Ok I've pulled my 2.7 with CIS to do a rebuild, I've got a 2.7 with carbs I'm installing while my motor is down, trying to make it to RRC.

So my question, can I install the carb fuel pump and just leave my FI pump in place, will the carb pump be able to pull the gas thru the other pump( power disconnected ) or will I have to take it out.

Or should I just use the FI pump and install a pressure regulator.

The FI pump is in the front trunk(75-76 location) was thinking of just mounting the carb pump on the firewall in the engine compartment.

This is just a temporary swap so trying to keep it simple, and easy to change back.

Thanks,
Jeff

It's worth a shot to see if the low-pressure pump can pull the fuel through the other one I guess. But whatever you do, do NOT try to regulate a FI pump down to 3-5 psi. The regulator won't be able to keep up and you could be looking at a ton of fuel overfilling the bowls, then down into the cylinders, or worse, spilling out of the carb onto the exhaust.

The best way would be to plumb in the low pressure pump where the FI pump is, but you already knew that

Thanks for the reply George, didn't think the pressure regulator would work, someone had mentioned it, didn't know if the technology had improved since I last used one.

Not sure I want to try pulling through the other pump unless I know it will work, want to do whatever once, don't have a lot of time to being doing things twice with my deadline.

Guess I'll just plan on swapping the pumps, unless someone knows it would work pulling through the FI pump.

Jeff

Disconnect the line from the fuel pump to the CIS inlet. If fuel flows without the pump being on, the lo pressure pump will pull through it.

If it doesn't, well.....

Duh, why didn't I think of that.....thanks Ron

It only take a little bit of hose to bypass around the FI pump.

are you doing?

I changed all my fuel lines to braided with AN fittings, so not quite that simple to bypass. Or maybe it is, do they make an AN coupler? But then can't remember if both sides are the same size.

WTF am I doing......did you read the first post
I'm being like you Mike, putting as many motors in my car as I can.
This will be #4 in 3 years.

Jeff

Unless your borrowed motor has a hot set of cams in it, I would transfer your existing CIS system to it and run it.

You're catching up for sure. Your mistake was putting the same manufacturer's engine in over and over. If you want to "one up" me, put in a Yugo engine. I won't even attempt that one...

BTW, Summit Racing has AN to barb adapters in male & female...

The engine was built with RS pistons and E heads, don't know what cams, but was running with carbs, wasn't sure if the CIS would work.

Not catching up or trying, mine are pretty basic installs just different motors, yours are custom and very impressive.

Thanks for the info on the fittings.

My 2.7L engine has RS pistons, MFI heads but cams are stock CIS. I run a stock CIS system on mine.

Friends keep trying to get me to run MFI, which I have, but the modification of the MFI system is more money than I want to spend (cams + modded pump).

Yes they do make double flare AN unions. If you can't find one look for the same size in a bulkhead fitting. Either will work. If they are AN4 or 6 I may have some laying around. LMK.

X2 - just bypass it

- better yet take it off & put it in a plastic bag for whenever

fwiw - most FI pumps on the market now have an internal check that prevents "flow-thru" - dunno about your oem 2.7 unit

p.s. - "was running with carbs" is not the same as "was running well with carbs" - lots of folks have discovered that the hard way

Thanks, not sure about the size. Won't get out to the shop till Friday, working 4 - 14 hr days is killing me, but the $ is good.

Well the FI pump is not OEM, just bought it. Guess I'll plan on bypassing it, might be able to find a fuel filter to put in place of the pump or just use a union.

As far as the carbs, they're on the engine so I'm going to run it with them first, if I can't get them to run right......I have rebuild kits for them, if that doesn't work.......I bought intake gaskets to swap to CIS, but no guarantees there either not knowing the cams.

It only has to make it to Moab and back, I've got 200 mile towing....what could go wrong.

Jeff

Started disconnecting fuel lines to drain the tank today and start making the changes to the fuel lines and pump. No flow thru the FI pump, but the return line flowed nicely and drained the tank in no time........... .....got me thinking..
Would the return line supply enough fuel to use as the supply line for the carbs?
That would really simplify things....cap the FI supply line, leave the FI pump where it is, disconnect power, the return line is hose clamps and rubber fuel line connected to SS tunnel lines. I thought I could run inline filters before and after the pump, tank was just out and thoroughly cleaned during the original -6 swap.

That would be the easiest solution.....but will it be enough volume?

Did some research the engine most likely has S cams so probably wouldn't work to well with the CIS.

Thanks for all the help.
Jeff

You have a very small orifice (1/8"?) on the return stub (inside the tank) and it is doubtful if you can get sufficient fuel flow.

I have fixed a couple of cars that wouldn't run because of crossed fuel lines.

Not your best idea yet.

3rd Image - 1st Post shows the outlet / return fittings

Oh well, thanks Ron. It was to easy to work.

Ok, finally got it worked out, the engine came with braided fuel lines with AN fitting, and an inline filter and pump. Laid everything out and figured out the fittings I needed.
Summit racing had everything....order placed.

I found a fitting to connect the in and out supply at the FI pump together, eliminating the FI pump. Found a fitting to plug the return line. Ordered a new filter screen for the inline filter, and I have enough lines with AN fitting to connect the carb pump to the supply line and then up to the carbs with the filter inline between the pump and carbs.

$40 in fittings and the fuel lines will be done.

Thanks for the help,
Jeff