Merlin - Fuel System Info
02-18-2002, 09:59 PM
#1
Burning Brakes
Thread Starter
Merlin - Fuel System Info
Merlin: Here's some info I got in an email today from a guy who's big in SCCA, it might be useful to you.
The only way I know to build a workable, works in every corner, puts out
the correct pressure always, no maintenance fuel
system is what most of the notes are saying.
2 Holley 12-801, 7 pound pumps in parallel near the cell and wire them
to two separate switches. They are relatively
cheap (Jegs $75), pretty bullet proof and repairable. They have been
building that same pump for a long time and it's a
well proven design. I have a spare pump repair kit that I have never
used in 22 years of on again, off again racing. Run
one pump from one back corner of the cell and the other pump to the
other back corner. There is an internal bypass
circuit and pressure regulator on the pump, so if the thing sucks air it
pumps the air in a circle until it sees fuel again. The
pump will run for a long time dry also, which the in-tank type pumps
won't do. Put 2 check valves in just downstream from
each pump to keep the fuel from going back into the cell when one pump
is off, and run everything teed into one -8 line
going to the engine. Near the engine, forward of the firewall, put in a
Holley pressure regulator 12-803 (Jegs $20) set to 7
pounds and you can run either -6 or -8 line to the carburetor from there
This is not the place to skimp on lines. I would
use either steel or aluminum AN fittings and steel braided line all the
way from the tank to the carb. I've run that setup in
every car I've ever raced from a Trans Am Corvette to the AS car and it
never fails and always gives you fuel pressure no
matter how hard you are throwing the car around. Give me a fax number
and I can send you a schematic of the
plumbing, but it's pretty intuitive.
Number 2:
I switched to two fuel pumps at the start of last season....and fought
fuel delivery problems all season long. Like the
suggestions of others, I used two check valves and a "T". I now think
that my two pumps were "fighting" each and
keeping my check valves closed to the point where little fuel was
actually making it through the check valves. It would
sound like I was on a rev limiter from about 2500 RPM and up.
To fix the problem, I just replaced the "T" with a new "Y" piece made by
Peterson Fluid Systems
(www.petersonfluidsys.com). This allows the fuel flow to move in a more
natural and unencumbered direction. I can
already hear the difference in that the check valves are not clattering
as much as they did in the old setup.
I also installed a new Aeroquip fuel test port dry-break fitting after
the "y". After hearing so much about different
dry-break pieces leaking, I was VERY pleased with this setup. No leak whatsoever (both parts are NHRA approved). The
part numbers are FCM3081 and FCM3083 and I picked mine up from Racer
Parts Wholesale. These parts are highly
recommended!
The only way I know to build a workable, works in every corner, puts out
the correct pressure always, no maintenance fuel
system is what most of the notes are saying.
2 Holley 12-801, 7 pound pumps in parallel near the cell and wire them
to two separate switches. They are relatively
cheap (Jegs $75), pretty bullet proof and repairable. They have been
building that same pump for a long time and it's a
well proven design. I have a spare pump repair kit that I have never
used in 22 years of on again, off again racing. Run
one pump from one back corner of the cell and the other pump to the
other back corner. There is an internal bypass
circuit and pressure regulator on the pump, so if the thing sucks air it
pumps the air in a circle until it sees fuel again. The
pump will run for a long time dry also, which the in-tank type pumps
won't do. Put 2 check valves in just downstream from
each pump to keep the fuel from going back into the cell when one pump
is off, and run everything teed into one -8 line
going to the engine. Near the engine, forward of the firewall, put in a
Holley pressure regulator 12-803 (Jegs $20) set to 7
pounds and you can run either -6 or -8 line to the carburetor from there
This is not the place to skimp on lines. I would
use either steel or aluminum AN fittings and steel braided line all the
way from the tank to the carb. I've run that setup in
every car I've ever raced from a Trans Am Corvette to the AS car and it
never fails and always gives you fuel pressure no
matter how hard you are throwing the car around. Give me a fax number
and I can send you a schematic of the
plumbing, but it's pretty intuitive.
Number 2:
I switched to two fuel pumps at the start of last season....and fought
fuel delivery problems all season long. Like the
suggestions of others, I used two check valves and a "T". I now think
that my two pumps were "fighting" each and
keeping my check valves closed to the point where little fuel was
actually making it through the check valves. It would
sound like I was on a rev limiter from about 2500 RPM and up.
To fix the problem, I just replaced the "T" with a new "Y" piece made by
Peterson Fluid Systems
(www.petersonfluidsys.com). This allows the fuel flow to move in a more
natural and unencumbered direction. I can
already hear the difference in that the check valves are not clattering
as much as they did in the old setup.
I also installed a new Aeroquip fuel test port dry-break fitting after
the "y". After hearing so much about different
dry-break pieces leaking, I was VERY pleased with this setup. No leak whatsoever (both parts are NHRA approved). The
part numbers are FCM3081 and FCM3083 and I picked mine up from Racer
Parts Wholesale. These parts are highly
recommended!
02-19-2002, 02:16 PM
#3
Race Director
Member Since: Nov 2000
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Re: Merlin - Fuel System Info (ddn)
This is a fuel system for a carberated engine not a fuel injected engine. If you read past posts he wants 50 psi not 7.
Sounds like a nice system thou for a carb.
Sounds like a nice system thou for a carb.
02-19-2002, 04:13 PM
#4
Burning Brakes
Thread Starter
Re: Merlin - Fuel System Info (norvalwilhelm)
Doh! I didn't even think about that. That's true, but the bit about the check valves and the Y fitting still applies.
02-19-2002, 10:34 PM
#5
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Re: Merlin - Fuel System Info (ddn)
Yup. Very easy to get that kind of pressure in a carb. Much tougher at 50psi. Thank you though, I do appreciate the effort! We switched from series to parallel & got 200GPH today. Fuel system is ready to rock. I'll post more later...
