I tried to do some searches, but I am still unclear. I recently swapped my 2.56 peg leg for 3.73s with an Eaton posi. Now my car gained about .8 in the quarter mile, but it feels like I could get even more with proper tuning. My carb is a Holley 600, and the trans is a TH350. First, with the new gears, I think the trans shift points are kinda thrown off. It holds first fairly well, then it jumps through 2nd rather quickly, then a slight bog into 3rd. When I leave it in drive and go 1320ft, it runs about 14.1 et. When I manually shift from 2nd to 3rd (holding it in 2nd until it winds up), I ran a best of 13.82@98.46mph. I am guessing I need at least 2 carb adjustments -
1)bigger jets and 2)swap secondary springs. Am I on the right track? I am thinking the bigger jets would get me more fuel, and the springs would allow the secondaries to open sooner? Btw, my 1/8 mile averages 8.8ish @ 77-78 mph, so at least I am getting additional 20mph by the time I finish the 1/4 mile. Any suggestions? :confused:

can you list details of ur combo? minus the heads and gears sounds like we have the same thing

my car barely holds onto 2nd too...i have a 650 spreadbore with mech. secondaries so i doubt your problem is fuel

check the sig in the original post, it's all there.

are the heads alum or iron?

what kinda pistons do you have?

I have iron GM 882 pocket ported, flat top 4 relief hyper. pistons, my dad is guessing CR between 8.5 and 9

I havent really heard of carb tuning based on gear changes...mostly fuel, air, ect related things

Leave the jets alone. If it is bogging going into 3rd then the sec are opening too fast.

guess i should have said "doubt your problem is LACK of fuel" :D

I was too interested in narrowing how close his combo was to mine to suggest too much fuel

is it vacuum secondaries? if its mechanical they just open when you punch it and stay open right? so if its vacuum it can be adjusted, if theyre like mine either hold it in 2nd or maybe ease out of it a bit

Mike, if u say they might be opening too soon, do u suggest i try a stiffer spring?

This doesn't sound like a sec. opening issue. By the third gear shift your sec. are open. Changing gears would not warrant carb adjustments either. The bog may be more related to the trans shifting into third at too low of an rpm. Does the bog go away if you shift manually? Is it actually a stumble or does it just not pull good after the shift? More rear gear could however effect the shift timing of the transmission which sounds like more of the issue. First of all you most likely will never get the same ET's out of your car letting it shift automatically, because no matter what adjustments you make it will probably want to shift between 5000-5500 rpm's. Do you have a shift kit in your trans? You may need to invest in an adjustable govenor kit sold by B&M to tailor your shift points.

Sounds like you just need to shift it manually..what RPM did you wind it up to before shifting into 3rd? What was your 60ft? What spring are you running in the secondaries?

umm, what rpm?.... did i mention i dont have a tach yet? :rolleyes:
actually my 60fts were all in the 2.0 range, which i thought was pretty good for BFG street radials. i did not even heat them up. as far as springs, i just have the stock spring that came with the carb, not sure what size that is. basically, when i leave the car in drive, it hits first, then chirps into 2nd, then a slight bog and then a good pull into 3rd. that got me an ET of 14.14@98.26. on a later pass, i tried a manual shift from 2nd to 3rd with a "seat of the pants" tach, and that got me to my best of 13.82@98.46. i tend to agree that maybe the new gears are throwing off my shift points. i do have a shift kit, but it was installed before the new gears.