Holley carb.

Hi John, yes it does matter a bit although depending on the application you could render the effect pretty minor or zero.

Primaries are usually at the front, and Holley carbs designed to be used in competition usually have fuel control measures designed to combat fuel slosh generated in that particular orientation. Primary and secondary fuel bowls have slightly different site plug heights for setting float levels and sometimes fuel bowl baffling is only on the secondary bowl to stop a rich stumble under brakes. If you paid a bit of attention to replicating the original fuel slosh management measures with the carb at flipped 180 degrees and jetted it specifically for that orientation you'd probably be fine.

The only bit I'm not sure about is mixture distribution at cruise if you had something like a Performer or Performer RPM intake manifold. Dual plane intakes are a wee bit compromised in terms of mixture distribution by design, and will be designed to have wet fuel/air emulsion added at the front in light throttle and cruise situations. Less of a consideration in an open plenum design.

Cheers, Andrew
 

Mike Pass

Supporter
Do you have a single or dual plane manifold? If you have a dual plane manifold then the right and left hand sides of the intake are separated. This means that the carb will have to have one primary choke and one secondary choke on each side. If you turn the carb "sideways" then the primaries will feed one side only which won't work. The carb can be only fitted with the primaries at the front or rear of the engine on a dual plane manifold. I don't think having the primaries at the front or the rear matters too much. I have my primaries to the front of the car because the throttle cable and the fuel pipe run is easier this way.
With a single plane manifold if you put the carb sideways one side will be fed preferentially by the primaries which will give uneven mixture feed to each side of the engine which is not a good idea.
The main issue as has been said is fuel slosh under acceleration, braking and cornering. the biggest force comes with braking. Fitting the plastic box tubes called "whistles" in the fuel bowls can fix this to a large extent.

Cheers
Mike
 

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Hi guys thank you for the replies ... I have a performer intake .. I put the carb on same as you Mike because fuel and linkage fits better . So hopfully not a problem then ....

Thanks again guys John..
 

Mike Pass

Supporter
I have a Performer RPM intake - dual plane. I have used both Holley 600 cfm vac secondary and 650cfm double pumper carbs which have been OK. I fit the whistles. I also use a 5 degree wedge plate under the carb to bring it level as I have a Renault box so the engine is tilted down at the front.
Cheers
Mike
 
Good question. I have to install my new Holley and whenever I have a 50/50 chance of getting something right it seems I ALWAYS get it wrong.......
 
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