Floats on Holley 4BBL Carb.

[AaronWhitt82]

Hey guys I have a Holley 4 Barrel carb on my boat and I'm going to replace the floats on it.
On the primary fuel bowl it has a center hung brass float and on the Secondary side it has a center hung nitrophyl float.
Question: Can I replace both with just nitrophyl or should I replace them how they are already set up?
Also which is better...... Brass or Nitrophyl????

I also have a question about the secondary metering block..... How come it doesn't have a power valve on the secondary side or metering plates??? It is just solid in the middle. Is that because it is a marine carb and it is set up different? The gasket on the metering block still has the cut out in the middle as if there is a power valve there and I'm not sure if it is the correct gasket or not???

Thanks!

 

[Maclin]

Re: Floats on Holley 4BBL Carb.

You can use either type, mixed or matched on the floats I would think. The float adjustment is done with the needle and seat assembly and performed while engine running so I do not think the float type would affect the ultimate setting.

Why do you want/need to replace them?

Regarding the power valve, that setup is not Marine specific, most vacuum secondary Holleys with secondary metering blocks are set up this way. Your gasket is correct, it is the same for both types of metering blocks. The power enrichment circuit (controlled by the power valve) is only needed on the primary metering circuit during transition from idle to main circuit for accelerating and other low vacuum conditions. Once the engine is just cruising and the vacuum is higher then the power enrichment circuit shuts down for economical cruising and idling. No need for a power enrichment circuit in the secondaries on a vacuum secondary Holley because they will always be used in a power enrichment condition and are calibrated as such, and the power circuit passages are not in the metering block casting. There should be the same type of screw in tuneable jets though if there is no metering plate. The jets would be a couple of steps richer than what is in the primary metering block.

 

[Maclin]

Re: Floats on Holley 4BBL Carb.

Here is what I believe to be the style of carb you have in an illustration from the Doug Russel marine site, showing two metering blocks but only the front or primary block shows the powervalve (part #12).

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

You can use either type, mixed or matched on the floats I would think. The float adjustment is done with the needle and seat assembly and performed while engine running so I do not think the float type would affect the ultimate setting.

Why do you want/need to replace them?

Regarding the power valve, that setup is not Marine specific, most vacuum secondary Holleys with secondary metering blocks are set up this way. Your gasket is correct, it is the same for both types of metering blocks. The power enrichment circuit (controlled by the power valve) is only needed on the primary metering circuit during transition from idle to main circuit for accelerating and other low vacuum conditions. Once the engine is just cruising and the vacuum is higher then the power enrichment circuit shuts down for economical cruising and idling. No need for a power enrichment circuit in the secondaries on a vacuum secondary Holley because they will always be used in a power enrichment condition and are calibrated as such, and the power circuit passages are not in the metering block casting. There should be the same type of screw in tuneable jets though if there is no metering plate. The jets would be a couple of steps richer than what is in the primary metering block.

Maclin - Thanks for the response.... I've totally been way too busy with my job and forgot about this post lol

Basically I'm just getting ready to finish up what I started last year before storage......

I rebuilt the carb myself and just have a few other things I want to put NEW on it which includes the floats.
I think I'm gonna to go with Nitrophyl instead of brass.
I don't think there is anything wrong with them, but they are the original ones so I figured why not replace them. I am aware of how to adjust the float level as well which still needs some tuning.

Thank you for explaining to me how the secondary side worked without needing a power valve as I was lost on that part and the Holley repair manual didn't really explain it that well.

The primary metering block has jet size 68 and the secondary side is size 73.

Once I get the boat out of storage I need to change the metering block gasket on the primary as I put the wrong one on there.


This is what kind of gaskets came with the kit so I had to put this one on the primary side

This is the one that originally came off the primary side

What is the difference between these two gaskets and does it matter if I used the one on top to replace the above one for the primary?

Oh yea before I forget too........ What kind of changes will occur if I put a thicker base gasket on that is square bore?

Thanks again!

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Holley gets weird with gaskets. You need to really look at what came out, and look at the new one, to make sure you don't cover passages.
As far as the thick gasket, all it is good for is cracking the base plate, unless you buy an inch-pound torque wrench. It is only needed if things are warped, and you have a leak- have all milled if so.

 

[ccmarsh]

Re: Floats on Holley 4BBL Carb.

You should invest in the torque wrench. It's very easy to tear the power valve gasket. Also look at the manual closely, the gasket that you pictured and said came off the primary side,according to my manual, is the correct gasket for the primary side. The other gasket you pictured is for the two barrel. The kit comes with both. If you give me the list number on the carb, I can probably find out for sure.

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

You should invest in the torque wrench. It's very easy to tear the power valve gasket. Also look at the manual closely, the gasket that you pictured and said came off the primary side,according to my manual, is the correct gasket for the primary side. The other gasket you pictured is for the two barrel. The kit comes with both. If you give me the list number on the carb, I can probably find out for sure.

