Need some Six Pack experience

[joes68340s]

I have a 340 Six pack and I cant feel anything or tell if all three carbs open It just feels flat no pull. I checked everything linkage carb opening full throttle just don't see anything It feels like a two barrel. The weired thing is I have a spare set of carbs and they do the same thing so Im thinking something is preventing there opening like springs maybe. The engine also falls flat at 4800-5000 rpm that's getting worse. But the carbs just aren't impressing me. I had a 440 Six pack and you could hear and feel them when cracked wide open.

 

[moparleo]

You need to check and/or adjust the throttle linkage. That controls the opening and timing of the rest of the carbs.

 

[joes68340s]

Ive gone by the service manual and checked for binding and adjustment. I can check again.

 

[DetMatt1]

Are there any other issues like hard to start or stalling? How's your ignition timing?

 

[Daves69]

Verify ignition first.
What are you using for your fuel pump? If mechanical, is it actually pumping at high rpm?
Are your outboards connected to the proper vacuum port? Have you checked the diaphragms on the outboards for leaks?

 

[joes68340s]

Timing, ign is good vac lines are good engine runs good idles perfect but I haven't checked fuel pressure just a cheap old airtek style pump.

 

[72ls5fla]

i would check how vacuum is being pulled at the port on the center carb.
disconnect the hose from the port and put a longer hose on it and use a VAC gauge.
if there is little or no vacuum, then you likely have a clogged up transfer hole.
it is in the PASS side throttle bore, just to the side of the venturi.

I have taken a can of carb cleaner (with the thin tube attached) and shot it in the vacuum port and looked to see how well it comes out in the carb.
u can also blow compressed air trough it, works well to dislodge foreign particles.
Also -
be sure the secondary vacuum diaphragms are good (like mentioned above).
be sure the small round cork gasket is in place (goes between the diaphragm housing and end carb). if these are missing or dry rotted, you can have a vacuum leak source, not allowing the end carbs to swing open.

bill

 

[joes68340s]

Is there anyway to pull vac engine off to see the sec carbs open.

 

[moparleo]

Is it possible to send us a close-up picture of the carbs and linkage ?

 

[rklein71]

Linkage has nothing to do with opening of the outboard carbs on a stock six pack, they just ensure they close together.

Outboard carbs open on vacuum created when air rushes through the venturi, so taking a vacuum measurement is useless (unless you hook up a gauge that you can see while driving and getting on it). Make sure each outboard diaphram is intact as stated above. If they are controlled by a very stiff spring, they might be opening up very late and you won't feel the transition. If one diaphragm is bad, neither will open, since a stock six-pack vacuum lines are tied together.

When my six-pack opened up, the engine really pulled hard, so it is obvious when the six-pack is working.

 

[moparleo]

Might not be a stock vacuum setup. We don't know what he has other than a six-pak setup. In 40 years someone could have made changes that is why I wanted to see what he has in a picture. My crystal ball doesn't work that good.
FYI we had another member with a similar problem and a prior owner had blocked the outboard carbs with a solid gasket under the carb bases. You never know.

 

[Chryco Psycho]

You can put a zip tie or twist tie on the rod where the vacuum pulls the linkage up & see if the tie is pushed down by it opening the rod or use a remote cam to video it

 

[joes68340s]

I would post but having trouble uploading. I think I will give that gopro a workout. great ideas Thanks.

 

[DetMatt1]

Some great info and suggestions being dished out here, nice!

 

[72ls5fla]

Linkage has nothing to do with opening of the outboard carbs on a stock six pack, they just ensure they close together.

Outboard carbs open on vacuum created when air rushes through the venturi, so taking a vacuum measurement is useless (unless you hook up a gauge that you can see while driving and getting on it). Make sure each outboard diaphram is intact as stated above. If they are controlled by a very stiff spring, they might be opening up very late and you won't feel the transition. If one diaphragm is bad, neither will open, since a stock six-pack vacuum lines are tied together.

When my six-pack opened up, the engine really pulled hard, so it is obvious when the six-pack is working.

The vacuum source that opens the secondaries can be tested while sitting in the garage.
the bleed hole is located above the throttle plates.
when you go WOT the VAC drops below the plates and increases in the throttle bore as the air rushes by.

so - if you hook up a vacuum gauge to the side port and manually go WOT you can see if the signal source is making vacuum.

if it doesn't, then the likely source is the side pods on the carbs.

Bill

 

[joes68340s]

Ok I went out and pulled the vac hose and checked for vac engine running. I have had the hose installed on the lower vac port and there is no vac signal not even ported vac. The upper port had straight vac when I attached the hose there was a vac squeal very light amost hard to hear. This location is opposite of my manuals have I missed something these are on new carbs.

 

[72ls5fla]

the hose for the choke pull-off should be attached at the baseplate by the corner bolt and the hose for the end carbs attached at the nipple on the metering block up top (will have a slight bend to it).

the upper port might have a very slight signal at idle, depending on idle speed and how you have the throttle plates and idle mixture screws adjusted.
but once you slam open the throttle, it should build up to where it pulls max VAC.

switch the hoses around and take the car for a ride - bet you will get that kick in the butt you are expecting.

 

[Daves69]

Ok I went out and pulled the vac hose and checked for vac engine running. I have had the hose installed on the lower vac port and there is no vac signal not even ported vac. The upper port had straight vac when I attached the hose there was a vac squeal very light amost hard to hear. This location is opposite of my manuals have I missed something these are on new carbs.

You had the hoses on correctly. The upper is distributor advance. Just below is the outboards diaphragm port. Hope you didn't compromise a diaphragm to get that squeal. Sounds like a leak though. I'd use a vacuum pump on each outboard separately.



Here are some tech items and also links to Binder's Installation and Tuning that may help. It includes how the outboards open..................

http://www.mopar1.us/6barreltips.html

 

[joes68340s]

Well I originally had the hose correct and couldn't get the outboards to open switching the hose to the upper curved port on the metering block and then the outboards work.

 

[72ls5fla]

hey --

what Daves69 is showing is correct. He is right about the upper port for VAC advance.
the port right below it (with short straight tube) is for the end carb signal source. I mis-spoke in my post.

so if you connect the vacuum line to it and don't get any feed, then there is likely a clog in the bleed hole.
I would spray carb cleaner in the port tube on the side and see if it will flow out in the throttle bore.
if not, then there is an issue.

The good news is that the secondaries are opening - so all the vacuum related parts on the end carbs are in working order.
If you leave things as is, with working secondaries you will not get any vacuum advance signal to the DIST. so you will be on mechanical advance only.