Electric fuel pump vs stock mechanical on AMC 360?

[MReno]

Anyone change to an electric fuel pump, and if so, what is required to eliminate the stock mechanical pump?

[dodgerammit]

I ran both for a while on my 84. In tank electric, feeding the stock one to eliminate vapor locking.
The pre 86 models have enough room on sending unit to easily mount a small pump on them. Later years would take a bit more creativity.
This was done on a carbureted engine. Are you doing efi?
Efi will need a block off plate, available at BJ's off road. I've read Chevy ones fit, but I just got mine there for certainty.
I decided to eliminate the mechanical after rebuild.

The basics are the same. Pushing fuel rather than pulling, meaning close as possible to tank, and near bottom of tank if mounting externally.
Return line on fuel filter positioned at 12:00.
Regulated to between 4-6psi if carbed.

[will e]

I left the stock pump in place and just routed a new fuel line from the fender. I have no doubt the stock pump is toast, I wouldn't try it in 'a pinch'. I carry a second electric pump as a backup. Saved me one day at Ouray with a quick on the side of the road repair.

I run a Holly Truck Avenger.

[rocklaurence]

The Chevy Big Block/Small block pump plates work. I think $6 on Ebay and Ive been running Electric for 6 years on my two rigs without any issues and it did eliminate vapor-lock. I have the Holly Red Top and Mighty Mite.

[MReno]

I have an Edlebrock 1405 Carb and was thinking that my tuning issues are related to inconsistent fuel pressure. Brock needs 6psi consistently.

So if I bought an electric pump, I could just connect this to the tank supply line (as close tot he pump as possible), and leave the mechanical (OEM) pump in place and run the new fuel line from the electric pump to the carb?

[dodgerammit]

I have an Edlebrock 1405 Carb and was thinking that my tuning issues are related to inconsistent fuel pressure. Brock needs 6psi consistently.

So if I bought an electric pump, I could just connect this to the tank supply line (as close tot he pump as possible), and leave the mechanical (OEM) pump in place and run the new fuel line from the electric pump to the carb?

You want to mount the electric as close to the tank (remember, pushing fuel, not pulling like the mech pump) and as close to bottom of tank (height wise) as possible. From there, line to return filter with return line oriented on top, then to carb. If pump is much more than 6psi pressure, a regulator is a good idea.

[letank]

no need for the mech fuel pump, I have used different pumps from the carter P4070 or P4602 and similar to the slim edelbrock and mount them as convenient as can be... the near the fuel tank location is a bear.... check my set up below for the later models... yes it is close to the exhaust, but works even at crawl speed, the red eldelbrock is promising because it is far from exhaust, receive cool air from one of the opening in the valence and is easy to mount, and to replace, no need to crawl under the vehicle

under the steering arm, you can see the isolation bracket (pict full size under the fuel and brake line link in my sig)



the red edelbrock

[will e]

I use the MR. Gasket version of the pump. Looks like Michel's picture (Letank). I have it mounted to the rear crossmember near the tank. As mentioned, I have had a failure but I carry a spare. I have an in cab fuel pressure gauge with the sensor mounted right before the fuel intake on my Holley Truck avenger. I also have a 'hidden' shutoff switch as well as a 'keyed' switch as theft protection devices.

I believe the general consensus is to remove the mechanical pump from the fuel system when swapping to an electric pump. The concern with leaving the mechanical pump in place is if it does get a tear in the diaphragm it will cause gasoline to go into the crank case. In normal operation the would generally cause the engine to stop running fairly soon after the diaphragm breach. With an electric pump pushing fuel there can still be enough fuel and pressure getting to the carb to keep the engine running. As the gasoline mixes with the crank case oil the results can be disastrous if the engine continues to run. How likely is this scenario to happen? Hard to predict. A complete rupture of the mechanical diaphragm is probably big enough that the engine will die from lack of fuel. The real question is risk to reward ratio. There is very little advantage leaving the mechanical pump inline and the possible damage to the engine is extreme. You be the judge.

Now onto the subject of the fuel return line. This is one of those hot debates similar to 'manifold vs ported' vacuum for the distributor. At least in our community it is. Some argue the return line reduces vapor lock by sending fuel back to the tank and cooling it off. I found that it actually contributed to my fuel issues. My Holley expects about 7lbs fuel of pressure. Your Edelbrock is similar, it rates at around 6 1/2 pounds. I have an accurate fuel pressure gauge and in regular driving I get about 6 lbs from the electric pump when the engine is not running. And about 4 to 6 while driving. It constantly moves. I do not currently have vapor lock issues. I am not running a return line.

I used to have vapor lock type issues. After a while of driving in warmer temps the engine would buck and stumble and die under acceleration or under load (like going up a hill). At the time I had a return line. I also used a cheap mechanical gauge and it read just two lbs at idle with the return line. Removing the return line fixed my issue. It was later I added the in cab gauge. Something I recommend, well worth the money.

So, if you've read this far I believe when you add an aftermarket carb to the environment the return line may cause insufficient fuel pressure to the carb. Perhaps the stock carbs were set up for lower pressure? Perhaps my experimentation was wrong? My suggestion is to check it out. Get a cheap inline fuel gauge (or better, a more expensive in cab gauge) and confirm the pressure yourself. If you have good pressure with the return line, good to go. If not, try plugging the return port as see if that helps.