Well I do have a torque wrench, but for Ft. LBS. I need to get one for inches.
Yes I am aware that the gasket I pictured is the correct one for the primary side and the blue non stick one is for the secondary side.
I ordered my rebuild kit through Summit racing and it was a Marine approved kit for a 4150. However the kit only came with 2 of the blue non stick gaskets as pictured above. I fabricated the one gasket and cut a little notch out so it was as close as the other one because I was anxious and wanted to get back out on the water and didn't want to wait a few more days to receive the correct one as I have no local parts store that stocks Holley parts.
So I am now ordering the correct one from Summit.

The list number on the carb is 75021-1, but when I called Holley to get a number for a rebuild kit the guy said he couldn't find that part number for the carb which I found to be odd.
There was also another number stamped on it which is 2408 and he said that wasn't the right one.

 

[ccmarsh]

Re: Floats on Holley 4BBL Carb.

Is this your carb? I'm just curious.

 

[Maclin]

Re: Floats on Holley 4BBL Carb.

I believe the blue teflon one with the small hole above the power valve cutoff is for the primary side, that hole is for the accelerator pump shot feed channel from the metering block into the throttle body. The one with the larger cutout instead of the hole would not seal well around that feed hole and the pump shot would suffer. I believe you can use the primary gasket on the secondary with no ill effects, but you must use the proper one on the primary side. The secondary metering block would not have the pump shot hole that is drilled into the channel. Also watch the orientation, the holes are not symmetrical, be sure the small alignment hole in the middle of just one edge of the gasket matches up to the tang on the block.

I may be able to locate the kit# I got for mine, I purchased it at O'Reillys after a search thru their books. I will try to look for it tomorrow, I am sure it would work for yours as well. Seems like it was around $30.

Oh, and DEFINITELY go with the more expensive blue teflon gaskets, they can be re-used several times.

As far as the base gasket, my stock one was just a big square open hole type and was in need of replacement. I like to try to match the intake configuration though so I did not replace it with the open hole style. My manifold is the cast iron single plane 2 plane with two oval holes, one for each left/right half of the carb. I found a nice black 5/16" (maybe 3/8", was the same as the stock one) 4 hole gasket for a 454 4bbl that worked for what I wanted after gently cutting the web between the holes on each side, leaving a strip down the middle that matched up to the manifold. The manifold had a notch in the middle ridge, that keeps pulses equalized. I think I got that gasket at Autozone by just having them let me look at all the ones they had. O'Reillys may have it also, I got them at different times. I would not go thicker than the stock, and be sure to get a gasket with the metal spacers in the bolt holes so you can't crunch down too far on one end and break the base plate.

The 4 hole type base gasket would do nothing extra for you and would have a lot of gasket "unsupported" which I think could cause problems later in life. I would go with just the open type or find one that matches the intake or mod one like I did.

 

[mkast]

Re: Floats on Holley 4BBL Carb.

Most carburetors employ what is generally called a power valve circuit. This circuit enriches the air-fuel mixture when the carburetor goes to wide-open throttle (WOT). At WOT, intake manifold vacuum drops to almost zero. When this occurs, the power valve opens and directs more fuel into the main power circuit, in addition to fuel delivered by the main jets. The Holley power valve employs a small rubber diaphragm that is opened by a small coil spring. The valve is held closed whenever sufficient engine vacuum is present. At WOT, engine vacuum disappears and the power valve spring opens the valve, directing fuel through a small, precise orifice in the metering block called the power valve channel restrictor. This restrictor determines the amount of additional fuel delivered to the engine.

Power valves are used most frequently on the primary side of a Holley carburetor. They allow the carburetor to operate with much leaner main circuit jetting for part-throttle fuel economy. Then, when the throttle is slammed open, the power valve adds additional fuel, creating the rich air-fuel ratio needed for WOT operation. Most Holley power valve circuits are designed to add the equivalent of 8 to 10 jet sizes of additional fuel. Holley does offer a power valve block-off part that closes the power valve circuit, but this means the jet size must be increased in order to compensate for the lost power valve circuit fuel. Imagine how bad your fuel mileage would be if you had to add 10 jet sizes to the primary side of your carburetor!

The problem with the Holley power valve is that it is the most sensitive circuit in the carburetor. The little rubber diaphragm has a tendency to tear or just plain fail at usually the most inopportune times. It is especially vulnerable to engine backfires. When the engine sneezes back through the intake manifold, it generally will kill the power valve. When this happens, the torn rubber diaphragm allows engine manifold vacuum to pull fuel through the valve, making the engine run extremely rich.

Power valve blowout protection can now be added to older model 2300, 4150 and 4160 carburetors. Consisting of a spring, brass seat and check ball, this kit will effectively protect the power valve and is easy to install. Included is the proper drill bit size, with stop, to facilitate installation. Detailed instructions are included.

Floats are weighed on a float scale to determine if they are usable.

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

Is this your carb? I'm just curious.

