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#2454475 - 02/20/18 09:07 AM 340 Six Pack vacuum advance
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
I'm working on some issues with carbs and timing and was wondering these things:

1. What is a good baseline for hg measurement for the distributor vacuum advance hose out of the center carb?
2. Is there any adjustment on the vacuum canister for a stock dual point distributor?

When hose is plugged into the distributor car will not idle correctly because it's advancing. If I unplug hose, engine will die. Seems to run better when hose is off and plugged.

Distributor has been gone thru and setup by Jeff at Advanced Distributors so I'm pretty confident it's in order.

I'd really like to use vacuum advance as it's intended but it's not a deal breaker and I was thinking I could just make it non operational but it makes me wonder if something else is going on that's causing the high vacuum.

Thanks for the help.............

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#2454602 - 02/20/18 12:45 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30798
Loc: Bend,OR USA
It sounds like you have the vacuum advance hook into manifold vacuum port instead of above the throttle plates for ported vacuum like they came stock scope
Which carb numbers are you using, OEM Holley or after market carbs like the BG six shooters or ?
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2454646 - 02/20/18 01:55 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 33622
Loc: Lincoln Nebraska
we need all related specs; initial timing. in hg vacuum. ported or manifold. how much timing when you plug the hose in. Rotor phasing OK?
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live every 24 hour block of time like it's your last day on earth

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#2454722 - 02/20/18 04:07 PM Re: 340 Six Pack vacuum advance [Re: Cab_Burge]
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
Originally Posted By Cab_Burge
It sounds like you have the vacuum advance hook into manifold vacuum port instead of above the throttle plates for ported vacuum like they came stock scope
Which carb numbers are you using, OEM Holley or after market carbs like the BG six shooters or ?


OEM original Holley carbs restored by Scott. It's plugged into the ported one on center carb.

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#2454726 - 02/20/18 04:24 PM Re: 340 Six Pack vacuum advance [Re: RapidRobert]
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
Originally Posted By RapidRobert
we need all related specs; initial timing. in hg vacuum. ported or manifold. how much timing when you plug the hose in. Rotor phasing OK?


I need to start out by saying that this is a fresh restoration and I'm working out a few kinks. Engine maybe has 15 hours on it.

Stock build 340 TA with original carbs.
Initial @18
ported
with hose plugged in it's at 18* when it settles down to an idle.

After reading more about it and talking to Jeff this morning, it may not be the vacuum just a carb adjustment issue. I've followed every guide I've found related to these carbs in particular the one that Tom Quad put out but I'm getting nowhere.

I've got all the gauges needed to perform a top quality tune and the only thing missing is the experience. Lol.

From what I've read about transient (run) and idle circuits it seems it's having a tough time moving from run to idle. When I gas and release it, it will set at around 1400 to 1500 RPM's and crawl back down and may or may not idle. Takes about 10 seconds or so. Scott restored them and outboard fuel air screws are setting where they were when they left his shop.

I have no hair left after this weekend. Argh

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#2454747 - 02/20/18 05:59 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 33622
Loc: Lincoln Nebraska
it almost sounds like the throttle shaft/butterflies are hanging up in the bores. I'm assuming the dist weights ain't sticking. yes this hobby has made more men go bald than any other (but we wouldn't trade it for nuthin).
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live every 24 hour block of time like it's your last day on earth

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#2454853 - 02/20/18 08:44 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Cab_Burge Offline
I Win

Registered: 08/23/03
Posts: 30798
Loc: Bend,OR USA
Originally Posted By Aar1064
Originally Posted By Cab_Burge
It sounds like you have the vacuum advance hook into manifold vacuum port instead of above the throttle plates for ported vacuum like they came stock scope
Which carb numbers are you using, OEM Holley or after market carbs like the BG six shooters or ?


OEM original Holley carbs restored by Scott. It's plugged into the ported one on center carb.

