Six pack tuning help needed, please

[roadrunner69440]

ok sorry if i sound like a tard,but is there any way I can save a post, this post as I am really considering a six pack setup and this thread really touches a lot of bases , btw Lew sounds like he knows his six pack from a 12 pack!

 

[69 GTX]

Sorry to hijack my own thread. Lew has been of great service and all his advice has been spot on. I also just purchased a new 6 pack and am looking forward to getting on and running. In our case the timing was a huge culprit. I also believe the milder the cam the easier it will be to tune. We have yet to drive the 70 RR because of wet weather here. As soon as we do I'll reprt back. I don't expect any surprises. I believe it's now to the point of small amounts of tuning.

 

[lewtot184]

carbs look good! i've messed with these things since 1970. i've ran them on 383's and 440's. i've tried the stock vacuum carbs, mech carbs, and corvette carbs. learned mostly the hard way because there isn't any good tuning info out there. a lot of bad internet advice. you don't need to throw a bunch of money at gadgets and carb services. always keep in mind that a 6-pak isn't a race set-up, but the near perfect street/strip intake combo. unfortunately i'm not running a set now but hope to get back into it in the future. i do miss the 6-pak!

i think the exhaust has a lot to do with picking cams. i don't like tight LSA's on cast manifolds; in fact i'm getting to the point i can't stand lumpy cams on drivers. heads play a big part on cam selection along with the exhaust.

 

[Meep-Meep]

Meep & Lew maybe you can help me a little here. Trying to help a friend with his 440+6. First a little history. 440 .060, 10.7 cr, auto trans. comp cam 540 lift 236 @ .050 dur. 110 lsa 10 inches of vaccum @ 800 RPM. Center carb has .118 holes in blades. 12 degrees timing base mech advance distributor. 2 problems we were trying to correct, rich idle & a near stall stumble when lifting off throttle at stop lights. I went through and set the outboard carbs so butterflys were closed. Long story short to get the idle close I had 1.75 turns on the idle screws on the center carb and outboards closed. I'm thinking that the outboards need some holes in the blades so I can use the idle screws on the outboards. We started with one turn out on the out boards but ended up having to screw them in to get the idle closer. I did use the blocking the bleeds on the out boards to determine this. I think we are going to pull them off so I can go through and verify where everything is. Also I'm thinking a power valve of 5 -5.5? I'm helping him so I can learn and then tune mine when it's done. Thanks in advance!

This is interesting. You have throttle blade holes on the center carb but none on the outboards? I'm pretty sure my center carbs don't have holes but I know the outboards do. I have a very rich condition as well and I'm running a pretty mild cam. Is this an auto or 4 spd car? If auto check vacuum in gear for power valve selection. You may end up with a 4.5 or smaller. I still haven't solved my over rich condition but I haven't tried really hard either.

 

[69 GTX]

We ended up with .070's in the outers .118 center 4.5 PV and 16 degrees of initial timing.

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Timing was the key for us!

 

[69 GTX]

We are waiting for dry weather for a road test. I actually think we may close some of the outer holes as we the idle right we couldn't get it to idle less than 850 but we want a road test first.

 

[66Satellite47]

Very interesting thread. When I ran 6 Pak in mid '70's, so few ran well. With mine near stock was best. Up a couple sizes in center carb jets, open end carb idle screws ( BIG help in transition), lightest springs with adjustable needle valve for end carb vacuum. I had mech advance distrib.

 

[lewtot184]

We are waiting for dry weather for a road test. I actually think we may close some of the outer holes as we the idle right we couldn't get it to idle less than 850 but we want a road test first.

the linkage that ties the carbs together may be tight.

 

[69 GTX]

We had the linkage unhooked.

 

[lewtot184]

We had the linkage unhooked.

somethings wrong. is the distributor retarding at idle? the edelbrock intakes are notorious for poor fitment.

 

[mac]

Very interesting thread. When I ran 6 Pak in mid '70's, so few ran well. With mine near stock was best. Up a couple sizes in center carb jets, open end carb idle screws ( BIG help in transition), lightest springs with adjustable needle valve for end carb vacuum. I had mech advance distrib.

what are you using for this adjustable needle valve for the vacuum?

