Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: chevy bb vacuum issue
          
   
   

Reply To Thread
Results 1 to 3 of 3
  1. #1
    tcodi's Avatar
    tcodi is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    parkesburg
    Car Year, Make, Model: 1950 chevy pickup
    Posts
    580

    chevy bb vacuum issue

     



    I have a bb402 that I just put some aluminum edelbrock performer heads on to upgrade my iron ones. After installing the heads I noticed that while driving above about 25% throttle I would hear a sort of whistling sound out the exhaust, but this was only under heavier throttle than cruising. Another new issue to the new heads was that I had trouble shutting down the engine. It would always kind of sputter a few revolutions before actually stopping like it was dieseling or something. I do have a vacuum guage in the cab that I monitor regularly, and at idle I would have 15in, and if I downshifted while driving to use engine braking to pull the rpm's up it would go up over 20in.
    Well, this weekend I was out and all of a sudden I noticed a major idle problem where it felt like it was going to stall every time I came to a stop, it never actually did stall but just barely. My vacuum at idle was barely 10in, and if I got up to speed and downshifted to pull up the rpm it would only get up to 15in. So basically I lost 25-35% of my vacuum all at once. I was hoping a vacuum line came loose but unfortunately that was not the case.
    I'm thinking maybe I made a mistake when adjusting the valves, which is why I had strange whistling and shutting down issues, and that maybe this weekend something happened to a valve or lifter that made the problem worse and my valves are not closing properly?
    I have a hydraulic flat tappet and I followed standard procedures when adjusting them.
    Also, this weekend the shutting down problems were much worse, it would sputter for a solid 5 seconds at least and then finish off with a big puff up through the carb.

  2. #2
    pat mccarthy's Avatar
    pat mccarthy is offline CHR Member/Contributor Visit my Photo Gallery
    Join Date
    Apr 2005
    Location
    bay city
    Posts
    10,546

    did you do a mid lift check to see if the push rods are the right length for the new heads sounds like a intake leak ?
    Irish Diplomacy ..the ability to tell someone to go to Hell ,,So that they will look forward to to the trip

  3. #3
    tcodi's Avatar
    tcodi is offline CHR Member Visit my Photo Gallery
    Join Date
    Oct 2004
    Location
    parkesburg
    Car Year, Make, Model: 1950 chevy pickup
    Posts
    580

    what exactly is a mid lift check? I do have a dial indicator, and I'm about to pull covers and start checking those types of things. But I guess I don't know what pushrod length would have to do with lift? Wouldn't it be the same lift regardless, the rockers would just contact the valves off center if the rods were the wrong length?
    Should I just put a dial on top of the pushrod, or place it on a rocker?

Reply To Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink