Weber 2 barrel progressive centering plate experiment

[dan filipi]

It's been obvious through all the jetting changes I've done so far that something just isn't right with my single manifold and/or the type 4 plenum because the 2 rear cylinders have always burned richer according to the spark plugs.

My theory is the primary throat sitting closer to the 3-4 runners (off center by 3/4") is a more direct shot of intake into those runners. This in turn is causing the 2 front cylinders to burn lean.

Today I made an adaptor plate to link up the 2-1 adaptor to the type 4 plenum.
The adaptor housing channels all air/fuel into a single hole like a 1 barrel carb, dead center between the runners.

My hope is this will cure the unevenness in mixtures to cylinders and maybe even let me go 1 step leaner in the primary jetting. I'm expecting the idle to be smoother also.

 

[sparrowhawkdesign]

Found it. Cool. What size hole in the adapter plate? So I guess the added overall height is not a problem? Hadn't thought about it before.

 

[dan filipi]

Center hole is about 43 mm.

Added height might cause me a problem with the manual choke I just did. Just another thing to re-mod if centering the carb proves worth the effort.

 

[ekvh]

I would love to see a pic of how high a Weber sticks up above the vw manifold. How much clearance there is above the stock frame.

 

[slabghost]

It'll be interesting to see the effects of this.

 

[dan filipi]

Without the adaptor:

With the adaptor:

With carb on top the throttle linkage pin hit the frame but the choke lever seems to clear.
Time for some adjustments.

 

[dan filipi]

Carb on and running.

I ran it 3,000 rpm for 5 minutes then shut it down.
Plugs are getting more even in color so I think I've answered my question centering the 2 barrel carb on the VW plenum does even up the mixture to front and rear cylinders.

 

[slabghost]

Congratulations! So test ride soon? No air leaks at the adapter plate?

 

[dan filipi]

Looks like no air leaks.

Need to rework the throttle linkage then test ride. Probably not til this weekend on that though.

 

[joedrum]

cool ...this is great test ..

 

[Steve83]

Nice! Does it sound any different?

 

[dan filipi]

Steve83 » Thu Dec 26, 2013 5:58 pm[/url]":19hx3q9g]
Nice! Does it sound any different?

It seems to have a little hum at idle.
Definitely less clanking going on in this loose motor.

 

[dan filipi]

Ride report....viewtopic.php?p=106401#p106401

 

[joedrum]

this is just great progress....

 

[Omega Man]

It sounds like you've found the right combo. What could be gained from the larger runner?

~O~

 

[dan filipi]

Omega Man » Mon Dec 30, 2013 5:35 am[/url]":2zlvr7ue]
It sounds like you've found the right combo. What could be gained from the larger runner?

~O~

I'm not sure anything, but I'm wondering if using the adaptor then runner sizing may not be so critical and chokes inside them may not be needed.

 

[dan filipi]

Just passing on what sparrowhawkdesign sent me because it's interesting to read that J&E Enterprises discovered an advantage in the straight flow riser back in the 90's and built it into their manifold.......

"The manifold incorporates a high-riser design that provides a straight flow before the air/fuel mixture has to turn corners. This improves distribution by eliminating directional effects caused by a partially open throttle."

I'm not saying that their riser is the same as I used (and found a very noticeable improvement in performance), but I am saying that it does lend some validity to adding a riser.

I've searched and searched but come up empty finding any more information or pictures about this manifold.

 

[sparrowhawkdesign]

Dan
I have been searching also but think this was just before the internet became popular so probably not much if anything out there. A friend in Alberta did manage to find the person that did the graph testing but he doesn't remember much about it. Still looking though.

 

[dan filipi]

At this point I'm claiming CGW originality using the 2-1 adaptor, as far as using it on an oldwing single carb setup and being the first to realize it's potential.

It's use has been a collaborated effort by the CGW members, particularly joedrum and myself studying and reading racing forum posts and their findings.

 

[sparrowhawkdesign]

dan filipi » Sun Jan 26, 2014 4:44 pm[/url]":21tzqidp]
At this point I'm claiming CGW originality using the 2-1 adaptor, as far as using it on an oldwing single carb setup and being the first to realize it's potential.

It's use has been a collaborated effort by the CGW members, particularly joedrum and myself studying and reading racing forum posts and their findings.

Without a doubt! :music: :music: :good: