Holley Flooding Engine and Spewing Gas

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Keystone

Keystone

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I'm having a problem on my 2bbl to 4bbl swap and could use an outside opinion before I go buy a completely NEW carburetor. The car is a 73 Dart with a rebuilt 318. It ran decently with the 2bbl but as it already has headers and a mild cam, I figured the 4bbl would really help it.

The carburetor is a used Holley 4160 I picked up from a member here. I bought a book and a Holley renew kit, tore it all down and put it back together with the new parts
4bbl Pic 1.jpg


4bbl Pic 2.jpg


I thought I did okay, but it's obviously not right.

Initially I had the floats set wrong and flooded the engine. I got that taken care of but then the best I could do was get it to run on less than 8 cylinders. Some of the pipes on the headers weren't getting hot, and I verified by removing a couple plug wires while it barely idled. I had the plugs out multiple times to try and dry out the cylinders, but it never improved.

For a sanity check I decided to put the 2bbl back on using an adapter. I also changed the oil because it was heavily diluted. I was also thinking there could be an issue with fuel pressure, so I put a gauge on to verify that. With the 2bbl back on it ran perfectly and was holding a steady pressure of just over 5.5 pounds.
4bbl Pic 3.jpg


4bbl Pic 4.jpg


To double check the float the levels, I put the Holley on the stand and connected an electric fuel pump and ran that for about a minute. I took out the sight plugs and fine tuned the needle/seat as per the manual. I also verified the bottom of the carb stayed dry. The electric pump only made about 3.5 pounds of pressure though.
4bbl Pic 5.jpg


Since everything seemed okay I put the 4bbl back on, but now it wouldn't even start. It fired about about a second then died and just cranked after that. I opened the throttle slightly and saw a plume of gas shoot up from the primary vent tube.
4bbl Pic 6.jpg

I'm pretty much at my wits end with this thing. Does anyone have any ideas before I throw it in the scrap metal bin?
 
You have some dirt in your inlet needle and seat... Remove the inlet valve and clean the needle and seat off and reinstall them...

The piece of dirt is not letting the needle seal properly to the seat... The dirt is on the sealing surface and not letting the needle close off the inlet which is allowing the gas to keep flowing...
 
He stated he checked that with a electric fuel pump...Id suggest you take a look at the idle transfer slots under the butterflys and make sure they are perfect squares, and that the secondary is not propped open by the little hidden screw to make up for a tall cams idle. Are the cold pipes matching the dual plane of the intake? then you got an idle issue with one side of the carb. probably just a metering block passage clogged with a piece of gasket. Use fine wires to probe those. Also check your power valve for a leak, common.
holley+41+e+copy.jpg

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Keystone said:
I'm having a problem on my 2bbl to 4bbl swap and could use an outside opinion before I go buy a completely NEW carburetor. The car is a 73 Dart with a rebuilt 318. It ran decently with the 2bbl but as it already has headers and a mild cam, I figured the 4bbl would really help it.

The carburetor is a used Holley 4160 I picked up from a member here. I bought a book and a Holley renew kit, tore it all down and put it back together with the new parts
View attachment 1715496910

View attachment 1715496911

I thought I did okay, but it's obviously not right.

Initially I had the floats set wrong and flooded the engine. I got that taken care of but then the best I could do was get it to run on less than 8 cylinders. Some of the pipes on the headers weren't getting hot, and I verified by removing a couple plug wires while it barely idled. I had the plugs out multiple times to try and dry out the cylinders, but it never improved.

For a sanity check I decided to put the 2bbl back on using an adapter. I also changed the oil because it was heavily diluted. I was also thinking there could be an issue with fuel pressure, so I put a gauge on to verify that. With the 2bbl back on it ran perfectly and was holding a steady pressure of just over 5.5 pounds.
View attachment 1715496912

View attachment 1715496914

To double check the float the levels, I put the Holley on the stand and connected an electric fuel pump and ran that for about a minute. I took out the sight plugs and fine tuned the needle/seat as per the manual. I also verified the bottom of the carb stayed dry. The electric pump only made about 3.5 pounds of pressure though.
View attachment 1715496915

Since everything seemed okay I put the 4bbl back on, but now it wouldn't even start. It fired about about a second then died and just cranked after that. I opened the throttle slightly and saw a plume of gas shoot up from the primary vent tube.
View attachment 1715496916
I'm pretty much at my wits end with this thing. Does anyone have any ideas before I throw it in the scrap metal bin?
Click to expand...

