Holley 3310 tuning help on a fresh 440

[moparedtn]

I'll try to make this as brief as possible...

Engine: '75 440 block, 906 heads, forged internals, darn close to stock specs.
Car: 1968 GTX 4 speed with 3.55s.
Cam: 509 purpleshaft.
Ignition: Mopar electronic ignition coversion kit, orange box.
Carb: brand new Holley 3310 vac. sec.
Fuel tank, fuel pump, lines, etc. are all new.
Exhaust is big-assed Hedmans and 3" all the way back with Flowmasters (yeah, I know, but that's what was on it when I got it).

I have "inherited" this car from the mentioned deceased former owner, so there's a lot of mysteries being figured out as I go, but she's a really pretty, very solid car now and worth the effort I think.

Motor was built by a (now deceased) lifetime Mopar dealer mechanic; no further info is therefore available as a result. Motor looks for all intents to be stock configuration, nothing tricky.
The car has been built back from pretty much scratch; was a former field find on which all rot was replaced with clean metal.
I have had it running several times and it starts and idles once warmed up on its' own.
I have about 8hg vacuum @ idle and the thing LOVES lots of initial timing, currently at 12BTC.

Today was the first time in decades the car has actually seen the road. Very momentus occasion, to say the least; very nerve-racking taking it out....

Problems: There is an off-idle stumble that clears with more throttle.
In addition, the carb surges when you just try to maintain a set speed that also eases with a quick little dab of additional throttle. Happens in any gear, any speed.

In other words, it's time to set the carb up for this combination to get good driveability and smoothness. This is my first Mopar project in decades as well and I'm no Holley expert, so I'd appreciate a sort of "Holley for Dummies" bit of help here.
In fact, I'm betting there's been a few billion folks that came before me running the 509 in a 440 and using the Holley 3310, eh?

Thanks in advance!

 

[Deleted member 214]

The bog could be due to too soft a spring in the vacuum secondary allowing it to open too soon. Get a spring kit and try some stronger springs. You can get a new quick change vacuum pod cover that allows you to change springs really quick if you want.

 

[WileE]

What size power valve are you running ?

 

[lewtot184]

that cam would like more initial timing and a faster curve. probably in the 16-18 range for intial; which means the curve inside the distributor needs work. the off idle stumble may be a lean condition due to poor idle or main metering calibration, float level issues, sometimes pump or filter location. one thing not to do is go to a larger squirter. when your trying to cure an off idle lean condition on a driver go to a more aggressive pump cam first.

 

[moparedtn]

What size power valve are you running ?

The one that came in the carb new - Holley says it's a 65.
I have a 35 sitting in my tool box I can try if you think that would help.

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that cam would like more initial timing and a faster curve. probably in the 16-18 range for intial; which means the curve inside the distributor needs work. the off idle stumble may be a lean condition due to poor idle or main metering calibration, float level issues, sometimes pump or filter location. one thing not to do is go to a larger squirter. when your trying to cure an off idle lean condition on a driver go to a more aggressive pump cam first.

You may be on to something with the pump cam. The engine also "stumbles" while idling when I try to goose it the first time; if I continue to goose it several times, it eventually takes the gas properly.

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Thanks for the advice so far, y'all. I was thinking (ok, hoping) for some reason that someone with an identical cam/carb setup that has gone before me could just say "these jets, that pump cam, this power valve" etc. and get me in the ball park?

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The bog could be due to too soft a spring in the vacuum secondary allowing it to open too soon. Get a spring kit and try some stronger springs. You can get a new quick change vacuum pod cover that allows you to change springs really quick if you want.

Wow, do you think the thing is trying to open the secondaries right off idle like that? Never occurred to me...

 

[Garys1969RR]

I had the same prob with my 451, 509 cam, 3310 Holley 780. We initially found that the automatic choke had been removed, so the choke pull off vacumn port had become a vacumn leak. After plugging that, and also changing the pump cam, that eliminated the off idle stumble, or flat spot. Seems to be a result of a lean condition right between the idle circuit, and the main metering circuit in the carb.

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After fixing that carb, I put it on another car, and went to a used 850 double pumper. Well this one does the same thing! I increased the jet size in the primary which helped. I race 1/4 mile, and really have to bring the engine RPM up against the torque converter when staging. Then when I nail it on green, it takes right off! But there is definitely a lean spot in there when cruising at 1/8 to 1/4 throttle. The engine sputters and misses. Add in some throttle and it smooths out.

