Fuel Pressure Gauge

[Redneckchevy]

Maybe i thought i did...Who knows...It was a long time ago since i had done it 

[Stewart G Griffin]

If i could revisit this topic.....because i really need to.  (me and my problems....)

1) i am also thinking/wanting to  put a fuel pressure gauge on my stock Q-jet with stock fuel line.  But of course it is very tight.  i suppose i could get a tube bender and bend the line slighly to the left (if viewing from the front of the truck)?  i don't really want to cut into the stock line.

a) Mr. Hauling, could you, if possible, post a picture of your test rig setup?


2)  If #1 above is not practical right now,  i am also thinking that i would put together a totally new fuel line just for testing purposes---this way i can just take off my stock line and put in the "temporary line" for quick testing and then re-install stock line etc.  What are some quick, easy, AND SAFE ways to do this?

i'm thinkng to get the appropriate fuel fittings for the pump output side and the carb input, do you know what sizes they are?  Then, a rubber hose.  And then, of course, a "T" fitting for the mechanical gauge.

By the way, the service manual says that if you have a vapor return line on the pump, the pressure should be 5-7.5lbs. and if you don't, 7.5-9lbs.    Which suprised me, and i think it's a bit high, but that's what the manual says for 83's.

[HAULIN IT]

Stewart, I don't have a picture, I guess I could take one, but it's real simple. I've made a couple styles. One, is just a "test" unit made from an extra "big nut" with a 1" long piece of fuel line & nut brazed on a washer (capping off end where the filter goes) brazed on with a 1/8" pipe coupler brazed on the side (for the gauge). The new fuel line nut threads into the carb's original "big nut", then the original fuel line goes in the new "big nut".  The other "perminant" set-up is non Chevy carbs have a longer "big nut" fitting where the fuel line goes into the carb (they have a area about 1 1/2" between where the inverted flare is & the treads that bolt into the carb. In this area, I drilled a 3/16" hole brazed on 1/8" pipe thread coupler (one that would be used to attach two pieces of 1/8" pipe) Now one of the small gauges (that have the 1/8" tread) can be screwed in or a 1/8" to tubing adapter (like for an oil pressure gauge) can be used or a 1/8" to #4AN fitting can be installed & braided hose can be used, this set-up, the original "big nut" is discarded. Understand? Lorne     

[Stewart G Griffin]

.........Not really.....i'm a little slow mechanically.  But you already knew that.  i sort of understand the second "B.O.P." version.  But then again not solidly.

That's ok;  i've found some stuff in the garage that i can rig up.  Do you happen to know what size fitting screws into the "big nut?"  i've discovered that both the pump and the carb input are the same size.

[frogman68]

.........Not really.....i'm a little slow mechanically.  But you already knew that.  i sort of understand the second "B.O.P." version.  But then again not solidly.

That's ok;  i've found some stuff in the garage that i can rig up.  Do you happen to know what size fitting screws into the "big nut?"  i've discovered that both the pump and the carb input are the same size.

Should be 3/8 tube

[HAULIN IT]

Stewart, Yes It's 3/8" tubing. Here's a quick scribble of them...It was easier than putting my coat & shoes back on to go to the garage, besides it's cold out there!
 The top one is the "test" version. Basically I took a 3/8" tube cut off 1/2" from the nut & sat it on a plate of steel, then slid a 3/8" fender washer over the tube & brazed the tube to the washer. Then laid the "big nut" on the plate (open end up) & brazed the washer on. with the 1/8" coupler mounted in the side, all you need to do is unthread the vehicle's fuel line & thread the new one in the carb & then the fuel line into the new "big nut".
 The lower one is self explanatory, I think. Lorne

[Stewart G Griffin]

OK, thanks.

Also, i forgot to mention, on pg.119, middle picture, of the rochester book by Doug Roe, he has an interesting idea for a pressure gauge take off.  He didn't go into detail about it.  i personally wouldn't want to try it.

[HAULIN IT]

Is that drilling & tapping the carb body just behind the "big nut"? I've seen that done & I agree it seems a little risky, the casting is not very thick there. For a perminate set-up I like the bottom one in my drawing. Lorne

[Stewart G Griffin]

Yes, it's drilling+tapping and i don't like it.  i think the best way is to bend the fuel line so that the inverted flare of the line ends up an inch or two to the left of the fuel inlet nut.

Example:


Then get an inline adapter for the gauge and the appropriate AN or NPT fittings.  Then, you have a leak free worry free and more or less permanent solution.  Or use your BOP nut idea.

http://www.jegs.com/i/JEGS/555/100520/10002/-1

[HAULIN IT]

While we're on the Q-jet nut discussion....Ponder this one a bit. I don't think you'll find it in the Summit catalog. Lorne

[smitty77]

Is that a y-fitting commonly used for multiple air hoses on one line.  Kinda like THIS but remove the quick connects?

[HAULIN IT]

Smitty, No...It's just a homemade piece. A regular Q-jet "big nut" with the inverted flare seat bored out. I buy steel 37* hose ends at a local hydraulic supply store & brazed it up. Lorne

[Stewart G Griffin]

So why do you have 2 lines going into the carb?

[smitty77]

Smitty, No...It's just a homemade piece. A regular Q-jet "big nut" with the inverted flare seat bored out. I buy steel 37* hose ends at a local hydraulic supply store & brazed it up. Lorne

Nice work.  Brazing seems to be coming a lost art.

[HAULIN IT]

Stewart, It was one of those things...I started with this, but shoulda used that, I have this & I have that. I found my air/fuel meter would continuously rise after about 100' out. I kept adding jet & smaller sec rods, but no fix. I talked to an acquaintance I met several years ago at a track. He has a Buick Skylark that he races in the FAST class (Factory Appearing, Stock Tire. Going LOW 11's with a Q-jet, cast iron intake & exhaust manifolds on bias ply Redline tires!), He was convinced I didn't have enough fuel going to the carb. I was running #8 hose from the cell to the pump (Edelbrock 120gpm), #6 to the carb. Doing some figuring with a flowchart, it should have been plenty. The small bowl of the Q-jet was something he had fought.
  I had an extra fitting on the cell, a couple feet of #8 hose, a spare 100gpm Carter pump, a filter I was going to put on my skidloader & coffee can of various fittings. I only had to buy the #6 hose. What I did was hook up the second pump on a toggle switch, she turns it on after the burnout (prior to turning it on, the fuel returns through the Carter pump, which helps eliminate stagnant fuel which would be worse with One #8 hose from the back to the front). My plan is to set up the second pump on a TH400 kickdown switch so it will come on automatically. I wanted to test it turning the pump on before leaving the line & then at the line (once at full throttle) to see if that way is ok. In the end, the meter holds steady & I ended up taking out a little jet which helped for daily driving. The other nice thing... if one pump craps out, I can still get home We set my brother's Mustang up with Two pumps, they are "Y'ed" in the back though & a #8 hose going to the carb & a #6 going to the NOS solenoid. When we did the Power Tours, we would run one pump per tank of gas then switch pumps to keep one from running all day. 
 As to brazing being a lost art, yea I agree Smitty. It works well when trying to make a sealed item, especially if made up of different thicknesses of metal. Lorne