Even just putting the rubber hose on can get a little piece of rubber in the needle/seat.
Fuel coming out the vent is a for sure indicator that the needle isn't sealing.
Of course as mentioned the floats have to "float" but since you set the levels on the bench lets say they do.
Pull the needle/seat assembly out and blow it out good.
 
Thanks everyone for the quick replies. I've had the needle and seat assemblies out more than once. Sprayed them off with carb cleaner then gently blew with an air nozzle.
In the book I purchased I saw a special tool for testing the power valve, but is there a way to check it without that? It looked rather pricey.
I still have some off the old parts like the needle/seat and the old power valve. I guess I could try putting those back and to see what happens since there's nothing left to lose at this point. I'll also go back to examine those passages pishta mentioned. I'll post back later today with the results.
 
Curious, are you using mineral spirits with the bench test?
 
Dont reinstall the old parts.

Do all final float settings on car running. Get the fuel level adjusted ,with sight plug out, to the bottom of the sight hole and tighten it.
If the floats are even good, check them for being filled with gas.
Let the idle speed screw out till the blades have closed...then open them about 2 turns...or until you see the throttle blades exposing about .020 of the tiny slot in the throttle bores.. you'll need to do it before carb goes on so you can look underneath to see this. HOWEVER..Technically if the floats are good, needle and seat work properly...NO LEAKS it should fire up and run on the mains , at least, even if the idle speed setting is too high... flat out it should at least run to do the idle adjustments and so forth.
Are the secondary blades closed enough?
There is a little flat head screw to set those from the bottom of the base plate.
 
Keystone said:
Thanks everyone for the quick replies. I've had the needle and seat assemblies out more than once. Sprayed them off with carb cleaner then gently blew with an air nozzle.
In the book I purchased I saw a special tool for testing the power valve, but is there a way to check it without that? It looked rather pricey.
I still have some off the old parts like the needle/seat and the old power valve. I guess I could try putting those back and to see what happens since there's nothing left to lose at this point. I'll also go back to examine those passages pishta mentioned. I'll post back later today with the results.
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That’s not a power valve issue. The only way fuel can blow out of the vent is the needle and seat aren’t shutting off the fuel.

Why it’s ok on the bench and not on the car I can’t say. If the float level is correct, the floats aren’t sunk and the fuel pressure is 7ish pounds or less the only way fuel can get out of the vent is the needle and seat isn’t doing it’s job.

When you were going through the carb, did you happen to remove the floats? Just curious. And IIRC those carbs had brass floats. At least they did in the 1980’s. I haven’t been into a newer one.
 
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yellow rose said:
That’s not a power valve issue. The only way fuel can blow out of the vent is the needle and seat aren’t shutting off the fuel.

Why it’s ok on the bench and not on the car I can’t say. If the float level is correct, the floats aren’t sunk and the fuel pressure is 7ish pounds or only way fuel can get out of the vent is the needle and seat isn’t doing it’s job.

When you were going through the carb, did you happen to remove the floats? Just curious. And IIRC those carbs had brass floats. At least they did in the 1980’s. I haven’t been into a newer one.
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They seem to be that black foam stuff now, but I have a brass float in the primaries and the black foam in the secondaries.
As long as they work right we're good.:D
 
If the rear needle and seat is not over flowing, swap it with the front. See if it follows.
 
What kit did you use? Most kits come with ALL of the different metering block gaskets. It's EASY to use the incorrect one. That's why I always try my best to get the old gaskets off in one piece and match the new ones up with the old ones. There is one metering block gasket that blocks off a hole or two but the rest line up perfectly. I bet that's what you did. I've done it myself......multiple times.
 
