For what it's worth, my 72 has 15x10 Draglite's with 5.5" backspacing and 29.5 x 10.5 Phoenix slicks. I had to trim almost all of the lip off the top of the wheel opening, then I rolled the chrome trim up to make a smooth "rolled" edge. I have about 1/4" clearance on the outside and 1/2" on the inside of the tire. It rubs a little going around corners, but I don't race around corners. Have fun.
I'm running the TA-413 cam; 234/244 int./exh duration at .050 and .500 lift. Right now it is installed at 107 intake centerline and I'm using the factory 1.54 rockers.
FWIW....I do some lurking at the TurboBuick board and they love the nitto's over the BFG drag radials personally - I have the 275-50's and i dont think I've ever actually hooked 100% and most of the time its alot less than that I either have to leave soft or pedal it slightly and i've tried Big burnout, small burnout, and varying pressures until i was skating and scared myself crossing the 1/4 line (think that was down around 13# or so.....)
For what its worth, don't be so quick to "blame" any sticky tire. Instead look to suspension improvements. Don't "let" tires stick, MAKE THEM!!:stmad: :Brow: There are some very fast wheels UP 8 second cars using BFG Drag radials (and the like), FWIW.....o No:
Well since it's the hottest day of the year so far ~96 degrees I think I'll go to the 1/4 mile drag strip. Anyone coming to Fayetteville Motor Sports Park for test and tune tonight? Tune in tomorrow for the scoop.
I'll be waiting...... After all you have been through, I sure hope it holds up to your expectations :TU:
Hoosier Qtps. For some of you guys running full weight Skylarks with Hoosier Qtps, what psi. do you race at? I'm currently running about 15 psi. Anyone run different pressures? John
Had a good (not great) day at the track . Not the best day considering how muggy and hot it was but hay everyone was a little off on their times. My plan was to shift at @ 5200 rpms for the first several runs while I did some tuning. After the tuning stage, I planned to rev it to ~5800 rpms to see what she could really do. First run, spin through first gear, shift at 5200 rpms. The result was a 13.28 at 104.8 mph. I was racing a modded Maxima that ran a 14.69 at 93.9 mph, margin of victory 1.6 sec. Second run, highlight of the night, against a new Z06. We came out about even but just off the line I pulled 1/2 a car length in first. This took a lot of mental control not to floor it in first gear and loose traction :eek2: ! I shifted at 5200 as planned, I lost some ground initially but pulled on him good through the mid 2nd gear rpm's. As I shifted into 3rd he started to pull on me some but I was too far ahead. The result was a 13.20 at 105.3 mph to a 13.28 at 106.2. Before the third run I changed the secondary rods of my Q-jet from 0.040" to 0.030" This was the most entertaining run (for the spectators). Again planning to shift at 5200 rpm, I started to spin about 60' out but I stayed in it thinking it would hook. Went into second and continued to spin at ~5500 rpms. Had to get out of it at ~70 mph because I was crossing up bad just past the 1/8th mile mark. Got back into it after I straightened up and ran a 14.14 at 101.7 mph. From this run I figured I was making a little more power and made no changes after the run. Forth and final run . I decided to turn it up and shift at 5800 rpm's. I hooked fairly well; it pulled hard through 1st and 2nd. As I was getting ready to shift into 3rd I hear a sputter and a tapping sound from the right bank. I let off the gas and was on the brake a ways before the finish line. Thinking the worst I sadly cost cruise to the ticket booth. This was the worst return road drive ever! Picked up my slip and gently proceeded to the pit and shut her off. My friends came over with smiles on their faces thinking this was the best run, they just thought I got out of it early. I'm almost sure the problem is valve train related, maybe pushrod adjustment nuts loosened? I talked with two experienced racers, independently they both said about the same thing. Should be minor but I decided to leave the car there to be safe. Anyway, for the record I ran a 13.36 at 94.1 mph. Going to pick it up with a trailer tomorrow morning. 60' times were only fair with the street radials, they were in the 2.15 to 2.20 range. Any ideas? It occurred at higher rpm's. The preload was set at .040" with the adjustable pushrods. I know roller rockers would be a better set-up and give me a much better ratio (1.6 vs. 1.54) but man $600? I also noticed as speeds approached 90 or so the car seemed to gently sway back and forth. The first time this happened was on the street a couple of days before. It occured on each run at the strip, guess it could be the 275/60-15 TA radials or the air shocks? Tire pressures in the rear were 26 (RL) to 28 (RR) psi. and 36 (FL) and 33 (FR) to help jack weight around some. I've always done this with success. There was a noticable crosswind as well. Here's a early evening picture before things got crowded.
