[Cliff R]

It's just not a good idea to "dead-head" with a rear mounted electric pump for long term street use. For "normal" driving, you aren't using 2 percent of the pumps capacity. Most have around 14psi relief springs, so ALL the fuel is being circulated right back to the inlet side of the pump. They get really hot, in short order without fuel flowing thru them to cool things down some.

The vane style pumps often start "howling" in protest when sitting in traffic for long periods of time. The gear type even get a tad noisey.

The gear type are just about dead quiet when you provide them with a bypass line to take some of the load off of them. They don't heat up much either, so common sense would tell the user it's liking that deal.......FWIW.....Cliff

[gearbanger]

Exactly and the factory deals that have a dead head are also in tank pumps and the fuel they are sitting in keeps them cool. No such advantage on our setups.

[grandville455]

My bird has twin holley blacks to two big holley regs, and they run cool , dead headed also..

[quicksilver97ta]

I read the Robbmc mech pump uses a .040 restriction on the return and still gives up 1 lb of pressure. My 5/16" return outlet dumping to 3/8" return line has got to be giving up some needed pressure then. How does the vapor return port work? Are they just another outlet perhaps from a higher part of the reservoir in the pump?

[quicksilver97ta]

Found this while searching. I see how the vapor return works, at least until the canister is full, then it would return fuel. The top of the vapor return looks tapered but nothing like a .040 restriciton. Hard to believe this builds much pressure at all !

[Formulas]

There is a restriction in the return outlet in the stock pump... i remember looking into the outlet and seeing it..

of course it could be configured differently on any manufactures pump.

you are right on suspecting it wouldnt build pressure a open 5/16 line bleeding off would be a challenge

[TCSGTO]

I am running the RobbMc 1100 pump and it keeps up with the Q-Jet just fine. I installed a -10 bung at the bottom of the tank and run -10 up to the pump,-8 to the Mallory regulator set to 6.5 psi,and a short 6" 3/8 hardline to the carb. I'm running the .135 seat too. I use RobbMc's pre and post filters and have the vapor return functional. It is the only mechanical pump I've tried, and I've tried alot of them over the years, that gets it done.

I've burned up 2 Mallory 140's and 2 Carter electrics running them dead headed on the street. They worked great for awhile but sustained idle and low speeds did them in.

Once you get enough fuel to it the Q-Jet will handle just about any street/strip combo and once tuned in it's a set it and forget it deal.

[harry k]

Originally Posted by Cliff R

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

smart a__ coments above


quote from mr.know it all
"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".

http://forums.maxperformanceinc.com/...49&postcount=1
content of link above
"After many years of excellent service" & bla bla bla




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 !




solid proof for ^^^^^^ dead head use

[Skip Fix]

FWIW my first Mallory 140 lasted 10 years alot of street and track miles. Replaced it with one and it's still going now 15 years later. Both have been dead headed, no relay.

It took the electric pump and 1/2"(-10) from the pump to the Q jet to keep it fed for a 400 HP motor.Still feeding a 550 hp motor with a Holley.

[harry k]

Originally Posted by Skip Fix

FWIW my first Mallory 140 lasted 10 years alot of street and track miles. Replaced it with one and it's still going now 15 years later. Both have been dead headed, no relay.

It took the electric pump and 1/2"(-10) from the pump to the Q jet to keep it fed for a 400 HP motor.Still feeding a 550 hp motor with a Holley.

oh wow really now
Skip i don't ever remember you hauling your car to California to "Harry K's" to get a "dead head" system installed

how did this possibly happened?

[Nicks67GTO]

How large of a return line do most guys need? I'm running the RobbMc 1100 pump and regulator and using the stock vapor return line on my 67 GTO. Is it big enough?

[Cliff R]

"I've burned up 2 Mallory 140's and 2 Carter electrics running them dead headed on the street. They worked great for awhile but sustained idle and low speeds did them in."

You mean you listened to Harry K and still burned up FOUR pumps! How can that be???

