DC&O Stack Injectors

[MCT]

Hey guys,

Be easy on me, I'm new here and am looking at a local Cobra that I will probably buy. It has DC&O Racing stack injectors. (I noticed the website seemed to be down)? The engine is a 302.

Anyway, I searched on here but could not find what I was looking for. The throttle pedal is extremely hard to push. The cable and all are fine and when you open the injectors and check it, no problem. Nice and smooth cable actuation. From what I can tell, and have read on another forum, the arm where the cable attaches is very short and does not give much of a fulcrum point to work off of. It just needs to be longer, which is what I may do. Has anyone come up with an idea for this? I have a couple but don't want to re-invent the wheel if someone has already come up with a fix.

Thanks in advance!

Marty

[Bob Cowan]

I'v never heard orf DC&O racing before today. But there are a few old pictures of their systems floating around the web.

It appears that they use a standard bell crank. If so, then you need to take a close look at how the bell crank is mounted, it's orientation, and how the throttle cable attaches. It could be something as simple as the throttle cable needing a little grease.

An IR system can be a bit finicky to get set up properly. They are very sensitive to things like balance, linkage design, and bell crank orientation. Much more so than a 4 barrel carb. 1/8" in either direction can make a big difference.

[MCT]

The unit is set-up just fine and the cable does not need lubed. It is an issue of not enough 'arm' length where the cable attaches. It is stock, and really a poor design when it comes to accelerator pedal pressure needed to actuate it. I was contemplating adding a bit of length to the arm where the cable attaches. Thanks for your comments, though!

[quicksand]

not familiar with that system, but maybe a go pedal mod would be easier?...just considering all the options

[Technic-Fan]

Originally Posted by MCT

The unit is set-up just fine and the cable does not need lubed. It is an issue of not enough 'arm' length where the cable attaches. It is stock, and really a poor design when it comes to accelerator pedal pressure needed to actuate it. I was contemplating adding a bit of length to the arm where the cable attaches. Thanks for your comments, though!

Just remember that a longer arm at the engine bellcrank will mean additional cable travel...and this will also lengthen the travel of the accelerator pedal throw. (Longer lever/pedal travel = less effort) So you could potentially bottom out the pedal before getting the throttle bodies fully open.

[Bob Cowan]

Originally Posted by MCT

It is an issue of not enough 'arm' length where the cable attaches. It is stock, and really a poor design when it comes to accelerator pedal pressure needed to actuate it.

Extending the bell crank out a little shouldn't be that difficult. You'd probably only need to add about 3/16" to make a big difference. The bell crank on mine is 1:1, and the pedal effort is perfect with a stock unmodified Mustang pedal.

By the poor design, I assume you're talking about the big throttle shaft and those bulky clamp on arms. That is a lot of bulk to be moving around.

How about adding a small spring to assist with throttle opening? I know that's contrary to common thinking, but I'd probably give it a try.

[MCT]

I was hoping just a little would do it. Good point on pedal travel, I will have to check it. It is very difficult to push, though I will also have to check the pedal to see where the pivot point is. Thanks for the tips!

[dallas_]

Another option is a mechanical linkage.
Some good threads here on how to do it. Pretty easy and you can make it adjustable to your specific needs.

Here is one thread on it: My version of mechanical throttle linkage

[tirod]

Perception that the linkage has little leverage is usually right. The trick is that when leverage is altered, so is the opening rate. Too much too soon gets the rpms up faster where the cam starts into the torque curve, and the pedal starts acting like an off/on switch.

Consider the entire assembly and all the potential adjustments, then you get a good pedal and appropriate throttle opening in a relationship that acts intuitively. It's something the factories even have a hard time doing. It won't hurt to sketch it out on paper, with the pivots included, to see how changing things can help or hurt. The whole thing is based on ratios of movement, 6" at the pedal becomes less than two at the throttle, with different arcs and radiuses.

It's partly the reason the factories use diminishing radius cams for the cable, like compound bows. Slow and easy to start, fast at full open.