Man.....how could you leave without even ripping the valve cover off ??? I never would have slpet the night just wondering. Your MPH is up there but those 60' times gotta go....DOWN !! where you on drag radials ?? I dont think I ever tried more than 20# at the strip with mine. I would alomst guarantee you better 60' with lower pressure You need to find yourself a patch of concrete in the middle of no-where'sville....bring a push broom (to clear off a launch pad) and a couple gallon jugs of water and practice your launch. Im far from being Mr. Dragracer but I'll tell you this - from practicing I know my car pretty well and how to launch it with minimal tirespin. Here's hoping you didnt hurt anything......
I hope everythings all right. Let us know whats up. BTW, how could you sleep? I couldn't even leave my car at the track when I windowed a block. I think I would have at least taken valve covers off, pulled spark plugs, checked oil/water, ect.o No: ou: Are the air shocks still on? Buy some slicksou:
Got the car home today. I peeked under the valve cover before we loaded it on the trailor . The end of the rocker shaft broke (passenger side) right at the front bolt hole. The end was still attached, the crack came from the bottom up as expected, I'm sure glad it did not come off. I have not measured the rocker shaft thicknesses but I know I have one that is new looking (driver side) and one that is older (passenger side). Should I just get a new shaft or a remanufactured set with maybe a better ratio than my 1.54? What material or treatment should I look for in a new (stronger) rocker shaft?
Get a new shaft or shafts. Rick Henderson had some shafts of which had grooves worn in them from under the rocker arms. Sounds like he caught his just in time. When you change your shafts, look for this wear. I'm a little concerned about mine now. Do you know how old your shafts are? John
You'll have to spend $325 at TA to get just replacement rockers since you no longer have a "core" set to give back. If it were me, and I'm crazy, I'd go the extra $300 and get the 1.6 roller rockers. They'll never give you any more trouble up top. And they look great. You'll get a little more HP with the better ratio. It's a win/win situation. The wife can't even argue about it. It's either $625 or the car sits and gathers dust. Wait, don't tell her that, she may prefer that. Or worse, just sell it! I have to agree that you must do something about your tires. If you're going to run drag radials, keep the pressure between 15-20 lbs for best traction. Or go for the slicks and really hook up. I went from 1.92 to 1.75 going from drag radials to slicks. They do work great.
Been there, donbe that! About 1.5 years ago I had a thread going about this kind of stuff... If I remember right the original 70 vintage rocker shaft on my car had a wall thickness of about .170 inches... The Melling brand replacements along with the Poston "heavy duty" shaft was a whopping .150 inches thicks... Well the original shafts were 30 years old when the aluminum rockers and simply wore them out... Over the next 6 months 2 of the Melling replacement shafts bought the farm. Wouldn't have been a big deal either time but the second shaft that let loose was about 200 miles from home. I did however discover how well the car will run on 7 cylinders for 200 miles!:jd: Both shafts broke at the ends on the driver side. SOOOooo.. to make the long story longer I call up TA. They don't really list their shafts as heavy duty but if you talk to Dave or Mike they will tell you that they certainly are... Well with the mellings in the trash and the Postons on their way back to Alabama (just a repackaged Melling) it's either $100 (I think) for a pair of these shafts or ante up the $500+ for the rollers. The TA replacement shafts are .220 inches thick! ROCK AND ROLL BABY!!! Year and a half later they are still going strong. I also divied up the $10-$20 for the studs and nuts for the rocker shafts as they were highly recommended. In conclusion:Smarty: you're choice if you want to spend the bucks or not but it doesn't take a rocket scientest to tell the differences in strength between those wall thicknesses. regards
Well, I finally got back to working on the car replacing the rocker shaft, check out the crack! Hay, I'm glad it didn't break off. If this happens to you make sure the pedistal is on the head is not damaged. Luckily? I used shims under the shafts to get the proper geometry so I just had to replace the shim as it is damaged and no longer even/smooth.
