Cam is in, car is running, now the TUNING begins!

[Kern Dog]

I just finished breaking in the cam in the Charger! Now its time to focus on tuning this thing to get the most out of it.
To recap, it is a 440/493 with Edelbrock heads, RPM intake, 2" TTI headers and 10.7 compression. I have a Lunati solid flat tappet cam 261/271 I/E with .556/.578 lift I/E. It is installed as suggested at the 106 centerline. I set the timing to 30 degrees total @ 3000 rpms, thinking it would be a safe baseline.
Yesterday during the break in process, the car started running warm at about 15 minutes. The fuel began bubbling in the filter and the fuel pressure dropped from 7-8 lbs down to about 3 or less. Once the engine started to stumble, I shut down to let it cool off. 2 1/2 hours later I started it again to finish. 10 minutes in, the same thing happened.... fuel bubbling and a pressure drop. Another 1/2 hour cool down, then I ran it the last 5 minutes.
Today I changed the oil and filter. I fabbed up a fan shroud and made brackets to mount it. On the test drive, the car started pinging at over 1/2 throttle. I backed off the timing and tried again. Still pinging, so I backed it off more. Now it didn't ping but it wouldn't idle, so I cranked up the idle set screw. It felt lazy, as if I added 500 rpms of stall speed. It didn't ping, but it felt slower than it did with the old '509 cam.
At home I set the rpms to 2900 and checked the total timing... 20 degrees! Then I saw the headers start to glow hot.
I guess the carb is running lean then, right?
Isn't that often the case? Glowing headers and detonation with minimal advance?
I have an AEM wideband guage here that I bought last winter. I had bungs welded into each collector too. I will need to run the wiring and mount the guage so I can see what the air/fuel ratio is. The funny thing is, I just UPsized the jets before putting the carburetor back on. It was 85/92 and I went to 86/94. I also changed from a 3.5 to a 6.5 Power Valve. It smells pretty clean standing at the rear bumper, but maybe it is running too lean.

 

[coloradodave]

Greg,
You said that your 'total' timing at 2900 rpm is 20*? Glowing red headers is usually because of RETARDED timing, where the charge is actually firing with the exhaust valve still partially open. What is the initial timing now and how much mechanical advance is in your distributor?

 

[67Satty]

I would set the initial to at least 16 to 20. If you have 20 total doesn't that mean you have close to 0 initial? Wouldn't that be the cause of things getting hot and glowing red? And couldn't it running hot cause the pinging? What are the idle mixture screws set at? Couldn't too lean be causing problems too? Have you tried putting a vacuum gauge on it and tuning it with that? Like hook it up, then first adjust timing for highest vacuum, then adjust idle mixture screws for highest vacuum and see where that gets you. Just throwing out some ideas.

 

[Meep-Meep]

Ditto on the retarded timing causing more heat coming out of the exhaust ports and the over all lazy feel of the engine. And it's a rich mixture that causes hotter EGT not lean. Lean will tend to ping. What that monster cam will want is initial advance and a lot of it. It may even want the distributor locked out at full advance. I take it that duration spec is at .050"? And the lobe separation is 108? The one benefit is you have more cubes to hopefully soak up some of that cam and I guess you will figure it out eventually.

It's quite possible you have even less idle vacuum than you had before so your carb settings are completely out the window. You might suffer from reduced signal to the venturi and that will cause a lean condition prompting you to jet way up. What you may need is a smaller carb to make this palatable on the street but that will be at the expense of top end power, and that's where the cam likes to run.

As far as the fuel getting hot it might be that you have no real air flow sitting in the driveway while heating up the engine at 2500 RPM (not a normal running condition). Before you think too much about it get it out on the road and see if that problem persists. It also doesn't help that the gas is no longer designed for carburetors so steps must be taken to keep the fuel cool.

 

[Kern Dog]

Maybe I didn't clarify. I've been a bit frustrated.
I started out with a total timing of 30 degrees at 3000 rpms. This put my initial at 16. Yeah, it idled great and felt peppy, but it detonated at part and full throttle. I backed it off in an effort to stop the knocking. It still knocked, so I backed it off more. I was experimenting. I would never expect the car to to run right with a total advance of 20 degrees.
The vacuum seems the same or better than before. The power brakes still work fantastic! I didn't check idle vacuum with a guage yet.

With the timing set at 17 initial, the 14 degrees of centrifugal advance tops it out at 31 degrees.

I expected the cam change to require MORE initial timing. It actually idled great and sounded fine at 17 initial. Vacuum was about the same. It has a bit more lope, but not a lot more.

I have other distributors I can try. I also have a box of jets and some power valves.

