Six pack bog

[b5blue]

  While you have the rear outboard off to adjust idle look at the idle port/needle to see where 1/8 turn and then 1 full turn puts the tip of the needle. Getting to understand how much turn moves that tip in or out will help you gauge what your doing. As you vary idle you'll need to keep an eye on float height as it acts as a leak/bleed to the bowls.
  I quickly found out removing and installing fuel lines to be a royal pain in the butt. Concerned that steel to pot metal bowl connections were getting stressed I bought a brass hose barb T and made a test/tune rubber hose rig that let me leave the factory steel rig on the shelf till done. Then it was easy to just loosen hoses to pull carbs and mess around.

[fizz]

Moving out the secondary idle mixture screws to 3/4 turn and 1/2 turn up on the floats DID result in eliminating the ping at transition, But, made my idle poorer even when I adjusted the primary idle mixture screws, which didn't seem to do anything. BUT, I am installing the secondary jet plates anyway, as it would stand to reason, like Coonhunter said, that the secondary carbs should need jetting changes with the modified, larger engine, so will deal with that some more then. I am confused that primary jetting would not have more control at that engine speed? Also, my engine wants about 24 degrees initial timing, but total of 38 pings under full throttle. I can adjust this for 24 and 34 or 36, BUT why does it want so much initial. I bought a kit with springs and gauges for curving the distributer, It likes idle rpm of about 1000 rpm, so I am thinking the springs that give me the most gradual, flattest curve advance, as I am only going to give it 10 or 12 degrees mechanical advance, which would have it all in before 2500 rpm. 

[firefighter3931]

The cam timing events coupled with the displacement and static compression will determine where it's happiest at idle. I try to adjust for max vacuum at idle and tune the mechanical advance and springs for the best curve. Shoot for 35* total at 2500 rpm. Anything more will not make anymore power and just risk detonation. 

It definitely needs more jet on the outboard carbs. The plates with screw in jets are a great tuning tool and upgrade. 



Ron

[b5blue]

My stock-ish 6BBL loved vacuum advance run off full manifold vacuum. It was a bit tricky to get the dizzy setup that as vacuum advance dropped away mechanical took over but I used a dual rate curve in my Firecore RTR dizzy. (I've no idea if this will help you though?) 12* initial +10* for vacuum with all in @36*.   

[fizz]

I have the Firecore dizzy, I will be starting @ 24 or 25 degrees 1000 rpm going +10 degrees to 35@ 2500, I am thinking looking at the curves I will never get to use a dual rate spring gaining 10 degrees advance in 1500 rpm. Since I am advancing so little I am looking at the curve rates that take me there in a flat curve with springs that don't start advancing till over 1000 rpm. I have no reason to think this other than simple logic. I do have a curve kit with 9 springs from firecore, so I have quite a few options.

[BSB67]

Moving out the secondary idle mixture screws to 3/4 turn and 1/2 turn up on the floats DID result in eliminating the ping at transition, But, made my idle poorer even when I adjusted the primary idle mixture screws, which didn't seem to do anything. BUT, I am installing the secondary jet plates anyway, as it would stand to reason, like Coonhunter said, that the secondary carbs should need jetting changes with the modified, larger engine, so will deal with that some more then. I am confused that primary jetting would not have more control at that engine speed? Also, my engine wants about 24 degrees initial timing, but total of 38 pings under full throttle. I can adjust this for 24 and 34 or 36, BUT why does it want so much initial. I bought a kit with springs and gauges for curving the distributer, It likes idle rpm of about 1000 rpm, so I am thinking the springs that give me the most gradual, flattest curve advance, as I am only going to give it 10 or 12 degrees mechanical advance, which would have it all in before 2500 rpm. 

Okay.  Did a trial, learned some stuff.  Good.

Not clear, does it now ping at 38°?, 36°?, 34°?, 32°? under WOT?

24° initial is not uncommon.

