[Jay S]

Originally Posted by jhein

Thinking about either of these safety switches, either tach based or oil pressure based, when do the come into play? Basically, when the motor stops running. No tach signal means it's not running, no oil pressure means it's either not running or it will be stopping very soon. But how often in an accident does the engine stop running? Probably not if it's a rear or side impact. Maybe not even if it's a front impact, at least not immediately. And if you're running soft lines, then what is the likelihood they're going to fail in any case? So just how important are these devices?

I do not do safety switches on the mechanical and electric pusher combinations, just the full electrics. With the engine shut off an electric 7 psi pump usually won’t pump much fuel thru most mechanical pumps. The full electrics have full flow to the carb all the time.

I usually start the car as soon as the electric pusher pump is under a load after the fuel line fills up to the mechanical pump. I don’t wait for the electric to fully fill the carb, once the mechanical pump has fuel to it, the engine does not have to crank over very much to start (about 3 seconds)

[jhein]

Originally Posted by Jay S

I do not do safety switches on the mechanical and electric pusher combinations, just the full electrics. With the engine shut off an electric 7 psi pump usually won’t pump much fuel thru most mechanical pumps. The full electrics have full flow to the carb all the time.

I usually start the car as soon as the electric pusher pump is under a load after the fuel line fills up to the mechanical pump. I don’t wait for the electric to fully fill the carb, once the mechanical pump has fuel to it, the engine does not have to crank over very much to start (about 3 seconds)

So with the oil pressure safety switch, I assume cranking will give you enough oil pressure to activate the pump so it will start right up.

If you don't have any kind of shut off system and you have the ignition on, the pump turns on, then what? The pump just runs and floods the carb?

[Half-Inch Stud]

Longk ago i enjoyed the notion of using the oil idiot switch to enable the Dizzy & Bright Oil alarm light. Add pusher pump enable, and it's all good. Cube relays to do it right.

Also has "Speedo-Alert" to crowwbar such stuff, but that became a nuisance.

Was typical for my car to have Carter pusher pump into stock mech pump. Was good even with return tap plugged..

[Jay S]

Originally Posted by jhein

So with the oil pressure safety switch, I assume cranking will give you enough oil pressure to activate the pump so it will start right up.

If you don't have any kind of shut off system and you have the ignition on, the pump turns on, then what? The pump just runs and floods the carb?

I don’t care for the Hobb’s oil pressure switch’s on a car, there is to much delay. It is ok on something industrial where you can hold the bypass button down until it starts, PITA on a car that you start frequently. The Revolution switch that uses the tach out put is a lot better deal. That is a well thought out safely feature on an electric pump. The only down side is after the car sits very long, on an intank electric feeding a carb with 1/2” lines, the 3 second prime feature isn’t long enough. You have to cycle the key switch on an off several times. It works best with higher pressure fuel injection setup that retain line pressure better.

If the carb’s needle/seat are working correctly and the fuel pressure is set correctly the electric pumps should not flood the engine. You can pull the site plug out of a holley carb and walk off and forget the pump is running, come back an hour later and the engine will start right up. Years ago I had a Predator carb on one of my cars and the needle and seat didn’t hold and if filled a cylinder full of fuel and bent a connecting rod. I am not sure the oil safety would have caught it because you have to bypass most of them until the engine starts. That would be far less likely to have happened with the Revolution safety or a mechanical pump with the pusher pump. The electric pusher pumps I have done do not blast much fuel thru a non operating mechanical pump.

[Formulajones]

Originally Posted by jhein

So with the oil pressure safety switch, I assume cranking will give you enough oil pressure to activate the pump so it will start right up.

If you don't have any kind of shut off system and you have the ignition on, the pump turns on, then what? The pump just runs and floods the carb?

