3/8 fuel line to factory carb lines
- Thread starter Bill Monk
- Start date
BadBee
Well-Known Member
LEW
Back then I ran a STEWART WARNER ELectric fuel pump in the trunk to the pump on the block, maintaining 7-12 lbs does that sound right?
lewtot184
Well-Known Member
i have a friend who has my old mech carbs and uses a braided hose and AN fittings. i think it's a pain in the butt for servicing the carbs but he thinks it's cute. if it were me i'd do a fuel log. you can do a 3/8" line to the log and 5/16" hose connections to each carb.
as a thought i went out to the garage and did a basic flow test with my parts washer. the parts washer only does 3-4lbs pressure. i stuck a brass fitting in the hose that is .250" i.d. to simulate the i.d. of 5/16" tube. it pumped a gallon in 50 seconds. if this was fuel at the carbs it would support well over 600hp. full throttle road tests on one my cars (app. 500hp), with pressure gauge and 5/16" line, showed the fuel pump to be the main player. i was getting 2psi at high rpm. re-worked the pump to get 4psi WOT and power gains were very noticeable.
another thought is the needle and seat assembly. everybody wants to go big and stock is .110" for all 3 carbs. we know two .110" in a big 4bbl can make big power with a high flow single plane intake. i think the three .110" may not give good fuel control. if i do this again i'll step back to .101". quick fuel had a tech article about .110" being a little large. three .101" have more area at the seat than two .110" and the majority of us can't come close to using all the fuel two .110" can flow.
lewtot184
Well-Known Member
those old stewart pulse pumps didn't flow very good, 40gph i think. that's why racers used two of them. maybe your gauge wasn't accurate?
lewtot184
Well-Known Member
yep. without accelerator pumps that set up is a fire hazard.
lewtot184
Well-Known Member
the vacuum carbs should treated as a vacuum 4bbl with two extra barrels, not much more than that.
the mechinicals were a fix for the '69 carbs that didn't open quit as well as the '70-'71 carbs. i'd treat them as something like an 850dp with a small cruise carb adder. something to think about on the mechanicals is that they have nearly identical venturi area and flow to a 1050 dominator.
for those using a mech fuel pump; the hp440's (4bbl or 6pak) used a different pump. it was an 8-9lb two valve pump but the return orifice in the vapor separator must have controlled the pressure. a 9lb three valve carter can be controlled by the return orifice size. they do have wild pressure fluctuations at low rpm but can be settled into a managable pressure by 2000rpm.
the mechinicals were a fix for the '69 carbs that didn't open quit as well as the '70-'71 carbs. i'd treat them as something like an 850dp with a small cruise carb adder. something to think about on the mechanicals is that they have nearly identical venturi area and flow to a 1050 dominator.
for those using a mech fuel pump; the hp440's (4bbl or 6pak) used a different pump. it was an 8-9lb two valve pump but the return orifice in the vapor separator must have controlled the pressure. a 9lb three valve carter can be controlled by the return orifice size. they do have wild pressure fluctuations at low rpm but can be settled into a managable pressure by 2000rpm.
BadBee
Well-Known Member
So would you say use the same set up as above except go to 3/8?
lewtot184
Well-Known Member
the problem with my friends set up is a "banjo" type fitting that connects directly to the float bowl. to play with the carbs this fitting is always removed and re-installed working the threads in bowl plus minor alignment issues that wreck the threads. do some kind of connection at the carbs that's easier on the expensive parts. i did a fuel log on my quads by using hose connections for ease of maintenance.
lewtot184
Well-Known Member
a log with hose connections at that carbs makes things so simple. once i made a log for vacuum carbs once upon a time, but truthfully i never had an issue with factory style plumbing ONCE i developed a good maintenance system to keep myself honest.
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