[glhs#116]

So.. As I'm getting things a little more dialled in with the new E heads and the bigger cam I'm finding other growing pains.

One, or so it seems, is the stock fuel pump. Right now I have a Carter, which may not be the best (had one fail already) but it is the stock style with the big can. This shape:
https://www.summitracing.com/parts/a...w/make/pontiac

Part of me would like to retain that because I like the stock style hard line pressure pipe up to the carb. Yes, yes, I know. I could theoretically make one (probably I couldn't actually). And I could run AN line. But, humour me, I just don't want to.

Now the problem seems to be that all of these "stock" style pumps are 40g/h rated. I just put larger secondary rods on the carb and the car definitely liked the change, but it looks like the fuel system simply can't support it. I'm not talking about running out of fuel on a charge from a stop. I'm talking about flooring it with the car already rolling at highway speed. You can feel that the car has good power until the fuel in the bowl and the pump reserviour is exhausted. Then it sags as you can tell that the fuel supply is simply not keeping up.

Does anyone make a higher flow pump in that "shape" (the stock "big can" shape)?

Sam

[ponyakr]

"...Does anyone make a higher flow pump in that "shape" (the stock "big can" shape)?..."

Not that I'm aware of.

The Carter M6907 pumps more gas. RobbMc makes a 550hp model, plus an adjustable model that is advertised to go up to 1100hp.

https://www.ebay.com/p/Mechanical-Fu...hoCNBYQAvD_BwE

https://www.robbmcperformance.com/pr...ontiac550.html

https://www.robbmcperformance.com/pr...ntiac1100.html

I'd say the only way to keep a big can pump AND have more fuel is to install an electric "pusher" pump, back near the tank. That's what I did on all my 455 bracket cars, back in the '70's & '80's. I used a Carter P4070 elec pump back near the tank, and flipped it on, just for the pass down the track. Ran off the mechanical pump the rest of the time. The mechanical pump will pull thru the Carter elec pump. Gonna run the same set-up on my current 455 bracket project.

https://www.ebay.com/p/Electric-Fuel...4070/191388380

The stock 3/8" fuel line was big enuff to supply my cars down into the high 11's. Most here will probably recommend switching to bigger 1/2" line, if you're makin big power. My engines probably made only about 400hp/500 torque, & never went passed 5500rpm.

[Formulajones]

You don't have a lot of choices. Like Pony mentioned you can step up to a RobbMC pump that may help, you'll still have to bend a new steel line though.
The Carter pumps suck, and I don't mean pun intended, lol. I had 2 brand new ones fail on me within 10 miles a piece just a few months ago, and the 3rd one they just gave me my money back.

All that work with the Robb pump and you might also find it's not a total cure. Because of where you live and the heat you deal with you might want to get away from that setup all together. I have mechanical pump cars that deal with the Arizona desert heat just fine but I'm also not trying to support a ton of HP with them either.

What I prefer to do here on anything that is beyond stock HP is go right for an in tank pump from Tanks Inc, and run 1/2" line to and from. Inline tube makes the stock appearing lines in 1/2" that are easy to install on these 2nd gen birds if you're really concerned about someone looking under the car. I then mount the regulator where the original pump mounted and I bend a stock steel line up to the carb from there.

A 255 LPH pump will support about 600hp, and have new car type reliability and quiet operation inside the tank, and do a much better job at pushing fuel and fighting any heat soak issues you may encounter in your climate.

This is exactly how I set up this firebird and you'd be hard pressed to think this car is anything but stock when you look at it.

[78w72]

there are not too many pumps that will flow higher but keep the factory hard line configuration. maybe you could try to get an adapter of some sort at the pump to allow you to keep the hard line?

another thing to try that i spoke to cliff about last week, is to change to a bigger needle/seat, you arent at a super high HP range to need the biggest n/s or go to an electric pump, but depending on the size thats in there, & if you didnt change to a bigger one it could be a very small .125-.130, for about $10 cliff can send you a bigger .135, .140 or .145 that will still be ok at stockish psi.

a bigger seat may be what you need to allow more fuel into the carb to fix your issue, along with a step up in the pump to the carter or robbmc linked above if you can make them work with your hard line. the robbmc 1100 is adjustable down to about 7psi, the flow increases a lot as you raise the psi, but the bigger needle seats cant handle the higher pressure on a regular basis so might need to consider a regulator if you go with the 1100, or just try the carter or 550 & see what happens.

another pump to look at is the edelbrock, supposed to support "up to" 600hp, but thats obviously exaggerated & not reality, but i had one initially & it was good to 520hp on the dyno, had issues at the track in the low 12's & high 11's.

best of luck figuring it out.

[Cliff R]

I've seen pumps advertised to support pretty big power, and they probably would in a dyno room with unlimited fuel delivery and "static" pulls on the engine.

In the real World with an engine being stuck between the front fenders and fuel tank nearly 14' back the rear of the vehicle, keeping a carb full sitting on a powerful engine in a quick car will find any/all short-comings in your fuel delivery system.

