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my first engine build

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Old 01-17-19, 07:33 PM
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my first engine build

hello everyone, I have lurked on this forum for a long time, and your help has been invaluable to me, however I have some somewhat specialized questions that I need some help with before I buy all the parts for my brigdeport rx7 build

build details:
1985 rx7 GSL-SE
GSL-SE housings/rotors and 12a irons
full brigdeport
weber 48ida setup

ive never tuned a carbeurator nor installed one before. this is also my first engine swap. im pretty confident I can do this, its easier than I had expected thus far. the only thing im a little fuzzy on is the exact way to install the carbeurator and run the fuel system. as far as I am aware, the stock fuel pump will work with the weber, and I guess I don't need a fuel return line if I do this set up?
basically I need someone whos done something like this to explain exactly how to make the stock fuel injection system work with the carb set up. tips for tuning could be helpful as well but I have an older friend whos good with specifically webers to help me with this. I don't like unknowns when im 8,000$ into this build. would suck If I messed something up right off the bat.

thanks in advance!
Old 01-17-19, 09:37 PM
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First off, why is everybody always mixmatching 12A's and early 13B's??? whats up with that. Seems easier to just buy a cheap FC engine and start from there. But hey its your engine.

Carbs are more simple than you are giving them credit for being. Just supply them with regulated low pressure fuel and they will do the rest. Yes, run a return line. Dead headed (no return line) is never a wise choice. You already have a return line in your engine bay. Just put an adjustable regulator there so you can shoot the unneeded fuel back into the tank. If nothing else it makes your fuel pump last longer and keeps a more steady pressure for the carb to work with.

What fuel pump are you planning on using?

Tell your webber guy that rotary engines like to be fat. When I talk with my buddies about AFRs and tell them where I'm at during full boost they cringe (about 10:1). You'll find that happy place for your engine while tuning; its just going to be more rich than you are expecting.
Old 01-18-19, 01:02 AM
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Originally Posted by Qingdao
First off, why is everybody always mixmatching 12A's and early 13B's???
it creates a 4 port 13b.
Old 01-18-19, 10:25 AM
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Originally Posted by Qingdao
First off, why is everybody always mixmatching 12A's and early 13B's??? whats up with that. Seems easier to just buy a cheap FC engine and start from there. But hey its your engine.

Carbs are more simple than you are giving them credit for being. Just supply them with regulated low pressure fuel and they will do the rest. Yes, run a return line. Dead headed (no return line) is never a wise choice. You already have a return line in your engine bay. Just put an adjustable regulator there so you can shoot the unneeded fuel back into the tank. If nothing else it makes your fuel pump last longer and keeps a more steady pressure for the carb to work with.

What fuel pump are you planning on using?

Tell your webber guy that rotary engines like to be fat. When I talk with my buddies about AFRs and tell them where I'm at during full boost they cringe (about 10:1). You'll find that happy place for your engine while tuning; its just going to be more rich than you are expecting.
thanks for the tips. We used 12a irons because they allow for a slightly bigger port than the stock GSL-SE irons. Also dont have any injector holes to fill.

I was going To try to use the stock fuel pump, do you know if it will work? Otherwise I was goingto use the Holley fuel pump and regulator from racing beat
Old 01-18-19, 11:20 AM
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using the stock pump shouldn't be a problem except needing to add a pressure regulator. not sure what pressure the pump puts out but it's way more than u will need for a carb.
Old 01-18-19, 11:32 PM
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Originally Posted by rxtasy3
it creates a 4 port 13b.
Meh, more good 6 port irons for me. hehe I MAKE them 4 port irons with my Dremel.

I'd go with a known good fuel pump for your carb. Carbs can be picky about fuel supply.

Are you using a down draft webber or do you have the flip over style intake with the side drafters?
Old 01-22-19, 06:11 PM
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Originally Posted by rxtasy3
using the stock pump shouldn't be a problem except needing to add a pressure regulator. not sure what pressure the pump puts out but it's way more than u will need for a carb.
is the pressure regulator compatible with the stock pump? specifically the holley regulator?
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