Normal fuel pressure 6 & under?

[cadipacer]

The Pacer has the 500" from 73 Eldo,,,, has the A/C Delco new mech-pump 3/8 line TO pump,, 5/16 out TO carb,, the pressure is 5.5. on idle then on the primarys 4.5 lbs,, then full throddle it drops to 2.5 lbs,, then of course starves and you hear the sound of air suckin in.,,, let off accelerator and it recovers...
I was told that it should have 7-9 lbs at idle???
they said increase 5/16 to 3/8,,,,
set float level as high as possible,,,
and have at least 1/2 tank of gas on full acceleration dump 1/8 mi or so..
OR get a ELECTRIC fuel pump and run through mech pump, ever heard of all this??? Its time to fun run and I"m soft pedaling because of the carb problem,,, thanks Phil

[cadillac512]

You should not have 7-9 lbs at idle.5- 6 lbs is plenty,especially with a q-jet.7-9 will flood the carb.
Do not attempt to cover up a fuel supply problem by raising the float level.It will run badly at all rpm rather than just full throttle like it does now.
3/8 line from pump to carb is a good idea.

You bet... a small electric pump in the rear at 4-6 psi pushing fuel from the rear of the car through the mech pump will likely solve your problem.I run that setup on my Malibu/472 and it cured the problem.
Get ready for a lot more power!
Terry

[cadzu]

http://img287.echo.cx/img287/5113/yup0wx.gif (http://www.imageshack.us)

[Caddycarlo]

I also agree with Terry..... could not have done a post that well put myself

[Gorf]

Is there any benefit to just completely bypassing the mechanical pump all together? I was thinking of doing that. Maybe I am missing some benefit somewhere (beyond the whole redundant pump scenario).

[cadfor]

I agree with everything stated above but have never been a big supporter of adding an electric pump to push to the mechanical pump. Just do away with the mechanical, set your psi regulator to 5-6 psi and run it straight to the carb. If the mechanical pump can't do it and it is new then either the suction line from the tank has some sort of restriction in it, is to small (go to 1/2", old swap rat trick). The pick up in the tank could have a plugged/coplapsed screen or pick up.
Had an old ford once that had the same problem, tried all the above, it turned out to be a rag was used by the previous ower as a fuel filter in the tank!!

[cj2/500]

Gorf , I'd keep the mechanical on yours. the fuel has a loooooooooonnnnnnnnggggggggggg way to travel :!: The pusher/puller method is a very efficient way to go. If you can afford one of the crazy expensive pumps like the holley blue, and an extra regulator, you'll never have delivery problems with a full 3/8 system. My sand jeep has just a holley red and an extra reg. This is a real no no with nitrous, but it doesn't have far to travel :) The gauge has never dumped below 3 on a full throttle nitrous pass. I would consider this system as barely enough and wouldn't reccomend it to anyone, but I've been getting away with it.

[DOC]

hey cadipacer,
how about some pics of the bad ass pacer. yours is the first one i've heard of. weight to power ratio sounds fun!

DOC

[cj2/500]

Cadipacer, do you have a true 3/8 nipple coming out of the tank? I'm pretty sure it came with 5/16 if your tank is stock. also a problem I've seen on AMC products is the "sock" in the tank. when they are pushed on the tube, the plastic peels and curls into the tube. If your car uses this style, I think it'd be worth a look. While your at it drill a hole and solder a 3/8 (or bigger) tube into the tank unit that follows the same basic curve as the original. Try to get a sock that fits the new tube. Leave the original line alone but plug it from the outside. this will allow you to use it as a return line if you ever choose to run an exotic fuel system :!: (also the sending unit is probably structured off of the original pipe)Just a few things I've run into with big blocks,hope it helps.

[cadipacer]

Thanks for all the quick respose,,, this is what I know, and have done:
The sock in tank is removed,,
the tank nipple is probably 5/16 so it can be drilled to flow better...
The use of MECH pump WITH ELECTIC is to regulate pressure to carb,( I was told by diehard 1/4-miler)
Was told to get the " blue" unit as someone mentioned above for the correct flow rate...
So the only thing odd was the advise on the 7-9 lbs is too much pressure..
Most of US agree about 5-6 lbs is enough..
The PULL is the problem from the tank,,
I did notice that I turned a corner hard in 'low range'
then layed full throttle, and the guage dropped fast to 2 lbs,then falls,,,
which leads me to- no baffles in gas tank, so 1/4 tank is not good( 22 gal tank)
for a suprise run on the street ,, othewise
it might fall down in 2nd gear.
I'm working on all these ideas everynight,, THANKS to ALL..

[RED caddy]

This set up i the best I've used: Holley blue pump, 1/2 inch hard line from tank to "spin on" style canister filter, (NAPA) mount pump and filter close to tank, and as low as possible. short 1/2 inch hard line from filter to pump. ( yes, filter first, then pump) The long run to the engine room should be 1/2 inch hard line, support every couple feet, or run in side frame if possible.
I use standard tubing flare fittings from the hardware store or NAPA, and aluminum tubing, ( soft drawn alum. tube is accepted by IHRA,NHRA ,NMCRA and most other sanctioning bodies as well) it is easy to work, and hand forms easily with the "slip over"style spring benders.
Screw a 1/2 in pipe to 1/2 in tube flair adapter into one end of a 1/2 inch pipe "T", ( I use brass, but steel is cheaper, however steel flair fittings are hard to find, and alum are too expensive for my CSOB building style) And a 1/2 inch pipe to 3/8 tube adapter in the other long end. I use a 1/2 inch pipe to 3/8 hose, 90 deg. adapter, (home desperate or NAPA) in the short side of the "T", for the fuel supply hose to the carb, and a pressure gage.
Run a short piece of 3/8 hard line from the adapter in the long end of the "T" to a convient location, and splice in a small "billet" fuel filter body,(Summit, Jegs or NAPA, about $10) with about 3 inches of hose on each end, then run 3/8 hard line back to the tank, set the end of the return line about an inch off the bottom of the tank, to minimize the splashing and aeriation of the fuel. (splash oxygenation)
Now go back to the "billet" filter body, throw away the sintered bronze screen, and measure the inside length and diameter,( the ones I use are app. 3/4 in. dia X 1.070" long, but yours might be different) make a LOOSE fitting plug,(cylinder) (a tight fit makes it a real b##tch to get out , and it seals against the rubber gasket in the holder anyway) from alum, brass, nylon,HDPE or any other fuel safe material, drill a 3/32nds hole thru the length, to start with, and install it in the Billet filter holder. The filter holder is now a return pill holder, just like we use on alcohlol and nitro motors, just lots cheaper...
Clamp off or plug the fuel line to the carb,(you don't want to flood the carb)and light off the pump, read the fuel pressure on the gage at the carb, with that pump and small "pill" the pressure will be around 12 to 15 lbs, open up the hole in the "pill" in small steps, untill you get the pressure you think you need, I run 4.5 to 5 lbs on my RED with a 950 Holley DP. (I got real trick, and machined my plug to accept Hillborn pills, 'Cause I have lots of them left over from my funny car days,LOL LOL) You can also drill out the fitting ends of the billet holder to a larger size, but it's not going to bother the return flow much, to leave them alone.
You now have full flow capacity of the 3/8 hose at a constant pressure, that will not change with RPM's or acceleration, and cooler,denser fuel at the carb inlet. With just a pump change , you can step up to EFI or NO2 This setup will easily support more horsepower than our beloved big block caddy's can make with a carb, even on alcohol... C-YA RED