Twin Weber 40 DCOE length

[Daniel]

Hey, I have a 1979 Datsun 620 with the l20b in it. I want to run the twin Weber 40 DCOE carbs, but I need to know the length from the runners to the end of the stacks so I can make sure I have clearance with my brake booster. If it’s close it’s fine I’ll just put screen filters on it. I’d appreciate the response if anyone has those measurements! 

[datzenmike]

You really need air horns to make the flow more efficient. hen you get your numbers try to fit them in also. On the 510 the rear horn may need a notch but this may be with the brake booster. The 620s all had boosters which moves the master outward. The good news is the bleeders may be pointing away from the engine.

[banzai510(hainz)]

mikuni had a short lenght intake manifold. I have one on my 510 and it clears with the K&N airfilters.

 

One can use the Airfilter socks if needing a tite fit.

assume a 79 is brake boosted

Edited August 1, 2018 by banzai510(hainz)

[G-Duax]

Mikuni short manifold:

[Ron1200]

Mike is right... to get best power use air horns (aka Velocity stacks).  However, many don't use them with acceptable results.  Alfa Romeo fitted dual sidedraft webers without them from the factory...

 

Mine:

 

This is what the inside of the air box looks like:

[Edit 4/27/2020: I can't find the original picture link that shows the inside of the airbox... 😒. 

Added pic below for clarification]

 

However, if you have enough room, you can make a big airbox and put velocity stacks inside it.

 

 

Edited April 27, 2020 by Ron1200
fix broken picture link

[distributorguy]

My Pierce 50 DCOE setup installed is 10" overall, 8" exactly to the face of the carb minus velocity stacks.

I removed the power booster and installed a larger master cylinder to accommodate.  

 

 

 

Edited August 6, 2018 by distributorguy

[Jesse C.]

If I remember correctly, someone made a manifold for the 620 that cleared the brake master. It is a bit curved up. I think Cannon made it

[distributorguy]

Yes, that's the same manifold I have from Pierce.  

 

That Alfa airbox is a serious choke point BTW.  Look at the sharp edges where air transitions into the carbs, and all the turbulence getting there.  Direct 90 degree air shear.  

[scooter]

On 8/16/2018 at 6:23 AM, Jesse C. said:

If I remember correctly, someone made a manifold for the 620 that cleared the brake master. It is a bit curved up. I think Cannon made it

i have seen these as well, they are in the shape of a big S and put the tops of the carbs the same height as the valve cover from what i remember.

 

the pierce one is about an inch shorter and raises the carbs about an inch and a half compared to the cannon PN 3825 manifold. 

 

Edited December 16, 2018 by scooter
added information

[datzenmike]

Someone should invent a better mouse trap intake for the truck.

[Tiger03447]

Cannon makes a good Weber manifold for this. Redline carries them with all the associated linkage parts, heat shields etc. Don't forget to put a heat shield between the carbs and the exhaust manifold. Surprising results may manifest themselves if you don't ...which I can guarantee you won't like!!!

[scooter]

the cannon ones have tiny ports as cast. may be good on a stockish l16 or stock motor but on something hot it requires alot of hogging out. the pierce one has huge runners as cast. i think the cannon would probibly work better on a stockish motor vs the pierce setup.

[Stoffregen Motorsports]

Rebello has been using a L6 manifold and cutting it up to fit the L4. It looks just like a Mikuni manifold as far as shape and length.