It doesn't quite work that way.
Cranking to get oil pressure to activate the pump will take just as long to start as a mechanical pump deal filling the carb.
What the idea of those switches assume is that there is already fuel in the carb, as there should be, don't know why you guys are going dry but that's a different problem. Anyway with fuel in the carb and in the squirter circuit, the car will fire off on that, it doesn't need fuel pressure, and once it fires off, oil pressure builds and turns on the pump. That's how they typically work.

As far as the pump running when you turn the key on, it doesn't flood the carb. If it is you have a needle and seat problem, again a different issue.

[Skip Fix]

My TA I cut out the mechanical and just have the electric. Mechanical was a restriction as well as a source for heat.

[78w72]

Originally Posted by jhein

I don't know but people have suggested that even if I don't have any obvious starvation, it's still happening. I don't know if that only matters for someone who is racing or if would have any noticeable effect in a street only car like mine. So you are running a mechanical pump? I had you pegged for a in-tank guy.

The starvation issue usually only happens at the dragstrip with good traction/hard launch, with a better robbmc mech pump it usually takes low 12's or into 11's & faster to show the starvation... on the street the tires break free and you lose that highj G force that causes problems with a mech pump sucking fuel through almost 20ft of curved & bent lines. If all you ever do is run the car on the street with no drag strip time, you most likely wont see the starvation problems and your 3/8 line will be ok.

Originally Posted by jhein

OK, both Mallory and Holey tech support say that their pumps (Mallory 110 and Holley red) will not allow the mechanical pump to pull fuel through them if they are off or if they fail. That seems to contradict what people have said here, at least for the Holley. I don't know which is correct but if they won't allow the mechanical pump to pull fuel through in the event of a failure then that's a no go. My intention would be to run it at all times, not just start up.

So now I'm back to either living with the limitations of the mechanical pump, which are not terrible, or going in-tank electric. I was on the verge of doing that a couple years ago but I soured on the idea. One of the reasons was because people advised that you should have the low oil pressure safety switch. I agree that seems like an important part of the system. But people said that the currently available switches were poor quality and not reliable. That really turned me off. But, when the fail, do they fail open or closed?

Did you see the link to the carter pump I posted? Should allow fuel flow even when off or failed according to what Ive read over the years from people that have used it as a primer/pusher pump... and its a lot cheaper piced that the others mentioned that may or may not flow when failed as their techs explained.

If you want to go the pusher pump route, the carter elect pump is probably the best bet for what you want... but going with the tanks inc set up allows for future upgrades to EFI and will supply the q-jet much better than a mech. But again for a pure street car, all that may be overkill if all you want is to fix a hard start issue after sitting awhile and dont have any drag racing or auto crossing plans. A primer/pusher pump fixes that for under $100 vs well over $1000 for intank set up.

https://www.summitracing.com/parts/crt-p4070

[jhein]

Originally Posted by 78w72

The starvation issue usually only happens at the dragstrip with good traction/hard launch, with a better robbmc mech pump it usually takes low 12's or into 11's & faster to show the starvation... on the street the tires break free and you lose that highj G force that causes problems with a mech pump sucking fuel through almost 20ft of curved & bent lines. If all you ever do is run the car on the street with no drag strip time, you most likely wont see the starvation problems and your 3/8 line will be ok.



Did you see the link to the carter pump I posted? Should allow fuel flow even when off or failed according to what Ive read over the years from people that have used it as a primer/pusher pump... and its a lot cheaper piced that the others mentioned that may or may not flow when failed as their techs explained.

If you want to go the pusher pump route, the carter elect pump is probably the best bet for what you want... but going with the tanks inc set up allows for future upgrades to EFI and will supply the q-jet much better than a mech. But again for a pure street car, all that may be overkill if all you want is to fix a hard start issue after sitting awhile and dont have any drag racing or auto crossing plans. A primer/pusher pump fixes that for under $100 vs well over $1000 for intank set up.

https://www.summitracing.com/parts/crt-p4070

Yeah, I looked at the Carter pump. I was just a little worried about the 1/4" size. I'm sure it would work. I know I started the thread with quicker starting in mind, but that's not the only consideration. Yes the Robb pump works with the 3/8 line, but it's not optimal. With a 1/2 line it would be better but that still means dropping the tank and replacing the pickup and running a new line. $1000 isn't chump change but, I spent $20000 on the motor so spending another 1000 to feed it properly doesn't seem out of line. Plus it will allow for future options. I just need to decide what I want to do about the safety switch business.

