[dreambird]

Thanks to all who have replied to my earlier posts regarding upgrading my fuel supply line. I need to do some measuring under the car, but I am seriously going to try to fit a 1/2" supply from the tank to the front while leaving the stock 5/16" line in place. I figured that the 1/2" will supply enough fuel for a 455 with either a electric setup or a mechanical setup and the 5/16" existing line could be used for either vapor return or recirculating fuel back to the tank. I have read good things about what Cliff has done for his fuel system - using a Comp 140 and a dead head regulator, teeing right before the regulator to re-circulate excess fuel back to the tank. Sounds like it has preserved the fuel pump from overheating.

So, here is the question of the day/week. What are the pro's and con's of running a good quality mechanical such as a Robb Mc verses something like a Mallory 110 or 140?

In your assessment of the two types of pumps, consider that the tank has been modified with a feed from the bottom of the tank for 1/2" supply and that the existing 5/16" line could be used for either fuel return OR vapor return.

Thanks.... Hope everyone had an excellent holiday.

[steve25]

Having fuel at less than engine temps when supplyed by a electric pump is good for power and makes jetting the motor less of a pain.

[rustedgoat]

With a bypass is heat still an issue? I prefer the mechanical for a street car

[OINK 1]

When you have a bad boy car that takes off, the weight of the fuel in the fuel line increases with acceleration and the diaphram mechanical pump can't overcome it.Ever more so with a 1/2" line. I use a Mallory / comp # 4110 electric. No regulator needed. Our 73 Ventura with the 428 goes 0-60 in 3.8 sec. No problems and I use a 1/2" line. RA4 ported heads, 800 cfm Holley spread bore double pumper.

I'd remove the old fuel line, put rubber hose around the fuel line at every mounting point. I also ues 2- 1"x1/8"x 4" long, Steel hangers for the pump, when mounting the pump, I use cut up pieces of bicycle inner tube @ the top of the hangers and @ the bottom were I attach the pump. This sound isolates the pump, you can BARELY hear it running, even with the engine off. !! remember filter before the pump !!

Pontiac Gregg

["QUICK-SILVER"]

Originally Posted by rustedgoat

With a bypass is heat still an issue? I prefer the mechanical for a street car

Thats kind of the whole point for a bypass, keeps cooler fuel moving through the lines, instead of setting still (moving slow) and getting hot.

["QUICK-SILVER"]

Originally Posted by dreambird

So, here is the question of the day/week. What are the pro's and con's of running a good quality mechanical such as a Robb Mc verses something like a Mallory 110 or 140?

Fuel pressure in the main fuel line. Much less chance of vapor lock with pressurized line from the electric pump. Mechanical pump drawing makes less than atmospheric pressure in the main fuel line, which lowers boiling point temperature and increases chances of vapor lock.

The strong mechanical pump, with return line, should be fine for the street. Insulate lines well around any source of heat.
Stronger than average street/race, electric has its advantages.

On my car, I run both. Just flip on the electric when needed.

[Tim Corcoran]

The answer to your question would depend on your performance level. It seems many people are anxious to jump to an electric fuel pump when a factory replacement AC Delco would work just fine. Unless your car is running faster than 12's in the 1/4 mile then the factory AC Delco will work just fine and it is quiet and reliable. I would get a new factory replacement pump for a 69 GTO as it come with the return line connection. Then use your 1/2 line for the inlet and the 5/16 line for the return. Simple, economical but very functional.

Tim C

[HWYSTR455]

Just to throw a wrench into the works here, it is possible to 'superheat' the fuel in the tank by using a bypass regulator. The EFi guys suffer this pretty often. This usually is when using a high volume pump for extended periods of low volume requirements.

I agree with Quick-Silver and Tim C, in most cases a factory mech works fine. I would use an app that was like a big car, full power, and make sure it had a return. Like a 68 Cat, GP, or Bonnie, AC, 428 or something. If the demand isn't there, then as Gregg said, by upgrading the line to 1/2", you may just complicate it.

Higher pressure can raise boiling point too, and help fight vapor lock.

If you're planning a fuel system, and you're going through it, design it with possible future power upgrades as well. Do it once, and you won't have to do it again later.

Generally, you don't want to go less than one-step smaller on a return line. But, you could always use the factory 3/8 feed line as a return, and not have to plumb 2 lines front to back.

Personally, I'd go electric, upgrade the feed & pickup, and use a bypass style reg.


.

[Murf'sDad]

Originally Posted by Tim Corcoran

The answer to your question would depend on your performance level. It seems many people are anxious to jump to an electric fuel pump when a factory replacement AC Delco would work just fine. Unless your car is running faster than 12's in the 1/4 mile then the factory AC Delco will work just fine and it is quiet and reliable. I would get a new factory replacement pump for a 69 GTO as it come with the return line connection. Then use your 1/2 line for the inlet and the 5/16 line for the return. Simple, economical but very functional.

Tim C

Hey Tim:

I don't know what I'll run in the quarter because I'll probably never run it but will a stock AC Delco replacement pump for my '76 400 feed about 450hp? It came with a 3/8" feed and a 5/16" return line as well. I don't mind upgrading if it is necessary but if OEM will suit my purposes, why not?

Stewart

[old66tiger]

I need to re-do my fuel system as well. Are there any longevity issues with Electric pumps as opposed to the mechanical pumps?.