RustyRatRod said:
What kit did you use? Most kits come with ALL of the different metering block gaskets. It's EASY to use the incorrect one. That's why I always try my best to get the old gaskets off in one piece and match the new ones up with the old ones. There is one metering block gasket that blocks off a hole or two but the rest line up perfectly. I bet that's what you did. I've done it myself......multiple times.
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LOL Repeat offender
 
TrailBeast said:
They seem to be that black foam stuff now, but I have a brass float in the primaries and the black foam in the secondaries.
As long as they work right we're good.:D
Click to expand...

They're some sort of hard black plastic
Float.jpg


I didn't check them to see if they actually do float, but when I had the bowls back off I shook them while hold the floats and there was no sound of fuel sloshing around, so I think they're ok in that regard.
 
RustyRatRod said:
What kit did you use? Most kits come with ALL of the different metering block gaskets. It's EASY to use the incorrect one. That's why I always try my best to get the old gaskets off in one piece and match the new ones up with the old ones. There is one metering block gasket that blocks off a hole or two but the rest line up perfectly. I bet that's what you did. I've done it myself......multiple times.
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I took the list number off the carb and used the kit recommended in a part number breakdown sheet I found. According to that sheet, the Renew kit is 37-119.
I tied to be very careful with the gaskets. I just disasembled and checked things over. This one could have been backwards, notice the hole on the left hand edge, one down from the top (sorry for the rotated pic)
Gasket.jpg
 
Alright, so here's the update. I took the float bowls off and cleaned both needle and seat assemblies again. I set the floats at parallel to the top of the bowls as a starting point figuring I could fine tune if things went well. I blew out the passages in the metering block and plate (on the secondary). I put it back on and gave it a try.

It cranked for about 7 or 8 seconds before firing but it immediately started doing the running on 4 cylinders thing again. It stalled out pretty quickly and a second attempt to start had it shoot gas up through the carb. So now I'm wondering if what I was seeing was the result of a backfire and not gas pushing past the seats? Or maybe I had more than one problem and at least eliminated that one.

I wrote down the cold/hot cylinders this time. Hot are 3, 5, 2 and 8 Cold are 1, 4, 6 and 7. That might be a clue. I'll try to see what I can determine on what cylinders are fed from what side of the dual plane.
 
Trying to set the idle with the screw on the throttle linkage?
 
Keystone said:
I took the list number off the carb and used the kit recommended in a part number breakdown sheet I found. According to that sheet, the Renew kit is 37-119.
I tied to be very careful with the gaskets. I just disasembled and checked things over. This one could have been backwards, notice the hole on the left hand edge, one down from the top (sorry for the rotated pic)
View attachment 1715497127
Click to expand...

That main body gasket isn’t correct. Don’t know what else is wrong, but I wouldn’t use that main body gasket.
 
Keystone said:
I took the list number off the carb and used the kit recommended in a part number breakdown sheet I found. According to that sheet, the Renew kit is 37-119.
I tied to be very careful with the gaskets. I just disasembled and checked things over. This one could have been backwards, notice the hole on the left hand edge, one down from the top (sorry for the rotated pic)
View attachment 1715497127
Click to expand...

That's what's wrong. See the large hole in the center of the main body gasket? You need one that isolates that small hole in the main body.
 
yellow rose said:
That main body gasket isn’t correct. Don’t know what else is wrong, but I wouldn’t use that main body gasket.
Click to expand...

RustyRatRod said:
That's what's wrong. See the large hole in the center of the main body gasket? You need one that isolates that small hole in the main body.
Click to expand...

Success! I went back and looked though the pictures I took when I dissembled it and sure enough, the gasket that was in it had one hole
Wrong Gasket.jpg


The correct one was in the box of leftover parts. I feel really dumb for missing that, but you guys really helped me out. It's purring like a kitten now! Thanks again :D
 
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