[jhein]

Originally Posted by Formulajones

It doesn't quite work that way.
Cranking to get oil pressure to activate the pump will take just as long to start as a mechanical pump deal filling the carb.
What the idea of those switches assume is that there is already fuel in the carb, as there should be, don't know why you guys are going dry but that's a different problem. Anyway with fuel in the carb and in the squirter circuit, the car will fire off on that, it doesn't need fuel pressure, and once it fires off, oil pressure builds and turns on the pump. That's how they typically work.

As far as the pump running when you turn the key on, it doesn't flood the carb. If it is you have a needle and seat problem, again a different issue.

Thanks FJ. When you set these up what you do for the safety switch, sounds like you may use the oil pressure type?

As for starting up, my car right now starts instantly if it has been run in the last 72 hrs. I like it so much I even posted a video about it, LOL. After 3 days though, it gets dry. I think that's probably normal for a Qjet. If it was a DD, it would always fire up instantly. If I went with the oil pressure switch, then putting a bypass switch in the car would take care of priming after a 3 day rest and also if the oil pressure switch fails. BTW, do you know if they fail open or closed? Or is the failure thing even realistic or overblown?

[jhein]

Originally Posted by Jay S

I don’t care for the Hobb’s oil pressure switch’s on a car, there is to much delay. It is ok on something industrial where you can hold the bypass button down until it starts, PITA on a car that you start frequently. The Revolution switch that uses the tach out put is a lot better deal. That is a well thought out safely feature on an electric pump. The only down side is after the car sits very long, on an intank electric feeding a carb with 1/2” lines, the 3 second prime feature isn’t long enough. You have to cycle the key switch on an off several times. It works best with higher pressure fuel injection setup that retain line pressure better.

If the carb’s needle/seat are working correctly and the fuel pressure is set correctly the electric pumps should not flood the engine. You can pull the site plug out of a holley carb and walk off and forget the pump is running, come back an hour later and the engine will start right up. Years ago I had a Predator carb on one of my cars and the needle and seat didn’t hold and if filled a cylinder full of fuel and bent a connecting rod. I am not sure the oil safety would have caught it because you have to bypass most of them until the engine starts. That would be far less likely to have happened with the Revolution safety or a mechanical pump with the pusher pump. The electric pusher pumps I have done do not blast much fuel thru a non operating mechanical pump.

Yeah, I was wondering if the 3 second deal would be enough.

[78w72]

Originally Posted by jhein

Yeah, I looked at the Carter pump. I was just a little worried about the 1/4" size. I'm sure it would work. I know I started the thread with quicker starting in mind, but that's not the only consideration. Yes the Robb pump works with the 3/8 line, but it's not optimal. With a 1/2 line it would be better but that still means dropping the tank and replacing the pickup and running a new line. $1000 isn't chump change but, I spent $20000 on the motor so spending another 1000 to feed it properly doesn't seem out of line. Plus it will allow for future options. I just need to decide what I want to do about the safety switch business.

That makes sense, always a good idea to properly feed a big hp engine like that... surprised with all the moeny you spent on the engine that you didnt consider the fuel lines being way too small for that power level. Just wanted to be sure you didnt overlook the carter since I didnt see it mentioned when you listed the holley & mallory that you said the techs said they wont flow fuel when failed.

If you do decide on the primer/pusher set up for now, then the carter is the best bet IMO. But bypassing all that to go intank pump is the better approach... hope you consider even just some fun time at teh drag strip during a test & tune event just to see what your $20 grand engine can do, especially if youre looking into sticky tires and full intank pump/EFI...

