440-6 rich idle challenge

[ramblinn]

.030 over, stealth heads, SRP pistons approx .006 in the hole, stock manifolds (preserve stock appearance), Lunati 60303, stock rockers, 10:2CR, TTI 2.5 exhaust.

Engine is on test stand with 727 attached (in neutral).  Carbs are new 71 repros, 64jets, 6.5PV, promax manifold gaskets.  Engine break-in was normal, now trying to work the rich idle issue, between 13-13.2 on AF meter.  Engine starts and idles OK at 850rpm, 20deg initial timing, 15" vacuum, however, the idle screw is adjusted such that the center is in the transition circuit - to get sufficient rpm. Center mixture at approx 1.5 turns, outboards approx 1/8 turns.  Adjusted outboard idle screws until finger over idle air bleed ports produced no change in rpm/vac.   

Adjusted the center transition slot to "square", then attempted to time engine for max rpm/vac without touching idle screw.  Highest rpm I could achieve was about 600 with timing at 32 initial, but engine won't start with that much initial.  AF reading approx 13.5 tho erratic.

Returned center to transition circuit (so it would start and idle), turned outboard screws full in.  No significant effect on AF, approx 13.2, rough idle, hard start. 

Is enlarging the outboard throttle plate bleed holes my only remaining option to get out of the transition circuit and push up the AF ratio - so I'm not when its idling?







   

[b5blue]

Initial timing @ 32* ? I'll try to dig up a link for you on 6pak setting up and adjusting tonight.  (Or PM me address and I'll mail you a copy)

[ramblinn]

Thx...I've got several of the 6pack tuning guides and have used a lot of their procedures.  I just can't seem to find a way out of the transition circuit at idle

[Chryco Psycho]

opening the hole in the throttle valve will allow it to close more , if you need to close it back up you can spot weld it , epoxy or just squish some solder into the hole .  You can also open the brass restriction inside the throat of the carb under the choke plate , it will bleed off vacuum at the top so there is less fuel pulled in at the bottom which will lean it out but still may not add enough airflow to keep the idle speed up . If you are going to open up the bleed size you will need numbered drill bits so you only go 3-4 thou larger at a time , it is brass so you may be able to put a small drop of solder back into the hole if you go to big , i would have the carb on its side if you try to solder it though

[b5blue]

My outboards are 1 full turn out on all 4 idle adjustment screws. 

[Chryco Psycho]

I typically set the outbaord idle screws at approx 1/2 turn out

[ramblinn]

opening the hole in the throttle valve will allow it to close more , if you need to close it back up you can spot weld it , epoxy or just squish some solder into the hole .  You can also open the brass restriction inside the throat of the carb under the choke plate , it will bleed off vacuum at the top so there is less fuel pulled in at the bottom which will lean it out but still may not add enough airflow to keep the idle speed up . If you are going to open up the bleed size you will need numbered drill bits so you only go 3-4 thou larger at a time , it is brass so you may be able to put a small drop of solder back into the hole if you go to big , i would have the carb on its side if you try to solder it though

when I work up enough courage to drill the bleeds...

is it possible to estimate the needed enlargement to gain enough airflow to get back to "square" on the transition slot?

should I see improvement in the AF/increase in idle with each 3-4 thou enlargement?

My outboards are 1 full turn out on all 4 idle adjustment screws.

wow - from everything I've read, most suggest the 1/8-1/2 turn out range, at least to start with

[Chryco Psycho]

Yes , a very small enlargement of the bleed will be noticable , if you get a numbered drill set see what fits now & just go up one step at a time , 3-4 thou makes a decent difference , just hard to go backwards , this is why I like the HP Holley & Proform carbs , the bleeds thread in & are easily changed out .

[b5blue]

I replaced my outboard's idle needles and seals, with the carbs off I could tell 1/8 - 1/2 turn is like "nothing" really. In Larry Shepard's "Six-Pack Engine" book I found the reference of 1 full turn from all in, it worked for me. (Using the "block off the outer holes in the top of the carb." trick to check.) I generally when by the large post in this link. (Down a ways in the topic.) I'm close, I still have a "sudden stop-drop in idle" and some choke adjusting to do but it is otherwise running great. All these settings vary with your build though. I'm .060 over with fairly stock rebuild, 346 heads, H.P. exh. manifolds and a resto R.R. Mopar cam. I'm just thinking if you put more idle fuel to the outboards and lean the center it would move you off the transition point. 
 
http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Board=QuestionAnswer&Number=5995396&Searchpage=1&Main=5995174&Words=+Warrant_Officer&topic=&Search=true

[ramblinn]

Interesting idea...more fuel to the outboards and lean the center.  As I mentioned in the first post, I tried pretty much the opposite - leaned the outboards - but that didn't work too well. The Lunati 60303 isn't radical, but does chop a bit at idle, 226 actual duration.  I think it boils down to my setup simply needs more air at idle, so I can get off the transition circuit.  Figuring out the best way to do that is the challenge.  Plus its still on the test stand, so I can't really test in gear.   

