Triple Weber Rebuild

[jmackro]

Are there versions of 1-2-3 that can take a TPS input?
DCOE TPS's and not expensive and they will give you a clean electrical signals at is related to manifold vacuum.

This is a great idea, but from looking at their website, the 1-2-3 people don't seem to have picked up on it. There is a list of features at: http://www.123ignitionusa.com/tune-models.html but an interface for a throttle position sensor isn't among them.

I suppose if you wanted to go the hacker route, you might be able to disconnect the MAP sensor and use those connections for your TPS. But what level disassembly of the 1-2-3 unit that would require is an unknown.

 

[Nicad]

That really looks beautiful. I also hope to benefit from the brainpower both you and Steve have put into your weber setups. This is the main thing I am scared of on my Coupe as I have no experience tuning engines other than simple Corvair 1 bbl Rochesters. (I have four of them though !!)
Has anyone had similar results and a recipe running 45s? That is what I have and they are still on the car waiting to get rebuilt. BTW, what is wrong with the soft mounts? I have new ones in inventory.

 

[jmackro]

Has anyone had similar results and a recipe running 45s?

What displacement engine are you planning to run those 45mm carbs on? A rule of thumb for sizing Weber venturis is:

Venturi Dia (mm) = square root (Indiv. Cyl. Disp (cc) X max rpm / 2500)

For example, a BMW 3.0 engine displaces 2985cc's or 497.5cc per cylinder. It develops maximum hp at 5800 rpm. So the optimal venturi size works out to 34mm. The target ratio of carburetor diameter to venturi is 1.25, so a 45mm Weber would have a ratio of 45/34 = 1.32, while a 40 would yeild 1.18. Both are "close enough".

A detailed explanation of Weber carburetor, venturi and jet sizing is at: http://www.dvandrews.co.uk/ Admittedly this just gets you close - a dyno or trial & error are needed for fine tuning.

BTW, what is wrong with the soft mounts? I have new ones in inventory.

There is nothing wrong with soft mounts. They are essential on inline 4's to prevent engine vibration from frothing fuel in the carbs or cracking the mounting ears. But you can dispense with soft mounts on an inline 6 since it runs more smoothly.

 

[Nicad]

Not sure of my displacement. It was originally a 2800, but the block has been replaced. It has a newer head and an Alpina cam with headers and most likely high compression pistons . (Surmised when I posted my compression numbers by local experts)

 

[COUPE9]

Visual help needed (of triple carb install)

I'm FINALLY getting around to swapping out the dual-Zenith's for a triple-Weber carb setup.

Does anyone have any images of the "plumbing" that occurs under the carbs, and what hoses (part numbers) i need?

I've seen plenty of pictures of the "completed" setup, but need someone to post images of all of the "underside" workings.

Thanks (in advance).

 

[Stevehose]

You'll need numbers 1, 3, & 4:

http://www.realoem.com/bmw/enUS/showparts?id=5374-USA-11-1984-E24-BMW-635CSi&diagId=11_3059

Also plug the block hole towards the rear where the small hose for the carb water choke attaches to.

The output from the heater core goes onto the back of #3 tee.

More here:

http://www.e9coupe.com/forum/showthread.php?t=11517

I'm FINALLY getting around to swapping out the dual-Zenith's for a triple-Weber carb setup.

Does anyone have any images of the "plumbing" that occurs under the carbs, and what hoses (part numbers) i need?

I've seen plenty of pictures of the "completed" setup, but need someone to post images of all of the "underside" workings.

Thanks (in advance).

 

[COUPE9]

Thanks Stevehose...

That takes care of the water/coolant... ...but what about fuel delivery and vacuum?... ...got any pictures of that routing?

 

[Ohmess]

Hi Brandon -- here is a picture of my initial hose setup using Steve's recommendations and Rob's heater bypass thread; the heater core bypass did not work in this position; it interfered with the carb horns:

This is the latest bypass setup:

 

[Ohmess]

This thread is timely, and inspiring. Yesterday I finally finished my vacuum (drawn underneath from cylinders 2 and 5 and connected to a distribution block for the brake booster and dizzy):

And today I am working on the linkage:

 

[stphers]

triple threat

Hi

I really like your fuel inlet one piece line. Where did you get it from?

Thanks, Rick

 

[JFENG]

This thread is timely, and inspiring. Yesterday I finally finished my vacuum (drawn underneath from cylinders 2 and 5 and connected to a distribution block for the brake booster and dizzy):

And today I am working on the linkage:

Do you have a photo of the underside of the manifolds showing the vacuum taps?

