TheSamba.com :: View topic - Bellcrank vs crossbar linkage

Wed Oct 19, 2005 7:34 pm

I've fought and struggled with cross bar linkage on my engine for months now. Almost a year! I started looking at the bellcrank linkage and thinking about it. I had the CB crossbar linkage, and went to the CSP bellcrank linkage.

Simplicity. There are very few points which can cause problems.

Corrosion resistance. The whole thing is made out of stainless steel, and the welding work is very very nice. I used to weld a lot of stainless, and I know what it takes to get it this nice.

Consider:

For joints, there are a total of 4 socket ends. There are 4 socket ends in the downrods alone on crossbar. That does not mention swivel ends and centering springs.

The long length of the rods removes a very significant amount of imbalance due to non-linear motion.

Adjustment - there is only the socket ends to have slack.

Cleaning and lubrication - with proper maintenance, there is no reason I can see that it won't last a long time. You can snap the swivels out of the sockets on the ones I have, and clean it all really well, and dab grease into the socket and snap it back on. Try cleaning and greasing heims, like the ones on the downrods I had on the crossbar. Those things were rattly and loose from the day I put them on.

Straight manifolds - with straights, the crossbar has one downrod translated out (left side) with a spacer shaft between the lower downrod and the carb throttle. This causes a moment about the throttle arm, and flex. I couldn't get rid of it, even taking the return spring load off the throttle arms. The left side would also sort of "stick" and then when it started to move, the moment spring action on the throttle arm would cause it to pulsate slightly at slightly open, due to the vacuum signal working on it. This also dumped extra gas down it by way of the accelerator pump. Hard to deal with this. I noticed that when I swapped my A/F ratio changed too! Riddle me that!

So now with the CSP linkage, the bellcrank has dual bearings, to keep the bellcrank stable. I took it apart to add an optional return spring (I recommend it), and looked it over. The sealed bearings look like really good ones. The unit is very rigid.

Complaints:

From an engineering standpoint, the bellcrank piece appears to be weak in the mounting department, in that it only attaches by ONE mounting point. With a little more thought in engineering, they could have made it at least two, maybe three, to make sure the plate was mounted very rigid. But when I got it installed, it does seem very rigid, so I will just keep an eye on it.

The bellcrank unit mounts to a bracket, which mounts to the case. The bracket is punched in a press and then it gets sent through a press brake for two passes. One of the punched holes (where the centershaft of the bellcrank assembly is right next to where one of the brake bends is done, and it warps the hole slightly, raising the edge of the hole up on the left side. This causes the bellcrank unitl to sit on the bracket slightly cocked to the right. about 3-5 degrees in the case of the one I got. I just put the bracket on a surface grinder and ground it down flat and true again, so the bellcrank would sit on it straight up and down - worked perfectly.

I'm no idiot when it comes to mechanical things.. I gave the crossbar due process. I adjusted the damn thing twice a week just to keep my carbs synched. Next time I will go bellcrank. The price was right too

Wed Oct 19, 2005 7:48 pm

Hail bellcrank ... Hail Gracchus! Glad it worked as well as you predicted. Keep the info going on the mount situation. Amazing ... and your engine lost a little weight in the process.

Wed Oct 19, 2005 7:55 pm

Thank you! Thats what I wanted to hear. I've been fighting with my CB cross bar linkage for over a year and a half and have been having the exact same issues that you speak of. Were there any modifications to do
to make it fit a wider engine? I'm sold on this linkage.......just gotta break down and buy it!

Wed Oct 19, 2005 8:25 pm

Weeeell, I will say that it's a little narrow for my engine, which is about a half inch wider than stock, and has tall wide manifolds. Nothing that a pair of coupling nuts and some 5mm threaded rod can't fix. I will just extend them about an inch each side. They go on, but I am not getting full throttle, and the rods are unscrewed about as far as I'm willing to unscrew them. I neglected to mention this, but with that being all that's wrong, it's just a matter of making stuff fit on my silly configuration.

I'm going to do that tomorrow. Bulletins as they occur. Pictures coming too.

Thu Oct 20, 2005 7:04 am

I hear yea.
the secret to making a cross bar linkage work is make your own.
One must have the linkage arms strait up and down or parrellel to the carb
I have a partially homemade one that has worked flawless for ever.
it uses large 3/8 upright heims to hold the main bar. (solid aluminum stock) the linkage arms are all heim connectors using aluminum push rod stock and is all legitamately strait up and down, even though the picture makes it look like its not.

