Hi all, first off I will give engine details.



old skool 13b 4 port

-Cermet B rotor housings clearanced for 10000rpm

-MFR stationary gear bearings and MFR hardened gears

-RB adjustable rear oil regulator, and shimmed front regulator.

-s4 na rotors and crank- new Mazda 2 piece 2mm apex seals, New Mazda 2mm corner seals(no plugs), FD corner springs, new Mazda side seals(clearanced to .003" and doubled springs on center plate side).

-all new viton seals and Mazda Water seals

-matchported oil pump land

-bridgeported just up to the water seal and small notch on the housing. Exhausts ported also

RB headers to 3 inch collected exhaust





Now I have a RB modded Holley 550cfm carb from a SP 13b 4 port. I am having issues with getting this carb to idle lower than 2500rpm. I cant really find any info on what RB does to modify carbs for bridgeports. I have been researching general Holley mods, and what I have found is that for v8 applications where a wild cam is used and there is overlap between intake and exhaust(like a bridgeport on a rotary) and where there is low idle vacuum, they recommend drilling some holes in the primary throttle plates. And if needed opening up the idle mixture bleeds.



Before I start drilling into a good carb, has anyone ever heard of this or done this. Or alternatively, does anyone know what RB does to their Holleys to make them run correctly on BP.



Also, I have a freshly rebuilt(MAzdatrix) Dellorto 48mm DHLA and manifolds. Will this potentially work "good" on my engine?

put on the dellorto and it is now idling at a grand and running great!!!yippeeee

The holley will work. If its idling that high, and the idle adjustment screw is turned all the way out, the maybe someone has messed with the idle adjustment on the secondaries. If you flip the carb over, you'll see a screw that opens the secondaries. Back it out to close the throttle plates. The throttle plates (primary and secondary) should be open just enough to see the transfer slot. Drilling holes in the plates will only raise the idle, not lower it. You drill holes when you cant get the idle high enough without exposing the transfer slot. You drill a hole, then back the throttles shut again. That way, when you stomp the throttle, your not already on the transfer slot, and the car doesnt hesitate from being lean. A lot of this wont make any sense if you are not familiar with the various circuits in a carb.

i use holleys on all my drag cars and i think 550 is way too small for a 13b bridgeported on 12a bridgeported i use 600 and 13b 750 cfms but i dont know how big are ur ports by the way check the size of the jets the carby has . By the way sorry for the partner that said to use a dellorto but them carbys suxk ass big time theyll never give u the acceleration of a holley plus u cant hardly get parts for it. good luck

Holley made a 550?

Holley made mechanical secondary carbs sized every 50cfm from 850 on down to 450, and then the 390.



Then there were weirdball versions in off-sizes, and a large number of vacuum secondary carbs too. This is just in the 4150/4160 model.



Every time I have to work with one, I am amazed that they are still selling. The primary reason for that seems to be that the competiton isn't so hot either, and with so little tuning possible, Holleys are hard to screw up.

So did the suggestion work??



Inquiring minds want to know.

Need a 600 or 750 Holley for my 13B street ported with haeders have a Jegs manifold

if you have please e-mail me with picture and price.

Hector