fuel delivery

[dougdel]

looking for some advice on fuel delivery,  currently I have a red holley pump, thinking of going back to a mechanical one. I have the vapor recovery type tank with the 4 port canister, 1/4" vapor line ran to the engine compartment with a cap on it to keep crap out. 340 engine, eddy airgap, proform 750 carb w/ elec. choke. experiencing some stumble on acceleration, that will be another subject. would it be good to take the 1/4" vapor line tie it into the pressure regulator and make it a return line?  If so, what do I do with the 4 port tank and vapor separator?  or should I just leave things as they are? 

[Cuda Cody]

Are you trying to fix your stumble?  I would guess that is a carb tuning issue and not fuel delivery.     You running a Holley?  Sounds like your stumble is happening on acceleration so it most likely is a problem transferring from the idle circuit to the run circuit.  Pretty easy fix.  First make sure your accelerator pump is working and adjusted correctly.  Then change out the pump cam.  You just need to know if your stumble is because of rich or lean.  What color cam are you running now?

[RUNCHARGER]

I would run the vapor line. With today's fuels I wouldn't use a mechanical pump on other than a totally stock resto. I'm just tired of fighting the fuel evaporation issue.

[dougdel]

It is a tune issue,  changed the iab's up several sizes to get a good idle, low to mid 13's on the afr. At cruise no tach 50-60 mph runs up to as high as 16.1 on afr. Slight stumble on acceleration. Thinking about changing squirter from stock 31 to a 35 and upping the primary jets from stock 72 to 75 or 76. Have to see what's in the jet kit I have.  It's a pro form carb, 750 street series 67208  voodoo lunati cam 10200703

[Cuda Cody]

Those Pro Forms use a cam like the Holley's, right? 

[dougdel]

Runcharger, so if I were to run the return, would I tap it off of the second port on my pressure regulator,  How or what would I do to the tank with the 4 vapor ports and what would I do with the whatever it's called divider canister with the check ball in it that the line attaches to the hen divides into the 4 ports to the tank

[dougdel]

Same cams,  when I get home from work I'll have to see which one is on it,  I think it may be the pink one set to the first screw hole. And I have the pump arm up tight to the diaphragm so I don't think there's any play it it

[Cuda Cody]

Here's the Holley Cam Chart that shows the colors.  If you have the pink on there then you are getting one of the biggest ramps of fuel already.  Any chance it's bogging because of a rich situation?

[RUNCHARGER]

The way I have plumbed vapor lines is to purchase a fuel filter with the vapor nipple, install it just before the carb and run the line back to the tank vapor nipple (leave the other 3 capped in your case).

[Cuda Cody]

I'm just baffled that with a pick cam you're getting a stumble.  That should be flooding that carb with fuel.   

[Chryco Psycho]

That chart is only  the total volume not the movement / degree of rotation , the pink cam is lazy for the first 10* or so , I would change the cam first Try Blue posiiton 1

[Brads70]

Holley pump cam info.... near the bottom of the page.
https://forum.e-bodies.org/reference-material/18/useful-drawings-blueprints-factory-bulletins-etc/70/

[dougdel]

finally had a chance to put a few minutes in this.  Changed the cam to the blue #1 position, made a huge difference in acceleration and idle,  idles at 12.3 on average on my afr its a digital gauge so it constantly changes.  About a 3 mile cruise at 50 mph afr just under 14, so when I have the time ill look at timing again and vacuum just to see what the numbers are.  Sometimes it sucks working nights all the time,  not much time for fun stuff.  Now its on to the seatbelts and loose steering

[Burdar]

Your vapor separator is your tank vent.  You should have a sealed gas cap and the tank should be vented through that vapor line in the engine compartment.  If you have that line plugged, your tank should be pulling a vacuum causing fuel delivery problems.

If you want to use that vapor line as a return, you can use a fuel filter with a return port and route it to that vapor line.  I'd cut the line off down at the frame rail so it doesn't go up the inner fender any more.  Back at the tank you could remove the vapor separator and plug three of the nipples on the gas tank.  Then run a hose from your vapor line to the fourth tank nipple.  IF you do this, you'll have to run a vented gas cap or your tank won't vent. 

[1 Wild R/T]

As the title mentioned... Fuel Delivery....