Hello all,

I am considering building a car for the local 1/4 mile paved high banked circle track. They say its the fastest in the world. The class is called Thunder Stock. I have pasted the suspension rules below.

13. Steering & Suspension: Steering must be STOCK. Absolutely no modifications. Camber is limited to a maximum of 5 degrees. Maximum sway bar size is 1.250 inches. Front control arm bushing material is unrestricted, stock dimensions must be maintained (no heim style joints)
Rear control arm bushings are limited to non-offset rubber or urethane (stock dimensions ONLY)
Minimum ground clearance is 6". Ride attitude must be maintained. Any spring rate is allowed.
Non-remotely adjustable spring spacers are allowed. Stock steering column is required, any steering wheel is allowed. Coleman HD front steel hub and rotor assembly is recommended.

The minimum weight is 3200 pounds with driver. The class is entirely Chevies. Last week the fast qualifing time was 14.469 seconds.

I have another thread asking about an engine combo. What would be a good car to stuff it in? A, B, or even FMJ? Would a B body work better, if they weight was brought down, due to it greater its width and longer wheel base? An M body might be the least expensive but how would the sideways t bars work?

Any input is greatly appreciated.

Anderson Speedway or Slinger Speedway? I've heard one of them recently stole the fastest 1/4" mile oval title from my track, I25 speedway, in Pueblo Colorado. Our record was a 10.48 from a Super Mod car back in '92. I don't think we've had any of them back there since then.

Biggest problem you will have with running any mopar on a high banked oval is t-bar sizes. The biggest you can stuff under a B body is 1.22, which is 400# wheel rate. This translates to the equivilent of a 800# spring for the chevy boys. When I was running at I25, we were running 1000# RF spring to be competitive. If your track has some serious banking, you will need the big spring rates to avoid bottming out the suspension, or you'll run at the back of the pack. Do you know what the fast cars in that class are running now?

You can sort of compensate some with sway bars sizes, but since you have a rule limiting that, you're in a pinch. Of course you could go out on a limb and run two smaller sway bars stacked on top of each other, but that would likely only get you through one night before they outlaw it.

FJM cars would be a bad choice because of the t-abrs they use. Way too soft. A body may work, but again you have a 3200# minimum weight rule and they can only runa 1.18 t-bar, which is 370#, so your giving up 30# of rate comapred to a B body.

Do you have wheel base limtiations to consider at all because they may dictate whether you can even consider an A body. Most entry level racing classes spec this to try and get larger cars out in those classes.

The rules say 1965 or new American cars, 108" minimum wheel base 3200 pounds minimum.

It is Slinger Super Speedway. The fast qualifier lap time was a bit less than 14.5 seconds last week.

Seems to me the biggest hurdle is tb size. I run both a and b/e bodies never noticed the hex sizes are different. The rule quoted here says " no modifications", i understand that to refer to steerong only, how hard would it be to switch to b hex receivers over to an a body and have firm feel make up some custom a body tb's?

I think Firm Feel will make you a 1.24" A-body T-bar.

Whats the coleman hub rule? Is that a specific hub? What part number? Sounds like that place puts a lot of load on the right front. -makes sense if it's the fastest 1/4" bowl

You could control the roll with shocks too. Do the shocks have to attach to the factory points and method or can you weld bungs to LCA and roll bar?

Run a FMJ spindle on the right front for most camber gain. Can you run the rebuildable Howe upper ball joints? If so might experiment with the taller pins for more caster gain when starting with 5 deg max static.

Run fitted Delin bushings for smoothness with no binding.

" Non-remotely adjustable spring spacers are allowed."

So this means weight jacks are allowed?

What are the specific engine rules?

Any picture of the suspension of some of the cars that are competitive in the class right now?

Thanks for all the replies guys! I looked up the Coleman hub, I think what they are refering to is for the GM fellows.

http://www.colemanracing.com/Hub-Aluminum-GM-Mid-Size-P3550.aspx

I emailed the track for the rules and they sent me a Word document. I do not know why they are not on the web site. This class is intended to be a lower cost way to race and the rules say you cannot do much modification.

I will talk to some of the racers and see if they are willing to share some information with me. I will also visit Allpar and do more web snooping to see what I can find. Moparts is my default stop!

Thanks again everyone.