If my memory is serving me correct, it's been over 30 yrs since I worked on a stock set of OEM Holley 340 six pack carbs blush, the vacuum advance hose should be on the nipple on the passenger side of metering block, not on any other one scope
I've work on a bunch of 440 six packs since then but not in the last 5 yrs whiney whistling grin
Six packs rock when set up correctly, no matter what the doubters say runaway grin
_________________________
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2454883 - 02/20/18 10:07 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Mopar Guy Offline
enthusiast

Registered: 10/07/06
Posts: 389
Loc: Sweden
You probably have to adjust idel mix on the outboard carbs to becaus there is no way Scott can pre adjust those Spot on for your engine ! There is an realy great artikel by Jerry Binder that is realy good that i can email you if you like !?

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#2454890 - 02/20/18 10:10 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Mopar Guy Offline
enthusiast

Registered: 10/07/06
Posts: 389
Loc: Sweden
You also might whant to look for air leaks on intake and carbs befor adjusting to mutch.

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#2455064 - 02/21/18 10:42 AM Re: 340 Six Pack vacuum advance [Re: RapidRobert]
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
Checked butterflies last night and they are closing all the way. Weights shouldn't be sticking because of fresh rebuild by Jeff @ Advanced Distributors. With vacuum unplugged from distributor, engine idles down correctly.

I also checked for vacuum leaks and didn't find any.


Edited by Aar1064 (02/21/18 10:51 AM)

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#2455069 - 02/21/18 10:51 AM Re: 340 Six Pack vacuum advance [Re: Mopar Guy]
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
I may have read it but please send it anyway.

Yes I realize that and Scott has been great and continues to be helpful as I'm dealing with this. There's no doubt that they were running great when they left his shop with only minor changes needed on my end.

They were running good on my car and on run stand (with electronic distributor) until I started dealing with ignition issues. I'm just not giving up on yet on points.

I started messing with carb things before realizing that I was having ignition issues hence the reason for sending it in and getting it setup.

Thanks for the help

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#2455090 - 02/21/18 11:37 AM Re: 340 Six Pack vacuum advance [Re: Aar1064]
RapidRobert Offline
Circle Track

Registered: 11/20/03
Posts: 33622
Loc: Lincoln Nebraska
Quote:
With vacuum unplugged from distributor, engine idles down correctly. I also checked for vacuum leaks and didn't find any.
that tells me that it is dist related, either a vac leak as of yet undiscovered or weights hanging up. I'm assuming you've vacuum pumped the can/hose & I would go inside the dist & go over it.
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live every 24 hour block of time like it's your last day on earth

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#2455116 - 02/21/18 12:28 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Sixpak Offline
master

Registered: 01/20/03
Posts: 6215
Loc: The Swamp
Make sure the fast idle cam adjustment on the center carb is correct. On a sixpak carb it's not a screw adjustment - you have to physically bend a sheet metal tab that contacts the cam in order to move it. There's a little slot in the part to insert a small screwdriver to bend the link. I had a similar issue where I could not get a 340 sixpak to behave at idle. Found that the fast idle cam was getting hung up on the linkage meant to engage it. Some careful adjustments by bending the link fixed it. Make sure the choke is working and the choke pull off is working too. Your car MUST idle off of all 3 carbs, and not just the center carb. That means adjusting the idle on all 3 carbs in order to get it to idle properly.
If your idle rpm is much above 1000 rpm you may start pulling vacuum thru the port to the distributor. Insure the fast idle cam isn't hanging up, then end carbs are closed at idle (adjust linkage properly) then adjust the idle mixture screws, starting at 1 5/8 turns out on all 3 carbs for a starting point. Do all adjustments with vacuum hose to distributor disconnected.
I found on that same setup the best idle quality I got was having all three carbs have the idle mixture screws turned out 1 5/8 turns. Use that as a start and adjust each mixture screw on the center, and end carbs by covering the air bleed nearest to that mixture screw and checking the idle quality. Covering the bleed should have no effect on idle rpm. If the rpm falls it's too fat, turn in 1/8 turn and try again. Speeds up means it's too lean, turn out 1/8 turn and try again. You may have to take the back carb off to get at the mixture screws. I like to adjust the front carb so it's working well and then swap the front carb to the back. Once you get it to idle cleanly around 950 - 1000 rpm, hook the hose up, then adjust the center carb idle screw; the one on the long arm that usually contacts the idle solenoid, to lower the idle if it picks up.