[b5blue]

  Long ago my 440 had the 509 cam and heavily ported closed chamber heads, swapping the high rise TM-7 for the six pack (It had been a drag car.) you'd think it would have needed modification. No mods just adjusting and it ran fine for years with no other tinkering. (With a 3.23 rear gear I "owned" 60-120 MPH!) Until I wore out the heads and bent some pushrods about 7 years later I had only had to replace the center carb's bowl as it leaked a small amount @ the float height adjust on top. (Mine is a 69 1/2 setup so it's 42 years old.)
  I'm interested in your dizzy's setup and curve, with the new rebuild I had Don at FBO set up a dist. for my car. It really woke up on the bottom end when I started using vacuum advance. (Don's takes full vacuum off the port nipple in the rear of the intake.) It was clear my six pack needed that feature and it's a tricky one to get right. (Having vacuum advance "in" then drop out as mechanical comes into play with RPM's increasing under load.)
  Again I'm not trying to steer you in any direction, just sharing my specific experiences. 

[BSB67]

Interesting idea...more fuel to the outboards and lean the center.  As I mentioned in the first post, I tried pretty much the opposite - leaned the outboards - but that didn't work too well. The Lunati 60303 isn't radical, but does chop a bit at idle, 226 actual duration.  I think it boils down to my setup simply needs more air at idle, so I can get off the transition circuit.  Figuring out the best way to do that is the challenge.  Plus its still on the test stand, so I can't really test in gear.    

Some random thoughts:

1) Don't fix stuff that you're not sure is broke.  The A/F meter is a tool, not the answer.  Don't chase after a number.  Maybe put it in the car and drive it - tune it.
2)  I've run 6 pacs for 35years from stock 383 to roller cam 500 cu. in. engines.  Never touched an air bleed, IFR or drilled a throttle plate.  In fact, the changes were small from factory original
3) Never ended up with less that 3/4 turn out on outboards.
4) Every intake manifold leaked at the head, but I have not bought a new manifold in 15 years.

Also, the carbs that I have and had are/were from 20 + years ago, and I believe that the quality has deteriorated considerably since then.

[ramblinn]

Some random thoughts:

1) Don't fix stuff that you're not sure is broke.  The A/F meter is a tool, not the answer.  Don't chase after a number.  Maybe put it in the car and drive it - tune it.
2)  I've run 6 pacs for 35years from stock 383 to roller cam 500 cu. in. engines.  Never touched an air bleed, IFR or drilled a throttle plate.  In fact, the changes were small from factory original
3) Never ended up with less that 3/4 turn out on outboards.
4) Every intake manifold leaked at the head, but I have not bought a new manifold in 15 years.

Also, the carbs that I have and had are/were from 20 + years ago, and I believe that the quality has deteriorated considerably since then.

On the recommendation from a local mopar friend I called Damon at Diamondback Engines in TX.  Like many of you guys, he's been doing mopar for a long time.  He also races NSS.  He listened to my story and said similar things.  Said to put the AF meter aside or just use it to check cruise and WOT.   Said he'd never drilled a throttle plate.  His - do this before you do anything else recommendation - was set up my test stand to "pin" the yoke so I can check things in gear/under load.  I've been thinking about this anyway, so that was further incentive.  He believes the 6.5PV may be too high and fluttering open at idle.  He also said I should go to #67jets.   Haven't drilled anything yet.  The challenge continues...thx all for replies. 

[ramblinn]

I rigged up a yolk hold on my test stand.  Started it up (still using 65jets, 6.5pv, 19deg base timing) and let it warm up.  Shifted to drive: rpm decreased from 850 to 750, vac decreased from 15" to 13".  Still idled fine but of course rich.  I may try a 4.5pv.  Short of enlarging the outboard throttle bleed holes I can't figure out how to get more air to this engine to relieve the eye burning at idle