 

[69 GTX]

Lew, Distributor is retarding fine. My guess is we have to much air flowing through the holes in the throttle blades. But that is my guess. Does that make sense to you.
On the test drive last night after we put the air cleaner on the idle increases about 200 rpm. We looked for a easy anwser but didn't see anything. Is this common? We decided to go ahead and drive it as is and it drove flawless. We just need to figure out how to bring the idle back down. It idles 800 with air cleaner off 1000 with it on. Any ideas?

 

[66Satellite47]

what are you using for this adjustable needle valve for the vacuum?

Yes, helps adjust the opening point & rate in addition to the springs. A little more adjustment capability.

 

[lewtot184]

Lew, Distributor is retarding fine. My guess is we have to much air flowing through the holes in the throttle blades. But that is my guess. Does that make sense to you.
On the test drive last night after we put the air cleaner on the idle increases about 200 rpm. We looked for a easy anwser but didn't see anything. Is this common? We decided to go ahead and drive it as is and it drove flawless. We just need to figure out how to bring the idle back down. It idles 800 with air cleaner off 1000 with it on. Any ideas?

have you taken the throttle blades off the shafts or loosened them at any time? i never messed with the holes in the the throttle blades before, never seen a need to. putting the air filter on and gaining rpm may mean restricting the air is richening the a/f ratio,...? hard to believe that a large filter would effect idle a/f ratio though,...? i think you have the throttle blade(s) cracked open on the end carbs. i always use some 600 grit paper around the edges of those alum blades to de-burr them on the newer carbs.

 

[69 GTX]

Rear plate is promax base, front stock, never taken off. We double checked them to make sure they weren't open or opening when filter was instaled. We ran of time. But I do know the advance is working because we are 16 at idle & 34 all in which is 18 which jives with the black bushing. We will do some more checking and let you know what we find. It is a K&N filter also. I never saw this one coming. It will be interesting to see what it is.

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In my mind the RPM raising is a lean condition, am I backwards on this? We had it set so when we covered the bleeds on the outers the RPM pulled down just a touch like you recomended.

 

[lewtot184]

if i remember correctly the promax throttle plate requires taking the throttle blades and shaft out and installing them in the new plate,....am i right? this is were i'd look. take the throttle plates off both carbs and hold them up in the light to see if the blades are seating against the body. if the blades are cracked open it screws the idle. this is why i hate all that aftermarket 6-pak junk! you can't re-engineer these carbs. the only problem they have is a lean idle and lean main metering on the center carb. i don't think you'll get by with less than 3/4 turn out on the mixture screws in the end carbs. that cam, in my opinion, is too much for cast iron exhaust manifolds; too much overlap.

 

[Meep-Meep]

Every time you remove the carbs you must readjust that safety linkage. Also never run without it!! It's the only thing that keeps the outboards from sticking wide open. Ask me how I know.....

Basic idle mixture adjustment on those should be a small amount of screw opening at the outboards to deal with the holes in the throttle blades then the main idle mixture should be done on the center carb since the blades are open about a turn to sustain idling. You can drive yourself nuts adjusting all six screws.

The mind set I have is the engine should idle and drive just fine if the outboard carbs were not present at all. Clearly the RPM potential would be severely limited on the 2 BBL, but for idle and around town shouldn't be an issue. If this is indeed true this suggests the outboard carb blades don't need the holes at all. Naturally plenty of 6 BBL's run well in their original configuration so our problems might be caused by something else. My cam isn't stock and my intake heat is restricted, and restricting the intake heat will have a drastic effect on mixture. These carbs were originally designed to run on different fuel and a hot intake so that has to be taken into account.

 

[mac]

Very interesting thread. When I ran 6 Pak in mid '70's, so few ran well. With mine near stock was best. Up a couple sizes in center carb jets, open end carb idle screws ( BIG help in transition), lightest springs with adjustable needle valve for end carb vacuum. I had mech advance distrib.

was kind of hoping you would show what you are using for the adjustable needle valve and your source to get one.

 

[66Satellite47]

was kind of hoping you would show what you are using for the adjustable needle valve and your source to get one.

Here's a pic. Unfortunately this setup was put together almost 40 years ago. Don't know where the valve came from. Sorry

 

[69 GTX]

Meep we took the vac lines off the outers while tuning and held them shut, to prevent disaster.

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Also like I've said in the opening post these carbs have been worked on by 4-5 people so trying to figure them out has been a task. Trying to figure out what is really needed and what was a bandaid for something not being correct.