At certain times my motor would "break up" when I start revving it hard. Like around 5000RPMs it would start poping out the exhaust and stumbling. But at other times it wouldn't miss a beat up to 6500RPMs. I couldn't figure it out. Then the other day I figured it out.

I occassionally drive my car to classes, which usually intails a bit of in town driving. So on my way home, right after leaving town I nailed it. It was breaking up like crazy. So I took it easy on the way home. I was taching 3000RPMs the entire way home. I was almost home after about 10 minutes of 3000RPM driving and I decided to nail it again. She revved out perfect.

The next day I drove my car to class. I kept the in town RPMs around 2500-3000. Leaving town I punched it and she didn't miss a beat.

The only thing I can think of is that I'm experiencing low RPM fouling do to my setup. At any rate, problem solved and she's running great :).

 

I don't understand how the problem was fixed?

 

By keeping my RPMs up in town. I think I'm running a little rich on the primary side. So it loads up the plugs if it's not turning enough RPMs.

 

I am glad you can drive your car without the rpm breaking up, but to be a PITA you really didn't solve your problem, now did you? :nono: You are masking the problem by not driving it the way you used to. I would suggest a quick tuneup, concentrating on the carb. Then, if that doesn't correct your problem, maybe a carb rebuild might be in your future.

Gary

 

Actually 3000RPMs with open headers is quite fun going down main street. I probably need to step the primary jets down to 74 or 72s. But I'm pretty comfortable with how the car is running now.

I downshifted it the other day for the first time. I banged it down from 4th to 3rd....wow, it's pretty crazy. I normally just always kept it in 4th gear and mashed the gas...the 454 has plenty of power to pass just about anything it needs to.

 

Except a gas station :D :D

Terry

 

It may be worth putting it on a dyno with a wide band sensor, and do some tuning runs. You may solve your problem and pick up some extra HP as well.

:cheers:

Mark

 

What about changing the spark plugs to a hotter range?

 

cool, that was an easy workaround.

It sounds like the carb is runningrich and carbon might be building up on the plugs. Run it lean and see what happens (besides more heat) :cheers:

 

Welcome back Bence :cheers: Don't be such a stranger :p: !

 

:cheers: :cheers:

 

I forget, are you running a MSD ignition system? I think its a must with a strip dominator intake. As you said before, they run rich in the lower rpm range by nature.

 

Bence....that's known as blowing out the carbon. I had the same problem with my 427 until I gapped the plugs at .045". This seemed to do the trick for me.

 

Sounds like you need to tune your carb, and really fix the problem.

 

Terry:
How true, how true....6-8mpg doesn't get you very far :D.

Cam:
That is the next step, I'm going to try a hotter plug. The plugs I'm running are for a '66 427 Corvette (that's what I told the guys at Advance Auto, because my heads are from '66 and need spark plugs with gaskets, not tapered plugs).

Mike:
Between my car, girls, work and school (in no particular order ;) ) I have my hands full. I try to frequent the board when I get spare time.

71,454,4spd:
You are correct. With a pretty hefty solid lifter cam, 850cfm carburetor, large port heads and the single plane strip dominator....it doesn't make for a very good low end combo :). It's the nature of the beast when you build a motor for high end HP. I learned to deal with it :D. I do need an MSD 6AL box or something with a rev limiter though. I remember gkull recommending a box to me but I can't remember for the life of me which one he recommended.

fontking1a:
You are correct. My buddies 514ci Mustang suffers from the same problem (big cam, big heads, big carburetor & Victor Jr. intake....it loads up on him a lot). Actually my plugs are currently gapped at .045". I'm going to try a hotter plug next. Probably next season I'll mess around with jetting the primaries when I take it to the track.

 

yep, if all else fails,
PUNCH IT and HOLD ON! :jester