Quote:
Originally Posted by spctomlin
I realize I'm hardly the first person to ask this sort of question and the search tool would eventually produce all my answers but I've spent the last three weeks wading through threads and manufacturer websites and still haven't been able to make a decision. Pozzi's website and threads from many of you here and on Pro-Touring have been very helpful but much of that info is now several years old or what works for one didn't work out so well for another and there just seems to be so many different ways to skin the cat. I'm always concerned I'm missing that one critical piece of information that'll come back to haunt me after I've made all my decisions. I know a good number of you have been paying close attention to and applying this stuff for years now so I felt it would be in my best interest to pick the brains of those who have had their finger on the pulse, so to speak. I'm running short on time and need to come up with something soon (my mechanic is fixing to have to move on to another commitment) so any help you guys could offer would be seriously appreciated.
I restored the car myself back in the late 90's and at that time installed a 450 HP small block and Tremec TKO 5-speed, PST front end rebuild kit, Eibach 1' drop springs (500lb), Vette Brakes 5-leaf mono-spring replacement springs (175lb), KYB Gas-a-just shocks, 1" lowering blocks, South Side Machine lift bars, four wheel disc brake conversion that uses factory front discs and calipers and 11" Lincoln rotors at the rear with 80's GM A-body calipers, a booster/master cylinder from a 2nd gen T/A and Wilwood proportioning valve, Chassis Engineering weld-in subframe connectors, poly bushings everywhere (including body mount) and the car already had a Saginaw quick ratio box and big solid front sway bar (1 1/8" I'm pretty sure) when I got it. It rides on 16" Amer. Racing Torque Thrust D's with 7" up front and 8.5" in the rear shod with Dunlop Z-rated 225/55 and 255/50, but I'll want to update those eventually, too. My suspension budget does not include tires.
I did some tracking with the car back in '05 (NASA HPDE 1-4) and then went through some life changes that caused me to have to mothball the car. I recently swapped out the motor to a 383 (around 550 HP/aluminum heads) and, because I no longer have time to work on it (small business owner, single dad of two) have hired someone to get it running again. While he has it I'd like to do something better with the suspension than what I threw together some ten years ago (don't really want traction devices...but don't want wheel hop issues, either). It will mostly see street duty with an occasional trip to the area race tracks for HPDE or DE events and I'm done with the drag racing thing, so getting a killer 60' time is not anywhere close to a priority. I don't need the ride of a CTS-V (it can only get better than what I had with the lift bars, I suspect), I don't care about gee-whiz looking parts and absolutely will never be showing this car. I simply want to extract the maximum amount of performance possible from it for my stated budget (which could be stretched a bit if it meant significant gains). I'm ok with having to cut on the car a little so something like the G-mod is perfectly alright...especially if it means more performance for less money. I'd rather spend money on better tires than tubular control arms if that means better performance at the end of the day and I'm fine with leaf springs in the back but am not averse to a bolt-in 4-link if I can pull that off with a good shock set up and still have money to address the front suspension. Brake upgrades will need to be considered and it appears the 3rd gen Camaro brake conversions are a popular budget friendly mod....but I won't consider that part of the suspension budget and will address it down the road (it brakes pretty good as is).
So consider this a chance to spend someone else's money the way you would if you could do it all over again. I mean, everyone loves doing that, right? 
Thanks,
Michael |
Hello Michael,
Since you are on a budget here are my recommendations.
First: Keep doing research before spending the money. Don't limit your research to Internet forums either. Read the "the unfair advantage" by Mark Donohue, Chassis Engineering by Herb Adams, Tune to Win by Carroll Smith. All these books have sections pertaining to our cars. The physics hasn't changed.
Second: My opinion is that your car isn't very far from the goal you described, and it will be able to go faster for less than your budget. BTW the car Jeff described in his post is mine. It is a budget build and it works well. With that out of the way. Just tune and optimize what you have, and only replace what doesn't work. This will allow you to meet your budget goal. Big changes have hidden costs!
Here goes:
Nothing is incredibly wrong with your current setup. The biggest thing holding you car back is tires. Why not tune it to work with better tires? Are you bored with it? I spent 3 years in NASA Time Trials winning a Championship & setting a track record in my class TTF. I figured out that spending your points on tires as it yields the biggest result. Suspension is is important too make the tires work, but nearly as critical. Getting the spring rates right for roll control & balance is the most critical thing. Wheels & tires will get you will get the best speed per dollar. They are your big limiting factor. A good combo would be 9.5 wide wheels with the best tires you can put on. You can be plenty fast with this on your current setup, and not break the budget. For a fast street tire on a budget build try Federal 595R tires. I like BFG Rivals for street/track use. Better yet keep your current wheels & tires for the street & get a dedicated set of track wheels and tires. NT-01's are my favors tires they take loads of abuse & grip to the cords unlike other R compound tires.
For the front of the car: Camber, adequate suspension travel, and no binding are the keys. Make sure the control arm bushings are well lubed with poly bushing grease, dial in 2.5 degrees of negative camber, make sure you have at least 1.5" (with current spring rate) between the frame & the bump stop. If the bushings aren't in good condition put on Global West Delrin bushings. The camber level is a good compromise for street & track. Before doing the Gulstrand Mod read the section on setting up the 1969 Camaro of the "unfair advantage" 10 times before cutting your frame. Solid subframe bushing are a good addition & cheap as well.
The rear: Do you have wheel hop issues on the road course with your current springs without additional traction devices? If you do try softening the rear shocks. Set the ride height in the rear to be 6mm/.25" higher than the front. Or if you feel the need to change Global West L2 work well for me & others. Run stiffer bushings -poly is okay if that is what you have- in the rear shackles as they cause big rear steering issues at high cornering forces. The L2's have a higher rate than your current springs so the cars understeer/oversteer balance will be affected, so expect a handling change towards more oversteer.
Brakes: Add ducting & race pads to make your current setup work. I like Raybestos ST-41's for track use. Our cars are horribly hard on the brakes , so no dual purpose pad works for the big track. You will need to swap pads even if you go with larger brakes. The benefit of your current setup is that the rotors are cheap to buy. Run the most ducting you can fit in to get cool air to those brakes. On a '68 this is easy for the front, as you have 2 huge openings below the grill. Run racing grease in the bearings, as they will see loads more heat. The bearings will fail very quickly if you don't.
Spend the rest of green on track days & having fun going faster with you car.
Regards
DEC
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