Upgrading Brakes and suspension

cobra427mnsi · #1 (**permalink**) 04-21-2004, 08:02 PM

Don

My CR is a '92. I have the Mustang II front end with the 11" rotors and Camero calipers. The rear end is a '90 mustang 8.8. The master cylinder and power brake booster are Mustang II.

I need this car to be able to stop much better than it does. What would you recommend ? Do you sell the upgrade parts? If not, do you have part numbers and suppliers ?

Thanks
Paul Hopper

dscott · #2 (**permalink**) 04-22-2004, 07:13 PM

Paul, what you have should work great. What type of problem are you having?
Don

arctic-snake · #3 (**permalink**) 04-28-2004, 09:15 AM

I have virtually the same setup as Cobra 427. I have to practically use both feet to stop the car. The vacuum lines are good. The check valve is good. The pedal is firm with no fade. I have recently installed a vacuum reserve tank with little/no effect. The pads are good. I have the vacuum line connected to what is shown by the carb manufacturor (rear base of carburator)to be manifold vacuum, however the vacuum is lowest at idle and increases as throttle is opened(ported). I suspect the booster is bad but I would like a second opinion before I go to the trouble of removing it. Any thoughts?

petek · #4 (**permalink**) 04-28-2004, 09:40 AM

You mean to tell me that you are driving your Cobra in April? Global warming and break up occured in Fairbanks before June???

(My folks and a couple of my sisters live in Anchorage. I lived there back in the late 60's / early 70's ... beautiful place!)

Ok... back to Cobras...

I've got the same thing going on with my CR. I've got a vacuum canister, good vacuum, booster seems to be working, but the brakes are nothing like the brakes on my Mini Cooper.

Like you, my Cobra has a nice pedal feel, not spongy. Stopping the car just requires all sorts of effort -- heck it is nearly impossible to lock up the tires unless I really but the boot into it!

On another thread I asked about 11" brake systems thinking that an 11" brake might give me better stopping power.

Ideas Don?

dscott · #5 (**permalink**) 04-28-2004, 02:39 PM

OK, here's the deal, remember I didn't design this system. For optimum braking the proper pedal ratio should be 6 to 1. This would mean for every 100lbs of force on the pedal it would multiply by 6 to the booster and master. The CR design brake box has a 2 to 1 ratio which means you have to drive the pedal as hard as possible to get any brake action. I have redesigned the pedal box and pedal to achieve a 6 to 1 ratio. I have not tried it yet but I have a car on the hoist that I modified and I also sent out 1 to a customer. We should know this week if it works or not. If it does then all that will be necessary to modify yours is to remove the pedal box (4 bolts), drill a new hole 2 1/2" lower for the pedal pivot and install a new pedal that I will have made. I'll let everyone know when we try it.
Don

petek · #6 (**permalink**) 04-28-2004, 08:38 PM

.... ok, you've had enough time. Did it work?

Thanks for continuing to improve the car Don!

arctic-snake · #7 (**permalink**) 04-29-2004, 12:20 AM

Yea Petec the streets are dry....warm enough? well that's a matter of opinion, I'd wear a snow suit if I had to.

Don,
That makes a lot of sense considering where the actuator rod is located on the pedal. Looking forward to the revision. I just may buy the whole pedal box assembly from you. I don't like the pedals and I read that you are using the AC pedals from FINISHLINE. My brake actuator rod has been spot welded to the pedal link, which I don't like either. Do yours come with an adjustable link? Also my accelerator pedal doesn't have enough travel to open my secondaries all the way and the offset from the brake and clutch pedals is excessive. Having a donor accelerator pedal that has been cut in half looks cheesy...having my carburators' performance cut in half is unaccaptable. I have been considering using the three pedal underslung configuration from AP RACING and just eliminating the power booster alltogether. If their pedal box was a 1/2" smaller I would do it in a heartbeat. Would you mind posting a picture of your pedal box and pedals (installed)when you have completed the fabrication? I have included a composite showing the accelerator offset and the spot weld on the brake pedal actuator. Is the booster actuator rod an integral part of the booster or can I replace just the rod with a two piece adjustable link?

