Got a question about Holley Carbs...Can anybody help??

[kennygene]

I've got a 650 Holley Double Pumper on my Dart 318CI Magnum Engine. It is a model 4165 with the large rear barrels. I'm having trouble with the carburetor being too rich. I recently removed the mechanical fuel pump to convert the engine to serpentine belt. In doing so, I had to add an electric fuel pump and had about 8-9 psi at the carb. Yesterday, I added a regulator and lowered the pressure to 6 psi. The lower pressure didn't seem to help at all. I've already checked float bowls and reset float adjustment and I'm just baffled. Can anybody tell me the best recommended pressure for this carb?
BTW, the needle valves and seats are new and are clean. I put 2 new filters on the car when I added the pump.

 

[Michael from the U.K.]

I had a holley once,brilliant and easy to work on,if it's running rich have you tried putting smaller jets in?:dontknow:

 

[kennygene]

Ran fine on the same engine before I added the electric pump and serpentine conversion. At first I had a bad voltage regulator which put too many volts to the pump and added pressure. I think I need to open the carb again and inspect the float levels.

 

[enforcer17]

Do you have jets in the front and rear bowls? Can't remember if your model does or not, if not, you might want to add a metering plate to the secondaries and then jet them properly. Holleys can be quite a pain until you get them tuned just right. 5-6 psi is pretty normal for a carburetor setup.

 

[VIPR PWR]

Check float Levels and be sure that the needle and seat are actually good---New, does not mean it's ok.....Is it bleeding fuel when you look down the bores?????

 

[FSTJACK]

The 4165 is a spread bore replacement.
This is not one of Holleys best versions of a carburetor.

Check the power valve and float levels.
With the float bowels off, and the bowels inverted, the top of the float should be level with the top of the float bowl.

Also use nothing but a genuine Holley brand carburetor kit, or parts when working on this model of carburetor. (This applies to almost all Holley carbs, Barry Grant, ProForm and a few are also good replacement parts for Holley brand parts). (Stay away from carb kits that come in a white cardboard tray when working on Hollys).

I would keep fuel pressure in the 4-5LB range.

Did you replace the fuel filter?
Did you run fuel through the new fuel system to flush dirt and contaminats out of the pump, lines, fittings ect into a catch can?
The needle and seats on the primary and secondary side are usually different.
A common mistake is mixing the jets between the primary and secondary sides.

If none of this helps hold it up to the phone so i can look at it........:elefant::elefant::elefant:

 

[kennygene]

Yes and no on the bleeding. The front bores do appear wet sometimes. I am having trouble with the secondaries closing properly so they are part of the problem. I think I'll take the carb off tonight and tear it back down. I want to inspect and tweak everything before I do anything else.

I wish my carb had the external float adjustments.

 

[FSTJACK]

Check your throttle base to main body gasket, there are several permutations and it is common for folks that don't do a lot of carb work to use an incorrect gasket which I have seen cause similar problems to what you are having.

The transition and transfer slot openings don't line up correctly.

 

[kennygene]

The 4165 is a spread bore replacement.
This is not one of Holleys best versions of a carburetor.

Check the power valve and float levels.
With the float bowels off, and the bowels inverted, the top of the float should be level with the top of the float bowl.

Also use nothing but a genuine Holley brand carburetor kit, or parts when working on this model of carburetor. (This applies to almost all Holley carbs, Barry Grant, ProForm and a few are also good replacement parts for Holley brand parts). (Stay away from carb kits that come in a white cardboard tray when working on Hollys).

I would keep fuel pressure in the 4-5LB range.

Did you replace the fuel filter?
Did you run fuel through the new fuel system to flush dirt and contaminats out of the pump, lines, fittings ect into a catch can?
The needle and seats on the primary and secondary side are usually different.
A common mistake is mixing the jets between the primary and secondary sides.

