Any HP gain by blocking fuel return line on 66 Lark GS with nailhead

6

66 buick guy

Active Member
After doing a little research on fuel return lines I'm a little confused..........I could order the stock 1/4'' return from yr one but I read some forums where people gained fuel pressure/HP by blocking off the return line..........Is this true? Or is the nail going to vapor lock like crazy on me if I do? A couple guys also said that the system works better with a larger return line.............Any suggestions guys?..............Yr one is offering me a 25% discount if I order the stock 1/4'' return by midnight tonight..............Trying to gain as much fuel pressure as possible and HP...........

66 buick guy

Mike
 
I think you may have been mis-lead. Fuel pressure has NO bearing on power as long as it is in spec. The fuel pump's job is to keep the carburetor bowl full under all conditions. Raising that pressure will only overcome the needle and seat and flood the carburetor.

What is your fuel pressure now? Do you have any symptoms of low fuel delivery?

The return line is no detriment to the system if you are holding enough fuel pressure. It provides a constant flow to keep the fuel cool and not vapor lock.

Keep the return line and check fuel pressure under ALL conditions.
 
The only advantage is under race conditions usually. At the top of the 1/4 all the inertia is pushing the fuel to the rear & if the volume is reduced because of a lack of fuel the possibilities of "Leaning out" on the top end can have detrimental effects on an engine. This would show up on the fuel pressure gauge. This would be for a higher HP car. I would keep the return at 1/4" & when racing use a shut-off valve.
Just my thoughts.


Tom T.
 
I'm assuming 7-10 PSI Texas John......now that you mention it I might splice the rubber line up front and install one....I dont have a fuel pressure gauge now....... but the car never seems to lack fuel..........and Tom, that's what I was thinking too......might as well stick with 1/4" because it's working fine now but that means another 95.99 for the SS line and 50 bucks shipping through yr one.....I'm just going to keep the extra SS 5/16" line if I do order the 1/4" line from them because shipping both ways is going to cost more than the line itself.....$50 each way. ...would it hurt anything to run a 5/16" return line?.......because my dumb ass ordered 2 of the 5/16" lines assuming they'd both be the same diameter ........
Thanks, Tom and Texas John.....

Mike
 
Hey guys, hows it going? Well, I put a fuel shut off valve on the return (I placed it so its super easy to get to under the hood) Modified a fuel pressure gauge with 5/16 hose, a 14 gauge steel bracket, and an LED light so I can view it at night inside the car........:) (probably not the safest idea having fuel line inside the car and me being a smoker but what the hell, we only live once right............The fuel pressure isn't dropping much at all at redline.......The pressure is a little higher at idle with the shut off valve shut..........I took her to the local 1/8th mile track last weekend and ran a 7.74 ET running straight LL 100 AVGAS, 26x8.5x14 MT Drag slicks...and advanced the timing about 3 degrees further than where I had it before...(which was 2 degrees advanced past stock on the balancer)..........I'm actually quite impressed with how well it ran......especially when it was 83 degrees outside with 70 percent humidity and an extremely high dew point.........Oh, and i also decided to change it to 3'' lead pipes, still running 2 1/2'' tails but going to change them as well when I get the cash.....Then off to Tom's roller rockers..........LOVE the "nailhead"'nailvalve" Keep them alive guys.............You all should have saw the look on my buddys face when I smoked his 81 El Camino with an 11.5:1 compression 383 CSB..........It was priceless...

66 buick guy

Mike
 
I'm not sure if I still have it Steve...I'll look for it.........I might have tossed it under the seat..........How do I upload it on here when I find it?............I'm still in shock from how well it ran......advanced timing and low lead 100 AVGAS with (I believe) CDL lead additive....

66 buick guy

Mike
 
You must log in or register to reply here.
Back
Top