Just looking for some confirmation and/or advice here: I've got a 70 Skylark with a built 455 (310 Cam, Ported heads, roller rockers, SP-1 intake, MSD ignition) It's got a new Holley 950 carb on it that I put on last year. Last year with the new holley carb, drag radials and the headers un-capped the car ran a best of 12.38 @ 110. (1.82 60') Over the winter I added 10X28 ET Streets, Aluminum wheels (took almost 100 pounds of rotating weight off the car) and I added a 3" X-Pipe with 3" tail pipes and Super Turbo side-side mufflers. The best I have gotten out of the car this year is a 12.46 @ 107 (1.72 60'). So I've improved the 60' by a 10th but lost 3 MPH. I want to try some better mufflers in the future, but for now I'd like to see if some jetting will help. I am assuming that I need to lean the car out assuming the mufflers are choking it a bit. Uncapping the headers is not an option at the track this year. I was also going to adjust the valves, but I don't expect that to help. Any ideas are welcome. The goal is to get 12.00's through the mufflers with this car.
How heavy is your car now? What did you do with your suspension? Are you using a air bag in the right rear? Do you have no hop bars? Are the rims correct for the tires? What gears do you have and what tranny and torque converter? I am usually around 1.68 60' or better on a good day and 113mph and et now around 11.80 or better. My airbag sprung a leak and it really effects how it 60's. Last weekend it was a 11.93 A lot of it is your combination.
Dave, Did you check your plugs at the end of your run? I have in the past pulled a couple of plugs at the end of the quarter. You have to have a special magnifing piece like they use at the Dr. office and look down inside the plug. What will get you close is to change jets by going two up or down. When I took it to the dyno last week, it was off three jet sizes according to the air/fuel monitor (too rich). Also tuning the "Carb tuning the Scientific way" is a good starting point. http://www.bob2000.com/carb.htm
Rick, thanks for the reply. Here are some answers. I'll probably jet two down and put in some fresh plugs. I definitely need to address the suspension, but that shouldn't affect my MPH. >How heavy is your car now? It was 3900 before I swapped the wheels so I expect 3800 next time I weigh. >What did you do with your suspension? Haven't touched the suspension at all. >Are you using a air bag in the right rear? Nope, I need to get a set. >Do you have no hop bars? Nope nothing there either. But the car has had Hotchkis rear control arms (non adjustable) since I bought it. >Are the rims correct for the tires? Yes, the fit looks good. The wheels are 8" wide, I realize 10" would have been better but I was afraid I'd have fitment issues. >What gears do you have and what tranny and torque converter? Gears are 3:42 (posi) TH400 trans. It's a 2500 TCI 11" converter. I don't have a tach, just a shift light so I'm not sure what the converter will brake stall number to. I expect to need a converter to get 12.00's but I'm trying to get my HP back to where the car run's 110 again. >I am usually around 1.68 60' or better on a good day and 113mph and et now around 11.80 or better. My airbag sprung a leak and it really effects how it 60's. Last weekend it was a 11.93 Are you running a Holley 950? If so what jets are you running. I have not even opened up my carb since I bought the car so the jets are whatever Holley puts in from the factory. The carb made such a big improvement when I put it on, that I just left it alone Thanks again for the response.
Oh, I forgot to mention one other thing...I added a Stage II hood scoop. I have not made an air-pan yet so I don't expect it to give me any improvement. The only thing that could be slowing the car down in my mind is the Exhaust/mufflers. I have not had a chance to un-cap it and try it again to see if it improves, or at least run's 110MPH again.
Wow, great information there...need to study that and check some stuff out. But for now I will try leaning it out a little and get some new plugs.
Dave, We have pretty close to the same combo. I am using a Holley 1000hp downleg boosters. If you took it out of the box and bolted the carb on, it can be pretty close. One thing that you could check is where the cam is on the squirters. I had to move them to the number two spot because I was having problems on launch. It cleaned it right up. The air bag is really simple to improve your 60's. I have one in the right side only. I gave the other one to John Biggs. Let us know how you do at the track.
Well, I went down to the shop to lean the car out last night, and first checked a few plugs. They were extremly clean. So clean there was no trace of tan or discoloration anywhere on the porcelan. Seeing this I decided to go fatter so I changed out the stock square jetted 78's for 80's. Took her to the track tonight and picked up 1 mph, but lost a little on the 60'. My guess is the car is happier. I need to address the 60' times so I can get more consistent. The last pass was a 12.50 @ 107 with a 1.80 60' The car spun for a couple feet. I'm running 15 psi in the ET streets. Anyway I'll start with an air bag and go from there.
your switch of tires is worth almost 2 mph. it may hook better with the et streets but the radial tire is way faster in the mid and high end of the track. the goodyear radials on my car were worth .15 in et and 2 mph over the bias tire of the equivelent size.
Adam, thanks for the reply. I had not heard that before, but another guy at the track last Friday said the same thing. He saw the difference on a dyno once. The radials were worth more HP on the dyno too. Here's a video of the car from last Friday. You can hear the tires spinning for the first foot or so. They had 15 PSI in them. I didn't want to go much lower since I don't have rim screws. http://www.blackholehunter.com/Dave_12.50.wmv