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That 509 cam seems to like alot of initial spark advance. I run 20 degrees at idle, 38 total. More timing seems to lessen the flat spot effect.

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Oh yea, this 850 has worked best so far. 12.42@110 MPH, 69 RR at 5400 feet elevation.

 

[moparedtn]

Thanks for that! Ok, sounds like we're getting a consensus on the pump cam. Which one should I try?

 

[coloradodave]

Bump timing first. Use as much initial as you can where the motor will still crank when hot but not 'ping' under acceleration. If the hesitation is off idle, like you said, make sure the accelerator pump lever is contacting the pump arm and that ANY throttle movement moves the pump. Also, check both floats to insure that the level (bottom of sight plug holes) is correct. Good luck.

 

[moparedtn]

Bump timing first. Use as much initial as you can where the motor will still crank when hot but not 'ping' under acceleration. If the hesitation is off idle, like you said, make sure the accelerator pump lever is contacting the pump arm and that ANY throttle movement moves the pump. Also, check both floats to insure that the level (bottom of sight plug holes) is correct. Good luck.

Lord, man, the timing is about off the scale now. :icon_eyes:
I would imagine that puts it around 15BTC?
New 900amp battery and a Dakota high-torque starter makes it pretty easy to crank over, too, maybe too easy but yes, I remember 25 years ago to my last 440 what knock sounds like on these and I haven't heard any yet, thankfully.
Sounds like a mariachi band under the hood, as I recall.
"Stock" timing is supposed to be like 5TBC, right?

Pretty sure this issue is all carb-related, unless the new Mopar electronic ignition/distributor has an issue and isn't advancing or some wild thing or another.

On the carb floats, this one obviously has those plastic ones in it. Does the seam on the plastic roughly relate to where the fuel level will be? I aimed those seams right to the bottom of the sight holes when I pulled the bowls off to look.
As much as this engine rocks and rolls at idle, trying to set fuel levels by pulling the sight plugs wouldn't be real exact if you catch my drift.
Got ya on the accelerator pump. I haven't messed with it from out of the box, but I'll verify there's instant action upon any throttle movement. It might even be at this point that I've got the idle screw up far enough that the thing is already engaging the accelerator @ idle; I'll check that too, now that I think about it.
Thanks!

 

[IQ52]

Man I could see this coming from the beginning of your posting. The initial timing (12 degrees) is insufficient for a 509 camshaft, believe it or not, it is. Set the initial for at least 18 degrees for that cam and maybe 20. Have a total of 36-38 degrees all in by 2500-3000 rpm. The carburetor may or may not be screwed up, but the timing is for sure.

lewtot184, Garys1969RR (who is running the 509 cam) and coloradodave are all correct. You wanted the advice of guys who are running the 509 camshaft, Gary is and I am. Cam timing is more important than the carburetor when choosing initial ignition timing.

Have you done a compression test? This will help to pin down the timing even more.

 

[coloradodave]

I'm afraid the seam on the Holley float won't help. If you have a problem setting the level when the motor is running, take off the bowls, invert them, and, setting a 1/4" drill bit on the (then) bottom of the inside of the bowl, adjust the float until the top of the float just touches the drill bit. You'll be close enough...I agree with IQ52; as I said, advance initial until it won't crank or it pings.

 

[moparedtn]

Man I could see this coming from the beginning of your posting. The initial timing (12 degrees) is insufficient for a 509 camshaft, believe it or not, it is. Set the initial for at least 18 degrees for that cam and maybe 20. Have a total of 36-38 degrees all in by 2500-3000 rpm. The carburetor may or may not be screwed up, but the timing is for sure.

lewtot184, Garys1969RR (who is running the 509 cam) and coloradodave are all correct. You wanted the advice of guys who are running the 509 camshaft, Gary is and I am. Cam timing is more important than the carburetor when choosing initial ignition timing.

Have you done a compression test? This will help to pin down the timing even more.

You're right and I defer to you alls' expertise in this, but man that seems like a lot of timing. Kinda freaky.
All righty then, up the initial timing goes!
Keep in mind I have the stock harmonic balancer on it, so I got one timing mark on it and the stock indicator on the timing cover which I think gives me around 18BTC +/- at the edge of it, so I'll run the timing up that far anyways.

Once I keep cranking up initial (advance line blocked to the carb) and keep going until I reach max vacuum @ idle - and the thing will still crank/start when warm afterwards - I assume I have some total advance issues to work out then, right?
Does the distributor supplied with the Mopar electronic conversion kit have provision to deal with that?