dscott · #8 (**permalink**) 04-29-2004, 07:21 AM

arctic, the pedal box won't change in size. The proper configuration for the box is to use a 1974 to 1978 Mustang II booster. The box is setup to accept it without any modification. I don't know why someone would have cut and welded yours unless it's not from a Mustang II. I would definitely change it. You are putting a lot of trust in someone else's welding ability. The rod is a separate piece but not available unless you find a salvage yard unit. You should be able to bring the gas pedal up by shortening the cable unless it is a stock Ford unit. If it is I would change to a Lokar universal cable and bracket. It will let you set the pedal for full throttle by adjusting the cable. If you have enough room to the right of the gas pedal you can cut off the outside edge of the mounting tube and use it as a spacer to move the pedal to the right. I do use the AC pedal for the gas.
Don

arctic-snake · #9 (**permalink**) 04-29-2004, 10:41 AM

Hi Don,
Thanks for the reply. I know you have a business to run and I do appreciate the time you take out of your schedule to help us out. The top end of the gas pedal is hard up against the firewall(when throttle is released), I have adjusted the cable as much as possible(it is a LOKAR). I can push the pedal until it hits the positive stop (adjusted down fully)on the firewall. I will look into an adjustable accellerator pedal or buy the AC pedal and bend it if needed to get the travel I require. The pedal offset I refer to is front to back,not the relationship across. The gas pedal is about five inches deeper in the footbox than the clutch/brake pedals. Looks like my booster needs to be changed out either way. I'll be waiting for news on the new brake pedal.

Thanks again

dscott · #10 (**permalink**) 04-29-2004, 10:57 AM

arctic, the pedal rod must be bent if you can't get full throttle. Normally there should be 2 or 3 " of play left when it is set proper. I can send you a new pedal rod or if you post a side view picture I can tell you if it's bent.
Don

petek · #11 (**permalink**) 04-29-2004, 11:17 AM

Is there no attachment point closer in on the carb side? I know there were a couple of attachment points on my ProJection, I just chose the one the gave the best travel.

arctic-snake · #12 (**permalink**) 04-29-2004, 11:40 AM

Don,
I have some errands to run this morning but I will try to get a side shot later today. I would be happy to purchase whatever parts I need to remedy this problem. Right now my brakes are my biggest concern. No point in having WOT if I have to practically coast to a stop

Petec,
I have adjustment left in the cable, that's not the problem. I have adjusted the cable to the point where the top end of the gas pedal is hard up against the firewall. If I tighten the cable any more than I have, the butterflies on the carb will start to open. I can press the pedal to the floor and my secondaries will not open fully, It's a matter of pedal travel.

TC Cobra · #13 (**permalink**) 04-29-2004, 11:49 AM

arctic,

I think what petek was referring to is the throttle lever (carb) itself. Usually there is more than one hole to connect the cable. If you use one closer to the throttle shaft itself, you'll have more movement of the butterflies.

Worth a try!

Dwain

petek · #14 (**permalink**) 04-29-2004, 02:00 PM

Dwain, yup, that's what I was talking about.

arctic-snake · #15 (**permalink**) 04-29-2004, 03:35 PM

Ah, I see what you meant. I had allready adjusted the secondary linkage. There is really only two settings. One allows for a progressive rate and the other is a one to one. I solved my own problem(who'd imagine) I reworked the pedal/cable fitting and massaged the pedal a little. Should be able to hit Mach I now. Now if I can get the dang thing to stop as fast as she goes. Thanks guys, I appreciate all the imput. Truth be told I think I enjoy working on my Cobra almost as much as I enjoy driving her.....I said almost.

petek · #16 (**permalink**) 04-29-2004, 08:05 PM

Yeah, hurry up Don! We want better brakes!

Ok, so we get a group of Cobras together, head up the Alcan, aim for Tok and then down into Anchorage. Then out of Anchorage to Haines Junction, pick up the Ferry down to Prince Rupert and then back to the U.S. Anyone interested in a road trip?

petek · #17 (**permalink**) 05-05-2004, 07:57 PM

How did the test go Don?

I've been thinking about what you were saying about the pivot points and such for the brakes. Are you dropping the pivot point for the pedal down and moving the brake attachment closer to the pivot point?

Art Burtt · #18 (**permalink**) 05-06-2004, 07:12 AM

I had to heat and bend my gas pedal lever over to the right to make it easier to drive. Getting that little snap ring back on the clevis pin with the steering wheel and seats in was a back breaker. I need a skinnier body!!!

dscott · #19 (**permalink**) 05-06-2004, 07:22 AM

The car will be off the hoist today so I'll let everyone know if it worked or not. I did move the pivot point down and shortened the pedal.
Don

arctic-snake · #20 (**permalink**) 05-06-2004, 09:47 AM

Don...You DA MAN !!! Let us know the results.

Art...I know what you mean buddy. I felt a little like a circus act when I was working on mine. Who needs Yoga anyway. I ended up laying on my back with my feet on the roll bar. Took me 10 minutes to get up and out.