If none of this helps hold it up to the phone so i can look at it........:elefant::elefant::elefant:

I rebuilt the carb last winter with all Holley parts. I just installed 2 new filters. The float bowls are level when held upside down.
I did not purge the fuel lines but will for sure when I take it back off.
I actually had the primary bowl back off a couple days ago checking the float and it was clean and the needle valve/seat worked fine.
Thanks for the fuel pressure information. According to what I've read, Holleys can hold up to 8psi but that seems high for a carb.

 

[FSTJACK]

I rebuilt the carb last winter with all Holley parts. I just installed 2 new filters. The float bowls are level when held upside down.
I did not purge the fuel lines but will for sure when I take it back off.
I actually had the primary bowl back off a couple days ago checking the float and it was clean and the needle valve/seat worked fine.
Thanks for the fuel pressure information. According to what I've read, Holleys can hold up to 8psi but that seems high for a carb.

With the side hung floats on a 4165 they seem to like lower fuel pressure.

I owned a carb and fuel injection shop for most of my career, so I worked on a lot of different carbs and types of injection(mechanical and electric).
After a time if you pay attention you see things that vary from the book in the real world.

I loved what I did and most days had a big smile on my face when going to the shop to open in the morning.


I'm retired and really miss it...:rock::rock::rock:

 

[kennygene]

With the side hung floats on a 4165 they seem to like lower fuel pressure.

I owned a carb and fuel injection shop for most of my career, so I worked on a lot of different carbs and types of injection(mechanical and electric).
After a time if you pay attention you see things that vary from the book in the real world.

I loved what I did and most days had a big smile on my face when going to the shop to open in the morning.


I'm retired and really miss it...:rock::rock::rock:

I enjoy your knowledge, there is nobody around here that understand or even works on Holleys. Everybody just buys those simple Edelbrock carbs and bolts them on. I've always like Holley and I'll get it working properly. I just have to make sure there'e plenty of beer in the garage.

 

[FSTJACK]

I enjoy your knowledge, there is nobody around here that understand or even works on Holleys. Everybody just buys those simple Edelbrock carbs and bolts them on. I've always like Holley and I'll get it working properly. I just have to make sure there'e plenty of beer in the garage.

There is no comparison between a Holley and an Edelbrock carb in my opinion.
I have worked with tuning on both brands and a Holley when properly selected and "dialed in" cant be beat.

The Holley is vastly superior in operation in most models.
Holley has their "dogs" but the 4150 and 4160 style carbs seem to be the best with regard to flexibility and power.

The proliferation of supercharged motors using carbs and making huge power is just amazing when you consider how simple a carburetor is in comparision to EFI.
In most cases you can actually make more power with a carburetor than with EFI in boosted applications. This holds true for normally aspirated as well.
The basic 4150, 4160 style Holley carb was first introduced in 1957 on Ford vehicles.
This style has been refined and improved over the decades and is still a viable alternative making good cheap power.

The Quadrajet is a very simple and excellent working carb, as is the Carter Thermoquad.

These carbs have been bad mouthed over the years mostly by folks that do not understand how they operate. They are simple and mostly trouble free with few moving parts to fail or wear out. The Qjet had a problem with the car and truck throttle base plates in wearing out the throttle shaft housing. The shaft never wears out.
I made tooling and fixtures to bronze bush the primary throttle shaft indicating it back on the true center line. They wear towards the rear of the base shaft, egg shaping the bore.
Once bushed they never wear out and you have what amounts to a carb when properly reworked and massaged gets reasonably good mileage and great power and last almost forever.

EFI has replaced carbs for a very good reason. This technology offers great dirveability and fantastic mileage.

But a $225.00-500.00 carb is hard to beat for a street/strip hot rod that is not EFI to start with.

Get your 6 pack and a selection of jets and power valves and dial that beauty in.
It is very satisfying to do it yourself.

 

[kennygene]

Power valves, I installed new power valves but only got a few with the kit. Which would be good to start with on an A body Dart with a 5 spd manual trans and 325:1 gearing? My altitude is 800 above sea level.
I think I installed a 6 on the primary and secondary. I may need to buy some jets and power valves to experiment with. First though is to get the thing working correctly.

