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fuel pump question for a circle track rx7

Old 06-25-06, 08:49 PM
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fuel pump question for a circle track rx7

my friend is building a circle track rx7 for our local track and we put a weber 48 ida carb setup from mazdatrix on and we have a carter 72 gph pump from when we used with the stock carb. well we checked the pressure after we installed the weber and looked fine, actually was reading 6 psi. so we took it to the track and and the engine wouldnt pass over 8200 RPM in 3rd gear and 6K on 4th gear, just sounded flat the hole time so he came in the pits and check the pressure and it was at 2.5 psi and i adjusted the holley regulator and still didnt move above 3 psi. the guy that sold to him the engine told us before that he use to be able to run 9k rpm 3rd no problem and basicly were running the same setup other that the weber and were running a megaphone (owner of the car choice). so what were doing wrong? do we need a bigger fuel pump?

car, 85 rx7 circle track only
engine mods, IT setup stock port 12a engine with weber carb, carter 72 GPH pump RB road race header, long primary with 2 i think is dynomax bullet mufflers and a megaphone at the end and 85 tranny and gsl rear with 4.88 gears

Last edited by eddierotary; 06-25-06 at 08:54 PM.
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Old 06-28-06, 06:57 AM
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How's the fuel filter?
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Old 06-28-06, 07:29 AM
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Old 06-28-06, 08:54 PM
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The Weber definitely wants to run at least 4 psi pressure, and a max of about 5.5 psi.

Fuel filter would be the first check, maybe complete drain and rebuild of fuel cell may be necessary. It appears you just bought the car. How long did it sit unused before you got hold of it? Fuel systems gel up and gunk up when left sitting unused.
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Old 06-30-06, 07:47 AM
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Fuel Pressure

It's all new. Cell is new, Weber Carbs are new, Pump is new and so is/are the Regulators, we have tried two. Going for a new Holley Pump this week. Ugh.
Changing the exhuast, I think the primaries are to long---RB Header to the back of car then into megaphone. Next we try a Racing Beat Header converting into 3" about 8" back of header with a magnaflow muffler then out the side. Our rules are open for exhaust and Carbs, stock rotors and housings. running a 12a
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Old 06-30-06, 09:15 AM
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If the new pump doesn't get you there, check the hard lines for clogs and obstructions. You're dropping pressure somewhere.

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