Location for a carb fuel system - what's "good enough"?

I'm on the cusp of being parts-ready to swap my Magnum 5.2 into my wagon. I still need to figure out what to use for an electric fuel pump setup and where to put it - I'm keeping the serpentine belt system on the donor motor, which means no provision for a mechanical pump.

The motor is not going to get much more than a reground cam in the near future, so I just need something that will goosh fuel to the front of the car reliably (in both autox and road trip terms).

My problem is I have a pretty crammed area for installation. I've read all of the holy inscriptions that decree one must mount the pump inlet below the pickup in the tank. I don't have a whole lot of places where I can do that on this car - the front of the tank is behind the axle, it takes up all of the space between the frame rails to the rear, and the area in front of the axle is largely occupied by the mufflers and shocks.

My situation is similar to this post (#13 if the anchor link doesn't work). I haven't measured but I'm not sure if I can get away with dangling the pump up there at my ride height.

Another view (not mine):

I have some space on the outside of the mufflers on the rear rail sections but it looks bad-idea close (heat and possible physical contact in turns/bumps, not to mention road debris):

I'm planning on using a Carter pump like this: http://www.summitracing.com/parts/crt-p4594

However I'm kind of stumped as to how best to mount it, given my rear end packaging. It looks like mounting it to the high point of the floor and dangling the bracket down as far as I can (to the left/right of the diff) is my best bet, but I'm really trying to figure out someplace else to put it so I'm not stuck straining around the diff to get at stuff if something craps out on the road.

I learned that the little buzzy-piston solid state pumps (like this) can tolerate pulling fuel better than rotary vane designs, but I'm also wary of reliability for these things. Mounting one of these further forward under the car would be way easier than the Carter, though I'm still wary of them getting stuck on some little rustflake that sneaks past the filter.

Is there some magic setup where I could get away with an electric pump in the underhood area? Is there another pump type in the same price range that can be mounted lengthwise perhaps?

The Carter pump is far better than the buzzy ones, use it. The pump will work fine if it is higher than the pickup, just keep it as close to the tank and as low as safely possible. I would keep it no higher than the top of the tank. I have that Carter pump on my truck as a transfer between the tanks and it is even with the top of the tank. It transfers fuel quite well, no trouble pulling the fuel up.

Is an in tank setup a possibility? There are in tank carb application pumps.

I have a pair of Facet solid state pumps on my RX7. They're buzzy for sure.

Can you fit something inline like this?

inline pump

Kenny_McCormic wrote: Is an in tank setup a possibility? There are in tank carb application pumps.

This. ^^^ Many of those old Mopars (like GMs and Fords) have very similar tank configurations with minor differences. For instance, in my 86 El Camino, I put a tank from a 96 Caprice Wagon to get an in-tank pump. Same straps, bolt-in swap. All I needed was a piece of filler hose to connect the tank to the neck.

That way you get dead-nuts reliability. Regulate for proper PSI and you're golden.

If you do an external, keep it as close as possible to the tank. Keep it low along the frame rail. As long as you always have gas in the tank, it will siphon itself but the first time you run dry you'll be on the side of the road giving your tank a blow job. The piston-type pumps work well for siphoning and getting primed, but running them dry (like if the pump is far forward and you run out of gas) causes failure FAST. Like; on the order of you get to make that mistake twice before you replace the pump.

The moral of that story is not to run out of gas, but it happens.

I've never been a fan of putting a pickup in the bottom of a tank. Just seems like a failure waiting to happen and then you have 20 gallons of hot fuel under your car. It sure is a good way to go when using an external pump, but not ideal from a daily-driver standpoint.

If I were doing it, I would look for a tank from a Ford/Mopar/GM in-tank pump car that has similar dimensions and strap it in. Second choice would be an inline pump low along a frame rail and try not to run out of gas.

curtis73 wrote:

Kenny_McCormic wrote: Is an in tank setup a possibility? There are in tank carb application pumps.

This. ^^^ Many of those old Mopars (like GMs and Fords) have very similar tank configurations with minor differences. For instance, in my 86 El Camino, I put a tank from a 96 Caprice Wagon to get an in-tank pump. Same straps, bolt-in swap. All I needed was a piece of filler hose to connect the tank to the neck.

Some of the 70s and 80s GMs had a pump in the tank (still produced) that is meant to go directly to the inlet of a Rochester.

Kenny_McCormic wrote: Is an in tank setup a possibility? There are in tank carb application pumps.

And an in tank EFI pump will work fine for a carb if you use a bypass type regulator.

On my Chevy C10, I stuffed a Walbro 255 lph kit intended for a '94-'97 Mazda Miata in my stock tank. Just put the hose over where the filter sock would go, and ran bolts through grommets to use as bulkhead connectors for power.

I wasn't planning on tapping the bottom of my tank, I'm sticking with the stock pickup. That B-Body forum topic I linked was more to illustrate how crammed everything is back there and one guy's mounting solution (less his pickup choice).

