Throttle issues...

What type of linkage do you have? CB-style horizontal hex bar or vertical bell-crank?? (or none-of-the-above).

Regardless, it sounds as though where-ever the throttle cable attaches to the linkage, either you have a radii bind which doesn't allow the throttles to completely open or;

The throttle cable needs a shorter lever attachment to the linkage to allow more linkage movement given the length of cable movement. If it's CB linkage with an Empi cable arm (they both use the same hex bar) the EMPI arm is longer than a real CB and wouldn't let the hex bar rotate as much as the shorter CB arm would.

If you have a transition setup, meaning that the pedal cable goes to a sort-of bell crank lever over the transmission which, in turn, has a rod that actuates another lever on a linkage bar between the carbs. That transition lever over the transmission often has multiple holes on both the cable and linkage side and you have to play with it on both sides to get to the right combination of holes on either side that matches your WOT position versus the floored pedal.

Are pictures of the linkage(s) possible?

Its a bastard set up....Porsche 901 transaxle and a Porsche 911 engine with Weber carbs and VW pedals. So yes, there is a lever set up on the transaxle, one lever is connected to a cable (which has been shortened) which goes to a VW pedal then the other lever is connected to a rod that has a hump in it to get over the axle. These two levers are connected. The rod has also been shortened, or maybe broken, as it has been brazed at one point. The rod goes back to a lever that then connects to the Weber throttles.

It seems to me that perhaps the rod that goes from the trans back to the engine is too short yet there is no room for lengthening it. It's like something binds or maybe the geometry is not quite right and although I can get full throttle when I disconnect I can't when its all connected up. I'll try to get pictures tomorrow. I had two of those rods and two transaxles...I hope I didn't get them mixed up although I can't really see how that would affect it? I think I chucked the other rod..

Yup, sounds familiar. The rear (slave) rod might have to be longer, in order to match the corresponding throw of the master lever connected to the pedal cable. We used to have a similar set-up but the slave rod had a turnbuckle adjuster on it to allow fine adjustments for different carbs w/o changing rods. You should be able to measure the full throw available at the transition lever(s) to get a ballpark length for the slave rod, then decide where, on the length of the master lever, the cable should attach for proper slave throw, or it might be best done by moving the slave rod up or down the slave lever until you get the proper push length. I think you're probably close.

Here's some pics. First is of the setup at the carbs, second shows closeup of rod coming up from transaxle, third shows mess at the transaxle after I removed the front transaxle mount. As you can see in the second photo the rod hit the bottom of the cutout in the tin thus limiting its travel. I ground the tin down so the rod had more travel and this helped considerably, but you still have to push pretty hard on the pedal to get that last 1/4 inch or so of travel. Looking at the last picture you can see the hobbled up mess that passes as the throttle cable...I'd really like to clean that up somehow, maybe get one made. Anybody ever deal with this place? http://www.flanderscables.com/

Looking at that last picture I think the issue may be that I could shorten the rod going back to the carbs and then lengthen the throttle cable. It looks to me that when I push down on the pedal the cable pulls back the lever but eventually it can't pull any more. If the cable were lengthened then I think it would have more travel and an easier travel too. Make sense or any other ideas?

At the transaxle is a pivot point with a bushing in it. Make sure the bushing is spanking new. As you have throttle full from the top, obviously the issue lies between your foot an the top. Even a little slop in that bushing, due to the angle of transition, multiplies out to quite a bit at the engine.

Start with the bell crank at the transmission, and go forward. Next stop in the little journey of fun is making sure the throttle cable is the right length. Perhaps the picture is a bit off, but it rather looks like there is some slop there. Pedals are also a likely point, but the bell crank bushing and throttle cable are cheap an easy - the VW pedals may require a little more work if the issue is that end.

angela

The pedal, when disconnected from the cable, has more movement than when connected to the cable. Its something to do with the bell thingy and the cable me thinks. I'll keep plugging away at it but I'm supposed to renovate a bathroom this week prior to the wife having buddies over next week. Priorities.

The cable pulls, right, not pushes? In your second photo it looks like the small bellcrank type setup won't have much travel if everything is perfect. Add in some slop, as in the worn bushing(s) that Angela speaks of, and it could result in that place alone causing a problem in full actuation.

Wait...you said it works OK at the back. Ignore me, I was being stupid, again.

You're right - it looks like it was built up by Rube Goldberg, but MAN, would I like to be messing around with that car as my own!

Go through it link by link making sure that each change of direction can move through a full arc where it should....and Good Luck!

I would say you need to shorten the tranny rod to the engine and lengthen the front cable so as to change the angle of the bell crank.  The easiest thing may be  to mount the cable further up on the pedal arm to get more overall travel. 

I did exactly that and it almost opens all the way now.  I'm going to leave that and turn my attention to other matters such as installing the new windshield.  I think that's the last thing to be done prior to getting it safety checked and then back on the road.  I can attend to other things after I get to drive it again.  Other than a few short spins last year its been over 8 years since I've actually driven the car around.

Throttle problem solved.

 

After screwing around with it I finally decided to do a cable hook-up, bought a kit for a VW and after some mods and other parts such as throttle cables from Harleys and an MG I now can get the carbs fully opened.  What a huge difference!  The 911 2.4S engine now really sings a different song.  The other issue with the throttle was the VW pedal, there just was not enough travel to fully open the Webers.  The solution was to remove the little tab at the front of the roller lever that stopped it from moving any further and to reshape the rear of the pedal as it has a profile that prevents any further movement.  it is set up now so that when the pedal hits the floor the carbs are fully open.

 

Glad you got it done... hope it didn't take all year though.