 

[Kern Dog]

The issue of power valves has been on my mind.
I changed out the 3.5 for a used 6.5 from a parts stash I got from a guy. I don't know much about them, but can a PV open but not flow well? Looking at the list of Power valves on the Summit racing site, they have Standard flow, high flow and 4 window types among a few others. I wonder if a higher flowing, properly working 6.5 PV could help.

 

[D575]

The issue of power valves has been on my mind.
I changed out the 3.5 for a used 6.5 from a parts stash I got from a guy. I don't know much about them, but can a PV open but not flow well? Looking at the list of Power valves on the Summit racing site, they have Standard flow, high flow and 4 window types among a few others. I wonder if a higher flowing, properly working 6.5 PV could help.

Check to see how much vacuum you have. THEN change the Power valve. Just saying.

 

[lewtot184]

what kind of distributor/ignition are you using? did you check to see where the intake valve is closing? what's the cylinder pressure?

 

[Sweet5ltr]

The issue of power valves has been on my mind.
I changed out the 3.5 for a used 6.5 from a parts stash I got from a guy. I don't know much about them, but can a PV open but not flow well? Looking at the list of Power valves on the Summit racing site, they have Standard flow, high flow and 4 window types among a few others. I wonder if a higher flowing, properly working 6.5 PV could help.

Just for reference, I run a 3.5PV, 32° locked timing for pump gas. your car may need 20+° timing at idle, mine did with the 312/590 solid.

 

[coloradodave]

Maybe I didn't clarify. I've been a bit frustrated.
I started out with a total timing of 30 degrees at 3000 rpms. This put my initial at 16. Yeah, it idled great and felt peppy, but it detonated at part and full throttle. I backed it off in an effort to stop the knocking. It still knocked, so I backed it off more. I was experimenting. I would never expect the car to to run right with a total advance of 20 degrees.
The vacuum seems the same or better than before. The power brakes still work fantastic! I didn't check idle vacuum with a guage yet.

With the timing set at 17 initial, the 14 degrees of centrifugal advance tops it out at 31 degrees.

I expected the cam change to require MORE initial timing. It actually idled great and sounded fine at 17 initial. Vacuum was about the same. It has a bit more lope, but not a lot more.

I have other distributors I can try. I also have a box of jets and some power valves.

Greg,
Before you start throwing parts at your motor, do as has been suggested here. Hook up a timing light and a vacuum gauge. Set your initial timing around 20* or where the idle vacuum is highest. You may have to readjust your idle speed down to around 900-1,000 rpm. Do the timing first. Then confirm that you have +- 34* maximum mechanical by reving the motor until your mark quits moving up. Once that is set, lightly seat your idle mixture screws and then back them out 2 turns each. Always adjust them both the same distance in or out. Turn the idle mixture screws in 1/4 turn at a time until you achieve the highest vacuum level. Remember, these screws do not lean or richen the MIXTURE, they just add more or less idle fuel. After this, road test the car. If it pings on hard acceleration, back the timing off a degree or two at a time until it doesn't. If it pings on light acceleration, change the advance springs in the distributor to bring the advance in at a higher rpm. BTW, Lowes sells a BIG floor fan for $49.00 that you can set in front of your radiator while you're doing the tuning. Helps to keep you cool, too. Good luck.

 

[Kern Dog]

Thanks Dave. I might just print this out as a template!
I plan to install the guage and then start tuning.

 

[Meep-Meep]

OK, thanks for clarifying on the timing experiment.

The PV is a switch and the fuel flow is largely dictated by the PVCR's (power valve channel restrictors). If you use the Holley PV with the square windows you should be fine.

The timing should be set first as stated and then drive with an O2 sensor to see where your mixture is. Pinging at part throttle can be way too much vacuum advance or fuel curve way off. Do you have vac advance? If so temporarily disconnect it. If the pinging stops check the amount of advance using a vacuum pump and a timing light. As I said before that cam might want full advance at idle or just off idle so a vac advance may be useless for this combo. In my opinion this is no longer a street engine so treating it like one may cause confusion. Fuel curve issues need to be checked with an O2 sensor so I suggest you get that puppy hooked up.

 

[Kern Dog]

The timing should be set first as stated and then drive with an O2 sensor to see where your mixture is. Pinging at part throttle can be way too much vacuum advance or fuel curve way off. Do you have vac advance? If so temporarily disconnect it. If the pinging stops check the amount of advance using a vacuum pump and a timing light. As I said before that cam might want full advance at idle or just off idle so a vac advance may be useless for this combo. In my opinion this is no longer a street engine so treating it like one may cause confusion. Fuel curve issues need to be checked with an O2 sensor so I suggest you get that puppy hooked up.

