wingjohn2

my 67 coupe has a 540 we just installed. Makes 780 hp at 6800 rpm. 3.36 rear end with dragvette 6 link, turbo 400. this is basically a street car though I don't take it on the street much. Has side mount headers, vbp front susp. with steeroids. the car weighs 3160 without me. I just put in a 3200 converter. I race at 5200' and the car is getting sorted. Shifting early, 6500rpm, I am going 7.30 at 110 mph in the 1/8th with a 1.85 60'. This is on worn out drag radials. I took it to Lewistown, Mt.. a little lower elevation and had to race on street tires..with a LOT of spin I went 125mph at 12 flat. Again, lots of tires spin...you can imagine with that 540, and I had to get out of it some to get the traction back, so I know there is much more there. My question is this. I am running a carter electric fuel pump (old), through the factory fuel line, (3/8") and was wondering if I might be running low on fuel pressure. So I took the car out on our local back road and stuck the guage under my wiper blade and ran it up to about 6000 rpm in third gear. I noticed that my fuel pressure dropped to about 3lb. I know someone is going to say put in bigger pump, bigger line, etc. But I believe most put the big ol' honking fuel system in and they don't actually need it. So is the 3lb enough pressure for this engine? If it dropped to close to zero I would be more worried I guess. Comments?

Fordracer9

It could be enough pressure, but I'm sure that pump does NOT move the volume that your motor wants. Have you tested the flow rate with a gallon jug and a stop watch?

wingjohn2

haven't done the gallon test yet but will shortly...thanks

Fordracer9

http://holley.com/data/TechService/T...0for%20NOS.pdf

Using this formula from Holley, you should want to see 1 1/4 gallons in a minute, or roughly 1/3 gallon in 15 seconds to feed that 780HP.

wingjohn2

I know the formula, and will crawl under asap...it is mighty cold in mygarage here in Montana, but will heat things up and see what I get for flow...I suspect I am not getting enough, but will let you know. thanks for the input.

Vesa

i quess 3 is enough, but you were not yet on 6800 and it takes some second(s) to empty the fuel bowl after which you notice the car to nose and then you have hit the very lean condition...780 might also be too much for stock fuel line especially if it has any dents...

wingjohn2

ya, true. No dents in the factory line, and when i took it to the 1/4 mile track I had to get off it a few times to slow down the tire spin. I will make an attempt to get to my garage today for a test...I will check the flow at the carb end and not at the fuel pump output as this seems to be more accurate..IMHO. Sure do appreciate the response. I am willing to bet I am not getting enough flow. Will post again soon as I check it out.

K RIPPER

3 POUNDS YIKES!!! 2 1/2 LBS IS bare min.for a mild street car however if it stays rock solid a 3 lbs. you could get by after you check volume and if volume checks out ok then find a long hill in your area... high gear @ 2500 RPM put gas down and run it up to about 5000 RPM if there are any issues w/fuel press. it will show up w/that test...the prob. w/fuel delivery is if you don't check it and it is low you cannot really tell by the performance of the car if its a new build it just won't go as faST AS IT SHOULD and the lean condition rears its head in high gear and w/all the noise you cannot hear the pinging or knocking from detonation.After you have checked/corrected all fuel press.concerns put in a fresh set of plugs run it wide open through all the gears when you lift in high gear shut engine down pull over band pull a spark plug w/magnifing glass and flashlight chech porcelain if you see any dark/silver spots you have detonation if none found you are good to go.Don't take this lightly as detonation will DESTROY the strongest motor quite easily. GOOD LUCK SOUNDS LIKE A REAL SWEET RIDE

wingjohn2

ok, now I am in big trouble. I just did the volume test here in the garage..not my shop...the garage... attached to the house. Guess what it smells like now...guess who is in trouble with the wife...ugh!!! The results? I stopped after 12 seconds cause I had pumpted only a quart...I know I should be getting a gallon in 25 seconds or thereabouts, according to my formula. So the quart in 12 equates to a gallon in about 50 seconds..ackk!
Since this engine did go 9.70 in a heavier corvette, I can see the volume is way off, so time to upgrade that pump and line. thanks for all the input.

383vett

Don't blow up the house. Gotta be careful especially if the water heater is nearby. Also, forget the street tire thing. You're going to kill yourself or wreck the car with that rubber under those horses.

wingjohn2

know all about the boom effect..no sparks nearby and all cleared out now. The street tires were a joke, I must say...it was like I was autocrossing again, doing the sidestep boogie. I ate my hoosier drag radials, so will be getting another set soon. Also a new fuel pump that is up to the task.

