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View Full Version : Non-Cad Edelbrock Carb/Supercharger Questions


Rem
07-14-2005, 09:07 AM
Sideling the Cad project temporarily, I have a question regarding a Ford 302 and hope I'm not out of line for asking on this forum, but I feel a lot of the mechanical advice here is much better and more detail oriented than the Ford forums. Edelbrock tech support is clueless for the most part also.

Merkur XR4 that has a 302 roller cam shoehorned in place. Dual Edelbrock 600 CFM carbs and mildy modified engine. Car runs great but just trying to make it even more unusual here. The car is a daily driver - not race only. Finally managed to squeeze an Eaton M90 supercharger in it and in the process now of the ductwork. I can probably figure out any glitches on my own (eventually), but thought that any outside info might help a bit. My questions are these.
1. Should I build an airbox or a blow-through carb bonnet? With a bonnet, all external sources on the carb have to be sealed and I am just not sure what kind of modifications I would be looking at on the carbs, so would an airbox be a better option?
2. We have an underdrive crank pulley and I have made a serpentine pulley for the supercharger that will give it an increased rotor speed. The old ratio was about 2/1 - it is now approx. 2.25/1. I have no idea at this point what the manifold vacuum will be like at an idle. Does anyone see any potential problems with the PCV valve or brake booster?
3. With no vacuum, I assume the vacuum advance on a supercharged/carbed system is deleted. Should I go with weaker advance springs on the mechanical advance?

Other questions will probably ( :lol: ) crop up and thanks in advance for any information or comments on this set-up. Any help is greatly appreciated.
:)

J-rod
07-14-2005, 01:29 PM
I'm not a big ford guy, but here's what I've got regarding your generic questions:

First, no matter if you use an airbox or a carb bonnet, you will still need to modify/make sure the carb can take the boost. There will be increased pressures on the carb as the air is forced through. The only way around this is to use a drawthrough system - compress the air and fuel instead of just the air.
Second, a vacuum boosted brake system may or may not work with your application. It all depends on how much boost you are running. Remember vacuum is any pressure less than atmospheric (14.7 psi). Usually vacuum is somewhere around 17-21 inches during idle, but I'm not sure what the equivalent pressure is for that.

Hope this helps.