Installed Promax modded Holleys, 6 pack fuel lines and Carter M6903 mech fuel pump

[biomedtechguy]

About to fire it up and check for leaks, but my bet is ZERO leaks!
The Promax AN -6 fittings and flexible stainless braided fuel lines are GREAT!
Took some reconfiguration of fuel fittings and line angles to clear everything.

 

[Lionized]

I have to disagree with you Lionized. When running a mechanical pump, I would recommend an inline filter before the pump to keep the gunk from getting inside the pump. The more precaution, the better.

Excellent way to strain the diaphragm of the pump and shorten its lifespan.
If this much work is being done to the fuel system it would be wise to pull the sending unit and check the condition of the sock as well as the interior of the tank.
Due diligence goes miles.

 

[OH71RRunner]

Looking good. Glad you finally got everything in and put on the car.

Are we going to get a video of it running soon?

 

[moparedtn]

Looking good so far. Looking forward to hearing it run now!

 

[biomedtechguy]

DANG!!!

ME!
The rear carb ONLY apparently has a stuck float, fuel fountaining out of the bowl vent.
Grrrrrrrrr....
I removed the sight plug, let the excess fuel come out, adjusted the fuel bowl nut.
Did that 2 or 3 times, no good.
They ran the carbs before they shipped them. I'm thinking loose needle in seat? Something in shipping? They were very well packed.
Looks like I may have to remove the rear carb, pull the fuel bowl and have a peek.

Any ideas before I do that?

 

[OH71RRunner]

My vote goes to float getting stuck.
Might be able to tap on the side or stick small screwdriver through sight hole and check for movement in the float.

 

[biomedtechguy]

Going to work. Back at it tomorrow. Any advice that may "unstick" a WFO float without having to remove the carb is welcome.
What-if I have to pull the carb and open the bowl, so be it.
They ran fine before shipping.

 

[hangn0ut]

What kind of pressure is that fuel pump rated for? Might need a regulator. I don't trust those little fuel pressure gauges. Had one that read 3 psi low. Was changing needles and seats out on an 8 barrel tunnel ram set up. This one then that one...then I checked the gauge against a good gauge. Off by 3 psi.

 

[Car Nut]

I used to have 6 pack abs long ago, (long gone), does that count?

They're still in there somewhere!

I still have mine, it’s just covered in fat...

 

[68 HEMI GTS]

Probably got some junk in the needle and seat from the new lines. You can swap it without pulling the carb off. You’ll have to reset the float after you get it going. You may be able to clean / blow it out but most of the time they’re garbage after acting up. Also check the size, it’ll be stamped on the flat at the top.

 

[kiwigtx]

The needle may have got stuck if your package was tossed around by a Fedex guy...just saying.

Try giving the top of the needle valve adjuster a thwack with a soft hammer - may be all it needs.

Also, while looking over your system and what you have done....go under the fuel tank and pull the vent lines off - check with air if possible to see the tubes inside your trunk are clear. Then 'rod' the small nipples on the tank with a welding torch pipe cleaner. These can become blocked over time, and they are simply soldered in position. One of mine was blocked years ago...caused all sorts of problems.

 

[biomedtechguy]

Try giving the top of the needle valve adjuster a thwack with a soft hammer - may be all it needs.

Will do.

What kind of pressure is that fuel pump rated for? Might need a regulator. I don't trust those little fuel pressure gauges. Had one that read 3 psi low. Was changing needles and seats out on an 8 barrel tunnel ram set up. This one then that one...then I checked the gauge against a good gauge. Off by 3 psi.

Stock pressure, high volume. The Carter M6903 is the "established go to" mechanical fuel pump upgrade and the same one Bob Karakashian aka "Mr 6 pack" runs. Besides, only ONE carb is having float issues.

You can swap it without pulling the carb off.

Please let me know how to do that!
Thanks for all of the replies!

 

[biomedtechguy]

Also, while looking over your system and what you have done....go under the fuel tank and pull the vent lines off - check with air if possible to see the tubes inside your trunk are clear. Then 'rod' the small nipples on the tank with a welding torch pipe cleaner. These can become blocked over time, and they are simply soldered in position. One of mine was blocked years ago...caused all sorts of problems.

I may do that, but this was a running car. I only had Promax install their parts and then run and tune the carbs.

 

[451Mopar]

You can remove the needle and seat by unscrewing it from the top of the fuel bowl. Check for trash in needle & seat, and also that the "O" ring is not nicked or damaged. Check fuel pressure. Had a problem with the end carb floats with the aluminum pivot arms bending with 9 psi fuel pressure. The center float had the brass pivot arm and seemed to handle the pressure without bending.

 

[biomedtechguy]

451Mopar

You can remove the needle and seat by unscrewing it from the top of the fuel bowl. Check for trash in needle & seat, and also that the "O" ring is not nicked or damaged. Check fuel pressure. Had a problem with the end carb floats with the aluminum pivot arms bending with 9 psi fuel pressure. The center float had the brass pivot arm and seemed to handle the pressure without bending.

THANKS!
I made a couple of phone calls, and that is my understanding as well.
Promax said that if the needle and seat have to be replaced it is a "Holley 110" Viton. Any opinion or knowledge on that?

 

[moparedtn]

451Mopar

Promax said that if the needle and seat have to be replaced it is a "Holley 110" Viton. Any opinion or knowledge on that?

Who would know better than the guys who actually did the carbs?

Now, about that stuck needle (hope it's that and not a sinking float!)….
have you actually tried the "whack a mole" on it yet?
Get a regular sized, sturdy plastic handled screwdriver, turn it handle side towards the carb and give the top of the bowl/float adjusting
screw a few firm whacks. If the bowl is actually empty, you'll actually hear the float/needle assembly start moving freely inside the carb.

Even so, I daresay anyone who has ever owned a Holley carb in general (4 barrel, whatever) knows this maneuver and has perhaps
even performed it on the side of the road when the carb float got stuck.
If you play with Holleys, you know how to do this. Just part of the turf with them.

 

[biomedtechguy]

I removed the jam bolt, removed the adjusting nut (I had screwed it down trying to fix the float so far a crescent wrench worked better) and removed the needle and seat assembly. Shook it and thoroughly cleaned it with Carburetor cleaner sprayed through the straw at high velocity. Shook it a few more times and reinstalled it....
NO FLOAT PROBLEM!

So next is removing the rear carb anyway so I can better tighten the fuel bowl inlet fitting (with the thin washer). I have a leak there, and it is nearly impossible to get a wrench on it in place.
I am confident that everything will work out.
Thank you all for your help!

 

[vintage chromoly]

I’m not a fan of “dead head” fuel systems, especially on a street driven car.

I’d plumb the system with a bypass regulator and a return line.

I agree that those little fuel pressure gauges are problematic.

 

[biomedtechguy]

I’d plumb the system with a bypass regulator and a return line.

I already have a return line-the factory return line. Fuel pressure from the Carter M6903 is a non-issue. The problem was a stuck needle and seat apparently.
How do you configure a "system with a bypass regulator" and will that work with my existing return line?

 

[biomedtechguy]

Leave the inline fuel filter. It will help your carb filters last longer by stopping all the big trash from getting to them.

When running a mechanical pump, I would recommend an inline filter before the pump to keep the gunk from getting inside the pump. The more precaution, the better.

Promax said to leave the fuel filter that is on the engine end of the fuel tank line in place, before the fuel pump, to keep the chunks out and he said it is low restriction anyway, which makes sense to me. Their 40 micron inline reusable fuel filter which is located just before the fuel pressure gauge is additional protection.