[Tom Wells]

Brian,

I've used the Holley MPFI setup for more than 15 years - maybe close to 20? Yeah, I was what amounted to a Beta tester for the things.

They're pretty good now though it would be good to have someone knowledgeable apply the final tweaks.

I use 60lb injectors.

The first setup I put together there was no manifold with bungs, so we had to drill & weld them in. Pain. That was on the 521.

The 557 has the Edelbrock 50665 manifold and was easier, although the manifold I received from Edelbrock was defective - and they refused to repair or replace it... I ended up filling their casting mistake at the front of the block with another piece of aluminum and it has worked fine for about 15K miles so far.

If you go this route, be sure to check the china wall at the front of your block to make sure the manifold extends far enough forward to capture the silicon bead that forms the seal around the distributor area.

The self-tune at first is pretty good.

Advantage was that the car no longer had any problems with underhood heat after a run on the highway. When it had a carb, the fuel in the bowls would boil the alcohol and geyser the fluid out of the bowl vents into the engine, which would promptly flood and quit. I tried for a couple of years with insulators, heat shields float levels - you name it. Never solved it. The EFI solved that.

I did have to use an Aeromotive Stealth (or was it Phantom?) in-tank pump and sump combo on one car and that works fine. On the Cobra I used a sump built into the bottom of the tank for the inlet to the pump to stay submerged while cornering. Think 3 dimensional drag racing fuel pickup tank.

Gas mileage is good, car runs fine on the street and track - for over 35K miles - no complaints.

If you're less concerned about the attendant problems of vacuum storage, air filters, airflow and linkage synchronization etc etc you might consider the 8-stack - it sure is pretty!

Unless you know more than the average Joe, the Holley (or similar) 1000CFM throttle body looks kinda liks a carb. Most folks don't see the fuel rails until I point them out. This throttle body gives an extra ~3/4" (forgot exactly) of reduced height compared with a carb so a taller air filter can be used.

If you are comfortably under (I think) 600 flywheel HP then maybe a throttle body with 4 healthy injectors might be another, possibly simpler, route to consider. You could use your present intake.

Keep us posted as to what you decide,

Tom

EDIT: Whoops! Almost forgot. My mileage seems to correlate quite nicely with the position of my right foot ;-) I'd love to know enough to tune that aspect of the setup; maybe I'll have to take a class from Holley (they do teach them in Bowling Green). As it is, 10 is probably the most frequent number I see if I'm driving gently. As to what's possible, a friend (Herb Smith) once tuned the carb on the 557 to achieve 16MPG at a steady 60MPH!

Tom