boost reference on roots blower?

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boost reference on roots blower?

Post by Sirshredalot » Thu Oct 08, 2009 9:23 pm

Hey guys,

IM helping a friend with a supercharged engine.

Hes got a mild 383 with a 142 blower on it...He has a race pumps fuel pump and regulator. but the regulator continually creeps up in pressure until it floods the engine out....will not adjust pressure period.

also it has no bypass...strange?

Does anyone have any experience with these? Can we just just substitute a good bypass an aeromotive?

Race pumps does not recomend any other regulator....but we are getting frustrated because everything is new and theykeep telling us theregulator has debris in it but it has been disassembled multiple times and is pristine.

Please and thank you

God bless

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Post by BrazilianZ28Camaro » Fri Oct 09, 2009 12:03 am

Probably the fuel pressure is overcoming the regulator's spring pressure.

You need a return line with a blower motor.

Install the regulator at return line and a fuel gauge at carb.

This way the engine will receive the full volume of fuel and only the unused fuel will be send back to the fuel tank.

hope this helps; :wink:
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Post by Eric68 » Fri Oct 09, 2009 10:59 am

I built and tuned one very similar (mild 383 with Weiand 177) and we had no problems with a bypass regulator and Aeromotive SS pump.

The combo responded very well to a larger 850 cfm carburetor -- boost referencing was not necessary in this case because the small blower could not pull enough vacuum on the bottom of the carb to close the power valve at WOT. Boost referenced power valve would be nice though.

You also do not need/want to boost reference the pressure regulator with a roots setup. (kind of obvious but I thought I would mention it)
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Post by Tokyo Torquer » Fri Oct 09, 2009 11:15 am

As Eric stated.. boost referencing is not needed for roots blowers as the carb is not exposed to positive pressures.. I have built a 350 with a 162ci mini blower and a single 750 holley.

You have way overcomplicated the fuel system needs for that motor. A good, cheap, tried and true mechanical pump like a Carter 172 can easily feed that motor's needs and no bypass needed or boost referencing needed.

1973 RS Z28: 401ci Dart Little M, Littlefield 8-71 supercharger @14lbs boost, Callies Magnum crank, Lunati rods, JE pistons, 7.8:1, AFR 227 Comp heads, T&D 1.6 shaft rockers. Reed solid FT cam (240/250@.050-.523/.542 lift-112 LSA), QFT 750 carbs

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Post by Ron C. » Fri Oct 09, 2009 11:33 am

You've just got a bad regulator. You can run a (dead headed) regulator like the holley 132-2 or something like the Moroso (by-pass) fuel log. I've run both types and they work very good.

Like mentioned, your application does not apply for the boost referenced regulator.

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