Holley 3310 setup and adjustments

[ERA649]

I have a new Holley 3110 on a 428 - out of the box with no adjustments the engine idles wrough - very wough - the engine starts to smooth out at about 1200 rpm . What is the best way to start tuning the carb.
Also can anyone recommend any books on carb basics.

Mike W

[KobraKarl]

Mike ,

It could be a couple of things, but if its"just out of the box" you probably need to adjust your idle mixture screws.

back your linkage idle screw off until the primary throttle blade is just opening

Turn the idle fuel mixture screws (on each side of your primary float bowl) all the way in GENTLY ! then back them out one complete turn, then back them out 1/4 turn at a time untill your engine does not pick up any more rpm. or if you have a vaccuum gauge until you have maximum vac.

then set your linkage idle

this should get you close, also check your timing ,

KK

[ERA649]

Thanks for the info KK --my timing is set at 8 deg BTDC - is that ok.

[Jack21]

There are tons of books and references availabe for tuning Holleys that you should be reading, and a Holley website with a lot of information as well.

The Holley 3310 was originally designed for the 396 Chevy big block, and comes out-of-the box with esentially the same jetting. Step one is the idle mixture screws as stated above. Second, take the slotted secondary idle setscrew out and replace it with an Allen head setscrew. Now, you should be able to adjust the secondary idle butterfly adjustment for more secondary air to lean out a too rich primary idle mixture.

You calculate your initial lead by subtracting your centrifugal advance from what your total advance should be, typically 32 to 36 degrees depending on cam and compression. i.e., if you're runing higher compression, say 10:1 (iron heads), 11:1, (aluminum heads), stay closer to 32 degrees total. If lower compression, crank in a few more degrees advance, but no more than 36 deg total. 8 degrees sounds a little low unless your 428 is mid-'60's factory stock.

Leave the option open to scrap the 3310 for a Speed Demon 750 double pumper. Demons provide much better a/f management than Holleys across the board, and the 3310 is the wrong carb for a 428 Cobra. (428 in a 4000# Galaxie with an automatic transmission would be a good choice, just not a Cobra).

[CJ428CJ]

For adjusting carbs it's usually best to advance your timing a lot. Set it at about 20 BTDC for adjustment. Do what KK says but if adjusting the idle screws doesn't seem to make much difference (if you don't notice the idle increasing or decreasing as you adjust), your power valve may be set to low. In that case, hook up a vacuum gauge and see how much vacuum you're getting. Your carb probably has a 6.5 inch power valve. You should install a power valve about 1-2 inches lower than your measured vacuum at idle. FYI, I had to install a 5 inch power valve in my carb and I found that my 428 likes a ton of initial advance. 24 degrees initial and about 40 degrees total.

Chris

[My427stang]

1. Set the timing to 12 initial, even 15 if it'll start when hot, but 8 IMHO is way too low for a light car.
2. Set the idle speed and then see if you have vacuum at the fitting off the metering block (if you do, your primary plates are too far open and you are out of the idle circuit, I'll bet bucks you are)

3. Assuming you are, pull the carb off and from the bottom back right under the vac canister, open the secondaries about 60 thousands or so using a little screwdriver on the secondary idle adjustment, just guesstimate, turn it in tighter 1 1/2 or two turns, but basically you are opening the back so you can close the front. Dont worry about how much, just open them a little. Holleys always use a secondary idle circuit as well, to keep fuel from going stale in the back bowls, you are just going to use it a bit more so you can close the fronts and be able to clean up the idle

4. Put the carb back on, it'll be idling high now, drop the primary idle down, adjust the a/f again and see if that port is alive again, if it is, add a little more secondary idle again and do the same thing

5. After you get it to where the ported vacuum is dead at idle (no vacuum at all) if it is still rich, you may have to swap plates in the back. You have a 21 plate which is jetted properly for yours, but the Idle Feed Restriction is a .059 i beleive on factory 3310's, if you go for a plate number 44, it will lean out the idle with the same main jet size BUT the part that will ehlp is that the IFR is .029

The last thing I have seen is that the 3310-4 has a 25 squirter, most others have a 31. The FE seems to like the 25 so the shot last longer. I actually changed my 850 from dual 35's and a 50cc pump to dual 25's and 30cc pumps. If you have anyhting other than a 3310-4 change the squirter to a 25

I bet the first part adjusting the idle to take more from the back will give you the 90% solution, chase the others if you need it

[My427stang]

Also, seeing one of the other posts. Power valves have nothing to do with idle. A power valve only works when two things happen.

1. The throttle plates have to be open, pulling fuel through the boosters

2. The vacuum behind it has to be lower than its opening value

So, at idle, when vacuum is high and plates closed, the thing doesnt do ANYTHING

Even if vacuum was WAY lower than its value, the plates are closed, so no air is being drawn across the booster to pull the fuel in.