It is a false notion that bigger, modified motors necessarily need more jet.  I suspect that it will need a little more, but of your carbs came with 0.089" meter plate orifices, then your not too far off.   I have dyno and track tested and tuned the 6 bbl on a bunch of motors, 300 hp 383 to 600+hp 500 in motors.  The jetting is surprisingly close for all of them. Going from memory, I think mine were around 78 to 80 in jet size.

Is your center carb idle mixture screw ineffectiveness new, or always been this way?  Or do you know for sure?

The outboard carb's main circuit have NO control at cruise as the throttle plates are closed. Cruising at 100 mph you are probably on the outboard carb's idle circuit.

If it pings at WOT above 3500 rpm, messing with the ignition curve will not help.  There are a bunch of things you can do to help reduce ping (They've been posted many times and includes fuel/delivery and jetting).  If those don't help, it is too much compression.

What are all of the cam specs?, what is your cylinder pressure?, What was the idle vacuum and rpm when it idled better, and what is it now?

[fizz]

Pings at 38, which is what I get at 24 initial until I get total advance turned back(this week) lost control of idle with primary carb idle mixture screws when I raised float and turned idle mix screws out on secondaries, so will start adjusting back a little, until I can adjust idle again. I have the lift and cam duration above in this post, I just don't have those numbers memorized. I probobly won't mess with it too much until plates get here, as I will go through all my initial settings again then. Static compression was 72, advertised compression with piston/head combination was 9.8

[fizz]

Pinging at wot, I wasn't getting to this point before as I would back out when it would ping at the transition. And thanks guys for helping

[BSB67]

Pings at 38, which is what I get at 24 initial until I get total advance turned back(this week) lost control of idle with primary carb idle mixture screws when I raised float and turned idle mix screws out on secondaries, so will start adjusting back a little, until I can adjust idle again. I have the lift and cam duration above in this post, I just don't have those numbers memorized. I probobly won't mess with it too much until plates get here, as I will go through all my initial settings again then. Static compression was 72, advertised compression with piston/head combination was 9.8

This does not help much as you did not answer most of the questions or your answers are unclear.

[fizz]

Sorry, idle rpm always seems to clean up at 1000rpm. 12 steady vacuum running good, 10 somewhat erratic now

[fizz]

Cam is hyd roller 560 lift, 243/251 duration

[b5blue]

I get ya, like my iron head problem you do the best you can but back out if it pings.

[BSB67]

Cam is hyd roller 560 lift, 243/251 duration

What are all of the cam specs: advertised, the LSA, and ICL

[BSB67]

Static compression was 72

What is this?

[BSB67]

Pings at 38,.....

Does it ping at 36°

[BSB67]

Pinging at wot

From what rpm to what rpm?

[BSB67]

Pings at 38,...

Does it ping at 34°?

[BSB67]

until I move up to black spring, then no ping, but seems like a little less power @ WOT with black spring.

Was there no ping at WOT through the full rpm range?  What was the time then?

[fizz]

Meant to type 172 compression warm with compression guage. Cam is Lunati Hyd. Roller with advertised duration 294/302, duration @ .050 243/251, lift .560/.565, LSA/ICL 110/106. We did degree the cam to make sure it was installed per spec. Has ZFR6F-11 NGK plugs. Initially, tried to have the car proffesionally tuned on a wheel dyno, came back with 28  degrees total timing, loose spark plug boots, spitting gas out of the exhaust at idle, and would not idle at all until hot, still needed 91 gas with 2 ounces octane booster per gallon. So, since between the original engine builder and the chassis dyno tuner, decided I would have to figure it out myself. So, idle first, float level on primary carb was set at mid window, adjusted to bottom of window. Primaries were set at top of window, set to just above bottom of window, idle mixture screws on primary hadn't been doing anything, were at 1 1/2 turn out. secondaries were about one turn out, turned them to 1/8 turn out, and then had control of engine with idle mixture screws, idled ok. Hooked up vacuum guage and set idle to where it ran best, which was 24 degrees and 12" vacuum and leaves me at current total of 38. Now, road test at these settings, ping at transition. Increased float level and turned out secondary mixture screws and road tested. No ping at transition but slight when under load WOT, higher rpm but didn't check. Idle quality not as good as before and no control with primary idle mixture screws, 10" vac slightly jumping needle. Need to check adjustable PCV valve.  I know 38 is too high and need to adjust. Also need to adjust either float level and secondary idle mixture screws back or both till I get control of idle mixture. That is where I am at right now. I appreciate that you are trying to help me out.   

