What size Holley jets should I use?

[greg82255]

Hello,

Just installed a Holley 4160 600 CFM on my 305. Running too rich, any suggestions for what size jets should be used on this engine? Not sure what size is in there now (bought the carb remanufactured).

Before I go and change the jets, what other adjustments can I make to try and lean out the mixture? '82 Merc 898, pre-alpha drive.

Installed a Holley 4160 and Edelbrock performer intake last winter.

Any help is appreciated, thanks.

 

[zbnutcase]

Re: What size Holley jets should I use?

What MODEL 4160 is it? List #?? And it better be a marine carb!

 

[greg82255]

Re: What size Holley jets should I use?

It is absolutely a marine carb, would never put a car carb in a boat. Not sure of the model # other than a 4160, I'm at work right now, I'll have to look it up and repost.

 

[jtmarten]

Re: What size Holley jets should I use?

The list # lookup will tell you the primary jet sizes. Most likely with a 4160 you have a secondary metering plate = non-adjustable. If the plugs are black, drop 2 sizes, install new plugs, and see if they come out a nice tan color. I think the max jet sizing Holley recommends is +/- 5 sizes from stock.

The power valve makes a big difference too, make sure it's good. They have multiple sizes available.

Also, make sure your flame arrestor is nice and clean too.

Once you have the list #, call Holley tech support, they probably can tell you right away which jets/PV combo will work best for your setup at your usual elevation.

 

[greg82255]

Re: What size Holley jets should I use?

Holley 0-80551

Model 4160 Marine 600 CFM 4-Barrel Vacuum Secondary Electric-Choke

Does that sound right for the model #??

 

[jtmarten]

Re: What size Holley jets should I use?

Yep. I'd also suggest the secondary spring and quick kit to easily adjust when the secondaries open, unless they open at the right time out of the box.

Mortec used to have a huge Holley listing of all the List #'s and specs, jet sizes, etc. Seems like their site is gone. You'll have to pull the primary bowl or contact Holley to find out the stock jet size.

 

[greg82255]

Re: What size Holley jets should I use?

The secondaries appear to be opening at the right time. I don't feel any kick when they open, just smooth acceleration.

Are there any adjustments on the carb that would allow me to lean out the mixture? If possible, I would rather try turning a few screws before I take the carb apart and pay for new jets.

 

[a70eliminator]

Re: What size Holley jets should I use?

Does it load up and stall at idle speeds? the air fuel mixture screws can fix that. The float setting will effect mixture, extremely high floats will cause flooding.

 

[Leardriver]

Re: What size Holley jets should I use?

Start with the 2 air/fuel idle mixture screws at 1.5 turns out from fully seated. If you can get to the float bowl without any obstructions, the float bowl comes off in 2 minutes. Jets are about $8 for a pack of 2. Use four sizes leaner to start with, like a #86 to a #82. Changing Holley jets is quick, cheap, and painless.

 

[greg82255]

Re: What size Holley jets should I use?

Changing Holley jets is quick, cheap, and painless.

Now that's what I like to hear... where can I buy jets? Order online or at an auto parts store?

I know that car vs marine carbs have huge differences, but are the jets any different?

 

[John_S]

Re: What size Holley jets should I use?

When is it rich? idle, accel, cruise, wot? While I haven't been inside a Holley in 20 years, it does make a difference in what should be adjusted or changed.

 

[zbnutcase]

Re: What size Holley jets should I use?

Nope jets are the same, and the 80551 comes with #63 jets stock.

 

[jtmarten]

Re: What size Holley jets should I use?

Anything off-idle runs through the main circuit, so there are only idle mixture and main jets. Accel pump can be adjusted, but is still 30cc's.

I'd be hesitant about dropping 4 sizes without knowing just how rich it's running. You could over-do it and go too lean, which is a worse scenario. The plugs will tell you.

 

[scoflaw]

Re: What size Holley jets should I use?

Blown or gummed up power valve will make it run rich. Power valve should be 1/2 of your idle vacuum #. If it's not responding to an idle/air adjustment, it's the power valve or a plugged circuit.

 

[jtmarten]

Re: What size Holley jets should I use?

If it's not responding to an idle/air adjustment, it's the power valve or a plugged circuit.

Or the primary butterflies open, just beyond the idle circuit.

 

[Leardriver]

Re: What size Holley jets should I use?

The auto parts stores around here have them (jets). You can always replace your power valve while you have the float bowl off, but the Holley power valve blow out problem has been solved for 20 years, and the legend is worse than the actual occurrence.

 

[Leardriver]

Re: What size Holley jets should I use?

Go on Holley's website and start reading the technical papers and adjustment instructions. They have a great site.