[quicksilver97ta]

I ran my newly installed Q-jet at the track and discovered it runs out of gas like so many others have posted about. This was after converting from a Holley which never had that happen so that was a new experience, the car nosing over like that in first. Freaked me out the first time! It did it worse sometimes than others and even when I had one run where it didn’t seem so bad the ET was waaay off so I’m guessing it’s a bigger problem than the very obvious nosing over.

The tank was full so there is no way I was uncovering the pick up in the tank. Fuel system consist of ½” pick up, no sock, ½” hard line all mandrel bent to the front sub frame, at the front subframe it’s ½” rubber line to the pump. Pump is a NAPA pump, large canister for an early 70’s 455.

I used the original 3/8” supply line for the return and I wonder about that. Of course the nipple for the return on the pump is the smaller 5/16 size. But I wonder what role a restriction there plays in a mechanical pumps pressure? I was checking out the RobbMc pump and the instructions for the return specify his fitting with a “tiny” hole and state that a regular fitting will yield a big pressure drop if used. Also, I run a Wix clear plastic filter in front of the carb but I did not remove the filter from the fuel inlet on the carb, so two filters. Possibly a little more restrictive? But both filters are brand spanking new.

I plan to set up a fuel pressure gauge to watch but I really wonder about the return line the way I have it and also the filters to a lesser extent.

[NHRASuperStock455SD]

running a Qjet requires a fuel system to match. You have a very small fuel bowl and a very small needle and seat.

We run 28PSI to regulator. Remember that 12V on your battery ends up about 10 without an alternator with everything on. I run 16V so going down the track I end up the proper voltage. If not 16V run an alternator.

Run a relay on the fuel pump not directed wire. The switches cant handle the amps. Ground everything all the way back to the battery. Do not use terminal grounds. Ground the engine to the frame in several places and ground the frame to the negative side of the battery.

Tubing is measured OD and hose is measured ID. So if you have 1/2 tubing it is probably about 3/8 ID. So you are very limited in HP especially if you have pressure/voltage issues.

If you are using a mechanical pump, then put an electric booster pump in the rear. Run it at least 20PSI with a blow off valve and return like back to the tank.

Aeromotive recommends 3/4 ID hose on the suction side of the pump and 5/8 ID hose at 24 PSI minimum to the engine compartment and step down from there. We run two hoses 1/2 from the 4 port regulator to the Qjet. If it isnt there on the inlet side of the Qjet.....ur running out of fuel.

If you do this, you will make more power out of the Qjet than the holley. Call Mike Beachy at 317-452-9051 and order a hanger adjusting tool. You can then tune your Qjet just by changing the hanger and never take the carb apart (once it is close).

[quicksilver97ta]

Thanks Lynn, I know others have used an electric and and made it work I just dont want to do that with this car. I want to stick with a mechanical. The hard line is 1/2" ID stainless (or .494 something, I would have to measure). The seat is Cliff's, still might be small but I did the best I could there. And the float is 1/4" per his spec.
I wonder about that return though. I can restrict it, block it, test ect, I just wonder if anyone else has been down this road and made these parts work?

[NHRASuperStock455SD]

Do you have that high performance mechanical or stock? How much HP is this engine? Remember the stock mechanical stuff was for what 370HP max out of a RAIV? You quickly run out of fuel trying to use a fuel system designed for 330-370HP when you try to run more.

First thing we learned in the early 70's about our Firebirds. We rejetted the carb, increased the fuel supply and curved the distributor, installed 1.65 rockers, and installed 3 tubed Doug Thorley headers w 3 inch collectors(someone gave us those). It was what we called a Catalina Motor which was the base 400/325HP. The car ran 12.90 w 4.11 gears. Of course the 1.65 rockers made the valve spring float about 5500.

[quicksilver97ta]

The pump is from NAPA and I can't remeber the mfg, probably the NAPA brand though as I just pulled up NAPA online, listed as OE mechanical type. Well maybe it's just not up to it despite line size no matter if I restrict the return or not. A friend has the RobbMc pump and 1/2" lines and according to him he still has some sort of issue but he is still sorting things out. Anybody run a mechanical only with their q-jet?

[boater bill]

I am running into the same issues with what seems the Qjet running dry at full throttle occasionally. it just falls on it's face and I quickly get out of the throttle. I'm running a 70 Q-jet with 1/2 hard lines to Mr Gasket mechanical fuel pump I believe is rated at 8 PSI, AN to the Qjet inlet. and no return lines.
I've had this happen with a full fuel tank as well.
the float level and everything is good.
And this is my new 400/461 that is estimated about 475 HP witha M-20 and 3.23's backing it up.

[Cliff R]

I couldn't keep up with my old whimpy 428 engine with any sort of mechanical pump pulling from a stock sump. I fought all sorts of fuel delivery issues till around 2001. Installed a sumped tank, 140gph electric pump behind the tanks, and 8AN lines/fittings everywhere.

I also run a return line back from the regulator, to take some load off the pump for street use. Been a great system, never had the first hint of fuel delivery issues since.

I agree with Lynn about making power, once you figure out the Q-jet deal, nothing else is going to outrun it, even on some pretty high powered set-ups. I also like being able to tune at the track in seconds without taking the carb apart. I use and prefer secondary metering rods that are machined from the same cores, vs messing with hangers (once you find the right hanger). I've actually observed carbs go lean when smaller tipped metering rods were installed, due to having a fatter upper section, shorter tip, or different included angle leading to the tips. This surprised me at first, then we started using machined rods for reliable metering changes run to run.

