Mech fuel pump with pressure reg w/ DCOE 40s...am I kidding myself?

[Konish]

I truly want to stay "old school" mech pump, and I've read some older posts with anecdotal experiences e.g. "I've been running DCOEs for 10 years with mech fuel pump w/ no problems..." etc. Thinking about giving it a go. Anyone still running the stock mech fuel pump with DOCEs? Anything to look out for (carb/float set-up wise) or have any recommendations on pressure reg etc?

 

R/

Dustin

[drzed]

I still run the mechanical pump with the triple webber 45's on my 240Z. No problems at all. Will run mid 13's at the track all day long. I did run an electric pump a long time ago but all the adjustments were the same. I think the regulator is set at 3.5 psi. All other carb adjustments are by the book.

[Lazeum]

Hi, I ran as well a mech fuel pump with my setup (F54/N42 with mild cam) and 40DCOE with 32mm venturis. I'm using a wideband to tune the engine and I had some issue with rich conditions at high rpm which proved the pump was good enough.

 

Now, I go with a new head, port & polish + a more agressive Rebello cam, I'll have to check it out again to make sure the pump can handle the extra air and fuel supply.

 

I also have a regulator setup at 3,5 psi (I have a electrical pump disconnected also)

[PanzerAce]

I'm running the mech fuel pump with my Mikuni 44's, never had a problem running. Only issue is if the engine sits for awhile and the gas evaporates out of the carbs, it can take 10-15 seconds before the engine will fire on startup

[Konish]

Sweet, thanks a bunch fellas. I was on the fence about going with the triples (inherited with the car badly in need of cleaning and a rebuild) or the ZTherapy SUs.

 

Everything in my head says go with the SUs, but everything south of my belt says go with the Webers. I'm embarrassed to say, they're going in because they look dead sexy whether they make more power or not is immaterial at this point.

 

R/

D

[Lazeum]

You forgot the noise as well the noise!

[brokebolt]

Well this sure spans the globe. Japan to Canada to France and back home to my state of California. Nice to see (or hear from) the Z community around the world.

 

Ya, old school is awesome (some will argue), triples are even better (IMO). Fuel bowl evaporation will occur on any carb set up, EFI is best for cold start.

 

As long as the pressure is set right and you don't suck the fuel bowls dry on hard, long accelerations then, ya, bolt up that old mechanical unit. I had issues with the stocker I had mounted up due the later problem. You can always add a second electronic pump back at the tank to help eliminate this problem (I did) but you will need a regulator somewhere in the system to prevent over pressuring the needle and seats in the carb bowls if you decide to use one of those electronic units alone or with a mechanical unit.

 

I run my Dellorto's (basically the same carb) at about 5 P.S.I. with no issues. Yes, set the fuel bowl levels per the specs (most manuals will give you a spec). Do run a return fuel line if you can regardless of how you get the fuel to the carb bowls, and a pressure regulator can be had at just about any auto parts store in the USA for about $20.00. If not here is a link to a source or reference for a cheapy I've used in the past for $24.95 USD.

 

http://www.summitracing.com/parts/SUM-G3131-1/

 

If link don't work search SUM-G3131-1 at Summit Racing dot com.

 

PanzerAce is right on the money about 15 seconds of cranking until fuel reaches the bowls using the mechanical unit. Electronic is just a tad faster, but not by much from my experience.

 

Happy motoring with that old school mechanical fuel pump.

[Lazeum]

From Paris (actually not, I'm in Poland far away from my Z ) I second what you just said!

 

There's a trick to start old car with mech pump. On mine, I've installed a kill switch to avoid to drain the battery when car is not used. It happened already 3 times to forget the switch, 3 times the ride I was expected was a rain check.

 

It also helps against thieves; my dad has tried to show off to some of his friends how nice my car sounds , he was never able to start it

[PanzerAce]

Yah, best way to start a carb car (especially triples I've found) after a *long* sit is to floor the throttle (so that you don't have to work against a vac), crank for ~10 seconds, foot off the throttle, then crank a few seconds more (and blip the throttle if you need to)

[brokebolt]

The other option for cold starting an engine equipped with a carburetor(s) is to add an electric fuel pump and a electronic circuit like that found on modern EFI cars where you kick on the electric pump when the ignition is 'on'. You will need to install a crash isolator switch (technical name maybe wrong). This prevents the car pump from running if involved in a collision or vehicle roll over. Safety first!

 

What PanzerAce says is correct and will work well for bone dry bowls.

 

Kill switches are always a great theft deferent. The MSD 6AL Ignition box has a wire for just that purpose.

[Lazeum]

Kill switches are always a great theft deferent. The MSD 6AL Ignition box has a wire for just that purpose.

 

Off topic but I do have a Mallory 6AL (very similar to the MSD version), which wire is it? I've never noticed such a feature. It could be very interesting!

[Daeron]

Everything in my head says go with the SUs, but everything south of my belt says go with the Webers. I'm embarrassed to say, they're going in because they look dead sexy whether they make more power or not is immaterial at this point.

 

R/

D

 

Acceptable Logic, to be certain!!!

[cygnusx1]

Since I will be installing a 280Z motor in my 240Z, I will be adding an electric pump to feed the webers. Mechanical would be easier if the motor already had it, and I figured it would work fine.

 

I plan on mounting the pump by the tank. In the engine bay, the stock 240Z fuel supply line will lead directly to the carbs. Down by the passengers frame rail, I will "T" off the supply line into the regulator to feed the overflow back into factory return line, which is right there already.

 

This will set up a "dead ended" line to the carbs which should be fine. I run this exact line route in my megasquirted 280Z Turbo at 36psi. Obviously this will be around 3psi.

 

Right now the Webers are in the waiting room, rebuilt, waiting for the car build to catch up.

 

[brokebolt]

Off topic but I do have a Mallory 6AL (very similar to the MSD version), which wire is it? I've never noticed such a feature. It could be very interesting!

 

I am not familiar with the Mallory stuff, but the MSD manual states:

 

"When using the WHITE wire to trigger the MSD, install a switch across the magnetic pickup VIOLET wire to ground. When the VIOLET wire is grounded, the vehicle will crank but not start. When using the mag pickup to trigger the MSD, install a switch to the WHITE wire and the other side to ground. When the WHITE wire is grounded, the vehicle will crank but will not start."

 

So you could control this with a relay, toggle switch or other means but the principle remains the same... theft deterrent!

[Lazeum]

So you could control this with a relay, toggle switch or other means but the principle remains the same... theft deterrent!

 

Way of topic but thanks!