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Posted by: vesnyder Sep 27 2008, 06:29 PM

I have been having issues with adjusting the carbs on my rebuilt 1911 so I thought I would see what a professional could do. This local mechanic specializes in Porsche's and has recently gotten a dyno so I thought I would have him adjust my Webers. The car was running fine but was rich at higher RPM's as confirmed by his dyno and sensors he was using to adjust. I had 28 mm venturis and 115 mains. It ran good but the rich situation gave me concerns particularly on a rebuilt motor. I went to pick it up after he had the car for several days and he said he was having issues. The car was running like crap, backfiring and missing. He said the carbs were adjusted good but it was either the distributor or the valves??? He had put in 195 mains and 34 mm venturis? Upon further inspection he had a 185 in one of the carbs? WTF? On top of that he charged me $320? I am done with so-called experts. This takes the cake!

BTW I am working with Jogn at AirCooled to fix!

Posted by: Mark Henry Sep 27 2008, 07:04 PM

If there is no issues with the engine (condition, timing, etc) the number one problem is always linkage...linkage...LINKAGE.

It MUST open and close at the same rate, smoothly, no bind, no sideload. I haven't seen many linkage set-ups I like and the ones for type 4 suck dog butt so I make my own center pulls from scratch.

Just had to fix up one of my setups that a respected porsche shop (Mantas) totally f'ed up. Nothing wrong with it, but the operator was clueless.

195 mains...WTF....I've done a 2.6l (44 webers) T4 and I don't think it's past 165's
BTW if you look at my main# it's wrong as I reem my mains, so it might say 135 but it's really 155... so # mean nothing to me.

Posted by: Mark Henry Sep 27 2008, 07:17 PM

my linkage on a 2.6l T4


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Posted by: Zundfolge Sep 27 2008, 07:20 PM

So is $320 the going rate for setting up carbs?

I understand the guy the OP went to is an idiot, but if I could find someone that did a good job to set mine up for that I'd seriously consider it.

Posted by: Jake Raby Sep 27 2008, 11:19 PM

320.00 for a day on a chassis dyno is fair, BUT he was obviously lost with the venturi and main jetting.

The issue with vents larger than 32mm in a weber 40 is the loss of carburetion... Meaning the huge vent slows the air speed to the point the engine is hard to tune. BIGGER IS NOT BETTER!

Try this
32 vents
130 main
200 air
F11 emulsion

Posted by: Racer Chris Sep 28 2008, 12:29 AM

I agree that 32mm venturis in 40mm carbs would likely improve the top end on your 1911, wiithout compromising a/f quality at idle and midrange. Anything bigger will kill low end performance and efficiency.

Posted by: SGB Sep 28 2008, 01:00 AM

Can't get this kinda qualified advise for mere money. Try Jake's setup. I'll bet it is the one.

Posted by: vesnyder Sep 28 2008, 10:04 AM

Thanks! I was moving in the same direction. What is the "200 Air" recommendation?

Posted by: r_towle Sep 28 2008, 10:58 AM

Nice and pretty.
Got a pic of one in a flat setup?? Not for a beetle??
The cable would not make it there?

I agree that every single one of the linkage setups Sucks...

If the original poster still has issues and cant afford a decent linkage setup, I can offer you this advice.

the CB style cross bar linkage properly setup (as best as you can get it) opens the carbs at different rates.
If you imagine a vertical plane running side to side and you measure the top of the drop link and the bottom on both sides you will notice they are are different angles. Out of the box this is how it sets up.

Start by making sure that side to side you have the drop links parallel...measure from top of one drop link to the top of the other...and bottom to bottom.
Make the parallel first.

Now to fix them so they match in the other direction you need one drop link to mount to the back of the throttle plate and the other to mount to the front.
This varies depending upon what throttle plates you are using..there are quite a few, but non of them fix the problem entirely.

Once you have it close you need to measure what the difference is...so if you are down to 1/2 or 3/4 of an inch you need to move both arms 50% of that difference to make them line up.
Go to the hardware store with the little ball bolt that is mounted to the throttle plate and find one of the little hex rod couplers...its basically a long nut threaded all the way through.
You will also need a tap that matches your ball bolt.
The hex bar couplers are 1/4 20 SAE thread...BUT...you can tap them for the ball cup..it works.
Pick up a few of those, cut them to length, tap them correctly and bolt them onto the throttle plate, then bolt in the ball bolt.

