[Chevelle-list] Cold primary on #8 :-(

[Leo John Costigan]

They share the same runner form the Carb base to the head port. Look at the intake manifold and you will see that four cylinders share runners.  Two even and two odd. This is for a dual plane manifold.  If you are using a single plane manifold then all 8 will draw from the Carb.

 

Dual plane manifolds usually will pare off with 1 4 6 7 runners and 2 3 5 8 runners.

 

5 & 8 are the rear runners and if you have a vacuum leak at 8, 5 will have a somewhat lean mixture. 2 & 3 will be far enough from the leak that they will not be affected, as 5 would be.

 

This is all assuming that you have a dual plane manifold.  A vacuum leak in a single plane manifold should not more than where the leak is.

 

Look at the top of your manifold and you will see how the runners are cast. Four runners will be higher than the other four. This works for two barrel and four barrel manifolds.

 

Leo

  ----- Original Message ----- 
  From: Pelle Andersson 
  To: The Chevelle Mailing List 
  Sent: Monday, August 21, 2006 3:16 PM
  Subject: Re: [Chevelle-list] Cold primary on #8 :-(


  I'm not sure I follow you here?
  I get the part that a leaking intake runner might cause low exhaust temp. due to a lean condition, sounds resonable
  to a rookie like me.
  But how's that related to #5 cylinder?

  Best regards
  Pelle

    ----- Original Message ----- 
    From: Leo John Costigan 
    To: The Chevelle Mailing List 
    Sent: Monday, August 21, 2006 10:59 PM
    Subject: Re: [Chevelle-list] Cold primary on #8 :-(


    Pelle, you might want to check for a vacuum leak on the #8 intake runner and also check the #5 spark plug and compare it with the other three on the odd side of the engine.  A vacuum leak will cause a cylinder to be lean and have a low exhaust temp.

     

    Leo

      ----- Original Message ----- 
      From: Pelle Andersson 
      To: The Chevelle Mailing List 
      Sent: Sunday, August 20, 2006 10:28 AM
      Subject: [Chevelle-list] Cold primary on #8 :-(



      The primary tube on #8 cylinder is much colder than the rest!
      Haven't checked anything yet!
      What's your best bet?

      Best regards
      Pelle
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