cray1801, I just installed the T/A No-Hop bars in my 71 Skylark ,My baseline set up was 5379 moog springs, KYB GR-2 shocks (cheap) Afco sway bar, factory traction braces , UPI adjustable upper control arms ,Boxed stock lower control arms , M/T 275-60-15 , 3.42 gearing . In baseline trim it would hook pretty well @ times ,but if it did break loose I could get out of the throttle & right back on it & it would hook up & go. I would always leave @ idle & let the convertor flash off the line (2800-3000) With the No- Hops & same baseline I would leave at idle (no brake torque ) & BLOW the tires away! Man was I disappointed with this set up ,worse than when totally stock. After several test runs I can tell you that the rear end of the car lifted on take off but I have NO front end lift ! Rule #1 is the front must raise before the rear lifts. I run -2 pinon angle & 18 # in rear tires. With this said I was able to hook up 1 time & the car shot out of the hole like a rocket & felt very different than my baseline. I am looking @ the car as I post this with the a arms hanging & springs out , (front baseline was a set of adj shocks set @ 90/10 & moog 5450 springs, & there is the problem I think , the springs are ment for a SS 454 A body they are short & I feel they are very good in the skylark on the road (handled great & rode well also) With the No Hop bars these springs will not transfer any weight to the rear because they have very little (stored energy) with out the No Hop bars the rear end would drop the front raised & the car hooked ,BUT it would hook to the point that it felt like it was moving backward before it would move forward (wasted time off the line for sure !) Long story short I am replacing the springs with a 260# rate & about 18.5' free length should give about stock ride ht. but with the stored energy the front should react before the rear & keep the front up longer out of the hole . Let you know how it turns out . thank ick
Interesting... My '72 Skylark has the original 350 AC springs from the factory as far as I know. Of course now with 455 with aluminum intake and headers the weight is really not that much different from 350-4 with AC. Oh, and battery is in the trunk over the right tire. The rear on launch does rise as the rpm's build while foot braking. I typically launch at 2000, when I release the brake and add some throttle, I have good/fair weight transfer as the converter goes to ~3600 rpm's. I "transition" the pedal to the floor in about 1.5 sec. The left front tire almost comes off the ground, or maybe it's wishful thinking cause I've never seen light under in the pictures. If I transition the throttle too quickly off the foot brake it will spin the tires. Seems like I'm somewhere between wheel hop and really planting the tires. What's the typical GM A-Body upper and lower link angles and where is instant center for good baseline setup? Is it common that the upper bar is angled more up at the front than the lower bar is (like mine)? Thinking a 50 shot would be fun to play with too, but only after I get it to hook.
Poly bushings in rear (& front) don't allow suspension articualation (move) as it's designed to do. Before replacing any parts try loosening up the bolts & double nutting them. Both front & rear & give it a try before you start replacing things. At least this will give you an idea of which direction you should be going in. Just my thoughts. Tom T.
Toss the air shocks and get cheap drag shocks for rear. Air bag in right rear spring, adjust as needed to plant. Keep rear sway bar. Drag shocks for front. 90/10 Adjustable rear uppers and set pinion angle as recommended. Battery in trunk. No front sway bar. Just my 1.50 worth. (60 foot that is) Oh yea, then go to the 4000 stall and hang on.
I put the car up on 2x10" and trash bags (low friction) and get it level. Looks like my pinion angle is +2, need to get that down around -2 deg. So given the clearance issue I've got with one of my upper control arms, it's time for some upper adjustable arms as a first step (lower profile and adjust pinion). I looked at the UMI Performance site and talked with a tech guy, I like their design. I ordered the 4037 upper arms (black), grease and spanner wrench. The attached shows the current "notched factory control arm and the new UMI units. :grin: Next will be shocks, air bag and rear tires....slowly getting ready for friends "rust-bucket" Chevelle
Moog 6204 front springs are great for front end lift: .609" dia wire, 18.61" tall. Lots of stored energy. Will likely need to get a spring compresser from parts store (loaner) to get get these in the pockets. Made all the difference on my car. Hooked like never before. Even hooked on the street! Auto Zone has the same part number under a different name, cheap, local.
Sound good Gary. How? and how much? did you preload using the upper adjustable control arms? I am concerned that softer springs will cause my M/T scavenger headers to scrape at dips more often. Clearance is at a minimum, 3.63" passenger and 3.37" driver side clearance at flange bottom bolt location. Driver side has never scraped but passenger side does more often than I'd like. The are also long which makes matters worse, flange is 42" back from front axle line. Currently my '72 Skylark wheel lip heights are 25.7" front (34psi 26x10.00R/15LT Mickey Thompson Sportsman SR tires) and 27.4" rear (20psi P275/60R15 M/T ET Street drag radials) with stock 350 AC springs all around.
Found a really good write-up on traction, one of those you read several times. http://www.baselinesuspensions.com/info/Launching_A_Drag_Car.htm
CRAY1801 You'll have the front wheel well at about 26.5" with that 6204 spring. I had to use a compressor that goes inside the spring to get it in. Not a big deal. My 67 has low profile engine mounting, but never had clearance problems except big speed bumps. That spring sure has the stored energy, to whip that front end up. It is a 67 El Camino 327 factory spec spring. With a 327, they really hold the front up, and my 455 BBB is not much heavier. As for preload, -1.5 to -2 degrees is common. That is trans vs diff. Drive shaft is not figured in unless your building a Bigfoot chassis or got 2 driveshafts. (Edited: I said "Axle" is not figured...)