At the end of the day, this is as close as you can get to perfect...you end up being a bit off so you can clear the air cleaner housing, but its alot closer than before.

If you are a picture guy, go to www.356registry.org, look in the technical section and read the article about carb linkage...
This has been an issue since Webers were first bolted on to porsche motors.

Porsche overcame this issue with offset carb manifolds and offet throttle plates on the Solex carbs...really subtle but they step it back just a little bit on both the carbs and the manifold so the end results are the drop links are on the same plane all the way through the cycle.

Rich

Posted by: chris914 Sep 28 2008, 03:25 PM

Posted by: chris914 Sep 28 2008, 03:30 PM

Posted by: gopack Sep 28 2008, 04:44 PM

That last one looks like mine. Who makes that one and are there the same types of problems as with the hex bar setups? seems to have worked well when the car was actually being driven!

Posted by: chris914 Sep 28 2008, 05:36 PM

It's made by CSP in Germany. Bolt it in, adjust the two arms to equal lengths, and drive away. I had to make the cable bracket and add a return spring.

Posted by: mattp Sep 28 2008, 06:53 PM

I really like the set up but cant seem to find it on net, is it the same set up they are selling in CSP canada for the type 1?
Where did you get it and how much was it?
How / what did you make your cable bracket out of, it looks like a great set up, very simple. Matt

Posted by: chris914 Sep 28 2008, 09:29 PM

Thanks, The bracket is made of stainless steel to match the linkage made by CSP. I had the bracket CNC from an AutoCAD file I drew up.

http://www2.cip1.com/ProductDetails.asp?ProductCode=C31%2D129%2D941%2D400

Posted by: watsonrx13 Sep 29 2008, 06:30 AM

Chris, excellent set up, it's what I've been looking for.

Can you post the dimensions of the cable bracket you made?

-- Rob

Posted by: ArtechnikA Sep 29 2008, 10:08 AM

Air Correction Jet.

A typical Weber jet stack is (top to bottom) Air correction jet, emulsion tube, main jet.

Carbs tend to run increasingly rich as the airflow increases. The air correction jet provides a compensating air bleed to progressively lean the mixture as airflow increases.

If your AFR is decent up to peak torque but fattens up too much after that, a bigger air correction jet is the right call. It's all about balancing all the nonlinearities...

Also - you can't be too quick to blame your wrench just because you have one jet that is marked differently than the others. Just as there are jet reamers that make the holes bigger (without remarking the jet...) there are jet gauges that let you measure the -real- size.

For background - the size of a Solex/Weber/Dellorto (maybe others...) jet is the diameter of the hole in hundredths of a mm. Eg: a 115 jet is 1,15mm DIAMETER. Flow is proportional to the AREA.

Posted by: Borderline Sep 29 2008, 10:50 AM

When I bought my 40's they came with a similar setup but not as purdy. I've found that when synching the carbs it helps to do it twice. The first time is the normal idle adjust and the linkage disconnected. The second time I put a little tension on the throttle cable to bring the engine up off idle so that it is controlled by the throttle linkage (~2k rpm). I then balance the flow a second time by adjusting the linkage lengths. This works well for my setup. Of course, I recall reading somewhere that this type of center pull system doesn't work because of the heat expansion of the engine. So make sure when you do your adjustments that the engine is good and warm!!

Posted by: r_towle Sep 29 2008, 10:53 AM

I need a new dictionary.

Rich

Posted by: Joe Ricard Sep 29 2008, 02:37 PM

Rob Watson you paid attention to my engine you would see a very similair linkage set up like the CSP unit.


Yep hook it up and balance flow side to side and leave it alone. I am using Spherical bearing vs. the clip and ball sockets. but pretty much the same.

Posted by: SGB Sep 29 2008, 07:37 PM

I believe he is right , though. Webers have a buncha little "corrective features" that adjust the basic venturi- vacuum draw fuel provision. I think it is just good luck that the characteristics of the t-IV work well with the chosen approach. I like the term...

Then there is that "non-linearity" induced by the linkage, of course. Thats another discussion. Oh wait, thats this discussion.




OK.

Posted by: watsonrx13 Sep 29 2008, 07:43 PM

Yea I know Joe, but you said you didn't know where it came from, that's why I was asking ....