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#2455711 - 02/22/18 02:12 PM Re: 340 Six Pack vacuum advance [Re: Sixpak]
Mopar Mitch Offline
super stock

Registered: 01/17/10
Posts: 1037
Loc: NW Chicago suburban area
I recommend the PROMAX outboard base plates... allows easy adjustment! Its the way it should've been designed in the first place (at least for the rear where you can't get to it with the carbs installed).
_________________________
Mopar Mitch "Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers! Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!

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#2455724 - 02/22/18 02:51 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Mopar Guy Offline
enthusiast

Registered: 10/07/06
Posts: 389
Loc: Sweden
I would NOT recomend Pro Max !

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#2460004 - 03/02/18 02:36 PM Re: 340 Six Pack vacuum advance [Re: Mopar Guy]
Mopar Mitch Offline
super stock

Registered: 01/17/10
Posts: 1037
Loc: NW Chicago suburban area
My PROMAX setup offers easy fine tuning; the factory setup does not. My carbs run perfectly. I've never heard any negatives about PROMAX products.
_________________________
Mopar Mitch "Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers! Check out MOPAR ACTION MAGAZINE, August 2006 issue for feature article and specs on my autocross T/A!

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#2460060 - 03/02/18 04:41 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Tommy D Offline
enthusiast

Registered: 10/02/08
Posts: 389
Loc: Harleysville, PA USA
I second the Promax metering blocks. Work great for me.

When checking that the butterflies are closing all the way, have a friend rev the engine while you're working on the engine. Assuming the rpm's will stay high with this method...when allowing the engine to return to idle, but while still idling higher than wanted, press the two outboard throttle shaft attachment points for the secondaries. If it goes back to normal rpm, that is your problem. This stumped me for a long time. I had to grind a sharp edge onto both outboard carbs butterflies in order to fix. All good now.

Another thing to check...don't over tighten the carbs to the manifold. They only need hand tightening with a ratchet extension. You do not need the ratchet. Too tight and the aluminum bodies will warp. That's likely what happened to mine. Once warped, they'll need the fix in my top paragraph. Good luck.

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#2460108 - 03/02/18 05:28 PM Re: 340 Six Pack vacuum advance [Re: Tommy D]
BradH Offline
I Live Here

Registered: 01/30/03
Posts: 13723
Loc: Valhalla... eventually
Originally Posted By Mopar Guy
I would NOT recomend Pro Max !


Originally Posted By Mopar Mitch
... I've never heard any negatives about PROMAX products.


I'll be curious to see if this expands beyond the above two comments. work
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#2461502 - 03/05/18 12:12 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
Aar1064 Offline
enthusiast

Registered: 05/14/13
Posts: 225
Loc: Ashland City, Tennessee
Sorry it's been so long reporting back but I've been busy trying to resolve this. I think I have a serious vacuum leak. A friend has a smoke machine and I'd like to hook it up to see what the results are. In order to do this, I'll need to block off all the ports. I can think of a few and want to make sure I'm not missing anything.

1. Ported vacuum on middle carb
2. Intake port
3. PVC port on middle carb

What else is there?

Some will say spray carb cleaner but I'm too afraid to do that. Others will say use propane but since fan is on engine, I'm not sure how reliable that is.

BTW-Over the weekend I replaced the intake gaskets and this didn't help or it did and I have another leak.

Thanks for the help

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#2465528 - 03/12/18 09:16 PM Re: 340 Six Pack vacuum advance [Re: Aar1064]
ademon Offline
master

Registered: 09/06/04
Posts: 6880
Loc: IL, Aurora
That's a high initial at 18* for a stock build, sure your throttle blades have enough of the transfer slot exposed???

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