I've had poor luck with mechanical pumps on really hard leaving cars......but with that said one of my very good customers and long time friend runs a stock pump, stock fuel system, and has went best of 11.71 with his 1969 GTO over 114MPH! We did have to use the largest fuel inlet seat in his Q-jet as he got a nose bleed when the car nosed-over in low gear with smaller ones in the Q-jet, but he's getting it done now with that set-up some 20 plus years.

Makes me really crazy too, because his results defy the laws of physics with these things and I can't get my car out of the low 13's trying to use the same basic set-up to feed my carburetor!........Cliff

[67drake]

FWIW , because you said you want it stock looking. I wanted to keep my original GTO looking as stock as possible underneath the hood. BUT I run. a RobbMac 550 but used a stock metal fuel line up to the carb, I cut it off and adapted it to the RobbMac at the bottom. Yeah it’s not stock, but who really looks down at the fuel pump? Easy to change back to original if I wanted to.

[tom s]

I run the Carted street pump,when I raced the tempest I fed it with a switched elect in the back thru 1/2 in line and 3/8 from the Carter to the carbs.Has served me well over 20 years.FWIW,Tom

[Formulajones]

I'm going to guess the stock appearance idea went out the window when you put aluminum heads on the car.

I wouldn't worry too much about pump appearances at this point, and the fact that if you have PS you can't see much down there anyway.

I removed the pump all together on the bird I pictured above, with a regulator in it's place, and you practically can't even see any of it down there, and the stock steel fuel line I bent to the carb doesn't give anyone reason to get any more curious about it.

[Formulajones]

Just to add, I do a lot of this sneaky stuff on many builds here and there is a bunch of this idea employed with my fathers car. We just did a little show yesterday with it and had one guy really look the car over and make the comment that "there is really a lot going on with this car but you can't see any of it unless you really get down and look at things, otherwise it looks like a typical stock 14 second muscle car"

That was the whole idea.

[78w72]

Originally Posted by Formulajones

I'm going to guess the stock appearance idea went out the window when you put aluminum heads on the car.

I wouldn't worry too much about pump appearances at this point, and the fact that if you have PS you can't see much down there anyway.

I removed the pump all together on the bird I pictured above, with a regulator in it's place, and you practically can't even see any of it down there, and the stock steel fuel line I bent to the carb doesn't give anyone reason to get any more curious about it.

can you post a pic of the regulator mounted on the engine?

[Formulajones]

Yes I can do that. I'll have the car on the lift today or tomorrow to check over some things. That's really the only way to get a look at it is from the bottom.

Here's a shot just looking at it normally as one typically would with the hood up, and as you can see it's virtually invisible.

[TCSGTO]

The Robbmc 1100 worked for me into low 11’s and sub 1.6 60’ times. I think the reason it has worked so well is the tank is slumped and the pump is fed with a -10 line which is basically a garden hose. The pump is set to 10psi and feeds a large port Holley regulator set at 5.5 psi with a -08 line, then -08 to the carb. It has a vapor return going back to the tank so hot restarts are never a problem.

If you are going to use one of these pumps, and are planing on running hard with good traction, go straight to the 1100. It’s better to have the extra flow & pressure and control it with a GOOD regulator. The lower level regulators from Holley and Mallory have a small 1/4” or less internal restriction that all of the fuel has to pass through. This one has 7/16” passages.

https://www.holley.com/products/fuel...s/parts/12-704

When using a mechanical pump system everything has to be up to snuff since pulling fuel up to the front of a car under acceleration is a lot harder than pushing it.

[78w72]

Originally Posted by Formulajones

Yes I can do that. I'll have the car on the lift today or tomorrow to check over some things. That's really the only way to get a look at it is from the bottom.

Here's a shot just looking at it normally as one typically would with the hood up, and as you can see it's virtually invisible.

thank u sir.

[78w72]

Originally Posted by TCSGTO

The Robbmc 1100 worked for me into low 11’s and sub 1.6 60’ times. I think the reason it has worked so well is the tank is slumped and the pump is fed with a -10 line which is basically a garden hose. The pump is set to 10psi and feeds a large port Holley regulator set at 5.5 psi with a -08 line, then -08 to the carb. It has a vapor return going back to the tank so hot restarts are never a problem.