The only exception to that, is what I described above, if the primary idle is open SO MUCH that it causes airflow across the boosters, it could pull some main jet fuel into the motor, and theoretically if it had the wrong PV it could also pull more through that circuit

However, say this to yourself PV does nothing at idle over and over LOL

[Steve R]

Mike W,
If you want to win this game, there is no substitute for knowing the rules. Go here and print it out. Leave it in your "throne room"
Read it when doing you business. http://www.bob2000.com/carb.htm
I have a certain book in mind for you to get. I'm just trying to get a direct link to a picture of it So you can go to your local Barnes and Noble, buy it and install it in your biffy.
Steven
here it is.

Here is a link to where I found it. http://www.holley.com/

[George Snyder]

ERA 629,

I agree with everything that My427 Mustang suggested you do.

The one thing I would add they may have been over looked is the carb to manifold gasket. If you reused the gasket there is a possibility that the ported vacuum circuit that he mentioned is not sealed from the manifold vacuum. I think I would start fresh with a new gasket if you haven't already. Then follow his instructions.

Take your time setting the idle mixture. The over all performance of the carb is effected by how accurate an idle mixture you have.

I would suggest that you purchase a few extra gaskets. You may be able to flip them over to get two applications per gasket. I am not familar with what the top of an intake on a 428 looks like, so I am saying maybe. I would never use the gasket over using the same side, they are too inexpensive to go thru the hassle if it leaks and you have to start over again.

Lastly, if the budget will allow? Start with Jack's suggestion.

Leave the option open to scrap the 3310 for a Speed Demon 750 double pumper. Demons provide much better a/f management than Holleys across the board. I, like Jack feel that Demon brand carbs are the best on the market.

What may be the best feature of the Demon is that you can set the idle front & rear at what ever you want with the carb on the engine. That feature alone is worth the investment to me!
Secondly, I believe that with the four idle mixture screw you can achieve a more accurate a/f idle setting than you normally would get with just two.
Good luck,
Bud

[GeorgiaSnake]

Thanks guys ! I have been trying to get my idle mixture set for several weeks. I think I have it nearly perfect now. I will double check it with a vacum gauge next.

Now more at idle

Randy

[ERA649]

Guys,
Thanks for the help, I will try all suggestions.
About the doulbe pumper suggestion-- I was told by a number of engine builders that a cobra is a lite car and the secondaries come in to hard with the DP and make the rear kick out-- what do you think of this theory?

[CJ428CJ]

I always thought light cars with high power to weight ratios were ideal for double pumpers. If you have a low power to weight ratio go with a single pumper with vacuum secondaries.

[Mr.Fixit]

Originally posted by CJ428CJ


I always thought light cars with high power to weight ratios were ideal for double pumpers. If you have a low power to weight ratio go with a single pumper with vacuum secondaries.

Mostly true.
You can sucessfully run a vac secondary Holley on a light car with good gearing, just put a really light spring in the secondary diaphram and sometimes, open up the orafice that has the check ball (in the diaphram housing) a little bit. You can get those secondaries to open almost immediately,

[scottj]

Originally posted by ERA649


-- I was told by a number of engine builders that a cobra is a lite car and the secondaries come in to hard with the DP and make the rear kick out-- what do you think of this theory?

High power to weight cars are ideal for mechanical carbs up until the point that you have so much torque that you can't pick up the throttle with out blowing the tires off the car.

The vacuum carb theory is commonly used in dirt Late Model racing (2300#/800+HP). Max torque and throttle response is needed when there's traction. But, as the track dries out the amount that the secondaries can open is restricted and delayed or the carb is switched to a vac secondary model. The vac carb works very well in keeping the tires hooked up off the corners, without limiting HP on the straights.

If your car "suffers" from way too much torque and throttle response for the available traction, it will make it easier to drive off corners IMHO.

Scott

[Rick Bagley]

Alot of good information here, I have a 3310 Holley 750 CFM on a 427 solid lifter engine, around 500HP. The only thing I would add is be sure the valves are adjusted and as stated the timing set before doing any carb. adjustments. My car performs great with the light spring (yellow), and primary jet size 74. I did put a Proform Body on the 3310, (good 95.00 investment). I have not changed the stock secondary metering plate. Idles great and the secondaries open up at the right time. Other adjustment are the same as posted. I did have to use a 31 squirter, came with a 28.

[Chaplin]

649-
How'd it go? I have the same carb and will be doing a little bit of tuning this weekend to try and get it dialed in a little better.

Mike

[ERA649]

Mike,

I hate to admit it, but haven't had time to work on it. Everything is taking a little longer then I thought. Maybe you should take a drive over here saturday and we can work on both of them.

Mike W

[Chaplin]

Mike-
Now that you have the car on the road, I was wondering where you wound up with jetting, etc. I'm still screwing around with mine and it would be interesting to compare notes.

Mike

[ERA649]

Mike,
I want to put about 1000 miles on the engine before I get real involved in tuning- my feeling is tha things will change after engine break in. waiting will also give me chance to get the feel of the car.

[ERA649]

I decided to dump the 3110 on Ebay, and install a Mighty Demon 750. I'll let you know how that works out.