Superformance Coupe Rear sway bars/ Modifying hood

[solly]

This a 2 piece question/

1) The current rear sway bars that came from the factory are 44.5 inches long, 1.25 diameter solid bars, with 48 spline ends. They attach to a 10 inch arm on either side. From a lot of searching the Internet and speaking to the folks at Speedway Engineering (manufacturers of NASCAR bars), the effective spring rate for this stock sway bar is approximately 486 lbs. per inch.

Advice from those who have raced this car is that these bars promote oversteer, and should be milled down to 7/8 inch (leaving the splined ends at 1.25 so they can still fit the arms. The effective spring rate at 7/8 inch, with 10" control arms is approximately 180 lbs/inch, a huge reduction. Anyone have any experience with this?

2) My new induction setup requires approx. 2 more inches of hood clearance. I'd hate to spoil the lines of the car by adding a scoop, but without that (or a bulge), I cannot get an air filter of sufficient surface area for the engine's needs, even with a K&N Xcellerator top. Any advice? Thanks

Has anyone done any hood modifications for more clearance?

[Woodz428]

Not sure about the sway bar. Dennis Olthoff has a larger lump on his hood to clear the induction system he runs. I can't recall for certain, but I think it has an air intake in the rear.

[Mike Simard]

That rear sway bar rate sounds much too high. On my regular Cobra, I used a Speedway 1" solid bar on a 12" arm which according to their charts is 272 lbs. It didn't necasarily have oversteer but if you were turning on a very uneven surface, you could feel the rear get loose because the sway bar wouldn't allow the suspension enough travel to keep the tire planted. Now I use a 1" .095 wall bar and the car feels just right. The chart shows this new rate to be 155 lbs which is almost half the old rate.
BTW, doesn't the coupe (FTF) have a nice suspension? It's nice the way the moved the control arm pivot points out to use a long control arm. I wonder what the camber gain per inch of travel is.

[CoupedUp]

WDZ,
You are correct. For Dennis Olthoff's One Lap car, he enlarged the hood bulge and has a rear facing air intake at the rear end of the bulge. Here is a pic (there are ones that show it better, but couldn't find one quickly):


In my coupe (FTF), I have the requisite 351w block with the requisite Edelbrock RPM dual plane intake. I am using a CV Products drop-base air cleaner that will allow me to run a 3" high filter. It's about all you can do without doing something drastic to Mr. Brock's beautiful lines...

Doug

[Woodz428]

Hey.. that's my Blue Coupe behind Dennis' One Lap Coupe.

[rcweingart]

DENNIS ALSO CUTS DOWN THE ENGINE MOUNTS ABOUT 3/8" AND THE TRANNY MOUNT ABOUT 1" TO LINE THE DRIVE SHAFT UP BETTER WITH THE PINION. THIS WILL GIVE A BIT MORE CLEARANCE AT THE TOP OF THE ENGINE.

WHAT INDUCTION SYSTEM ARE YOU USING? I HAVE AN EIGHT STACK ROUSH EFI THAT SHOULD FIT WITHOUT ANY PROBLEM.

[CoupedUp]

Hi Ron,
Congrats on getting your car - drop me a note when you get time and let me know how your build is going. Any pictures of the car?!

Doug

[DaveR]

Solly,

Using your numbers = 7/8, 44.5, 10 - my calcs tell me that you are going to have less than 40 lbs/inch. Wouldn't want to go to all that trouble for very little control.

[solly]

Straight from Dennis Olthoff: "grind rear sway bar to 7/8". Peter Brock told me to go as low as 3/4". Don't know why they made them so big in the first place.

Just found out today about lowering the engine and tranny in this email from Dennis. I have not yet experienced any diveshaft vibration:

Peter and others

The drive shaft needs to have some offset. All the cars we have done have no problem with vibration be it 5 or 6 speed.
The secret is lowering the motor 3/8" and the tranny 1". The side offset ends up being fine. If it was pefectly straight the u-joints would wear out in less than 200 miles.

We have redone 5 coupes already. All had a driveshaft vibration that was cured with our mod. The factory has now changed this as well.
Some customers never noticed the vibration. It is only felt under hard accel.

Cheers
Dennis.

Thanks for the input. My current induction setup is the pretty standard Performer RPM manifold, victor Jr. heads and a holley 770 cfm Street Avenger. Even with a 1.5 inch dropdown base the tallest filter I can get in is about 2.5 inches.

[solly]

The sway bars cut down to .875" oked out to about 170 lbs./inch at 5 degrees of twist. Haven't driven it yet, but I really didn't notice any oversteer with the original roll bar (because I played with the tire pressures to compensate). Still a big drop from the original bar's 460 lbs./inch (approximately).

Looks like i'm going to need to spoil Peter's beautiful lines and slightly increase the hood bulge. I don't know if I want a rear-facing "cowl induction" setup like Dennis' because of carburetor mixture leaning possibilities. Maybe a scoop and sealed carb. The stock setup just pours superhot underhood air into the carb, and without a filter top there is no way to get enough air into the carb with 3" high 14" diameter air cleaners. Air flow in cfm just about makes it even with the K&N Xcelerator top I installed. Smaller engines (I have a 427) should be OK the way it is.

Has anyone installed dedicated air scoops anywhere else on the body? If there is a way to pull in some cool air I can avoid messing with the hood. Or I can wait until November to drive the car.

[solly]

Does anyone know what the 2 scoops at the base of the windshield are for? What do they do? Could some ductwork be attached to them to pull in cooler air into the engine compartment?

[CoupedUp]

I know one is for the "cold air wall" that separates the engine compartment from the passenger compartment. This is why the passenger compartment and foot boxes stay nice and cool. Can't remember what the other one is for.

Doug

[RRD]

does anyone know the diameter of the front bar on the coupe? i have a much modified 435" all aluminum windsor powered griffith 400 , with 8.8 irs, which sometimes i hallucinate is a distant relative of the daytona...

thanks.

rd

[solly]

I believe it is 1 1/4" diameter, 38" length, with offset arms.

Rear is 1 1/4" diameter, 44.5" length, straight arms (arms are 10")