range.
With tire spin, the engine can zing right through the bad section of the tune.

Cool stuff, appreciate the help.

What octane fuel are you using with that boost level??

C-16, plan was to run 23-25 pounds but due to a shorter tire being used rpm/boost is alot higher than anticipated.

If the rich condition was caused by timing would it still produce the black smoke usually associated with too much fuel?

Sure if its not burning it... with that fuel its slow
burning and would like the timing... just get a good
curve on it

Had our last chance at figuring this out on the weekend. Changed the digital 7 out for a known good one and pulled timing out at a slower rate proportionately to boost pressure. Same thing car would hit 4500 and start to breakup. If it spun it would clean up and rev to 7500.

Black smoke? Popping from exhaust, or carb? Any video?

Listen to Monty.

If it was me, (it was last year) Monty told me to run all grounds to a copper bar and ground it to the battery. AND put firecore plug wires on it.
After I did it woke up.

Will try and post a video, but i havnt had one person say there was black smoke coming out of it and i would have to think on the passes it doesnt clear up at all it would be pretty clear. Im not sure if this helps but i was looking back at some data and it seems like the last time the car ran clean i was pulling an additional 10 degrees at the release of the foot brake and ramping it back over 2.5 seconds. I took this retard off because the car was really slow in the 60 and then would knock the tires off further down the track.