Your gears are fine considering the torque your engine makes. You have a great all around gear now.
If you didn't have the engine on an engine dyno, then you don't know the true peak hp rpm. Chassis dyno is not correct in giving peak engine power rpm. Post what your engine combo is and we can give you an idea.
What timing are you running?
Have you had someone confirm with you that when you floor the gas pedal, the carb actually goes full open?
It's a BluePrint Engines 540 and it came with an engine dyno sheet so I know the numbers are correct. I can check exactly where the peaks are. I actually haven't verified my throttle is fully opening that is a great idea. Running 35 degrees total timing.
In any event, before spending any money on gears or converter or anything, get more practice with what you have, and work on getting the launch down perfect, IMHO. Can't legally go any quicker than 11.50 on an NHRA track without a roll bar anyway.
This is true and I was told as much pretty quick after my 11.50. Planning on a rollbar this winter.
the 60' was 1.67 on that run. My 1.58 60' was actually on a 12.19 run where I had to lift at the end because I was worried i'd break 11.50 and get the boot.
Something is off....that MPH and ET don't show anywhere near 680 Hp unless the car weight is 5200 lbs.
At 4000 lbs for a fully loaded '72, it is only showing you 540 Hp flywheel, maybe 470 Hp at the wheels.
if it really is 3600 lbs, its even worse....465 Flywheel Hp and 435 wheel Hp.
Gearing will effect ET, but it won't effect MPH much....MPH is almost completely dependent on vehicle weight vs power regardless of gearing.
the 60' id good for a street driven car....but total HP is sorely lacking somehow. Time to do some serious carb, ignition tuning. seems to be WAY down on power unless the dyno was a lie.
What size/brand carb, and what are your ignition timing specs...initial, total mechanical advance, what RPM is total advance reached??
what's the exhaust system consist of?? Header primary tube size and length??
See above about legit dyno sheet
The tuning comments may be true, though it does start and run beautifully with no backfiring, bogging, breaking up etc. It's only got about 600 miles on it since I installed it last year.
I'm running an 850cfm Holley 4150-style. Running an MSD Digital 6AL. Initial timing is 14 degrees and total timing is 35 degrees.
Exhaust is 3" all the way back but I have cutouts for race time. headers are mid-length 1.5" primaries.
What fuel pump set up are you running? I think you got some more potential mph there but wanted to see if anything might be holding you back.
Running a Holley Ultra HP billet mechanical pump rated at 170gph
Originally Posted by blue_69_malibu
Folks...it was the OP's first time out. Let me him breathe a little bit.
thanks man but I can take it! i just want to get better at figuring this stuff out.
121 mph with 28" tire and 3.50 gear is less than 5600 rpm even with 10% converter slip, you need to raise your shift points up as you said, you might want to raise the fuel levels in the bowls and use a pump cam that delivers later as you are at part throttle when you leave. 680 HP needs fuel volume I assume you have some type of upgraded fuel pick up from the tank?
I'm running a 1/2" sending unit from RobbMC and -8 lines/fittings all the way to the carb