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Dellorto 48 DHLA Carb & Manifold

The installation was very straight forward.  Unfortunately, I was too dirty to document the process step by step.  When I get a better digital camera, I will tear it all down and redo it, documenting each step.  The first thing I did was remove the air pump since it is in the way and also not needed.  Next, I tore the old intake manifold off with the original Nikki carb still attached.  I then removed all the vacuum solenoids and associated crap to be left with just a bare engine.

Installation of the new manifold and Dellorto carburetor starts fairly simple.  The first thing I did was to clean the motor around where the old manifold used to sit, which involves removing 16 years worth of road debris.  I then cleaned the intake ports on the engine, just incase I got some junk in them while cleaning the rotor housings.  I also prepped the recess for the coolant passage O-rings as well by cleaning them.  The new manifold does not utilize them, so they could just be sealed off, but I was not prepared for that at the time of installation.  Once everything was ready, I placed a new intake gasket on the motor, placed the coolant passage O-rings in their spots and placed the manifold and carb in it's new home.  Once each nut and bolt is tightened down, I started attaching all the new hoses.  Of course, there is the fuel line, then two lines for the oil-metering pump, vacuum off the manifold for power assist for the brakes and lastly, a hose coming off of the base of the air cleaner housing to connect to the vapor recovery system (I am going to remove this since I have taken the charcoal canister out).  Lastly, I connected the throttle cable.  Oh, I almost forgot, just like when I installed the carb, I had to rig something to mate with the original oil metering pump rod, which consisted of hose and some zip-ties.  It works for now, but I will be making a new rod very soon!  Once all was in place, I double checked my work to make sure everything looked good, then I started the beast!  After the new line and carb filled with gas, it started right away!  Perhaps 10 seconds max of cranking.

Fortunately, I have not had to use the choke yet, so I have not connected it.  I probably will connect it eventually, but I am thinking that it will not be necessary.  The Rx-7 still starts when it is cold, I just need to give it a little gas for the first minute or so to keep it running reasonable.

Removing the old fuel system is far more time consuming than the actual installation of the new setup.  I think I spent one hour max from no intake to a running car.


So far, I am VERY pleased with the power gains and over all appeal of the new system.  I put the Racing Beat header and pre silencer system on a few days later to realize the full potential of the system.  The car is very fast now, hopefully I can get some real numbers to post to see how I am doing.  I still have to do a little tuning of the carb because the idle is at about 1500 and it likes to stumble if I try to launch real light.  However, it absolutely screams once it is going.  The whole tone of the engine changes to a much meaner, more aggressive sound.  Under full throttle, it has a very deep tone that gets louder and louder as the Rpm's increase.  When power shifting into 2nd from redline, the rear will actually hop, so I have had to be careful with that!


I have replaced the weak fuel pump with a real Holley pump, and I have had excellent results, plus much quieter operation (a vane type pump sounds just like a fuel injection pump, a nice quite hum).  The motor also does not stumble under light launch conditions either.  I have also made a new oil metering pump rod to replace my "rig".
Dyno numbers coming soon!