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I saw Mitsubishi Colt drive to Orlando Speed World with a pair of slicks and a streetable 4.3 Chevy power plant with a simple single turbo blowing through a Holley 600 and a 350 automatic transmision and posting low 10 seconds ET's all night long. The driver indicated he was running 8-10 LBS. of boost depending on track conditions and that his best ET so far was 10.1. It is certanly a set up that could work reliably. Of course a Colt is very light and it has a full leaf spring rear end but I think there is potential for a light Z.

Well my memory recall is not what it used to be. I went back and located the best write up I could find on the topic of modifying the Holley for a blow-through application and I am pasting the link here. Good luck! http://www.hangar18fabrication.com/blowthru.html Good photos too.

There are a number of mods needed due to the fact that we are not enclosing the entire carb. The Holley manual has a chapter on the mods needed to pressurize the carb from the top. The yahoo blow-through-carb user group also has plenty of information on the mods needed. Basically you need to eliminate the power valve (it is a back fire problem any way on older carbs) and re-jet 2 - 3 size up to compensate the power valve loss. You also need to change fuel floats to non-collapsible type, and seal vents of the fuel bowls. You also need a boost reference line to seal the throttle shafts and that is done from the bottom of the carb via a small spacer drilled in the proper place to align with the shafts. The carb full enclosure is a big project ($ + many technical requirements) due to the number of items that need to be able to interact with the carb (fuel lines, linkage, other hoses) additionally the space requirements are a problem on the L6 and under the hood space. We are still going to have some clearance problems so we are probably going to open the hood area above the Turbonetics intake plenum and add some kind of a scoop or bubble (like Mitsubishi Eclipse hoods) just to make sure we have no issues there. The installation should look pretty clean. By the way the intake manifold is the old Bob Sharp racing 4-barrel manifold. Similar to the one that Arizona Z car sells I believe.

The T3 is going to feed the IC and the intercooler is going to feed the Holley from the top via a turbonetics air plenum. Additionally, we are going to have a Mallory boost sensitive fuel regulator with a return line to the gas tank as well as a Mallory electric fuel pump capable of handling even FI if we wanted to go that way. We are also planning to keep the boost under control with a manual boost adjustment controller and the HKS blow off valve. There will be a gauge to keep track of the exhaust gas temperature. Additionally, we are installing the L28et oil cooler and 2.5" to 3" downpipe and exhaust system. Next will be a stand alone electronic ignition with capability to retard timing based on boost. A NOS plate under the holley for an additional 50 - 75 extra HP (No turbo Lag hopefully). It is just not happening all at once. Will keep things tamed around 7-10 ponds of boost until we go through the learning curve. The mecahnical 600 holley may give us the control we need to keep things in line on low boost condition. My guess is that a two barrel holley at 300-500 cfm should be quite similar to the mechanical 4 barrel (double pumper) under higher boost conditions.