Having the relief valve open all the time does NOT allow any fuel to pass thru them, at least not enough for any cooling effect. Some get away with dead-heading them, most that do a lot of street driving, and get stuck in traffic, etc, find that it just makes sense to take the extra time to run a return for the pump, so it's constantly flowing fuel thru it for cooling. Avoids cavitation as well, which can be heard more on the vane type than the gear type......Cliff

[harry k]

Originally Posted by Cliff R

"
. Some get away with dead-heading them
......Cliff

now we are contridicting with ourself here

[Cliff R]

I've been at this hobby since the 1970's, and still have never once seen a rule book on any of this stuff.

Some folks are smart enough to know the right way to do things, others dumb enough to keep giving poor advice, and there are even others who don't give a rats but either way.

If you like doing things one way or the other, and they work for you, and you are happy, then I'm happy for you.

Did anyone miss the post above where a guy burned up FOUR, yes that is FOUR pumps running them dead-head.

I've observed pump life shortened considerably by running them dead head, and observed pumps running extremely noisey after sitting in traffic, lots of low speed driving, idling, etc. We've corrected both issues by installing return lines, so for some applications we know it works better. Doesn't mean it's for everyone, just giving some good sound advice based on many years of actually doing this, no more to it than that.........Cliff

[harry k]

the point here is:
you dodge the many posters that are saying that it works for them for many years with dead head system and in return you start your book writing skills to sidetrack the readers to make them believe that your method is better way ....
me me me and we we we !!!!!!!!!

[Cliff R]

Nice Harry.

What I really do is provide readers with methods to do these things that we have found to work, thru many years of actually doing it.

Cripe, you have already pointed out that you can install the wrong length metering rods in the primary side of a Q-jet, then go back in and install the wrong jets to make them work, and come up with a good end result. Does doing things like that make your methods the best way to get the job done?

I'd much rather install the right parts the first time in, get a perfect end result, then go on and work on something else.

Same deal here with fuel systems. Folks have been "dead-heading" fuel systems for decades. The manufacturers of the pumps involved also send diagrams with them saying you can do this. So if it works for some, I'm happy for them.

If I can provide a flow path to pull about 136 more gallons of fuel thru a 140gph pump in one hour or so of street driving at light load and low rpm's, then that's what I'm going to do. I know the additional fuel flow will help cool the pump, and it woln't be hammering as much fuel up against the PR valve and back to the inlet.

Two things will happen here, the pump will run cooler, and the brushes will last longer. Same end result for the user as far as fuel delivery to the carburetor and vehicle performance is concerned.....FWIW.....Cliff

[shaker455]

Originally Posted by 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.

Yes, I went thru this too with my Qjet once I upgraded my combo.

It can be very frustrating when your trying to have a fun night at the track.

I run both but we went in opposite directions, I went to the Holley and you went from a Holley to the Qjet.

I found you don't have to modify alot of the fuel system with the Holley to keep the engine supplied for a 1/4 mile run with fuel longer because of the large bowls compared to the Qjets smaller & centeral location.

Bottom line is the price to pay is leaving Hp on the table.

Going dry is a sign that the overall problem is supply reguardless of the carb.

Seeing you have the 1/2" line in place I would say try the RobbMac mech 550 or 1000 pump.

As for the filters, the Qjet has a very small inlet opening right after the filter so the factory filter is going to be an obstruction.

I would suggest removing the factory and Wix #33003 bulb style filter and replacing it with a Summit or Jegs billet inline high flow unit that filters 10 microns and can support up to 1000 Hp.

http://www.summitracing.com/search/D...?Ns=Rank%7cAsc

For assured deliverly the elec pump is the last word and I like the Holley HP150 that comes with a dead head reg for about $225.
If your doing a fuel system a bypass regulator and return I'm sure would help keep the strain off the pump for normal street use.

[Cliff R]

"Bottom line is the price to pay is leaving Hp on the table."

Jeff, once you get your car to running deep into the 11's in full street trim, and DEADLY consistent run to run, you will fine NOTHING between the two different carburetors, provided both are correctly set up for the application, and if you do, you need to go back and figure out what you didn't do right with the Holley!!

Seriously, the problem with the Q-jet is NOT simply bowl capacity, it's one needle seat assembly to feed the power level vs two.

