Went with my blown alcohol buddies to do some testing. Figured I'd take the chevelle since it should be a nice day and low volume at the track. My first run netted me a 14.11 at 103.7mph. 60' was a dismal 2.113 on BF Goddrich T/A's 255/60/15's. I was disappointed but it was my first run ever. I have been tuning cars for years but have never made any passes till now.

Next run was a better mid 13 run (slips are in the car except for the best run - I have with me). I was trying to fiugure out how to launch it since it just wanted to spin badly off the line.

Finally settled on 18 psi in the tires and heated them pretty good. Here's the best run of the day.

R/T .645 graemlins/sad.gif
60' 1.955
330' 5.403
1/8 8.22 (MPH wasn't working)
1000' 10.676
1/4 12.741 @108.53 :D

What do you guys think for the first trip?

I know I can do a lot of tuning. I never touched the timing. I know the carb is too small and I need some traction badly.

Oh and BTW - never took the spare or jack out of the trunk.

Troy.

Not bad..get some stickies on the there,and you'll be in the mid/low 12's easy when your 60 ft. improves

graemlins/thumbsup.gif

your hooked now ,you should have never made that first pass

Originally posted by JUNK YARD DOG:
your hooked now ,you should have never made that first pass That was my problem :D LOL

Yep- I'm hooked. I have spent every spare thought on what to do next to make it faster. I guess tires will yield the best bang for the buck. Next is probably a carb. I gained almost 3 mph by just removing the air cleaner so I know this thing wants to breath. I'm going to ask around and see if I can borrow an 850. Unfortunately all my racing buddies are running injected blown alcohol cars with funny car size slicks so they can't help.

It was kind of funny cuz the guy running staging told one of my friends that I needed to bring a helmet next time. My buddy says why didn't you say something earlier? He says, "when I saw the car, I thought it was probably a 15 second car... I didn't expect him to be running twelves." Anyway it was a blast and I will go back with some ammunition for better times. I have been contemplating changing to a UD/Lunati CAM but I think I'll see what I can do with this CAM first.

I'll keep everyone informed.

Troy.

Cool! What track were you running at?

12s are cool !!!!!!!!! Great job Troy.

Milan

Thanks guys. I was running at Bradenton Motorsports Park (used to be called Desoto Memorial Speedway). It's a pretty nice track. There was almost nobody there cuz they weren't running the normal Saturday program. I could have made 100 passes if I wanted to. I found out the drum brakes aren't going to get it. After three passes I was going to the end of the track to turn off. I already have most of the parts for the front disc conversion - just need to get it done.

BTW - actually went heads up against two 5.0 mustangs and one late model SS Camaro. Smoked 'em all. :D :

Troy.

Just curious, why do you say you need a bigger carb? Were you not winding the engine as far as you think it can/should go? All your numbers seem inline. Well, inline with mine any how (within .02 at every point). Our 1/8 mile times are actually slightly ahead of the NHRA’s 1/8 to 1/4 mile conversion.

Brake - just an educated guess. It's a Holley 750 on a 460ci motor and I gained the extra 3mph after removing the air cleaner. How much more is there if I open up the flow to an 850? Don't know for sure just guessing. I want to find one to try. What's your combo?

Someone correct me if I'm wrong.

If your air cleaner is the restriction, sticking a bigger carb under it isn't gonna help. The air cleaner is still gonna be there as a restriction.

Maybe it will help...since you'll get more flow (if there is more in the motor).

Tim,

Don;t know, but a vacuum gauge will let you know if the 750 is restricting you. It did on my 427, although " by the numbers" it shouldn;t have. Screw the numbers, the number that was relevant was the increase to 5" of vacuum above 6000. Went to an 850, which was a bugger to tune for streetability, but I did, adn the top end was much nicer.

( now I run a brace of carbs capable of moving 1125 cfm of air - too big??? NAW!)

Oh, I guess this is as good a time as any to ask.

What are the disadvantages to "too big" a carb? Poor throttle response I hear all the time. Anything else? Once the engine gets going, is there a such thing as too big?

And if you say "carb signal" explain it to me. Does that mean there isn't enough vacuum to draw fuel?

Tim.

You're right about the air cleaner. It will probably be off the car when I run again anyway. However, I have to believe that just doing that did not remove all restrictions from the intake of air. I want to try the 850 at the strip. I may not even run it on the street. Just want to see. A cold air box would probably help as well. Just thinking about different posibilities.

Gene - I thought about the vacuum guage. I'll have to figure out how to rig one up to watch from in the car. Is your's permanent? How did you go about doing it?

Troy.

I recently tossed a vac guage on. Got a nice Autometer. Came with plenty of tubing to run it into the car. Right now I sort of have it hooked on the, now unused, column shifter. It came with a T fitting and I just spliced in where I run my vacuum advance on the back of the manifold.

BTW, I put a 950HP on my 454. It's stock bore and a pretty mild cam. I haven't been to the track with it yet but the carb works mint on the street.

Tim.

Like Tim, I have it mounted in the car. I found it invaluable for carb tuning, and now, to see if my valves are out of adjustment ( solid cam). They are VERY good diagnostic tools. Its the only aftermarket guage I have in the car. I'm running it off the unused tranny vac port at the rear of the intake.

While I would go ahead with the disc brake conversion, you should knopw that I use Praise DynoBrake shoes in a manual 4 drum system and have no trouble slowing down from 120. Big bucks though at $240 for 4 and hardware.

Yes, a big carb requires careful accelerator pump tuning for the street, in my experience. The charge velocities are slow at low rpms, so throttle response can be sluggish, but I'll tell you , you;d never know I had a big ol 850 on teh 427 if you drove it. No flat spots at all, instant burnouts, 7000 grand in a few seconds. BUT it took alot of tweaking, and finally had to contour my own pump cam to eliminate a flat spot. Worth the effort?? I have had some racers say that they were more consistent with a smaller 750 carb vs the big 850, and being bracket guys, that was important.

Fuel signal is something I can't define exactly but understand intutitvely, so rather than post misinformation, I'd like to see someone else give it a whirl...

The only area it's come up for me is the 1125 cfm tripower, where at WOT clearly the fuel signal is somewhat weak since the motor only needs 830 or so cfm at 6800 ( my redline). now, you;d think you'd want to richen up the jets to compensate. Au contraire, leaner was the way to go. On BIG rats, where you have 510-540 hungry inches, yes.

So in that case, a weaker fuel signal called for a leaner jetting for max power. Found the same to be the case in the 850, where it was run as 73/79 jetting. Now, you'd think the front was very lean, but thats what it wanted.

Again, sometimes, I have found out by just doing stuff to do it and disregarding "common' knowledge" you get an unexpecetd result.

Which is the main lesson of carb tuning I've come away with. Throw the book out. Test it and see. There are some general relationships, but for folks to quote" the rule for power valves is.." is crazy. I idle at 10" and use a 105. Is it rich at idle. No. In some cases that won;t work, but in mine it does.

Be open minded and willing to play around. You can make almost any carb work on any combination IMHO.

Thanks guys. Lots of good information. I will put it to the test over the winter. The good racing weather is just getting here in Florida. It's hard to make good power when it's 110º in staging with 90% humidity. I'm going to get some tires and borrow a carb and do some tuning. Perhaps I can get into the 11's by spring.

Troy.