Gary that sounds like a good front spring, little extra ground clearance will be good with softer spring. My current springs (stock as far as I know): Front - 0.645" cross-section with an OD of 4.91" and I counted 12 coils including ends. Shocks were replaced at some point (white). Rear - 0.550" cross-section with an ID of 5.5" (yes ID), and counted 6 3/4 coils. Air shocks (also white) with 25 psi. (minimum recommended). It's easy to get pinion angle measurements wrong so I rechecked things this morning. My engine/transmission is angled down at the rear at 2.5 deg. and my 10.5 rear is 0.2 deg. up in front. That comes to 1.8 deg. negative pinion angle... right? Side note the drive shaft is 0.2 deg. up at the rear When the adjustable upper control arms come in (and no-hop bars) I thinking set pinion slightly more down in front by adjusting pinion angle with driver side adjustable upper control arm and set a little preload with right (passenger) side control arm. Maybe one turn shorter on that side then see if it goes straight. Is this the preload you were referring to? Lower control arms are boxed, sway bar and poly bushing everywhere except body to frame. Thanks for the inputs! I'm considering springs and single external adjustable shocks up front. QA1 shocks look really nice but hesitant due to cost and possible fitment issues. Also considering shocks for the rear and keeping rear springs for now (suggestions?). I do have a set of air bags not yet installed.
I would try the umi lift bars I ran Lakewood lift bars and had no traction problems with a 4200 stall and you should consider advancing cam alittle more to bring up lower end torque ,also think a smaller tire you should be able to come out full throttle if traction is positive.
If you drew lines representing the centerlines of the tranny output shaft and the pinion shaft, they should be parellel at full throttle and the rear pinion line should drop downward when off the throttle. About the preload; I found that leaving the left side alone and using the right side for preload, prevented loosing my pinion angle setting. Also if the car pulls to one side at launch, use the right side arm to adjust for straight launches. Write down any right arm changes to keep track of where you are. Straight launches are more important than preload and you never know if the LOWER arms have perfect lengths and mount positions. Keep adjustments (preload or straight launching) on the upper right arm anyway. For pinion angle CHANGES, always do both upper arms with equal turns. Air bags...I eleminated airbags when I installed a Hellwig anti sway bar to frame/axle. With driver weight in front seat, adjust the Hellwig links evenly. The bar is so stiff, you won't need ANY preload on anything. Just adjust upper right control arm to go straight if the car tries to steer to one side at full power launch. Yea, love those .609 dia front springs. Most are .645 or bigger. If you don't get lift, install Global West Del-a-lum a-frame Bushings. Actuall, they are like bearings. New original rubbers locked my frontend down. Worn out bushings worked great but rubber was falling apart and one inner shaft was almost against the a-frame!!!!
Getting closer to actual work.... Which is likely the better setup for a low to mid 11 second `72 Skylark using drag radials and 3.42: #1. IC 37.2" with 183% anti-squat #2. IC 44" with 164% anti-squat The change above is with a 3" rise vs. a 2.5" rise to the rear of the upper adjustable control arm. My lower bar is up in front by 1.7" in both cases. I know the first scenario will hit the tires harder and quicker but am concerned what will happen after the initial hit? Springs and adjustable shocks next step.
Craig, for what it's worth awhile back when I was experimenting with the mounting locations on my no hop bars ( I have 5 holes ) at the track, I started with the second set of holes. Problem I had was the car would just hit the tires too hard. It was difficult to get a run in without any wheel spin. I decided to go with the bottom setting. This moved my IC fwd just a bit. The car responded better. Didn't hit the tires so hard and it made my sixty foots a little more consistent. I'm in your boat right now as my engine makes 60 more hp. My qtr mile times and mph are a lot better but my sixty foot times remain unchanged. They're the same as when I had 60 less hp. ???? ou: What rear coil springs are you running ? John B.
A good match for the 6204 front spring, is a Moog 5379. It is a good height, yet soft enough to help the 6204 front spring transfer weight to the rear. I gained significant traction on that rear spring (on the street). Street traction is a good way know your getting there. I removed my world famous Moog 5385 rear "Cargo" spring that is standard on Buick GS restoration jobs. These are tall and stiff. Installed the 5379 and got instant results... great spring for traction.
John, at least your 60' is better than mine... And good question on ride height with 6204 front and 5379 rear. I like the 6204 over the 5230 due to the tight headers to ground clearance situation with current setup. I can always cut a coil if really needed. Running stock springs for 350 AC car, as far as I know. I'm thinking the Art Morrison no hop bars for my setup, they raise the UCA rear point by only 2.25" giving me the best compromise I've found so far. Any recommendations on factory 4-link books on how to hook? I've heard about Dave Morgan's "Door Slammers" but wonder about others?
Ride height with ...........................6204 front and 5379 rear Rocker panel clearance (not frame) 10.0 front and 10.5 rear. Tire diameter.................................26" front and 28" rear Weight distribution...(3610 total).....1940 front and 1670 rear
