circle track q jet

[racingjmg21]

 I was needing some help on which carb to run on a asphault 3/8 mile circle track. The 3 carbs i have are 17084226,17080204 or 17058253. The motor is a sbc mainly stock with a 450 lift cam rule. not sure on the duration i am thinking around 240 or 250 advertised. we run hei distributor and turn the motor between 6400 and 6800 with stock exhaust manifolds.
 
  1. The olds carb does not have idle air by pass is this something you have to have on a circle track carb?
  2. I have read that you can leave out the metering rods, power  piston and the apt adjustment. Can someone tell me more detail on this and do you have to plug any holes when you do this?
  3. What will be a good recipie to start with on one of these carbs. I do have cliffs book.
  4. Is there any tips someone can give me on a race quadrajet that will not be used on the street that might save us some time and headaches?

  Thanks everyone, I really enjoy this site lots of helpfull info!!!

[Cliff Ruggles]

Those carbs are all pretty much equal from a performance standpoint.  Biggest difference is front vs side fuel inlet location.

I'd use the one in the best overall condition.....Cliff

[racingjmg21]

Got the carb rebuilt and  we used reciepe #3 the carb sounds awesome from 2000 rpm up. It does have a stumble between 1000 and 2000 rpm. It seems like the accelerator discharge holes may be a little big they really dump the fuel!!!! The holes are drilled to .030 
   We did go to the last hole on the accelerator arm and that helped some but still a stumble or hesitation at low rpm. We run circle track and rpms are kept up between 2500 and 6500 so hopefully it will ok. We go to the track in about 2hrs. wish us luck!!! Does anyone have any ideas???  Can they be filled and redrilled??

       Thanks Everyone!!!

[Cliff Ruggles]

Stumble going to full throttle, or primary side only?....Cliff

[racingjmg21]

Cliff,

  The carb we ended up using was the 17084226 .076 jets and 51m metering rods  and recipie #3 it stumbles a little on the primary side only. You can hold it about 2000 rpm or so and go full throttle in nuetral and it is awsome.  But from idle it has a stumble first. Looking inside the primary side it shoot a real healthy stream of fuel and a puff of smoke when starting, then clears up you just have to push it out of the shop because it is real rich even with fans running.
   Another issue we had last night was with the idle mixture screws. we could not get them to have any effect on the vacum gauge.  Gauge showed 12 to 13 at 800 rpm would not set still just bounced back and fourth no matter where the screws were at.  The idle mixture hole are .085 and 1 round was cut off of the springs. When screwed all the way in it had very little effect on idle.  It did not seem to hurt anything on the track it ran pretty good last night, like i said before circle track we usually keep rpms between 2000 and 6000. We are running tonight also it is a 2 day memorial day show.

[Cliff Ruggles]

Take a look into the primary side at idle and see if fuel is coming off the booster (nozzle drip).  Sounds like it may not have enough idle fuel for the application.

We set-up all of our circle track carbs to run straight off the primary jets.  The metering rods and power piston are not needed for that type of racing.....Cliff

[racingjmg21]

Cliff,
  Will check on the nozzle drip. What modifications are need once you  remove the metering rods, power piston and apt. screw and spring??  Vacum ports, jet size, ect. ??

       Thanks Cliff

[Cliff Ruggles]

Reduce the jet size, block the vacuum supply to the power piston, or just leave it in the hole with no spring under it.  I would have to know the carb number, and the main airbleed size to recomend a starting point for the jetting.....Cliff

[racingjmg21]

The carb we ended up using was the 17084226 with recipie #3 it currently has .076 jets and 51m metering rods. What do you gain by leaving metering rods out???

      Thanks!!!!!!