Jump to content




Custom Intake Manifold

Started by e30.Alex, Jan 29 2015 10:24 PM

  • You cannot reply to this topic
3 replies to this topic

#1
e30.Alex
Posted 29 January 2015 - 10:24 PM

  • Granny
  • Pip
    • Group: Members
    • Location:SLC Utah
    • Drives: none fixing them (87 CRx mystery? 85 BMW Frankenstein)
So I would like to make a custom intake manifold for my 87 crx DX for bike carbs but I would like to know is there a way I can make the CVCC work I was thinking of running a tube mounted at a 45 degree angle in side the runner and out to the CVCC port

So would this idea work?
If it does sound like something that would work how close to the carb should I mount the tube?

#2
EuphoricBlue
Posted 29 January 2015 - 11:17 PM

  • Leadfoot
  • PipPipPipPipPip
    • Group: 2011 Contributing Member

How pacient are you? What you are suggesting is better than having no fuel mixture in the CVCC runner at all. But it's still far from ideal. The CVCC is intended to have a rich mixture around the plug, igniting a lean mixture in the main combustion chamber.

 

You'd be much better off soursing an SI or Canadian DX head first, you can then bench build and port match the custom manifold, then just bolt everything on.

 

Another tip, try to avoid gravity fead bike carbs. The carbs that use a low pressure electric pump will give you FAR less trouble.

 

If you do decide to stick with the tube (It will work, just finiky) Run the tube into the intake runner with the mouth a little off center in the bore, on the side of the runner where the slider of the carb opens, and about 2" away from the carb.

 

Intake runner \/

-------------------------

<Head          Carb>

 

          /````````|

         /     /````'

------/     /-----------

___/     /

CVCC /

````````


#3
e30.Alex
Posted 29 January 2015 - 11:44 PM

  • Granny
  • Pip
    • Group: Members
    • Location:SLC Utah
    • Drives: none fixing them (87 CRx mystery? 85 BMW Frankenstein)
Thank you vary much I do have a friend with a si head I was just wondering if it could be done or was a good idea or if its waste of time I know his si head needs to be rebuilt

I know to stay away from gravity carbs I got the fuel pump and carbs off the bike also my dad was a Yamaha master tech for years that's why I feel confident that we can get them tuned and work its just the CVCC I'm worried about

Is it bad if I blocked off the CVCC port

Me and a friend have carbs to a CBR he has carbs off a 98 CBR 600 and I got 87 CBR 1000 carbs this way we can play with both and see what's the better option

#4
EuphoricBlue
Posted 30 January 2015 - 02:02 AM

  • Leadfoot
  • PipPipPipPipPip
    • Group: 2011 Contributing Member

You don't want to block off the CVCC entirely. The spark plug is in the CVCC chamber, and that chamber has a "screen" separating it from the main combustion chamber. If you simply block off the port the only AF mix getting to the plug is what gets past the screen from the main chamber. This results in pretty crappy ignition. Essentially, to get somewhat reasonable ignition with blocked off CVCC passages you'd need to pull the head to remove the screens. At which point you might as well swap to a non CVCC head.

 

Don't get me wrong, you CAN make CVCC work with bike carbs... But it's only worth the effort if you're looking to overcome that challange.

 

If you don't really care about making CVCC work, you will get better and easier results bench building to an SI head and then just bolting the stup into place.

 

 

Also,

I had mid 90s CBR600 carbs with matching pump and a spare manifold... So with 10 dollars worth of band clamps and rubber elbows and a couple of weekend hours I cobbled this together just to see how willing it would be to run. Turns out, very willing. I never did run the car like this, but 7 years later, I still have those carbs kicking around... and now the emissions testing has stopped... So I might revisit it... If I ever get any of the other projects done. >_<

 

When you do build the manifold, make sure you're leveling the carbs in relation to the head correctly. If my memory isn't failing me, the plane where the fuel bowls bolt to the carburetor body needs to be level, this results in the barrels sitting at about a 30 degree angle.


Back to General Posts


  1. Red Pepper Racing
  2. → 1G Honda CRX/3G Honda Civic
  3. → General Posts
  4. Board rules