[jhein]

Originally Posted by 78w72

That makes sense, always a good idea to properly feed a big hp engine like that... surprised with all the moeny you spent on the engine that you didnt consider the fuel lines being way too small for that power level. Just wanted to be sure you didnt overlook the carter since I didnt see it mentioned when you listed the holley & mallory that you said the techs said they wont flow fuel when failed.

If you do decide on the primer/pusher set up for now, then the carter is the best bet IMO. But bypassing all that to go intank pump is the better approach... hope you consider even just some fun time at teh drag strip during a test & tune event just to see what your $20 grand engine can do, especially if youre looking into sticky tires and full intank pump/EFI...

I got a lot of different opinions about the fuel system when I did the motor so I thought I'd give them mechanical stuff a try.

I've got sticky tires back on it now, the Nitto NT01. I haven't tried to hook with them from a stop, but from a roll they stick pretty good. At WOT in first they get a little loose but not bad.

[Singleton]

Originally Posted by jhein

I don't know but people have suggested that even if I don't have any obvious starvation, it's still happening. I don't know if that only matters for someone who is racing or if would have any noticeable effect in a street only car like mine.

My GTO, (in signature), had the 550 RobbMc mechanical pump for several years with no noticeable fuel supply issues. Also used the RobbMc 1/2" tank pick-up along with 1/2" lines.
About two years ago. frustrated with the same issue you're describing with the empty fuel bowls, I decided to ditch the mechanical pump and went with the Tanks Inc setup with the in-tank 450lph pump and 1/2" supply and return. Used a cheap quickfuel bypass regulator plumbed-in after the carb, no hobbs switch.

I didn't expect any performance gains, since the car ran really strong on the street with the M&H drag radials, 495cid, 4sp, 4.10 gears. But after the electric pump install I was shocked at how quicker the engine pulled to redline. Like I said before, it ran great on the mechanical pump, but there was a noticeable difference after the Tanks Inc set up.
So the dry fuel bowl issue is solved and a slight fuel starvation issue that I didn't know about is also solved. And if I decide to go EFI, most of the components are already in place

[jhein]

Originally Posted by Singleton

My GTO, (in signature), had the 550 RobbMc mechanical pump for several years with no noticeable fuel supply issues. Also used the RobbMc 1/2" tank pick-up along with 1/2" lines.
About two years ago. frustrated with the same issue you're describing with the empty fuel bowls, I decided to ditch the mechanical pump and went with the Tanks Inc setup with the in-tank 450lph pump and 1/2" supply and return. Used a cheap quickfuel bypass regulator plumbed-in after the carb, no hobbs switch.

I didn't expect any performance gains, since the car ran really strong on the street with the M&H drag radials, 495cid, 4sp, 4.10 gears. But after the electric pump install I was shocked at how quicker and stonger the engine pulled to redline. Like I said before, it ran great on the mechanical pump, but there was a noticeable difference after the Tanks Inc set up.
So the dry fuel bowl issue is solved and a slight fuel starvation issue that I didn't know about is also solved. And if I decide to go EFI, the components are already in place

That's great info. Thanks.

[78w72]

Originally Posted by jhein

I got a lot of different opinions about the fuel system when I did the motor so I thought I'd give them mechanical stuff a try.

I've got sticky tires back on it now, the Nitto NT01. I haven't tried to hook with them from a stop, but from a roll they stick pretty good. At WOT in first they get a little loose but not bad.

The good mechanical pumps can work veery well, to a point. I have a 467 with 72cc E-heads & OF cam, 3.23 gears in a 72 firebird, I can do every type of launch or WOT runs on the street with M/T drag radials or normal street radials without any signs of starvation... originally it had an edelbrock mech pump that is similar to the high flow carter pumps and it was fine on the dyno or into low 12's on the first shake down runs using old hard BFG drag radials that were almost as bad as normal street tires, but once I got some new M/T drag radials and had some experience with launching the car it had terrible starvation issues... so I upgraded to a robbmc 1100 pump, 1/2" pickup & lines... it ran low 11's but on the best runs with decent traction/60ft, it would cut out occasionally, some times it was fine down to 11.2, but other times it would fall on its face about half track and ruin the entire run. So im now at a point where I decide to go faster with a tanks inc set up to fix the starvation issue, or just be content with a low 11 sec car running stock unported e-heads and a q-jet. car runs about perfect on the street though and its a 90% street car.