 

[Ohmess]

In this picture, you can see the barbed outlet from number 2 pretty clearly pointing downward toward the bell crank; the outlet from number 5 is mostly obscured by the manifold itself, but it points downward at the same angle. You can just see the tip of it above the starter. The connection there was difficult because of the proximity to the starter. I ended up having to use a small brass elbow on the connection to number 5 in order to avoid kinking the hose. The small vacuum distribution block I used, sitting on top of the oil filter housing in this picture, ended up straight below the number 2 outlet barb. I used an anti-pulse valve in the line to the distributor.

This is a Korman manifold.

 

[Ohmess]

Hi

I really like your fuel inlet one piece line. Where did you get it from?

Thanks, Rick

Hi Rick -- I bought the carbs, manifold and related stuff as a package from a guy here who was planning to go to fuel injection. The inlet piece came with the package. I received a bunch of paperwork; I will see if I can find out the source. I had thought it was Pierce Manifolds, but I just looked and the one they have comes in three pieces.

 

[Stevehose]

Ohmess' one piece fuel line is ridiculously cool, that was made by Steve Bingham before he passed away? Here's mine with braided hoses, I have DCOM carbs which have manifold vacuum ports for each barrel (and one ported which is capped in blue), they are linked with the thin braided hose in the picture, then goes to the distributor. I have a port for brake booster off the manifold (the large braided hose on the left):

Thanks Stevehose...

That takes care of the water/coolant... ...but what about fuel delivery and vacuum?... ...got any pictures of that routing?

 

[Ohmess]

Yeah, knowing Steve he may well have manufactured that himself. I'm surprised he didn't go with the zinc screw upgrade on the tops of his carbs (which I plan to do).

Does my linkage look right to you? In order to get my accelerator pedal positioned close enough to the stop so that the stop actually engages as the throttle plates were fully opened, I had to remove the arm on the engine side of the firewall that links to the bell crank and re-index it. In its current position, there is some tension on the pedal spring; the idle speed adjustment screws actually stop the upward movement of the accelerator pedal. I am wondering if I might be stressing the throttle shafts.

 

[Stevehose]

Are you saying that when foot off pedal, the tension is pulling down on the front linkage piece or that when pedal is floored it is going over center?

I will look at mine tonight.

Yeah, knowing Steve he may well have manufactured that himself. I'm surprised he didn't go with the zinc screw upgrade on the tops of his carbs (which I plan to do).

Does my linkage look right to you? In order to get my accelerator pedal positioned close enough to the stop so that the stop actually engages as the throttle plates were fully opened, I had to remove the arm on the engine side of the firewall that links to the bell crank and re-index it. In its current position, there is some tension on the pedal spring; the idle speed adjustment screws actually stop the upward movement of the accelerator pedal. I am wondering if I might be stressing the throttle shafts.

 

[rsporsche]

i like the one piece manifold too, is that a Korman piece? it keeps all of the carbs in the same alignment.

the fuel line is smoking hot ... looks like an amazing piece of art.

 

[David]

Looks like a Swiss watch. I ran a breather like that and it just made a mess of things.

 

[Ohmess]

Are you saying that when foot off pedal, the tension is pulling down on the front linkage piece or that when pedal is floored it is going over center?

I will look at mine tonight.

Foot off, tension is pulling down because of the tension from the pedal spring pulling the pedal upward.

If I re-index the arm on the end of the pedal assembly to allow the pedal spring to slacken, then the pedal is too far away from the pedal stop and the pedal stop becomes useless. (The pedal also is sloppy when initially applying pressure.) I was primarily concerned about stressing the throttle shafts without any stop on the pedal/linkage and also was concerned about the possibility of going over center. I seem to recall your recommendation to avoid allowing Webers to get into an over center position; something about sticking at wide open throttle and a huge jolt of adrenaline, if I remember correctly.

So, given all this, I set my linkage up this way to make sure the floor mounted pedal stop opened the throttle butterflies fully, but did not allow an over center condition. When I let off the pedal, this setup led to the tension I described; I don't see how changing the lengths of the linkage rods will alter this situation.

I know there is a alternative bell crank assembly; it looks more like an L with equal length sides and has a more direct ratio of movement between the forward movement of the pedal rod and the upward movement of the rod linked to the carb. As you can see, mine looks like a Z and creates more downward movement on the carb rod for any given rearward movement of the pedal rod.

 

[Ohmess]

I had been planning a breather, but I don't want oil all of the place after I just cleaned and installed all this stuff.

Steve -- on your catch can, is it just a receptacle, or do you run a rubber hose dangling under the car to create a vacuum into the can at speed? I'm with you on wanting to avoid dumping that crap back into my carbs.