Thu Oct 20, 2005 12:27 pm

Yeah, it's really frustrating to mess with. There are a few issues that I think need addressed on existing versions, maybe one day I will make a kit to end all kits. The lack of GAUGE on many of the parts is what hurts them the most. Flimsy parts suck.

Well, finding 5mm coupling nuts proved to be a tough assignment for the day. No one local had them, and McMaster Carr doesn't have them, so I have some more looking to do. In the meantime I just found some T nuts that I could re-tap a little larger (10-32's are very close) and used the shaft part of the T nut to tie a stud to the end of each pushrod for now. Works fine, but isn't as strong looking as I would like. I'll probably have to make some. We'll see how these do for now. Ideally I would get some stainless rod stock and make some of my own that are the right length, but this works.

So far so good. And it cleans up the bay a bit too.

Thu Oct 20, 2005 2:35 pm

I switched from the CB crossbar linkage to the Scat centerpull and like it a lot. Gas pedal is smother with Scat then it was with the crossbar. I also like the clean look of the linkage down low. Makes the whole engine compartment look better.

I did have to do a little grinding and tweeking to make it fit, but no big deal.

Tue Mar 14, 2006 10:03 am

resurecting an old thread!!!!, working on the install of the new cpr 2110, usiing drla 36s for now, but with new manifolds and guess what?, nothing fits. left side carb base doesnt clear fresh air outlet, and cross bar doesnt clear back of alternator, and the crossbar is scewed, left side is about a 1/2 inch closer to shroud than right side. the grinder and i have solved all the clearance problems but its a rancher job, i to am going to try the csp bell crank, mharney, are you still satisfied with its operation? Can some one tell me where i can get new carb bases and tops that dont have all the bs for the cross bar linkage?,

can someone give me the us # for csp, its not on their website

what about their shifters, has anyone tried?

thanks.

Tue Mar 14, 2006 11:49 am

Rob, I like the CSP linkage a lot. It has thus far stayed synched.

As far as air cleaners goes, I don't know which air cleaner set you have, but some of them just have bases that the crossbar attaches to that is independent of the air cleaners, and if so, you can just remove the plate. If they are cast like the CB ones where the base is integrated with the air cleaner base, you can either get their cast universal ones, or some other ones like the ones in the Redline or EMPI kit.

Tue Mar 14, 2006 1:13 pm

thanks for the response, i am ordering today.

Tue Mar 14, 2006 1:21 pm

http://www.csp-shop.de/cgi-bin/shop2/shop_main.cgi?func=start&wkid=52351525745

Go to engines on the upper left, then page down to carburators and linkage on the right.

That's the german site I believe.The US shop has the same stuff and if they don't have it they can get it from the German shop.
US number 1-626-445-0108

US site
http://www.classicandspeedparts.com/s/

Tue Mar 14, 2006 3:21 pm

I have used the CB Performance hex bar set up on offset manifolds, with Dellorto's for years on 4 different cars. I have never had the problems that you described. Was I just lucky ? The only thing i have had to do was replace the ball studs and internal springs. I have never had to adjust it very much. I set the Dells and I'm good to go for at least a year. I use the steel cross bar that does not wear out the end holes. I have experience with only one set up with the CSP linkage. It seemed to me that it took a lot of petal effort, at least more than it should have. I would expect to have cable problems down the road. Just my 2 cents.
Paul

Tue Mar 14, 2006 5:42 pm

Paul Wilson wrote: I have experience with only one set up with the CSP linkage. I would expect to have cable problems down the road. Just my 2 cents.
Paul

You expect him to have problems with the cable?
Did yours break?
What problem or problems did you have with their linkage?
Was it the crossbar or bellcrank linkage?

I also orderd a bellcrank linkage from them (not here yet) and would like to know what to expect. I have done searches for the bellcrank linkage and no problems showed up on the search, just good reviews.

So please speak up now.

Tue Mar 14, 2006 6:05 pm

ditto, i dont understand why the pedal effort would be incrased unless the pedal travel was less, doesnt make sense.

Tue Mar 14, 2006 6:33 pm

I noticed a hang-up on my bellcrank with the return spring. I had to make some changes to that, and now it is smooth as silk.

Tue Mar 14, 2006 7:36 pm

To me it seemed like the bell crank didn't have the correct leverage and took more petal effort than was usual. That set up was also for Dellortos. This was on a customer's car so I didn't get to play with it very much. I am not trying to cut down the bell crank linkage kit as I don't have that much experience with it. These were just my observations. With a little tinkering it probably would work fine.
Paul

Wed Mar 15, 2006 7:38 am

Yeah, I know you're not baggin the linkage, and it really comes down to what you like best and what works best for you.

This engine has 48 IDFs and it doesn't take much imbalance to become apparent. I can have my other engine with a pair of single Solex 35's pretty far out of sync and it's not nearly as apparent. Bigger vents and butterflies means a lot more sensitivity to tune down low.

I just found the linkage to be sloppy, and I don't like sloppy mechanisms like that. I took a little video of the sloppy linkage and sent it to CB. They were stumped and sent me another set of swivels. Still bad. The steel they use on the crossbars could stand to be harder or at least have hardened ends. The steel wears pretty quick (even with grease, you bet), and you are then sloppy.

I replaced the crossbar with some stainless that I sourced online and cut it to length and had a machinist locate and drill the end holes, to the same dimension as the swivel stud ball, and that worked better for a long time. Then the downrods started to wear some too, not bad but enough (even with grease, you bet).

With the crossbar, you have what.. about 6 points to consider for slack, and with the bellcrank 4, PROVIDED that the bellcrank assy is tight, and the CSP unit is tight with very nice bearings on it.

The only thing I could possibly need to correct for is the angles of the rods, and really they're not far enough off that it makes any rough spots on driving it. If the angles are too far off, the amount that the rods are actuating the carb levers at any one position could be different from one another, and in my case it's not enough to be able to feel, though technically I know it is there. I could work that out with about a 1/4" offset on one of the carb linkage ends. Hasn't been an issue so I haven't done it.

But that's just me. Right?

Wed Mar 15, 2006 8:12 am

Sounds like a good topic to put in the sticky's index.

Wed Mar 15, 2006 12:15 pm

mharney, I have never examined nor even installed/run the CSP linkage, but do have some experience with both the Scat and the stock Kadron linkage which are both also center swivel designs. Before you all poo-poo me for using the Kad linkage, let me state that in order for it to work, the four ball end receptacles on the bars themselves must all be in top condition- it does not tolerate loose or worn receptacles.

I also have practical experience with the CB crossbar linkage, as well as with Berg's. Have had continued success with both of them on different engines.

One inherent weak point I can see with the center swivel design is that you set up the linkage on a COLD engine. When the engine warms up and expands, it expands sideways so that the carbs on their manifolds move ever so slightly away from their "cold" position. Ideally, the crossbars would be made of a material that has the same amount of expansion so that the bar ends at the carbs do not hold back the expansion and thereby partially open the throttle arm. As you all know from readjusting the linkage when the engine is warm to achieve a decent idle, you only need a tiny movement on the carb arm to change the engine speed, like one turn of the linkage bar's ball end. A few years ago when I would occasionally buy a German VW magazine that had alot of CSP parts, I think this CSP bellcrank linkage came with an improved feature- that the end ball receptacles were now on a spring, which would accomodate the thermal expansion of the engine.

I think the reason that the CSP linkage has just one attachment point to the engine, that being at one of the case perimeter studs, is that in Europe, this linkage is commonly used with "Porsche style" fan shrouds that do not offer an upper fastening point like the Scat and the Kadrons do. Then again, even the stock T3 dual carb linkage had a case perimeter mount that prevented twisting.

On the CB linkage, using their "offset" manifolds brings the carbs equidistant from the firewall so that the crossbar is sitting at right angles to the car's centerline when viewed from above. That feature helps alot. Also, at VW meets, I often see the cast arm of the CB linkage onto which the accelerator wire is attached, is located a segment too high- nearly horizontal and parallel to the ground. This would indeed result in a tough pedal travel until the arm rotates downward in its arc. Best location for that arm would be at about 2:00 position as viewed from the left side of the engine, with carbs in their idle position. With full throttle, ideally the arm would end up at the 4:00 position.

On one engine I have the CB carb bases and air cleaners, and the Berg linkage on Dell'Orto's. I simply put the left base on the right carb (and vice-versa) so that the CB linkage attachment point was then facing FORWARD, close to the firewall. That provided the clearance for the Berg downrods.

Either way, I'm glad you got your engine to run its best.

Wed Mar 15, 2006 3:26 pm

Rome, now that you mentioned it, I did notice on the CSP linkage, I would adjust everything at operating temp. Then when cold, it seem to take a long time for the carbs to settle down and idle properly. I never thought about expansion of the engine. I sure am interested in how this linkage works out.
Paul