Oh, to answer your other question, no I haven't done any compression testing. With this being a supposedly fresh build and it REALLY throwing exhaust pulses out the rear (sucker THUMPS out the rear!) and no signs of oil pressure issues or smoking at all, I hadn't really gone there yet...

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I'm afraid the seam on the Holley float won't help. If you have a problem setting the level when the motor is running, take off the bowls, invert them, and, setting a 1/4" drill bit on the (then) bottom of the inside of the bowl, adjust the float until the top of the float just touches the drill bit. You'll be close enough...I agree with IQ52; as I said, advance initial until it won't crank or it pings.

Ok thanks for that tip - if memory serves, the floats aren't that close to the top right now, so I'll make that change pronto.

 

[coloradodave]

All you really have to do now is to advance the distributor an 1/8" at a time until it won't crank or the flat spot goes away. Buy and install a timing tape so that you can see what the total advance ends up being. You want to shoot for 34-36* total with the vacuum disconnected. With a stock distributor, you'll probably have to have the advance slots welded to reduce the amount of mechanical advance. For instance, say you end up with 18* initial advance where it runs great and starts good. You would then need to limit the mechanical advance in the distributor to 16-18*. Again, you want all the advance the motor can tolerate, usually all in by +-3,000 RPM in a street motor.
Dealing with the vacuum advance can wait until you get the flat spot taken care of. And, yes, the "new" gas has changed the tuning parameters immensely.

 

[Cornpatch MO]

Speaking of Holley acc. pump cams, I have different colored ones that can be installed each in two different ways. Is there any information that would tell me how each cam reacts? Thanks for a reply...............MO

 

[lewtot184]

I've acquired a bunch of distributors/parts over the years (the older style) and pretty much make my own stuff. currently i'm using a 9 degree advance plate, very light factory (purple) primary advance spring with a short thin wire secondary spring. I also run a vacuum advance; 100% street car. total timing is 35 degrees with 17 degrees intial. the light primary spring brings the centrifugal in early and the engine idles at 24 degrees at 950rpm. total centrifugal comes in around 2300rpm. this engine uses an engle k65 solid, [email protected] lift. starts and drives nicely. idle at 15" of vacuum in neutral, 10"-11" in gear.

 

[62 Dart Convertible]

Get a timing tape on the harmonic asap! Takes the guess work away!

 

[Gpuller]

Like others have said get the timing correct before jumping into the carb. My car had the same symptoms you have. Once I got the timing dialed in the hesitation went away.
I'm running a old MP .484 cam much like the .509. I found that my combo likes 20deg of initial timing. I just kept advancing until the idle picked up and vac got better. Then I used an advance timing light to find where it ended up. Motor still fires when warm. I have a Firecore dist and limited the total timing to 35deg. They have two screws to limit the amount of mechanical advance. Do not have the vac advance hooked up either, you probably will not need it.

 

[lewtot184]

Get a timing tape on the harmonic asap! Takes the guess work away!

amen! I can't operate without one.

 

[Garys1969RR]

Get a timing tape on the harmonic asap! Takes the guess work away!

The way I do it is: Lay the correct timing tape on the harmonic balancer, with the zero on the tape even with the groove on the balancer. (This is TDC). Then mark 20 degrees and 38 degrees with a steel point. This is to the right of the groove, if you're looking at the front of the balancer. Then I take 2 pieces of masking tape and cover it, leaving a narrow gap where the 20 and 38 degrees advance marks are. Tape off everything around the 2 small gaps, hit it with several light coats of white spray paint, and you have your marks permanantly on there! Plus you can still use the timing tape again.

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The white paint lines are easily visible with a timing light, and they are permanantly on there.

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When your mark lines up with the hole on the timing cover scale, then that is your timing advance. I have done this with several balancers, and it works great! You can see the mark creep up from the right as you rev the engine.

 

[SlinktRR]

Don't be afraid of spark advance with these low compression big blocks, especially with the purple cams. They eat it up. For reference I have a 71 383 with 8.5:1 static compression and a .484 purple. I get 10hg vac and run 40 total with vacuum advance on 93 octane, so you are in the ballpark. Go out for a drive with your tools and advance until it pings, then back off. Once you have it running well, if it doesn't ping going up a hill then you are good. Its nice having the distributor on the front of the block!

congrats on your new car and have fun getting it back on the road!