427Hotrod

I've been using an Aeromotive A1000 on mine for years with no issues. I've got a -10 line feeding the regulator and a -8 return. I put a sump on the bottom of the stock tank.

One big difference will be when you get it to hook and it REALLY has to pull...it will use a lot more fuel. Spinning and sliding around really doesn't take a lot of power or fuel.

Tell us more about the car and motor. And how did you get it down to 3100 lbs?? Got any pics?

JIM

K RIPPER

Just one more thing to consider,don't get crazy with an over large fuel line as one thing you must consider that is the weight of the fuel in the fuel line,filters ,lines you may have as much as 2 quarts of fuel pushing back against the pump the harder the car hooks the bigger potential for problems again there is no check or test to see if there is a problem it just won't give all it can give esp in 1st & 2nd gear this tidbit came from a famous but "grumpy" racer who hails from malvern pa. If using a pump w/no provision for a return line incorporate one into the system generally return should be appx.1/3 size of primary fuel line if you "dead head"the fuel line it has the potential of fuel pressure increases while in low demand situations with the possibility of losing your float adjustment if it creeps high enough..you could in all likelyhood slap a holly blue on w/a 3/8 line and have no probs. But when you want to make sure your chit is absoult right....the prev. Post was right when fuel delivery is right and you're not a'slippin' an a sliding and broiling those hoosiers you get that 540 fat block in high gear it will pull like a saturn 5 rocket on full afterburn and that is enough power to send you to the moon ps how bout some pics and timeslips when done ....goode luck

wingjohn2

new 250 gph pump installed now, new lines, #10, new filter etc. Had to modify the original tank for a return line too, but seems to be working OK,,will get to the track in two weeks and see if it made a difference, but not sure I will see anything in the 1/8 mi. I was going 7.30 at 110mph at our 5500" track with worn our srag radials.. the only trip to the quarter was on street tires and I didn't nose over, but, then again, where was a whole lotta slippin going on. New drag radials are going on, so I will post the times.

Split327

I'll take a guess, if you get that monster to hook you'll be down in the 6's with less mph in the 1/8 and you'll have a bump on the back of your head when it snaps back when that baby leaves the line. I love it.

wingjohn2

well, the first test and tune was cancelled, so looks like next weekend. will post my times with the new fuel system and the drag radials. ANXIOUS

Fuzzy Dice

I will be interested as well...I recently had fuel issues...we put in a new holly blue, reg and filter...then a dyno tune...we bumped up the fuel pressure from 6.2 lbs. to 8 lbs. and the motor loved it...more power with each bump...then we played with the timing...we settled on locking it at 35 degrees which also gave us a 13.7 A/F ratio.....

I run a 461 BBC in an 81 Camaro...1/2 inch copper fuel lines (old school, I know) and an 830 cfm APD carb...with me in it I launch at 3700 lbs...I went 7.19 in the 1/8 last weekend on a 3200 DA...you should be deep in the sixes if you can hook...

L79racer

Post some pictures.

mackeyred96

That's the same set up I have, runs 8 lbs of pressure. Works great.

wingjohn2

well crap! Everything was great until I checked my fuel pressure...it is jumping from 4 to 6 lbs, then at the top of second gear is just blubbered like no fuel then picked up. Tried adjusting the pressure up...no help..got it to come upo from 3 to 5 to 4 to 6..wildly bouncing around. I am thinking I got a lousy pump here. Any thoughts would be appreciated.Damn car actually slowed down...of course, with no fuel it would. It is a mallory 250 pump, but was a friends used...he swore it was working great. I have-10 lines to the regulator, a =8 return to the fuel tank. The return I plumbed in from the side of the fill then down into the bottom of the tank. The regulator has a cap on one side to block it off. The other outlet has a -8 to the carb. UPDATE
I am frustrated here. Just insalled a new mallory 255 and I am draining my fuel bowls dry, everything else is ths same, looks like I will have to pull my tank to find what is restricting the fuel flow. My running pressure is at six pounds throug a holly regulator...3port...-10 from tank through a big filter, I think it is 11 " long but do not know the micron, then -10 to the pump, a -6 return to the top of the tank, and -10 to the regulator and then -8 to the carb, a 4500. any ideas???