 

[WOT]

Did it ever backfire with the new power valves? Nothing kills a power valve faster than a backfire. And, you can't really tell that it won't hold vacuum by looking at it. The symtom is that it will run rich at idle and low throttle settings. A bad base gasket can cause a vacuum leak that will allow a power valve to open at idle as well.

I like that carb though: spread bore with a power valve on both the primary and secondary. You should be able to really dial that carb in well. You could upgrade to a metering block with externally swapable main jets. That way you could easily change metering for summer and winter.

 

[kennygene]

I've had this carb for years and it is in great condition. The throttle plates are nice and tight. The shafts are good and tight in the body.
I'm going to keep working on it and get it right. I hate to buy too many parts since I'm planning to go to electronic fuel injection next winter. I'd just like to get it working properly without flooding and then maybe tune it in for some test n tune racing.

 

[WOT]

Is it rich at idle or wide open throttle (WOT)?

 

[kennygene]

It is rich at idle and low throttle. WOT works well but only after about 3k rpms.
BTW, no backfire on the new power valves.

 

[WOT]

OK, so it's not the power valves. They open at WOT at low rpm. So, if it doesn't clear up until after 3K, then you have a different issue.

This may sound stupid, but check to see that you actually put the jets back in both sides. You'd be surprised at how well will it will run with no jets at all. At dead idle, very little signal makes its way to the main jet, so it will only run a little rich. Then as you tip into it, it will start to flood out. Since you are running a spread bore, it can still run without totally dying. I think with no jets, it is equivalent to running 120 size jets or something. If it is only on the primary side, then the leaner (and larger, spreadbore) secondary side will clear it up at higher rpm, at WOT.

The other thing it could be doing is spilling over from the the floats. Pull the sight plugs and see if gas pours out the holes. If so, your floats are not stopping the gas like they should. You can do this without the motor running (and the associated fire hazard) because you have an electric fuel pump.

Also, check to see that you didn't swap the metering plates from the primary and secondary as they have different jets in them.

 

[Black1]

This is very interesting! I am loving the different opinions and general knowledge being pass on here! Carb tuning and maintenance is almost a dead art in most places in the USA. Especially with Webers (but that's a whole different animal). :rock:

 

[rottenronnie]

I had an Engineer buddy and his 750 Holley DP was shooting fuel out of the vent tubes after he installed an electric pump on his stroker. He insisted 7 psi was just fine and it shouldn't be doing that. I agreed, it shouldn't be doing that..

Anyway, he lowered the pressure to just under 5 and it solved the problem.

FSTJACK- Thermoquads! TQs were my faves.. Once those plastic floats were replaced with brass, the (2) stacked o rings under the jets (that the previous rebuilder didn't realize stuck in the well) were replaced with one (like it should be), the air door was set to the correct opening and the secondaries were wired together to prevent the choke lockout from jumping and preventing the secondaries from opening, they WERE a great carb!

They would support an engine with an unholy amount of power and that triple- venturi worked really well at atomizing fuel through the primaries. The more emission oriented carb with the single electronic vent in the front was a little funky but the others with 2 standard vents worked great. They also had a unique sound with that wide-open secondary design. They moaned on a low compression engine but wailed on a high compression one !

I was never a fan of Quadrajets, they had 49 parts when everyone else was using 2 to do the same thing. Or maybe it just seemed that way???

The stock 570 c.f.m. AFBs on my 426 Hemi were also super simple and totally reliable. The Hemi had such a bad manifold, it was the most extreme staggered jetting I had ever seen (and still is). Also, using tabs on the boosters to redirect the air/fuel stream was cool...And they could be unscrewed and move around. I remember trimming the weights on the secondary velocity valves to get the transition just right with the auto and 3.23s.
It used to trap at 113 in SECOND gear !!! For a 4000 pounder back in the early 70s, that was rockin'!!! I used a Mr. Gasket DC StreetSpark distributor at 34 total and it worked surprisingly well. No vac. advance on those so mileage was only so-so...

The 440 6 pack I had was also a hoot. THAT setup also had a real unique sound at w.o.t. esp. with small(ish) primary headers and a bit of home-porting on the 906 heads.

Ronnie