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Old 03-22-2008, 10:44 AM
red65mustang red65mustang is offline
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1406 is set up more for economy out of the box...98 jets and .075 cruise rod step, .047 rich rod step....for normal driving intown "pep" it may be a bit lean.... but.... as always..... tune the carb last

(a comment: 90% of my driving is intown, a .072 cruise rod/98 jet makes a world of difference for "pep" on my "particular" set up and combo"....for a tiny bit better hwy mpg I do stick the .075 rods in it for the 500 mile round trip to my daughters home...cause I'm turning 70mph=3400rpms!)

(hope this is clear enough, numbers are only to illustrate, your will be different) )
every motor/tune up/car/gears/etc has a TT "sweet spot" at hwy cruise where the motor is "totally loafing as much as possible" which is what the vac guage is telling you....that base+cent+vac= TT can be anywhere from 44*-54* "if" you were cruising at 2800-3200 so that the cent advance is all in....(very likely the "truck" this dist came out of did cruise 70mph=3200)

the great thing about a relatively low CR motor and a relatively light car is it will tolerate a "wicked quick" cent curve with out detonation....just adding even a tiny bit more timing sooner makes way more hp/tq at those rpms for alot more pep accelerating...."fair" chance your ride can tolerate all in full centrifugal timing 20* at only 2500-2800 (to also gain more cent timing at your 2k cruise rpms)....(and that's why I posted (definitely) recurve the dist will give some balls....

(some dist's have adjustable vac advance some don't....some can adjust only 10 crank*'s, some adjust upto 20 crank*'s+....some clockwise is more *'s/some counter clockwise is more....find the screw turns spec table for your unit if you verify it is working correct)

most common is they adjust using a 3/32" to find best TT cruise timing Hg @ 2k, just measure the no vac advance actual timing at 2k (say it reads 28*after the re-curve at 2k) then plug in the vac advance at a low idle rpm to a manifold source to see how many *'s are added by the vac adv to the (say 14*) base...(say the) timing with vac adv plugged in at 500rpms reads 24*=that vac adv unit is set to add a max of only 10*'s additional to the cruise total (likely on a truck dist) when the Hg is high (most are all in/max *'s added at about 16Hg+ just for reference at 500rpms idle)

we now know at 60mph your motor is only at 38*TT...2k=14b+14c+10v...

vac adv plugged in, read the motor HG in your garage at 2k (= max Hg the motor will make with "no load" on the motor at 2k) (say it is 20Hg) go for a test drive at 2k with 38*...Hg reads (say) 15 on a level road at 60mph "with a load" on the motor (likely with only 38*).... add about 4* more vac advance *'s to the TT by turning the adjust screw (and read how much was added by that particular unit by comparing to the 14*base...note: one full turn may add 2* or add 8* all are calibrated different for the original oem car/truck drive train combo)...and test drive again...Hg reads 16...add 4 more vac adv and try again...etc...

just a guess but somewhere around 48*TT your Hg will read 18 and more vac*'s added won't read higher....adding more than needed btdc timing total actually works against the motor...

it read 20Hg with no load at 2k in the read 15Hg(?) with 38* at 2k and a reads 18Hg(!) with a load at 2k =less gas into the's that simple (very very roughly, each Hg added typically can be/will be worth 2-3mpg more hwy mpg)

when you do add more vac adv *'s to the also adds more *'s with less Hg/more load so you do need to check for heavy throttle ping on a steep grade...hope this unit's chart pic' helps explain (that is not your vac unit calibration..happens to be a Accell unit and reads in dist *'s...)

"fair to good chance" that once the dist is set up correct for the cam and cr and car weight...the tranny will shift may well be down 20- 30HP/50+ft/lbss at it's present shift points WOT....don't tune the tranny till after the motor is tuned

yup, when you mix and match parts to build a ride....
"every" part needs to be re-tuned to work best with that combo....
find the build sheet on any oem car or truck....there are about 50 to 100 specific parts selected for that specific car combo...including parts in the tranny (and which specific model dist curve and vac adv unit) ....

"flaming cats" did crack me up...but likely women would be whackin' you side your head with their purses! (maybe "ghost" painted flaming cats? "ghost flames!)
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