Gotta admit, the Gonkulator is way cool! I've been meaning to ask for one and eventually got around to it. Here are my particulars:
Engine:
428CJ+.030" 432CID
bore- 4.160
stroke- 3.98
rod length- stk, 6.488
carb type/CFM- Holley 750CFM DP
intake- Alum Police Interceptor
cyl head type- CJ
comp ratio- 10.7:1
Exhaust- Hooker Comp +
cam- Crane solid lifter grd# f248
duration@.050- 248
lift/lash- .587/.020
windage tray/pan type- Fact CJ windage tray, alum Cobra "T" pan
air temp- No scoop, back of hood lifted 2"
acces- just alternator & flex fan
mufflers- 3" X pipe and Hooker Max Flos, turn downs
body- '68 Mustang notchback
weight- 3100# "no back seat, sound deadener, etc"
trans-C-6
rear- 3.89 Locker(street) 4.57 strip, if I'm not lazy!
converter stall- 3800
tire dia- 27 x 10 drag radials
chassis setup- primative! slapper bars but properly set up!
stk height front, raised about 2" rear.
I usually allow some slip for the auto trans so one issue is the 4.57 gear was overrevving thru the traps. But, some tires expand so ya never know until you get a hi speed rpm/mph reading in my experience. Given that caveat here is what the "Gonk" said -
Engine as described, gross:
Torq 478 at 4100
Powr 448 at 5500
3.89 gear:
so-so traction
1.89
7.95 at 88.9
12.38 at 110.4
better traction
1.65
7.61 at 89.4
12.02 at 110.7
The "Gonk" cannot really distinguish between those two, getting traction is as hard for the Gonk as it is for me.
Trap rpm was about 5600 assuming about 6% slippage.
4.57 gear:
so-so traction
1.90. Too much inertia loss?
7.98 at 89.3
12.43 at 108.8 out of revs
better traction
1.63
7.59 at 89.9
12.02 at 109.1
Also, the Gonk said the engine was optimal at more like 3 advance instead of the 5 advance crane advertises.
This Gonked to:
Torq 478 at 4200
Power 454 at 5500
Only a 6hp difference and not much in et, with 3.89 gear
1.66
7.60 at 89.6
12.00 at 111.0
So it was .02 sec and 0.3mph faster, not worth pulling the front of the engine in my opinion. But, lots of folks rave about retarded cams so that as ground 5 advance may be too much, maybe something to try.
The 4.57 would in fact be better if the true tire diam thru the traps is larger, and if traction is good.
Now, do you have any timeslips to send back?
Or, plan to go get some?
Comparisons are helpful!