I haven't been able to find any in-tank setups that hang off of the sender/pickup (just the really expensive cut-your-tank-open ones or things rated for EFI) and swapping to a different tank isn't reasonably possible. The tanks for these cars have a depression in the rear half for the lower cargo/spare tire area that changed in later model years.

As for an inline pump, I looked at those earlier and ended up gravitating toward the Carter canister style for some reason. The one linked is a little bit beefy for my application, but this one looks good: http://www.summitracing.com/parts/atx-e8012s/overview/

Any reason to stick with the Carter over something simpler like that? I'm not clear on how those things operate internally.

As far as locations go, I jacked big stinky up to get some pics of the areas I can feasibly use to mount a pump. The floor area above the diff has a good 6-8 inches clearance from the diff with the axle at ride height so it's viable, but it is above the top of the tank too.

There is some space in between the passenger rear rail extension and the trunk depression, behind the tank (dimmer thing to the left of the muffler below). This is as close to the tank as I can get. The lines would be completely under or alongside the tank, which is good for siphon/gravity feed purposes, but the caveman part of my brain doesn't like putting the pump behind the tank for some unquantified reason.

I also have some space inside the passenger frame rail above my endlink mount point (that's the fuel line you see):

Or I have this little pocket inside of the rocker panel ahead of the rear wheel (fuel line there again):

I also found this illustration in Carter's general install instructions highlighting good pump locations - I guess height matters more than distance according to them?

What do you guys think?

stick it right after the 90 deg bend in the last photo just before the clip. it will live happy there the only time it will pull hard is the 1st time after you install it or run out of gas.

Mounted my Holley blue pump on the duster where the rear leaf fronthanger bolts to the unibody. Works great eexcept loud as hell.

Ive also mounted a piece of angle iron to the gas tank straps at the front of the tank on a roadrunner for an ezefi conversion. Never anypickup problems above 1/3 tank in eeither location. Both ar in line with, or below, bottom of tank for gravity feed.

Have you looked at an early 944 pump. Run I with a FPR set for carb use and a return to the tank. They are small not buzzy and very reliable. You could put the FPR and the return at the pump and run a single line to the carb if vapor lock I not a concern.

Early 944 pumps look about the same as those Airtex inlines, yes?

Wow, lots of overthinking here.

Get a Holley or Carter pump made to work with a carb, bolt it up wherever it fits, get on with your life. It ain't that hard, guys.

Yes, they SAY you have to mount it below the level of the pickup. That happens exactly never in the real world. I've seen them bolted to the top of the inner fender on a Chevelle (replacing the failed mechanical pump) and it worked just fine aside from looking really hokey with ten feet of rubber hose going everywhere.

Knurled wrote: Wow, lots of overthinking here. Get a Holley or Carter pump made to work with a carb, bolt it up wherever it fits, get on with your life. It ain't that hard, guys. Yes, they SAY you have to mount it below the level of the pickup. That happens exactly never in the real world. I've seen them bolted to the top of the inner fender on a Chevelle (replacing the failed mechanical pump) and it worked just fine aside from looking really hokey with ten feet of rubber hose going everywhere.

i have an electric pump bolted to the inner fender of the chevelle right now replacing the failed cam lobe driving the mechanical pump to move the car around before i pull the motor. works fine.

i'd put the airtex type pump in the last pic posted on the inner rocker.

Secret_Chimp wrote: Early 944 pumps look about the same as those Airtex inlines, yes?

Yes

I think they are made by Bosh if I remember.

I have had great luck with Walbro pumps here are the measurements for there's

Secret_Chimp wrote: I haven't been able to find any in-tank setups that hang off of the sender/pickup (just the really expensive cut-your-tank-open ones or things rated for EFI) and swapping to a different tank isn't reasonably possible. The tanks for these cars have a depression in the rear half for the lower cargo/spare tire area that changed in later model years.

You don't need something actually meant for your tank, and you don't need one rated for carbed fuel pressure. The fuel pressure rating is the maximum the pump can deliver. Using an EFI pump with a bypass regulator is perfectly acceptable to get carbed fuel pressure, and you can bodge a lot of things onto the fuel sending unit with a little creativity.

The Bosch pumps are available and effective, used in millions of cars, various configurations.

OHHHHHHHHOOOOOO YEEEEEEAAAAAAAH

I've just finished installing an inline Airtex pump. There ended up being a perfect spot against where the floor humps up before the axle for the rear seatback.

The engine will run just fine, but if I switch the pump on with the engine off, I can hear the ignition being triggered (dizz makes that little "beep" discharge noise with the pump motor pulses). If I unplug the distributor from my MSD box, it stops triggering when the pump is on by itself.

I'm running the pump circuit breaker off of the starter relay (same as my 6AL box), but I tried switching the power source directly to the battery and it still makes the noise. The relay power wire is just using the existing routing on the firewall between the starter relay and the fuel pump relay (mounted where the ballast resistor used to be) which I suspect might be causing the distributor to sense. This distributor is a standard old-ish style that uses a reluctor wheel and a magnet.

The money question: does this matter at all? I'm not sure if it's just an artifact of the power wire between the pump relay block and the starter relay, or if it indicates an installation issue that may cause me trouble later on.