I have a zz4 in my 68 with a holley 3310 carb. I previously had a Quadrajet. I am having a problem with it running rich. I have one of those Air Fuel monitors from edelbrock and cannot tune it any better than 12.5-1 AF ratio. The problem is I have the mixture screws out about 1/2 turn. If I go in any more it starts to stumble. Any suggestions? Timing is set perfectly. Engine runs great but rich.

Check the float levels. If they are too high I have seen fuel drip into the venturi thru the nozzles at idle. Even if you don't see this, the float level can make a difference.

I like to set a holley float level to just below the threads for hard cornering. No fuel coming out.
A 68 main jet on the primary is a good start. Some 3310's came with 70's or 72's in the primarys.
David
David

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67 RS 327
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David,

Thank you for the response! I really appreciate it! I actually did not check this althought the instructions for the carb did say to do so. I would think that on a brand new carb this would already be set at the factory. I guess I am wrong.

I was having the same problem with my 3310-3 carb. Lowered float and helped. Still a little rich, but not as bad.

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Jay 69 SS-350

A common cure for a rich idle is to install a "v" shaped piece of wire in one of the idle passages in the primary metering block. "How to Supertune Holley Carbs" book has a good description of this mod. The best part is that it is easy to undo.

I bought a 3310 from The Carburetor Shop a few years ago and they had performed this modification. The wire was about 1/8 of an inch long as was very fine.

Is it rich at idel or all the time let me know .I have had lots of runing rich problims i may be able to help.

Well, I checked the floats and no dice. They are set up perfectly. Fuel just begins to dribble out the way they are set. I can't tell you how much I tried doing everything by the book to minimize any problems. I have to admit I'm a bit frustrated. I bought the recommended carb and I thought it would all work out perfectly. I'm ready to give up and sell everything on Ebay!!

Anyway, it seams to run rich all of the time. 12.5 - 1 AFR. When I drive it is stays right there. Am I in danger of hurting my motor by running this rich?

I can't believe this! I just received the latest issue of Hot Rod 9/00 and there is a great article called, "Goof-Proofing the Holley 3310". It talks about this carb when stock runs too rich in a small block. I'm really glad that GM recommended this carb for me! It tells me how to fix the problem but no way I'm comfortable with doing it myself. Just thought I'd throw this into the discussion.

Gene,

I have a similar book. It does not recommend enlarging the air bleeds as per the Hot Rod article. Instead the book recommends the wire method to restrict the idle feed restrictors in the metering block. It's hard to drill a smaller hole.

In your Carb Shop carburetor which way did they insert the "V"? Tip first or legs first?

Carl

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Carl,

The V was placed "legs first". Leg 1 was inserted into the hole coming from the main well (Hole A) and Leg 2 was inserted into the hole going to the idle well (Hole B). These two holes are located at the bottom of slots shaped like half of a "Y" on each side of the power valve. Hole A is drilled at an angle into the side of the slot and hole B is drilled straight into the metering block. Therefore, there is about a 45* angle between the two holes. Hence the need for a "V" shaped piece of wire.

I had to add this in a second post.

Doesn't it pi$$ you off that we have to fiddle with a carb that was desgined for an engine that hasn't been produced in over 30 years? (Note: for those of you that haven't seen it, the Hot Rod article indicated that the 3310 made it's debut on the L-78 396).

This really sucks (no pun intended). 400 HP small blocks are literally a dime a dozen in the world today and we have to put up with the crap discussed above to get our small block cars to run well with 30 year old metering system settings. Of course, I guess we could buy a $600 HP series to get more modern settings that might help with the problem. No wonder Demon is kicking Holley's behind (or so it seems to me).

I think Holley should be selling carbs with metering systems more in line with engines that are being built today.

Gene,

Yes.

Yes this does kill me. I am not that knowledgable with carbs so I tried everything possible so I wouldn't have a problem. Even bought an air fuel monitor and stuck it in the exhaust. I guess I should have bought a fuel injection kit!

Here is the first response I recieved from Holley tech. I didn't try it yet.

maybe out of the box but it can be tuned in, if we drop somemore jet sizes
the main can be fixed. now we can fix the idle, if we get the idle clean
every other ciruit is better off, use the set screw coming up from the
bottom base plate on the secondary and crack the secondary open a little to
give it a little more air then your idle will be clean and the rest of the
curve will be easier to tune. do not use the mixture ratio meter to tune,
it all depends on what the motor wants for fuel then you are not running
standard fuel either.

Not the best use of English but I think I get the point. I'll let you guys know what happens...