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best suspension set up for autocross

22K views 20 replies 10 participants last post by  tony@roadstershop 
#1 ·
what is the best suspension setup for a '77 chevy short bed stepside with a 2" drop and should i get a bagged set up? I'm a student at wyotech in sacramento, ca in chassis fabrication and intend on autocrossing my truck, in the years to come, at the goodguys in plesenton, ca.

any tip and trick to setup a stock system would help greatly, due to the whole starving student.
 
#2 ·
Lots of camber. Play around with different front and rear sway bars to get it as neutral as possible - too big up front and it understeers (plows), too big in the rear and it oversteeers (tail happy). Biggest brakes you can afford, then save your money for some "R" compound tires. Most courses you will not get above 2nd gear, but you will be close to redline - if you don't have a rev limiter, be careful in the 'heat of competition'. Your 2" drop will help lower your center of gravity.
It's not a suspension trick, but a harness type belt will help you stay put in your seat - hard to cut tight corners when you are sliding all over the seat.
Check with your local SCCA to see if they might be holding an Evolution Driving school. Three one-day classes that don't cost a fortune and will greatly improve your driving. You and the instructor will be using your truck so you will know exactly what it and you are capable of (also a good person to ask about how your truck handles). Sounds like fun.
 
#3 ·
should i stagger my rim/tires? i am currently looking into LMC truck for my sway bars. any suggestions on the size to start with. i will be getting a 350 sbc and th400 for $400 and will be tearing it down to see if everything is good. might bore it and turn it into a stroker, but that will be later down the line i currently have a 307 cu.in. and th350. with a hard reverse gear.

unfortunatly i still have to smog it so i don't think that i can 'blow' it. i was also thinking, just thinking, if a turbo will do. im just wondering if the turbo lag will hurt me but if you say i will be near redline the lag shouldn't affect me right?
 
#4 ·
I don't have a recommendation on a starting point for the sway bars - sorry. You will be topping out at redline at points on the course, but you need fast throttle response when you are coming out of tight turns. Try to keep turbo lag as brief as possible. I don't know if making a TH400 a manual shift is hard (other guys here will know), but a surprise downshift coming out of a turn might end with you murdering a few cones.
Stagger won't help, you need to turn both ways.
I don't know if GoodGuys runs classes the same way the SCCA does, but some mods may put you into classes where the competition is tough. I'd suggest checking their rules then shooting for a certain class.
For example, my daughter ran her GT Mustang - would have been F/Stock, but because she had adjustable shock towers to give her more camber, that put her in F/Modified - much tougher class.
 
#5 ·
suspension mods.

An old Friend, Bruce Cambern, retired head of Ford racing, set a record no one has come close to with his much modified Cobra in the 2009 Optima, check out the Utube video, He redesigned the suspension for the third time I know of, He has posted a lot of info on the Club Cobra Forums. and posts as #3170, The Vin of his 66 Cobra. A lot of the Autocross courses in Michigan used to make you do 2 tight loops around a cone. He had a A/C throttle positioner solenoid so he could just flip a switch to a pre adjusted RPM instead of trying to foot feather the gas pedal. Since the front suspension compresses in a hard turn the outside de-cambers and leans in, wanting to turn in. His suspension design has the tires do a little toe out VS ideal akerman angles,, He still ocasionally races in Northern California, but says at his age doesn't like to trailer all over the country like he used to. If you see him at a track he might give you a few Ford Secrets. you won't be in the same class ! !
 
#7 ·
Cool, about the Ford Cobras.

For the Chevy pickup truck, just know those suspensions/steering are from the early sixties and are some clunky stuff. You'd do better with an '88-up, but if you've got the truck and you're a student anyhow, what's it matter...

The drop spindles are good, then cut the springs so the lower a-arms are about level with the ground (just un-clamp the a-arm inner pivot bars to drop them and pull the springs out). Swaybars are going to be vital, as a practical rule find the biggest front one you can find (maybe a stocker from a heavier truck) then "tune" with the rear, finding junkyard stuff you can adapt in and change until you get neutral handling (front and rear let go at the same time) or whatever it is you prefer. You may need no rear bar at all with your leaf springs and light tail. If it wallows around much, get shocks from a 3/4- or 1-ton at the wrecking yard. There, you've just spent $100 (if that) and you're off to a start. Now have the fattest tires you can pony up for, at least P265-60R15s on 8" wheels. Finally, take it out to a parking lot and drive it like a crazy man, with somebody taking video. When you watch it later, see if the front tires are leaning out too much? (You may need to give in some negative camber or lower it a little more just for the sake of the geometry.) Or anything more. In the pre-video stone age I used to have friends drive by me in my own car so I could watch and see what it was doing.

Turbo motor? Nnnnn... I wouldn't get too far ahead of myself. A season actually out there with everybody, and you'll be in a better position to judge what you need, or just want.

With that, go out and get a good chassis book and learn the basics because it sounds like you're going to need them for this and school. When I was a kid I had a '67 327 Nova which was possibly one of the worst handling cars on the planet. As a solution I bought a book How to Make Your Car Handle by a guy named Fred Puhn, couldn't figure any of it out and none of it seemed to have practical application for me, but it still sounded better than all the bizarre-*$$ advice I was getting. Two years later I knew that book by heart, understood the principals and had one of the faster cars on L.A.'s Mulholland drive (no it was not the Nova). Good handling cars became an endless source of pleasure for me and 30+ years on I still really enjoy the handling (and fabrication) aspects of cars more than any other thing such as engines, and it started with going directly to an expert who took the trouble to accurately lay out the basics for guys like me, I hope he made some good money off it.
 
