Flat Spots Under Acceleration - Running Lean?
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Flat Spots Under Acceleration - Running Lean?
Since I made the following adjustments, I have experienced flat spots occasionally under acceleration:
Spiral core ignition wires
2.5" crossover pipe in exhaust
'DR' Secondary metering rods (had 'DA' which had the carb jetted richer)
Am I now too lean? One benefit of the above changes is that my gas mileage has improved (I suspect improved combusion). Perhaps leaning the secondaries went too far? I haven't had opportunity to put the car on a dyno since these changes.
Please advise. :seeya
Spiral core ignition wires
2.5" crossover pipe in exhaust
'DR' Secondary metering rods (had 'DA' which had the carb jetted richer)
Am I now too lean? One benefit of the above changes is that my gas mileage has improved (I suspect improved combusion). Perhaps leaning the secondaries went too far? I haven't had opportunity to put the car on a dyno since these changes.
Please advise. :seeya
Drifting
Joined: Jun 2001
Posts: 1,809
Likes: 0
Re: Flat Spots Under Acceleration - Running Lean? (TedH)
I don't see signatures when I pull up the web page, so what kind of carb are you running?
Also when are the flat spot occuring, when the sec. kick in, also do you know the RPM they are occuring?
Also when are the flat spot occuring, when the sec. kick in, also do you know the RPM they are occuring?
Thread Starter
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Re: Flat Spots Under Acceleration - Running Lean? (Tominator)
The flat spots occur betw 2000-2500rpm. The carb is 'qjet rebuilt by Lars'. Jetting: '74' main jet, '42' main metering, 'DR' secondary metering rods.
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
Re: Flat Spots Under Acceleration - Running Lean? (TedH)
i would pull #5 & 7 spark plugs and compare to others.
As Lars is the resident qjet expert, i expect he had it jetted right, and it is now too lean. Qjets are pretty "lean" stock, where holleys are too rich WOT.
email lars with your question.
As Lars is the resident qjet expert, i expect he had it jetted right, and it is now too lean. Qjets are pretty "lean" stock, where holleys are too rich WOT.
email lars with your question.
Race Director
Joined: Oct 2000
Posts: 15,009
Likes: 79
From: central FL, near the beach.
Re: Flat Spots Under Acceleration - Running Lean? (Tominator)
yes, sometimes a new c3 would burn a hole in a #5 or #7 piston running at very high speed. Might see a white insulator or tiny ***** from heat(things that melt turn into a very tiny round speck, a ball)
Ted should just switch the rods back and it will probably run fine. Looking at the plugs would be a learning experience, over a period of time. :sleep:
Ted should just switch the rods back and it will probably run fine. Looking at the plugs would be a learning experience, over a period of time. :sleep:
