Discussion Forum - Northstar Chevelle Club

Lost in the 60s · President

My carb issue...

Enganeer · Mega Poster

Part of the reason I jumped into the ls1 swap for the elky was I was getting ticked off at my 64 carb issues. I am down to a intermittent bad fuel pump or obstruction in the vent.

What type of fuel filter do you have? You may have something lodged and blocking the needle open.

I would swap out carbs and see what your pressure is. Is your gas tank vented properly? If pressure does not change, try opening the fill cap and see if it changes.

67ss · 1K+ Club

I'm thinking there must be something wrong with the float since you already tried multiple needle and seats.

Chris R · 2K+ Club

I had float issues too. Raw gas going down the carb and just decided to get a rebuild kit and went through the entire thing with non-stick gaskets and set it up right and be done with it. Ran like a champ after that and never gave me any problems after that. You may not have to rebuild it but a good float adjustment might work.

Lost in the 60s · President

67ss wrote:
I'm thinking there must be something wrong with the float since you already tried multiple needle and seats.
Yeah, I'm disappointed that it wasn't just a high pressure issue that I could remedy with a regulator. If it floods over with 2lbs, there has to be something drastically wrong with the set-up on there now.

John D · 2K+ Club

Give this a read... Tuning a Holley

Tony Hoffer · Moderator

sinking float or not enough pressure to seat the needle?
. anyway I have some Holley stuff layin around here if you need something we can sort through the box.

Lost in the 60s · President

I swapped out the entire rear bowl/float/needle assembly from another 3310 I have here. I turned the key on to run the pump and NO LEAKS !! I was able to adjust the fuel level in the rear bowl and the pressure gauge read 3lbs. Still a little low for an elecrtic pump but what the hay, take it for a test drive. Ran better than it ever has with no loading up at idle and full throttle to 5k rpm in all 4 gears. Got back in the shop and opened the hood for one last leak check and the pressure gauge now reads ZERO ??? Now I need to get another gauge on it and see what the problem is. Either a bad gauge or weak pump ? Arg.....can't things just cooperate and work right once ...

jim larson · 2K+ Club

Maybe someone has a reliable gauge and/or pump that you could use for a test. Could there be some kind of obstruction between the pump and gauge or between the fuel supply and the pump? Sounds as if your narrowing things down.

SShink · 3K+ Club

If the gauge is bad, that's a minor thing. The key is that you got it running good/better than it did before! Frustrating for sure... but hang in there, it WILL get better!

Lost in the 60s · President

jim larson wrote:
Maybe someone has a reliable gauge and/or pump that you could use for a test. Could there be some kind of obstruction between the pump and gauge or between the fuel supply and the pump? Sounds as if your narrowing things down.
I actually have a "vintage" fuel pump pressure gauge I can use. I will need to remove the one in the fuel line and insert a nipple for the hose. If it still reads low, I'll go looking for a restriction. I have a new sending unit and tank filter, so I would swap that out if I remove the original to check. The vent tube was capped off when I got the car and the tank would build vacuum. I replaced the rubber hose to the original vent tube in the trunk and that works again.

dashboard · 2K+ Club

Hey man, 5K in fourth, that’s what I‘m talking about....that had to be fun. What was the Speedo reading?

Mitch I have a small Holley graveyard here if you need something to try. I have a nice 650 mechanical secondary’s, manual choke and a 750 vacuum secondary’s, electric choke carb if you would like to use them for troubleshooting.

Got your hood on yet?

Lost in the 60s · President

dashboard wrote:
Hey man, 5K in fourth, that’s what I‘m talking about....that had to be fun. What was the Speedo reading?

Mitch I have a small Holley graveyard here if you need something to try. I have a nice 650 mechanical secondary’s, manual choke and a 750 vacuum secondary’s, electric choke carb if you would like to use them for troubleshooting.

Got your hood on yet?
Looks better, eh ?

dashboard · 2K+ Club

Looks great with a hood, I think your Velle wins the prize for the one that has come the furthest with the best documentation. When I was in trail behind you on the fall cruise warm-up, it was remarkable when I thought back to the day we removed the windshield last winter.

Then the car had no steering, suspension, drive train, interior, front clip or rear end. Parts where all over your shop, Yep, it has come a long way.

Lost in the 60s · President

Thanks Kevin. I'm still a little surprised at how quickly it all came back together too and I can actually drive it. I LOVE having the 4 speed... I haven't driven my Camaro since I got the Chevelle back on the road...

On to the carb. Last evening I wanted to drive it to Roseville and was concerned about the zero fuel pressure after the hard runs the night before. I turned the key to get the pump running and the gauge fluttered back up to 3lbs and stayed there. Pretty sure I have the restriction others have mentioned. I'm betting it's the sock in the tank sucking shut after the high demand for fuel. I have a new sending unit and I think it came with the filter. I'll be changing that out before the 29th and retesting the pump pressure. I did drive it last night and it ran good to Roseville but didn't want to idle correctly on the way home again. Hoping that will straighten out with the fuel delivery fixed.

Lost in the 60s · President

I just pulled the old sending unit out. Nothing wrong with the sock. I put the new unit in anyway for the ground wire to the gauge. I had the wire on the old one clamped on with a vise grip... The fuel pump is a Carter with no specs printed on it. There is a number stamped in it that I will do a search on later. He also had a clear plastic paper filter just after the pump, so I removed that and even though it doesn't really look bad, I can't hardly blow thru it !!! I may have found the restriction... I'm going to see my Dad now and will get a new filter on the way home. Pretty nice that you don't have to remove the tank for this on the first gen Chevelles.

Lost in the 60s · President

Put the new filter in and turned the pump on. 4lbs steady. Took it for a short drive up to the Marathon because I had run the gas down really low for the sending unit removal. On the way home I took 'er down the "test" road. I forgot that the carb should make that moaning sound when I step on the throttle from 2500 rpm. Stopped and did a 2500 rpm launch and 5k shift thru the gears. It's like a whole different car....

Backed in the shop and popped the hood expecting to see 4lbs on the fuel gauge.....nope......1 lb..... It sure doesn't run like it's starving for fuel but I'll have to wait to test it with another gauge until next week. Sunday is already overbooked.

Lost in the 60s · President

Just did a search for the fuel pump. Turns out it's probably the best part the PO put on the car. Rotary vane with no shafts or seals to leak and internally regulated to 6 psi max. Guess I won't need the regulator I bought. If the pressure really does drop after running a while, I'll look into a rebuild kit for it.

Bowtieman427 · Active Member

So what pump do you have ? dead heading or have a return setup ? If you changed all filters then you may have blockage in tank or the pump is gummed up. From a performance perspective best to run the regulator as close to carb as possible.
Sounds like things are running better then they were before.

jim larson · 2K+ Club

Lost in the 60s wrote:
Just did a search for the fuel pump. Turns out it's probably the best part the PO put on the car. Rotary vane with no shafts or seals to leak and internally regulated to 6 psi max. Guess I won't need the regulator I bought. If the pressure really does drop after running a while, I'll look into a rebuild kit for it.

Just remembered that I have a new fuel line for a 66, if your interested or need one. From Inline tube. Just taking up space. 1/2 price.

Lost in the 60s · President

jim larson wrote:
Lost in the 60s wrote:
Just did a search for the fuel pump. Turns out it's probably the best part the PO put on the car. Rotary vane with no shafts or seals to leak and internally regulated to 6 psi max. Guess I won't need the regulator I bought. If the pressure really does drop after running a while, I'll look into a rebuild kit for it.
Just remembered that I have a new fuel line for a 66, if your interested or need one. From Inline tube. Just taking up space. 1/2 price.
The line from the tank to the front looks good but i may try blowing air thru it just to eliminate a possible restriction in it. Shhot me a PM what you need for it. I may pick it up for a future frame off re-fresh.
Jim, the pump is a Carter model P4389. I changed the whole sending unit and in-tank filter, so no blockage there.

jim larson · 2K+ Club

Mitch, Looks like it sells for around $100 for the SS line, so $50. The steel lines sell for around $70.

Sounds like a good idea to blow air though the line, just in case.

-- Edited by jim larson on Wednesday 19th of October 2011 05:30:53 PM

Chris R · 2K+ Club

If Mitch decides he doesnt need it. I might be intrested in it.

Lost in the 60s · President

jim larson wrote:
Mitch, Looks like it sells for around $100 for the SS line, so $50. The steel lines sell for around $70.
Sounds like a good idea to blow air though the line, just in case.

-- Edited by jim larson on Wednesday 19th of October 2011 05:30:53 PM
Yeah, put my name on it and we'll get together over the next few months. Are you planning to attend the October meeting, since it is reasonably close ?

Bowtieman427 · Active Member

66 SS BBC has 3/8" line with 1/4" id the pump is rated MAX 6psi with 1/4" NPT which is fine, but this is probably rated in the most ideal condition "free flow". Perhaps the best you will get from it is 4psi given the max is 6psi & most likely does not account for loss variables in the real world like friction loss in line, bends, turns, fitting friction, line length, filter restriction, acceleration & the delta difference in potential from tank to carb (going up hill).

here are some good links if interested.
Explians importance of return lines
http://www.lmengines.com/fuel_lines
Calculator
http://www.lmengines.com/fuel_lines

jim larson · 2K+ Club

Lost in the 60s wrote:
jim larson wrote:
Mitch, Looks like it sells for around $100 for the SS line, so $50. The steel lines sell for around $70.
Sounds like a good idea to blow air though the line, just in case.

-- Edited by jim larson on Wednesday 19th of October 2011 05:30:53 PM
Yeah, put my name on it and we'll get together over the next few months. Are you planning to attend the October meeting, since it is reasonably close ?

Not sure about Saturday. I am helping a friend harvest his corn and separate his cattle. If I find out that I am attending, I'll bring it along in case your there.