Thanks for the input Jim. I have 1/2" lines from the sump to the carb, no regulator and a Holley HP125 pump. The fuel pressure under hard acceleration is right about 4.5 lbs. (I haven't looked at it through the traps). 6psi rock solid at idle or cruise. I will be able to record RPM, throttle position, manifold pressure, and air fuel ratio when I take the car out next time. I might be able to plumb in a fuel pressure sensor as well.
3.89 gears or so and 950 or 100 cfm carb to start with. and as jim asked what about your fuel delivery system?
Excellent.. and yes, fuel pressure in the traps is critical.. if for some reason it gradually drops off, and the carb leans out on the big end, you might not be able to feel it, but I have seen a 600 HP motor on the dyno lean out in a fuel pump test, and it sounds perfect, just is down 80 HP... JW
Steve, I think Jim is on the right track about making sure fuel pressure is good. I understand your frustration about not going as fast a you think your combination should go. I' thought, your old combination should have gone faster too. Getting the car to hook is a key factor. But I would think you still should be able to get a better et. easing into the throttle. I don't think going to a shorter tire is going to gain you anything. I've actually gone faster with a bigger tire. Scott Pettit
The last time out it sure seemed to hook up way better. I think that was a combination of a well prepared track at Woodburn, and adding the rear sway bar to the car. It felt really good on the 12.03 pass...... I was sure I was going to see an 11 something, but the harder I tried the slower the car went. I started thinking about it and I believe the fuel filter I have on the car may be restricting fuel flow. I have another, inline filter to try. What gears are you running in your car Scott?
I agree, I've seen this myself. Use the large diameter filter, 2" or so will usually do it. Disconnect the fuel line close to the carb and see how long it takes for the fuel pump to pump a gallon of fuel, 35sec. or better is good goal. Those see through filter are typically CRAP!
The more I think about it, the more I think the fuel filter may be my problem. Here is the one on the car now. Its flow rate is 90gph. http://store.summitracing.com/partd...&N=700+4294925239+4294839051+115&autoview=sku Heres the one I bought but havent installed yet. Its flow rate is 130 gph. http://store.summitracing.com/partd...&N=700+4294925239+4294839051+115&autoview=sku
That car should definitly be in the low to mid 11 range. I have gone 11.30 at 122 with 550 hp or so and the same converter and 342 gears. I have been running 11.5-11.9 on regular street tires with no traction.
The 90 gph flow filter you've shown is not likely your problem, I'm running that same one with 3/8 fuel line located at the tank. In addition I'm using the Rob high flow filter at the engine for smaller particles. Other details; Mallery 140 pump, 5/16 return line at regulator. Your 1/4 mile trap speed and 60 is not standing in your way for a 11 sec. pass.
It will be a couple weeks until Im home again but I will get video of the runs when I'm out next time.
Steve, I'm running 4.33 gear's w/ 30x10.5x15 slicks and an A-1 4500 converter. I just leave at 1800rpm's and let the converter do the work. It will leave harder if the brakes would hold the car or I used a transbrake. Something just isn't adding up with your car! I should go faster. You know where to find me on Wednesday nights so I will keep my thinking cap on. Scott Pettit
I have been thinking about this alot, not much else to do but work here. I built the car with a target ET of 11.50 and Im a half second from that goal. There are a few disadvantages that individually probably wouldn't be a barrier but taken as a whole they might add up to half a second.o No: 1. Less than optimal gear ratio combined with a relatively tall tire. 2. Smaller carb than engine could use. 3. Aircleaner installed 4. 2.5" exhaust through the mufflers 5. Front sway bar installed
Well, my car runs through a 2.5" dual exhaust. I have a Trans Am front sway bar. My air filter is a K&N with top. And I about the worst shocks you could have for the drag strip. I really think, like others have said, that if you get a slightly bigger carb, and go to a 26" slick, you'll probably get pretty close to your goal.
You have got plenty of power to put you in the mid-low 11's, my car has a little bit less motor than you, and I'm running 11.80 at 111.00- 112.00.I think you need to get your 60 ft down, and you will be there.:beers2:
Just to let you know, way back when (15 years ago) I tried my Dodges 26" X 9" tires compared to my 32 X 14s I used to use and got absolutely no difference (.02) between them at our SHORT TRACK. I think he should try some shorter tires anyways, with those times and the new compounds these days it should hook better no matter what. Mickey Thompson has down to a 20.5" diameter slick, if you could borrow some to try first it would be best. And you should keep the sway bar if you want it to handle on the street, it won't make a big difference at the track unless you tune the rest of the suspension too. Looking forward to see what happens, with all these ideas everyone has you'll be busy.
Whamo. Last year when we got our car running we took it to the track. Had fun, but not real happy with time. By the end of the first season, we had shaved off over a half second in our 1/8th mile time (no 1/4 mile tracks left). During the winter, we made other changes, and now have lowered our times by a full second from our first weekend at the track. Every car is different, and you can get a lot of good advice from experienced people here. Figure out how you want to use your car, and follow the advice that matches up to that. Our car is driven daily, with good weather and we are serious drag racers and go to various tracks in our region. Our ride, based on your list: 1. 3:42 gear with 26" tall M/T ET, down from 28" 2. 950 Proform carb now, up from 800 Qjet, also SPX intake from performer increased time by .30 in 1/th mile. 3. We had K&N with lid, but now run none at track. No hood room. 4. 3" exhaust and added cut outs to open headers. Same track time open or closed. 5. No front sway bar and cheap summit 90/10 shocks.
4. 3" exhaust and added cut outs to open headers. Same track time open or closed. Mark how did you check this? Back to back and once or more?I want to chasis dyno my 31/2" when i get it done hopfully buy the end of May. I was going run it through the cutouts then mufflers no tailpipes then through 3" tailpipes just to see if there is a power differance but the real test will be the track but the weight differance may play some factor. Jamie
Thanks too everyone for the input. Depending on the weather I should be able to make it back to the track next weekend. When I do I should be able to monitor and record throttle position, manifold pressure, fuel pressure, rpm and of course air fuel ratio. I dont plan on changing anything until I have a baseline to work from. I will post the results here as soon as I have them. Tinkering with the car is why I have this hobby anyway. If it flat ran as well as I wanted it to right off, where would be the challenge?
back to back passes at the track. Some weekends we open them up and some we don't. Tyler runs in modified and pro foot brake classes, and he runs with mostly trailered full race cars. He is usually the only Buick at the track, and only street legal car, and certainly the only driven daily car in the classes he runs. So, he enjoys pulling up beside a fox body caged mustang during time trials and beating them through the mufflers. Really upsets those guys and they want to know how much NOS or boost he is running.....We just tell them to wait until the real race car is finished. It may have both.