#9 ·
For the Chevy pickup truck, just know those suspensions/steering are from the early sixties and are some clunky stuff. You'd do better with an '88-up...
I'd look under those trucks again.

You are apparently thinking of the 1960s trucks with the "truck arm" suspension. The 2WD versions of the 1973-87 trucks have virtually the same suspension design as the 1988-98 2WD trucks - upper and lower A-arms in the front (stamped steel), worm and sector Saginaw steering box, and parallel leaf spring rear suspension. Yes, the front suspension pivot points might not be ideal, but that can be altered with some work.
 
#8 ·
lower it, loose the rake, solid metal bushings in the a arms
AFCO Racing: Shocks, Springs, Cooling, Brakes

fully adj shocks remove a leaf from the rear spring pack,
biggest tire you can stuff under it. and afford,
1973-87 3/4 ton front sway bar, box the lower a arm
run the tuffest bushings you can in the sway bar ends and tune with different bushings in the frame mount bushing cases.
add a little ballast in bed right infront of axle.
remove as much wieght as you can from behind the rear axle,
move fuel tank to pass side to balance driver wieght.
move battery to under bed before rear axle,
if track only remove everything you can to make it lighter..
solid tie rod links
some have drilled the crossmember to add 2 extra u bolts to the lower a arm mounting for a total of 4 per side.
adj. proportioning valve for rear brake bias
rear disc brakes
read
How to Swap GM Rear Brakes to Discs - Car Craft Magazine


IROC REAR SWAY BAR INSTALL
Camaro sway bar install - The 1947 - Present Chevrolet & GMC Truck Message Board Network
 
#12 ·
WOW, getting a little warm in here. haha. Thanks for all the info gents'. Although, i would like to race and win, I still want to DD my baby around the street and have a good ride, and not feel every pot hole in california. Is there a decent pair of coilovers that i can purchase to effectively tune the front togo back and forth from street to race, or maybe a quick swap at the track?
Like I stated earlyer, I'm a starving student and don't own, have access to, a welder so fabrication is out of the question......for now.
soooo, no on the turbo what about supercharger. I will be getting a 350 and before I just throw it in, I'm going to be taking it apart, and boring it out if possible, to see if there is any damage to the block and/or components.
 
#15 ·
With no money and no fab skills or equipment I will recommend this.
1). Keep the 307 and TH350.
It doesn't take a ton of HP to do an autocross course and the 307 with a few upgrades will be plenty strong for this.

2). Rebuild the stock suspension with a 4/6 drop and polyurethane bushings.
2" spindles and a 2" coil in the front with a flip kit in the rear.
Lowering the CG will do more for the handling then you realize.

3) Add some decent sway bars.
Go to Hellwig or one of the other aftermarket shops for these.

4). New shocks will be requisite when you drop the suspension.
Go with a known manufacturer and stay away from the "low rider stuff".

5). Put on a set of low profile tires and wheels.
!7" wheels will work well and go as wide as will fit. Keep the front to rear stagger to a minimum to reduce push as you enter a turn.

6). Steps 2 & 5 alone will make vast improvements on the way your truck handles. Do those first and work up from there as your skills and money situation improve.

7). As you are making these changes the truck is still drivable and you are learning, so take small steps to begin with.

8). Have fun doing it!
Mark
 
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#16 ·
You could use an adjustable shock, just not coilovers. A supercharger is more manageable than a turbo for autocrossing, but can get expensive. I focus on handling to start with, you can always add more power later.
I looked up the Goodguys autocrossing rules. The event at Pleasanton is the only one they have where your truck is allowed, otherwise it's too new. https://www.good-guys.com/events/goodguys-autocross
One class for all the trucks means you could have some tough competition, but I know from experience you don't have to win to have a blast cutting corners and making cones fear for their lives.
 
#18 ·
I wouldn't discount the 60-72 truck arm suspension in the rear. Look at every NASCAR and NASTRUCK out there. They all use this truck arm setup. For handling, they work VERY well. For hauling a heavy load, not so much, hence GM dropping them in later years and making leaf springs an option during these years.

Your biggest problem is going to be weight transfer. With a light back half of the vehicle, getting it to hook up coming out of corners will be the hardest part. A big thing that helps that is an engine set back. Getting more weight moved to the rear and off the front will gain you the biggest benefits. The other problem you have with a truck platform is frame twist. Until you get into later years with boxed frames, most open C types just have too much twisting action which make dialing in a suspension very hard.

Another trick when I used to autocross was to dial in a little toe out. (1/16"). This would make turn in quicker but a little more twitching in a straigth line for daily driving.
 
#19 ·
When one get serious about autocross one can spend a great deal of cash on suspension..We used to take a whole box of springs with us to the track when we were doing test and tune..As well good bucks were spent on shocks that are adjustable..Sway bars are a whole nother story to get the balance right on a particular rig,,

All is not lost though just get out there and run the truck study and make mods as the budget fits and someday you will run up front..

Sam
 
#20 ·
thanks mark,

i will be swapping out the 307 to 350 due to the fact that i still have to smog the truck, california....meeeh. seeing that they only made it till '74 i can't have it in the truck. the th400 is a plus that im getting with the 350. package deal for $400. (i will r&r both of them before putting them into my truck)
 
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