I didn't get much done today, but I did reset the timing to 33 degrees total. This puts it at 19 initial. The vacuum advance is plugged. It idled great and sounded fine. I set the idle to a hair over 1000 rpms in neutral, 700 in gear. I hooked up a vacuum guage and it read 10 inches at idle in Park and 4 inches when in gear. I have not touched the idle mixture screws, but I suspect that the in gear idle vacuum could come up with adjustment. I wanted to establish the timing to where it theoretically should be, then get the wideband guage installed.

 

[daredevil]

I didn't get much done today, but I did reset the timing to 33 degrees total. This puts it at 19 initial. The vacuum advance is plugged. It idled great and sounded fine. I set the idle to a hair over 1000 rpms in neutral, 700 in gear. I hooked up a vacuum guage and it read 10 inches at idle in Park and 4 inches when in gear. I have not touched the idle mixture screws, but I suspect that the in gear idle vacuum could come up with adjustment. I wanted to establish the timing to where it theoretically should be, then get the wideband guage installed.

You should be getting close now.

 

[Michael789]

I would pull the plugs and take a look at them as well,I know using an 02 sensor for the fuel curve reading is a good ideal but I think sometimes you just have to do things old school and look,read the plugs to see how close your fuel air ratio mixture actually is.It will definitely answer your questions about how rich or lean the motor is running ,how hot etc. I've always felt to get a really good tune reading the plugs is a must to go along with all the scanning/data logging.It will also help with detecting your heat range and timing.Your plugs can tell you everything your power plant is doing. You need to check them on a wot shut down of the motor .If you have it on a dyno that would be great other wise you'll have to take it out open it up and shut it off then pull a plug.Good luck.

 

[Kern Dog]

Thanks Mike,
The 2" headers makes it really difficult to remove the plugs without touching the tubes. I have only tried removing the plugs once with the engine still warm and I will not make that mistake again. My hands are slightly over average size and the limited space in there makes skin burns a certainty.

 

[Kern Dog]

*******UPDATE*******UPDATE*********UPDATE********

I got the wideband guage installed. I haven't jumped into tuning much yet, just wanted to pop in to post this:

Engine as is without touching anything: 9 1/2 inches idle vacuum at 1000, 4 in gear at 700-800. Idle mixture screws were only 1 1/4 turns out from being seated. IN GEAR the guage reads between 15.0 and off the guage which tops out at 18.0. When I revved it above idle in PARK, it pegged past 18.0!
I had a feeling it was lean!
I seated the idle mixture screws, then backed them out a full 2 turns. Idle vacuum went up to a solid 10+ with 5+ in gear. At idle, the guage reads between 14.0 and 15.0. It still pegs when I lean into the throttle.
Here is a thought: The primary side is running lean with the 86 jets. Being that I have 5.0" of vacuum and a 6.5 Power Valve, I think the PV may be covering for the UNDERjetted primaries. When I rev the engine, there is no additional fuel to keep the Air/Fuel ratio in check.
Sound right so far?


************************************************************
UPDATE UPDATE UPDATE

I switched the 3.5 PV back in. The idle readings went down to 13.0 to 13.6. Kinda odd for it to richen up when I went to a smaller rated PV. I turned the idle mixture screws in to where they sit at 1 1/4 turns out again and the A/F reading came back to the 14.5-14.9 range.

NOW it goes off the charts lean when I put it into gear or hold the brake and ease on the throttle.

I thought I knew a little about carburetors, but tell me if i have this right:
* The IDLE circuit works when the primary throttle blades are closed. The main jets are NOT in play when in the idle circuit.
* The primary jets begin to function when the engine is put under a load and the primary throttle blades open.

If the above is true, would that mean that my primary jetting is still too lean? I understand that you are supposed to make only one change at a time which is why I only changed the power valve when I had the bowl off.
Looking at the gaskets I used, they actually are fine. They are a rubber like red gasket that came in a Demon rebuild kit I had.

 

[Kern Dog]

Now I have # 88 jets in the primaries.
When in gear at a 750-800 rpm idle, it is around 16.0 but pegs to the lean side when I lightly power brake it.
I have not taken it out on the road since installing the guage. I figured that if I couldn't get it close to 15.0 under a light load, it would only be worse out on the road.

 

[Budnicks]

86-88's ain't enough of a change, Go up about 5 jet sizes "swing for the fences", see if it changes anything now you have a gauge installed, it couldn't hurt...

 

[coloradodave]

Greg,
Have you sprayed carburetor cleaner around the base of the carburetor and all your vacuum takeoffs on the intake manifold?