Actually that looks similar to the one I have, but mine isn't black and is just a bare aluminum looking color.
Also the one you have pictured doesn't look like it has a secondary diaphram setup on it as mine does.

This is what mine looks like:

Mine is 600 CFM, Dual fuel inlet with electric choke.

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

I believe the blue teflon one with the small hole above the power valve cutoff is for the primary side, that hole is for the accelerator pump shot feed channel from the metering block into the throttle body. The one with the larger cutout instead of the hole would not seal well around that feed hole and the pump shot would suffer.

Are you sure about that? The mechanic at the Marina I went to said the brown gasket with the extra cutout is for the primary metering block and that it should only be used for the primary side and then the blue one is used for the secondary.

I may be able to locate the kit# I got for mine, I purchased it at O'Reillys after a search thru their books. I will try to look for it tomorrow, I am sure it would work for yours as well. Seems like it was around $30.

I appreciate the help, but I don't need another rebuild kit at this time. Just a mix up with the metering block gaskets that I need to switch around and get the correct one. If you could provide me with the kit # that would be great when the time comes again that I would need one.

I would not go thicker than the stock, and be sure to get a gasket with the metal spacers in the bolt holes so you can't crunch down too far on one end and break the base plate.

The only reason I was asking about the thicker base gasket was because some people said the thicker the gasket the more "bottom end" you get, but I didn't really know if it was true or not.


Thanks again!

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

mkast -

Thank you very much as well. Your response explained alot and helped me understand the system a bit more.

I don't know what I would do without you guys!

Thanks again!!!!!

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Is this your carb? I'm just curious.

That is a double pumper, instead of having the weighed plate above the secondaries, it has a accel pump.

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Actually that looks similar to the one I have, but mine isn't black and is just a bare aluminum looking color.
Also the one you have pictured doesn't look like it has a secondary diaphram setup on it as mine does.

This is what mine looks like:

Mine is 600 CFM, Dual fuel inlet with electric choke.

Need a pic from the other side of your carb, in real life.

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Are you sure about that? The mechanic at the Marina I went to said the brown gasket with the extra cutout is for the primary metering block and that it should only be used for the primary side and then the blue one is used for the secondary.



I appreciate the help, but I don't need another rebuild kit at this time. Just a mix up with the metering block gaskets that I need to switch around and get the correct one. If you could provide me with the kit # that would be great when the time comes again that I would need one.






The only reason I was asking about the thicker base gasket was because some people said the thicker the gasket the more "bottom end" you get, but I didn't really know if it was true or not.


Thanks again!

That thicker gasket theory is from drag racing, which supposedly creates a stronger signal to the carb, to open the secs faster.
You have a boat, and not a drag boat-not needed. and when I used to drag race- proven to not make a difference; want to raise the carb higher than a perfect engineered double plane manifold? Buy the higher single plane and lose all bottom end- higher rpms only.

 

[AaronWhitt82]

Re: Floats on Holley 4BBL Carb.

Coors - Thanks for explaining the base gasket difference. The one I have on there now is a square bore that is I think .063" thick and pretty close to what I took off.

As far as the carb goes I got that pic from Summit racing. That one is a 4160 750 CFM

I wish I could get pics of my carb, but it is in storage over a hour away and I don't have access to it until the end of April.

However I'm still trying to figure out these damn metering block gaskets.

Every replacement metering block on Summit Racing shows it comes with this gasket:

What is the difference compared to this one:

I'm still not sure which one to use on the primary side....


I also can't figure out when I call Holley that they don't have a list number for my carb.
PN 75021-1 ?????

 

[Coors]

Re: Floats on Holley 4BBL Carb.

the one on the left is between body and metering plate- see the small hole above the large cavity? Use the one with the small hole. That is for the accell pump. The skinny gasket goes between the plate, and the float body.
The reason I ask to see other side of carb is- does your's have the pump lever at the back (secondaries) of the carb.
I seem to remember that the sec pump was always on the starter side. Is this carb new to you, or some-one else installed it?

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Welcome to Holley's world- I don't use them anymore, basically like you said- here is the list #; and no help.
A carter or quadrajet works good.

 

[Coors]

Re: Floats on Holley 4BBL Carb.

Coors - Thanks for explaining the base gasket difference. The one I have on there now is a square bore that is I think .063" thick and pretty close to what I took off.

As far as the carb goes I got that pic from Summit racing. That one is a 4160 750 CFM

I wish I could get pics of my carb, but it is in storage over a hour away and I don't have access to it until the end of April.

However I'm still trying to figure out these damn metering block gaskets.

Every replacement metering block on Summit Racing shows it comes with this gasket:

What is the difference compared to this one:

I'm still not sure which one to use on the primary side....


I also can't figure out when I call Holley that they don't have a list number for my carb.
PN 75021-1 ?????

the lower pic looks like for the sec metering plate with no pump, just the baffle above the sec's, that you don't have, from pic.