Ancient History

[Arnaldo Echevarria]

At 02:44 PM 9/3/96 -0500, you wrote:
>I think 12 mpg from a 455 is fantastic.  Can't see how you get this
>good -- FI or carbed.  What's your rear end ratio?
>
>tom

OK, I new I'd get some mail when I said that, so for the curious, my car is a:

'78 Trans Am
1970 455 2bolt main from a Bonneville
stored heads from that motor (10.25:1 cr too high)

HEADS: using 6X heads (2.11", 1.66" I think)
       approx CR between 9.0:1 to 9.6:1 (too much conflicting info)
CAM:  .444/.465 lift, hydraulic, stock rockers.

Manifold: stock 4bbl

headers (1 7/8"), flowmaster transverse muffler (2 little mufflers inside
one big
case, 2 1/2" tubing)

Best time with old rotten 245/60/15 Grand Prix tires: 13.3 @ 107mph
(75degree weather)
(This is in Orlando, Fl)
Best time with new 295x50x15 BF radial t/a's:  call me next week.

Tranny: TH400, just rebuilt
Torque converter: $20 new unit.  can't be that good.

REAR END: 3.08 posi  (to answer your question...)

Actual mileage:
11-12 city if the secondaries don't open.
<9 if the foot gets heavy :)
12.5 - 13 highway, cruising at 2600rpm, which is about 65mph.
11 mpg cruising at 3200rpm, or about 80mph

(and yes, speedometer error is accounted for, I'm not one of those
30mpg 5.0L owner  ---- but then again, two years ago in car craft some
guy with a 455 got 20MPG(??!) in one of the real street eliminators.
Yeah right! ..or did you see the buick turbo v-6 that got 48mpg and ran
low 13's in the 1/4 mile?)


timing: 10 degrees with 87 octane gas,
        12-14 with 93 gas
        (with vacuum advance)

CARB: quadrajunk 4bbl 750cfm (got it for free at junkyard, I've rebuilt it;
actually it works pretty good but gas mileage still sad)
.....when I had the holley 600cfm vacuum secondary carb, I couldn't break into 
the teens for gas mileage.  Holleys suck for gas mileage.(besides the fact that
the carb was too small)

Weight of car: 3720 w/out driver

I'm actually considering lowering the rear end ratio some more.  I've had good
luck with ultra-low geared cars and long stroke engines.

For example, I used to have a '83 trans am with:
305 (believe it or not, relatively speaking, big stroke vs bore)
.465/.488 cam
9.8:1 cr (93 octane gas only on this one)
t-5
2.73 gears (!!!!!) 
--> final drive ratio: 2.06:1.  This car would go 72mph at 1900RPM in 5th.
Everyone would tell me that ohh it'll kill the engine it'll lug it it can't
handle
it bull!
With time slips to prove:
14.3 @ 102mph
21 mpg (with a HOLLEY! My friend had a similar setup with a Q-jet and got 23mpg)
...now that car was a BLAST to drive.....
(sorry to get off topic)