On the subject of a qjet fuel bowl going dry, there was a thread about this sometime last year that I cant seem to find, I think you (jhein) started it and "FJ" posted a test he did putting a full cup or more of fuel in a container on the garage or house counter, he said it didnt lose any fuel after like 3-5 hours so I/we/you have something else going on.... well, just last week I remembered that thread and how the test wasnt what fuel does when in a hot engine/carb... I filled a tablespoon or a little more of fuel in a small metal container, about the size & amount of fuel in a q-jet bowl, I set it right on top the carb after a short drive but fully warmed engine at ~180°. After letting it sit with hood closed for about 1.5 hours I came back to check & sure enough it was completely dry, not even a residue of wet fuel left. Granted inside the carb isnt exposed to open air but the carb is fully vented. That test is more of a real world scenario for fuel in a q-jet than a big cup of fuel at room temp, based on what I found after a short time, fuel definitely can & does evaporate at a pretty fast rate when heated like an engine. This was non ethanol fuel too.

Why some carbs/cars dont have this issues is beyond me, but it is a very real problem for many cars when they sit for a week or more, probably a combo of things from evaporation to drain back depending on the mech pump used?

[jhein]

So about 2 weeks ago I decided to remove a RobbMc in line fuel filter that I had right before my pump after I realized that it wasn't needed since I have a sock on my pickup and the Qjet filter in place. I had to move the car before I did the job so I knew the bowl was full. When I removed the line from the pump, not a single drop came out. The next day when I went to start it, it fired right up instantly like always. So I don't seem to have any drain back. I believe it's just good old fashioned evaporation which in my environment with my fuel takes about 3 days after a hot shutdown. It's also likely that most of it occurs while the engine is still hot. With the hood down and the air cleaner in place it probably stays warm for quite a while. Once it cools down the process must slow down.

[jhein]

OK, well, I just ordered the new Tanks inc setup. I'm planning on removing everything this week and then putting in the new stuff when it gets here the following week. Yeehaw.

[78w72]

Originally Posted by jhein

OK, well, I just ordered the new Tanks inc setup. I'm planning on removing everything this week and then putting in the new stuff when it gets here the following week. Yeehaw.

Nice. Who did you order from, Tanks inc is located about 20 mins from me here in Iowa. I researched the prices and found its a lot cheaper to order from places like summit or speedway than direct from tanks inc, I even called TI and said im local and can pick it up, but still cheaper via summit.

Which tank & pump size did you order? Which sender? What set up for return line & regulator? They offer a notched tank that fits some applications better.

Please start a new thread with pics & details on the parts and installation as you go along.

[jhein]

Originally Posted by 78w72

Nice. Who did you order from, Tanks inc is located about 20 mins from me here in Iowa. I researched the prices and found its a lot cheaper to order from places like summit or speedway than direct from tanks inc, I even called TI and said im local and can pick it up, but still cheaper via summit.

Which tank & pump size did you order? Which sender? What set up for return line & regulator? They offer a notched tank that fits some applications better.

Please start a new thread with pics & details on the parts and installation as you go along.

I just got it straight from them. It was just easier and I'll be sure to have all the right stuff,

I went with the square tank, slightly larger capacity and I'm not planning on tubs (famous last words). I got the GPA-4 pump, Carb regulated plumbing kit, wiring kit, tube sender. I also got the Russell tool to push the tubing onto the fittings.

[jhein]

Any advice on what type of sealer to use on the fuel pump block off?