-- Rob

Posted by: chris914 Sep 29 2008, 10:42 PM

I can send you the AutoCAD file tomorrow if you want.

Posted by: watsonrx13 Sep 30 2008, 06:08 AM

Chris, PM sent...

-- Rob

Posted by: Gint Sep 30 2008, 05:29 PM

I also asked Chris if he minded if we made it available on the site. This way folks that want it later could download it from here. Simply refer to this link.

http://www.914world.com/image/CSP_Bracket.dxf

Posted by: curt Oct 1 2008, 09:41 AM

Hello All

Been lurking here a while and this subject caught my attention as I too am not thrilled with my crossbar set up for the Webers.

Anyway, Chris, thanks for posting the photo of your setup. Have not seen that setup before and am inclined to toss my crossbar set up for this one.

Just a question or two before I go and do this.

Since the whole setup is located toward the back of the engine, what throttle cable do you use to reach it?

Do you by any chance have a photo of where the arms connect to the carb throttle arms? Basically, what kind of throttle arm is on each of your Webers to connect all this up?


Lastly, I've heard that one of the disadvantages of this type of linkage is that the throttle settings will be disturbed as the engine heats up.
What has your experiance been? Have you noticed this effect at all?

Hey, thanks again for posting the info and also the cable bracket .dxf file.

Curt

Posted by: 9146986 Oct 1 2008, 12:20 PM

Years ago there was a discussion about carb linkage and four cylinders, and I seem to remember that someone had a problem with the center mounted bell crank linkage and thermal expansion of the engine. Is this just BS?

Posted by: Jake Raby Oct 1 2008, 12:33 PM

I also carry the CSP unit and have a modified version of it as well.

Posted by: Mark Henry Oct 1 2008, 02:19 PM

You just need a hair of slack in your cable for expansion. Most likely there was an installation/set-up issue

Think about it...as it expands the linkage would equally adjust with the expansion, as long as it has slight slack on the wire (at idle).

Posted by: chris914 Oct 2 2008, 03:07 AM

Because it is a little longer I used a Terry cable. But even thou it is longer I did have to re-route it. I circled it in yellow in the picture. Were the cable passes though the body I put a piece of hose around it to protect it.

The arms came with the CSP setup and they are made of stainless steel. Stainless steel is heavier but it just looks and feels so dam nice.

As far as the engine expansion I looked at it as this way. The expansion is really small, it is more or less equal on both sides, and I tuned everything once the engine was warmed up. Having said that I haven’t noticed any major difference between cold and hot. Or at least no more then you would expect with cold carburetors warming up.

I did have to add an extra spring to make the linkage snap back properly and to satisfy the Autocross rules.

I’m much more happier with the CSP setup.



I did fix the filter in the air cleaner cover. It was bent from previous metal cover.





The spark plug wires do look closer to the arms then they are.

Posted by: Racer Chris Oct 2 2008, 08:15 AM

I have done a couple of installations using this linkage. I made an alteration to the bellcrank and made a different cable mount that better accomodates the stock cable.




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Posted by: chris914 Oct 2 2008, 12:12 PM

That’s interesting. I take it that your linkage is setup to push instead of pull.

Posted by: porsche914gt Oct 2 2008, 01:18 PM

Jake, I cant find the linkage at the Type4 store.
Do you have the link?
Thanks.

Posted by: curt Oct 2 2008, 01:55 PM

Chris914 and Racer Chris thanks for posting the photos for folks like me who have not seen this linkage before and how its mounted.

BTW, Chris914, I looked at your website and the autocross photos and videos. Really cool, your car scoots.

Yeah Jake, I also looked on your type IV website store and did not see the CMP liknkage.

I am not sure how to handle the lack of a throttle cable mount.

Does the CMP product line include one for purchase?

Thanks again guys for the photos and info.

Curt

Posted by: Mark Henry Oct 2 2008, 02:27 PM

The CSP unit looks OK, But I'd still bend up my own arms.
I like the arm to be 90 degrees from the throttle shaft (and center crank) so there is no side loading on the shaft at all. Makes for a smoother more accurate linkage.

If you look at my pic on page one, you can just make out how it's bent on the end to achieve this.

Posted by: Racer Chris Oct 2 2008, 05:39 PM

Yes.