Moparchat is where quite a few Mopar circle track racers hang out. I'd post this question over there. The 73 C-Body spindle is taller , uses the same upper ball joint, bigger brakes, and will use stock lower ball joints if you slightly machine/slot them. I work as a tech inspector at a local Nascar track and we have had a few Mopars built. Research the Chrysler kit car for some good idea's. Truth is most tech officials are mainly chevy guys and some ford but know next to nothing about Mopars.... the ball is in your court!

http://www.moparchat.com/forums/forumdisplay.php?f=40

Back in the day, we used to take torsion bar from a 2wd chevy truck and have the hex resized to fit the Mopar. Mid-late 60's truck maybe.... I cant remember. They were big bars.

Alot of tracks require what they call a safety hub on the right front. Usually has a larger spindle and bearings. Again, way back when, the hub was much like a 3/4 ton full floating rear hub on a truck.

sorry ,i say dumb things-why not use a travell limitter on the lca and wind the bar tighter against it?seems like a good way to stiffen up the right front.i bet the PHD guys drill me on this

also you can play with the length of the sway bar ends to get more swaybar out of the same size bar.

also if you like cheeting-couldent a sneeky racer make a swaybar act as an auxilary torsion bar buy welding it solid out of teck sight?

Use a C body torsion bar socket in both the control arm and cross member with a custom torsion bar from Firm Feel. I think the hex is 1.5".

Good luck with the track and car setup.. I raced my Challenger there -- at Slinger -- with a Wisconsin autocross club about 30 years ago. at that time, my Challenger was running F/Stock with the SCCA Solo II program. Its a fun high-banked race track... with an infield to also run on.

I have done a litle bit of research and the the GMs use front coils with a spring rates of 750 to 1000 lbs/inch. I seem to recall a factor of 2.2 (?) between the spring and wheel rates for those cars so the wheel rates would be 341 - 455 lbs per inch but that could be wrong, does anybody know the ratio between the spring and wheel rate on GM G bodies?

The stiffest FirmFeel bars are for an A body at 370 lbs/inch. Those are 1.18 diameter. 1.25 bars in the a body length would be stiffer but that math is beyond me.

Here is my goofy idea. The shock absorbers must fit in the stock mounts. Could a coilover shock fit that would add more spring rate than the available T bars can provide? Or is that just crazy?

Thanks!

i heard a rumor that lowre control arm bushings are a problem in roundy mopars?

i was thinking or tuning the sway bar into a pair of transvers mounted torsion bars by lokcing it up in dead middle of the k frame pass thru.volare meets duster,how would that lock up the suspension?

I'd have to go back and try to find my notes on my set ups, but I seem to recall that the GM arms I used were either just shy or just over a 50% motion ratio for the springs. I'd imagine metric chassis are similar, but may not be exactly the same as the earlier F and X body stuff I was using. 50% is a close enough ball park to say a 800# GM spring is a 400# wheel rate.

I know a 1.22 41" B body bar is 400#. Not sure what a 1.22 37" A body bar would be, but it would be higher. Of course, with a 3200# minimum weight requirement, this would give the nod to an A body potentially being more competitive than a B body.

When you say coil over, I assume you are talking about a clamp on coil overload assist and not an actual coil over racing shock/spring combo. The former is a band aid for loads, the latter a component specifically outlawed by the rules requiring stock, make to make suspensions utilizing OEM pick up points. Yes, you could clamp one of those overload units in place, however, the shock tower is not designed for that amount of loading so eventually you will bend something. I also assume they do not provide rates on any of those so it is a swag on what amount it will help. There is a motion ratio involved with the shock mounting locations, so if they claim a 500# load capacity per inch, it may only provide an effective rate increase of 50# at the tire contact patch. Will that be enough to help, maybe. However, you still have tech inspection and rules compatibility to deal with and if the overload spring is the crutch that makes you competitive, I'll put money on it being made illegal after your first main event win.

Turning a sway bar into a torsion bar is an interesting trick that could be effective. The mounting would present certain challenges since you cannot clamp a round bar tight enough to provide a consistent spring action. The hex ends on FJM cars was huge to absorb the leverage produced. I suppose a hex mount inside the K frame to match the t-bars hex would work, but then you would need to bend the opposing end to simulate a sway bar and mount in a manner that won't deflect. That might work for a while. I'm also not sure how that would impact roll couple percentages since you could then radically alter it from side to side. Eventually, someone will figure it out and again, likely outlaw it.

What about using a c-body box, pitman and idler? they would quicken the steering rate quite a bit. Tim

Yes and combine with the C body hexes would allow much larger t-bars. However, these would be custom t-bars. There aren't a lot of custom t-bar makers out there. Firm Feel may play, but you would have to ask if they can even make anything bigger than 1.24 as they do not advertise larger sizes for C bodies already, so there may be limitations in what they can make with their tooling.