What are YOUR tune up specs?

[Kern Dog]

Hello, I'm trying to maximize the tune in the Charger. I don't expect to crack the 20 mpg threshold, but I'm sure that there are gains to be had with the right moves. The combination:
70 Charger 440 based 493 with Edelbrock RPM heads and intake, MP '509 cam, TTI 2" headers with 2 1/2" exhaust. BG 850 VS carb jetted 85/92 with a 3.5 PV. Timing set to 17 initial, 31 total plus vacuum advance. I have a 727 with a GV OD. 3.91 diff, 3.05 final in OD.
I got 12.8 mpg on a tank while doing total freeway driving at 60-62 mph.  A friend in a convertible stated that while there was no visible smoke, he could certainly smell fumes coming from the car. I think that an air/fuel ratio guage could help determine how much leaner I can go. I'm just curious as to the specifics of other members cars. Thanks, Greg

[Brightyellow69rtse]

92 damn thats a big jet. i got a wideband and i love it. after having this its the only way to go. takes the guesswork outta everything.

[Kern Dog]

The Air/Fuel guage is next.
I agree... The hard data it provides will give direct evidence of each change made.

[tan top]

 deffo a  air fuel ratio gauge  , will save hours & hours !!  even days ! of time &  countless gallons  of gas , plus falling out with the next door neighbours ,     i got to get one my self  , although been saying that for few years    

[oldschool]

 you probably need closer to 35-36 total timing. set it without the vaccum advance hooked up. if it was me i would probably plug the vaccum advance, unless you have an adjustable one, that you could limit the advance....

i also agree a 92 sec. jet sounds big. on all of my 500" motors i use a 72 front and 79 rear. try to get a AF reading to see where you are at....

[oldschool]

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[Charger_Dart]

how did you limit your mech advance to only 4*? you probably need closer to 35-36 total timing. set it without the vaccum advance hooked up. if it was me i would probably plug the vaccum advance, unless you have an adjustable one, that you could limit the advance....

i also agree a 92 sec. jet sounds big. on all of my 500" motors i use a 72 front and 79 rear. try to get a AF reading to see where you are at....

I also run my 500" on 72 / 78 jets using a A/F meter to find the right mixture. My motor also has the MP 509 cam and RPM intake. For timing I have it set at 19* initial and 34 total without vacuum advance. Engine runs well and the plugs are nice when I check them. One thing I found was that I could only get 10 inches of vacuum at idle so I was running a 4.5 power valve. I could never get rid of a light  throttle, cruise, lean miss that I had. Went to a 3.5 and it made no difference, then went to a 6.5 and it cleared up entirely. 

[Brightyellow69rtse]

if you wanna think mpg think of it this way. if your pulling 10mpg and your pig rich as i suspect you are. a wideband confirms it, and you really drop on the jet sizes. youll save tons of money in fuel since the mpg is crap to begin with even a small change is amplified considerably. 

[Kern Dog]

The engine detonates with mechanical advance over 32 degrees. I've ran without vac advance AND with it. It gets better mileage WITH.
I had a guy at a shop recurve the distributor years ago. When I brought it in, the wide advance curve of its original setup meant that I had 32 degrees max with 10 initial. It was lazy off idle that way. If I ran it up to 17 initial to get better off idle performance, it knocked heavily as RPMs climbed.
Currently, it runs great and rarely detonates. I'm just looking to improve the overall package. Who knows... maybe in all of the tuning, it may improve power AND economy!
I started this in an effort to make the car MORE fun to drive. We build these cars for many reasons. Mine was because I wanted to drive it. I don't expect to eclipse 20 mpg, but if I can gain 1-1.5 mpg and run cleaner, I'd say Mission Accomplished.

[Brightyellow69rtse]

if your pig rich and you lean her out youll gain performance and economy!

[Kern Dog]

I think so too, but I don't think that I am running rich by a large amount. There is very little smoke.

[1974dodgecharger]

get a 'BLOWER' it creates less reistance for air to travel to cumbustion chambers and drive conservatively 

[Cooter]

get a 'BLOWER' it creates less reistance for air to travel to cumbustion chambers and drive conservatively 

Um, Superchargers make very little to no boost at cruise speeds. If belt driven, They actually hurt MPG/power by robbing power from the engine when not making Boost.

[elacruze]

My timing specs are pretty common, 18* initial with 14* mechanical and 18* vacuum.

The initial and total have a fairly narrow range for most engines, the initial moving more depending on your camshaft.

Where people get into trouble is in the middle; on my engine, I carry 18* all the way to 2500 RPM before beginning to advance the mechanical. I have 10.6:1 compression and only 238* on the cam, so I have a lot of dynamic compression and it rattles easy in the normal driving range with any 'common' timing curve. If you can improve your idle with more timing, you need to bring the advance in later.

Also, leaning the mixture will require less timing until you reach about 14:1; then it goes the other way-as you lean beyond stoichiometric the mix burns slower and demands more timing. A lean mixture and low cylinder pressure (cruise condition) requires a lot of timing for max economy. At highway cruise, I have 50* timing in and have seen 14.6 MPG with a 3.76 final drive ratio at 65-70mph with room to improve.

[oldschool]

   i use 26* initial timing, 10* mech and no vaccum advance. my total is 36*. my idle quality is very good.

[oldschool]

I think so too, but I don't think that I am running rich by a large amount. There is very little smoke.

you cant go by how much smoke it produces. when i started the tune on my charger i was 10.1 WOT af ratio. it didnt smoke any at all, when i was done tunning, i picked up 100hp at the wheels.

you really need the check it with a af meter. go to a chassis dyno shop, they can check it and tune it.....