[firefighter3931]

The idle quality (and manifold vacuum) dropped when you retarded the base timing....that is normal. 

You'll need to go inside the distributor and shorten the mechanical advance using the adjustable stops. The RTR distributor has 30* of adjustability. Looking at the window just adjust it so that one third of the window is open and 2/3 is closed. This will give you 10* of mechanical advance. Then you simply adjust the base timing at idle to 24* and you're good to go.

The std advance spring package is 2 medium weight (blue) springs and I suggest trying it with those installed. Full advance should be all-in by 2300-2400 rpm which is a good street tune.

Once that's all squared away you can begin with the carb tuning. It's going to want increased jet on the outboards I would think. 


BSB67 has some very good suggestions and should get you dialed in. 


Ron

[c00nhunterjoe]

Sorry, idle rpm always seems to clean up at 1000rpm. 12 steady vacuum running good, 10 somewhat erratic now

Please elaborate on "erratic". This is a big red flag to me.

[fizz]

Needle jumping about 2 by at idle, which is new, but possibly because of where I have the pcv valve set, which can be set for lower idle vacuum. Also did that when it came back from engine builder and tuner, but got rid of that when I adjusted valves and set carbs. But what are you thinking, coo hunter?

[c00nhunterjoe]

A video of the gauge would help. Your description isnt really good enough. A rhythmic ticking of the gauge will point to a cylinder. Whether it be a burnt valve or a plug.  If its erratic, could be sticky valve. Depending on what the needle is doing will point towards the problem. This needs to be assessed and addressed prior to any tuning. Could be something as simple as plug gap, but it needs to be checked.

[BSB67]

There are a few different things going on independent of each other, so you just need to start taking care of them one at a time.

Which PCV was in it when it had better idle?  If the fancy PCV is new in this mix, take it out and put the old one back in for now.

Question:  What heads do you have?

For now, I would not mess with the distributor or change the timing.  Keep it at 24° initial, and 38° total. If it pings above 3500, changing the timing curve won't help.  I think the initial and total are close to about where it should be.  We'll do some trials and final tuning later.  Which heads you have might matter.

Put fresh spark plugs in it.  When you tell me which heads, I'll recommend a plug.

When you get the plates, put 80s in all four corners.  Turn the idle mixture screws 1/8 turn in from where they are set now (about 5/8 turn out?).  Reinstall.  Start car let it warm up a bit.  Check to see if fuel is dribbling out of the boosters. Recheck the float levels, set as recommended earlier.  Recheck again to make sure that fuel is not dribbling out of the boosters while idling.

Idle should be better, but maybe not perfect.  That is okay for now.  Go for a test drive.  Do some WOT.  Pay attention to if and when it pings.  If it still pings, reduce total timing to 36°, retest.  If it still pings, reduce the timing to 34°, and retest.

Report back.

[firefighter3931]

I'm pretty sure Fizz has a set of closed chamber aluminum Stealth's on this build based on the ZFR6F-11 plug he is using. That's the recommended NGK plug for the Stealth heads. Heat range is 6 which is correct for a pump gas build, from my experience. 

The 172psi dynamic reaing is pump gas friendly....if it pings the problem is either ignition or fuel delivery related.

With regards to total timing ; I've had several similar street builds using closed chamber aluminum heads and all have made their best power number with 34-35* total timing. The latest is a 426 street wedge with 9.8:1 compression and a mild hyd flat tappet Crane grind. That combo made best power at 34* total timing and the numbers went backwards as timing was increased. 

I would get the timing curve dialed in before fooling around with the jetting....but that's just me. 

My rule of thumb has allways been ignition first....then fuel delivery. 



Ron