Fuel pressure is equally as important as fuel inlet seat diameter. I've done a LOT of testing in that area, and can keep up with my new 455 using a .135" diameter seat and 6lbs pressure. I gained NOTHING going to larger seats, but it will fall off if the pressure is not kept above 5psi for the entire run......Cliff

[67cruiser]

I took Cliff,s advice last yr. and added A Mallory pump with my no.8 from tank to carb. and no.10 for a return, , so far not a issue, Tons of fun so far, Only question i have is im running the biggest RobbMac filter 10 micron and im worried its to restrictive, getting a little bounch from 6 psi to 8 filter is clean. Robb mac bronze style filter is really small visually, i may try something differant before end of the yr. See you at Norwalk Cliff, thanks for all your help. Next step working on the govenor.
Oh ya .135 needle and seat no clip with his blue pump!

[chitownTA]

I made it down the track with the robbmc 550 pump and 1/2" lines/pickup running 12.50s at 109mph. No nosing over at all. About 6.5 psi using the supplied return fitting to stock return line. .135 needle/seat.

The return fitting has a tiny orifice inside it to keep pressure up but still keep a little fuel moving.

[quicksilver97ta]

Ok Chi, I'm glad somebody has. Have you observed the fuel pressure while racing? I have made arrangements to try a RobbMc 550 pump. It will be a while before I get to do all this testing but I'm glad to have a plan in place. Thanks for all the replys.

[chitownTA]

Sorry no I did not have a gauge set up at the track. I never felt a drop in power down the track. My et should have been a bit quicker but I had a slight stumble off the line giving me a 1.9 60 ft. This was with stock port KRE d ports and 60919 cam.

[quicksilver97ta]

Well I'm hoping for good results. I havnt even done any real street testing on this new carb. The traction at the track wont be duplicated but I think I should be able to see something wrong on a guage even on the street. If I make any improvements they should show up too.

[Region Warrior]

Like Lynn and Cliff, got to get the fuel to the carb.
That NAPA pump isnt enough. Try a Robbmac if nothing else.
I have 140gpm pump at rear, and regulate pressure just before the carb.
3450lbs = 12.0 @ 114 all day long in 90* + heat w/a RAIV cam, 10.1 cr, stk th400, 3.42's.
High 11's in good air.
0-140 WOT not a prob.

[quicksilver97ta]

Yeah, the electric is the best way to go no doubt about it. I remember reading Cliffs post about his set up a few years ago but at the time I decided I just was not going to do that with this particular car. It previously had the battery in the trunk and electric pump but now it has a new trunk pan, new tank, battery is back in the original location under the hood and running a mechanical pump. The nicer I made the car the more I liked the original ‘appearance’ theme.

An in-tank pump has crossed my mind but hopefully I can get it sorted out without it.

[Cliff R]

I like everything about having my electric pump behind the sumped tank but the looks of it. I tucked it up high and hit it with semi-gloss black paint so it's not easy to spot.

The fuel return set-up is a must for cars that will see a LOT of street use, IMHO. I "fried" my first Comp 140 pump in just a few hours running it "dead-head".

With a return, the second pump lasted over 10 years and only needed a brush replacement.

I just swapped back in the original last summer, which was factory rebuilt under warranty, still going strong.

They are also a LOT quieter with a return system in place......Cliff

[harry k]

"The fuel return set-up is a must for cars that will see a LOT of street use, IMHO. I "fried" my first Comp 140 pump in just a few hours running it "dead-head".
With a return, the second pump lasted over 10 years and only needed a brush replacement.
I just swapped back in the original last summer, which was factory rebuilt under warranty, still going strong.
They are also a LOT quieter with a return system in place "

been runing mallory comp 140 "dead-head" for 25 years till now (since 1987) in personal firebird that sees lots of hwy driving and 8+ years in customer project car AGAIN same way no return line & noise wise you can't hear those quite pumps to start with !

but then again "opinions vary in this site"
end of this conversation....

[gearbanger]

I have also fried a Holley HP150 pump running it dead head, even though holley claims it doesnt need a return. They just cant sit and circulate through the bypass like that. They have to fight more pressure and it builds up heat in the fuel which can cause cavitation. I like to go to cruises so we sit in gridlocked traffic alot. I went Robb Mc return style reg and havent had any more issues and the fuel pump is quieter that way too.

[Cliff R]

"I have also fried a Holley HP150 pump running it dead head, even though holley claims it doesnt need a return."

You just needed to drag your car out to California to get Harry K to set up the dead-head system for you.....

But then again, opinions vary on this site, end of this conversation!.......Cliff

[Todd1035]

The recirculating fuel system is superior to any deadhead system on a q jet or single Inlet small fuel bowl type carberator in a performance application. For driving and getting ice cream the a dead head system will get you by. Made a big difference in my last car for controlling the fuel curve, especially in cold weather. Almost .15 for me

[gearbanger]

Of course it can work, new corvettes have gone to a dead head type system. But these aftermarket pumps are just not as tough as factory stuff with 100,000 mile warranties. Sometimes it works, sometimes it doesnt.