If you are going to use one of these pumps, and are planing on running hard with good traction, go straight to the 1100. It’s better to have the extra flow & pressure and control it with a GOOD regulator. The lower level regulators from Holley and Mallory have a small 1/4” or less internal restriction that all of the fuel has to pass through. This one has 7/16” passages.

https://www.holley.com/products/fuel...s/parts/12-704

When using a mechanical pump system everything has to be up to snuff since pulling fuel up to the front of a car under acceleration is a lot harder than pushing it.

yeah im in the same boat & same times, but tank isnt sumped, just a robbmc 1/2" pickup & -8 lines from tank to pump & pump to carb. i ran the pump dialed all the way down to 7psi but that really restricts its flow ability, so i added a regulator but used a small mallory one that you mentioned & still have issues on hard launches & full WOT runs, currently i have to launch off idle & roll into the throttle or i have traction issues or it falls on its face sooner. i have a bigger robbmc regulator i will try soon though. & i also will change to a bigger needle seat cliff sent me & see if that helps before throwing in the towel & going electric.

i think a bigger needle seat would be a good thing to try for the OP's issues, especially since he doesnt plan to race the car at the track, just needs to fix the issue at rolling highway speeds.

["QUICK-SILVER"]

If the word "sag" means loss of power instead of "nose over" with your foot on the floor......I suspect you've got something going on besides fuel delivery. If coolant temp climbs fast when it happens, that would indicate not enough total ignition timing.

I've seen this happen in high gear only and not feel it in first and second. Engine goes through lower gears too fast and isn't under as much load as high gear.

Clay

[Formulajones]

Originally Posted by 78w72

yeah im in the same boat & same times, but tank isnt sumped, just a robbmc 1/2" pickup & -8 lines from tank to pump & pump to carb. i ran the pump dialed all the way down to 7psi but that really restricts its flow ability, so i added a regulator but used a small mallory one that you mentioned & still have issues on hard launches & full WOT runs, currently i have to launch off idle & roll into the throttle or i have traction issues or it falls on its face sooner. i have a bigger robbmc regulator i will try soon though. & i also will change to a bigger needle seat cliff sent me & see if that helps before throwing in the towel & going electric.

.

I for one would like to hear how the changes you're planning work out.

[78w72]

Originally Posted by Formulajones

I for one would like to hear how the changes you're planning work out.

oh i will post how the changes worked out, good or bad.

im very happy with the times ive been able to get out of the car/combo so far & should just be content with it since its more of a street car than drag... but because of the fuel starvation & traction issues, i know theres more in it if i could fix or improve either of them.

but, getting down this fast i need to get a better driveshaft, im using the stock one now with a stock yoke... after seeing taman break his i definitely want/need a better one before i try to go faster!

[ta man]

Originally Posted by "QUICK-SILVER"

If the word "sag" means loss of power instead of "nose over" with your foot on the floor......I suspect you've got something going on besides fuel delivery. If coolant temp climbs fast when it happens, that would indicate not enough total ignition timing.

I've seen this happen in high gear only and not feel it in first and second. Engine goes through lower gears too fast and isn't under as much load as high gear.

Clay

Low fuel pressure can show up as a sag in power in top gear at the track without nosing over.
For example back in 2009 ,my last engine the first few times out was stuck at 112mph...felt great down the track. Since I just went from running 13.0's to 12.1/12.2 with a head and cam swap the car felt super fast. A short time later my Holley Blue pump gave up ..I replaced that pump with a Mallory 140..immediately went to 114mph..later on increasing from 3/8 line to all 8an picked up another mph.
This engine eventually with only some intake and exhaust work ran 10.9 at 123 mph...

Without proper fuel supply I would have struggled doing any sort of tuning and become frustrated and wonder why its not going quicker.
Any given test n tune night anywhere there are many many high dollar builds struggling with fuel supply issues..and many don't know it. Running your your engine lean because of fuel supply issues is never good.

[redhawk44]

Originally Posted by Formulajones

I'm going to guess the stock appearance idea went out the window when you put aluminum heads on the car.

I wouldn't worry too much about pump appearances at this point, and the fact that if you have PS you can't see much down there anyway.

I removed the pump all together on the bird I pictured above, with a regulator in it's place, and you practically can't even see any of it down there, and the stock steel fuel line I bent to the carb doesn't give anyone reason to get any more curious about it.

On that note I just had to replace my pump. I put a Holley 12 389 11
It's supposed to put out 110 gph. Isn't stock but it works good.

( https://www.amazon.com/Holley-12-389...8583735&sr=8-1 in. )

[KEN CROCIE]

KISS. Ponyakr and Tom S are on the right track. Use a Carter electric back by the tank to supply the old (or new) stock mechanical pump. The mechanical will suck through the electric up to a certain point, depending on the suction ability of the mech. My own cars would usually run up to about 70 mph at cruise before fuel pressure started dropping. This was the advice I gave to my customers in the "way back when". There is a better Carter elec. solution with the P4602RV pump ,which is the street /strip P4594 combined with an automatic mechanical bypass system, the purpose of which is to allow the mech. pump to have unrestricted flow while the P4602 is turned off. This approach will handle a lot of street HP and still look stock up front.
A cautionary tale:
A few years ago I was Restoring a Trans Am with one of our TurboForce kits. I couldn't get adequate fuel flow up to the Carb. It turns out the pickup line in the tank was corroded to about half of stock diameter. We are all dealing with 50 (or so) year old cars. You might want to check it out.