The "reserve" capacity of the Holley fuel bowls is NOT a fail safe to making power. They still need to be kept full on hard runs, or the A/F goes lean, just like the Q-jet.

WAY back when I was testing fuel systems, and trying to run a crappy electric pump feeding a mechanical deal, my 850 DP ran no quicker than my q-jet anyplace. Both went lean past 5000rpm's, the Holley wouldn't let the engine "nose" clear over, but it still lost power on hard runs, just like the q-jet.

When I upgraded the fuel system, I also back to back tested the 850 DP against the Q-jet, and both carburetors ran almost identical ET and MPH, just like they did before the upgrades.

Before the current fuel system was put in service (sumped tank, electric pump behind the tank, 8AN lines/fittings everywhere) my car was a solid 12.40 to 12.60 ride, with a best ever ET of 12.37 @ 109mph.

The very first runs with the new fuel system netted 12.0's at 112, with both carburetors.

I continued to back to back test the big 850 against the 1977 Pontiac Q-jet at the track (have dyno'd them as well) as I made changes to go faster. Even did the test at the HPP Shootout a few years ago, with lots of witnesses, including Tom Vaught. They are almost dead even run to run. The Holley has a slight mid-range advantage (cleaner fuel curve with 4 jets feeding 4 boosters), the Q-jet runs a tad more MPH (more top end power as the dual plane intake likes it better). There is still less than .03 seconds between those carburetors, and .30 MPH on any given day......FWIW......Cliff

[Skip Fix]

I think some combinations can just do well with different setups. My pump is within 3 " of my tailpipe so it does get heat and has still done well. I ran an electric Carter for years on my daily driver 409(throwing papers every morning too) and it was the booster for the mechanical and dead headed. I'm running 10s with the stock 3/8 pickup and some guys don't, so go figure.

Some guys get by with a "plain" mechanical also-heck my 180 HP smogger motor in the TA with just a cam addition no porting, no headers 2.56 rear gears needed a little AC electric booster for the mechanical pump for the Q jet.

My concern on bypass systems is will it bypass too much if you are just marginal on supply.

[shaker455]

Originally Posted by Cliff R

"Bottom line is the price to pay is leaving Hp on the table."

Jeff, once you get your car to running deep into the 11's in full street trim, and DEADLY consistent run to run, you will fine NOTHING between the two different carburetors, provided both are correctly set up for the application, and if you do, you need to go back and figure out what you didn't do right with the Holley!!

Seriously, the problem with the Q-jet is NOT simply bowl capacity, it's one needle seat assembly to feed the power level vs two.

The "reserve" capacity of the Holley fuel bowls is NOT a fail safe to making power. They still need to be kept full on hard runs, or the A/F goes lean, just like the Q-jet.

WAY back when I was testing fuel systems, and trying to run a crappy electric pump feeding a mechanical deal, my 850 DP ran no quicker than my q-jet anyplace. Both went lean past 5000rpm's, the Holley wouldn't let the engine "nose" clear over, but it still lost power on hard runs, just like the q-jet.

When I upgraded the fuel system, I also back to back tested the 850 DP against the Q-jet, and both carburetors ran almost identical ET and MPH, just like they did before the upgrades.

Before the current fuel system was put in service (sumped tank, electric pump behind the tank, 8AN lines/fittings everywhere) my car was a solid 12.40 to 12.60 ride, with a best ever ET of 12.37 @ 109mph.

The very first runs with the new fuel system netted 12.0's at 112, with both carburetors.

I continued to back to back test the big 850 against the 1977 Pontiac Q-jet at the track (have dyno'd them as well) as I made changes to go faster. Even did the test at the HPP Shootout a few years ago, with lots of witnesses, including Tom Vaught. They are almost dead even run to run. The Holley has a slight mid-range advantage (cleaner fuel curve with 4 jets feeding 4 boosters), the Q-jet runs a tad more MPH (more top end power as the dual plane intake likes it better). There is still less than .03 seconds between those carburetors, and .30 MPH on any given day......FWIW......Cliff

Cliffy,
Your results are misleading & bias so your worthless posts are dismissed.

As you know your time is better spent writing a book or serving tables.