carb jetting for 1/4 mile gurus

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bignasty123

bignasty123

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Going to the track ib 2 weeks. My car runs good im gonna mess with the jets.
I have 408 stroker ,Braswell 950 carb the jets are 84 square. U suggest gooing up or down first. And what am I looking for more mph
 
Frankly, in this day and age, with the costs you spent to build something like a 408, if this was me, I'd spend another couple hundred on a wideband O2 setup.

I bought one because I'm playing with EFI. (The original setup was narrowband) I would not be without it. My new EFI is native wideband, so an add-on is not needed.

You can "rig it" and pull it back out when done, and plug the bung on a carb'd engine.
 
I do have power valves front and rear.
I have bung in my exhaust with plug. Maybe forced to get wideband but a session at the dyno is the same cost. So now the question is dyno session or wideband
 
Make 2 passes, get a baseline, then jet it up a step. If it goes faster (in MPH, not ET) keep jetting up, if it goes slower try jetting down. Basicly you are trying to get the most MPH out of it.
 
if it's running good dont mess with it.. :D
why chance leaning it out fouling and all that mess. if it's running strong dependable etc just work on the lights, get consistent times, take home the money

are you trying to get in a different bracket?

you could put her on a diet. that will speed you up also

just looked at your other post
71 valiant pro street
Ported eddy headed 408 stroker 11 to1
Hyd cam, forged bottom end, ported victor intake, Braswell 950 carb, msd ign, dougs headers
904 rmvb, 3500 vertor low gear
12 point cage 2 seats
Mini tubbed 83/4 391 gears Detroit locker, 26x10.5 m/t slicks on it now
Perfect paint, all original panels and bumpers no glass all steel old school build
Ss springs and snubber 1.5 60 ft and with no tuning it ran 7.4x in the 1/8
And it was running really hot each pass, and had a miss after 5500...cooling issue fixed, miss fixed, now have to start tuning with my wideband it pig rich
Click to expand...

if you get a dynamic 9.5 converter you will probably knock off 2 or 3 tenths, you should call them.
 
67Dart273 said:
Frankly, in this day and age, with the costs you spent to build something like a 408, if this was me, I'd spend another couple hundred on a wideband O2 setup.

I bought one because I'm playing with EFI. (The original setup was narrowband) I would not be without it. My new EFI is native wideband, so an add-on is not needed.

You can "rig it" and pull it back out when done, and plug the bung on a carb'd engine.
Click to expand...

How was the narrow band? I got one for free that I may try, I don't really have time to read a ton of numbers while going down track, I already have enough going on lol
 
It is all steel, just trying to dial in my application, I plan on some glass parts just want to dial in the combo first.and I'm gonna by a wideband.thanks guys
 
flyfish said:
Make 2 passes, get a baseline, then jet it up a step. If it goes faster (in MPH, not ET) keep jetting up, if it goes slower try jetting down. Basicly you are trying to get the most MPH out of it.
Click to expand...


Exactly what I was going to say. Keep jetting up until you slow down in MPH
 
I think 84's are good, but w/o power valves. Thats all I run on my 433" small block. 9.50's 9.60's @ 138. But I have a friend with Iron w-2's and he is in the 90's with his combo. again no power valves. Remember adjust only one thing, get a "best base line" and move from there. Fuel then timing, not both at once...Timing about 34 degrees total. Good start. Fuel demands will change depending on the vacuum signal on the carb. In other words, engine sealing efficiency will affect A/F ratios. Enjoy the track time..!
 
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