318, 340, or 360?
What's wrong with a bad *** 273?
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Nobody going to touch this? OK I'll go first; what's the thread title again?
I tell you what tho, I bet I can get mid 20s to near 30 mpg out of one of those 273s,
Without an overdrive.........Into the 30s with a 5-speed stick, and it will still fry the OEM sized tires in first gear, in that Barracuda.Maybe even whatever fits in those stock rear tubs.
Ima thinking the Aisin AX15. Somebody here is gearing up to make SBM adapters. This is an ideal candidate for a 273/318. I think the ratios are 3.83-2.33-1.44-1.00-.79od. You can run that with a 2.76 equipped 7.25 with an LSD and let her buck.
The starter gear would be 10.57, and the cruiser;2.18, would get you 1868@65mph.
Second would get you; 32@2700, and 60@5100
Third gear would get you about 95@5000.
So those numbers will work best with; a lot of Dcr, TightQ, decent heads, and a torquey cam.
I'd pump the compression up so high that it would require anti-det.injection. Ima thinking close to 11/1Scr with a 262/270/106 cam. That'd be close. At 11.0Scr that gets a Dcr of 9.14@189psi and a
VP of 129. The compression distance is 122* and power extraction is 120*. Overlap is a bit generous for the combo at 54*, so headers will pump up the power. Yeah with iron heads it will detonate. But there's ways around that.
Between the 129VP and the 10.57 starter, this is a tire-frier.
Between the 9.14 Dcr and the 2.18 final drive, I can totally see fabulous fuel mileage.
The other gears are bang-on for having street fun. And guess what; more performance is just a rear gear swap away. But 3.55s are about the max to run, still tho,right in the ballpark. Lessee, 3.55 x .79od is 3.195 final drive, and 65 is still just 2740.
If I was stuck with a 273, or was trying to prove a point, I think this is about what I would do.
Oh one more thing; Wait til you hear that hi-comp 273 screaming for mercy pulling two gears all the way to 60/65. Ima thinking Purple Hornys and 2.25s.
Then stuff it into OD and and cruise in quiet comfort at 1868rpm.
If you need a frame of reference;
a 360 would need an Scr of just 8.8 to achieve a Dcr of 7.38@144psi and a
VP of 127; with that very same cam. The 273 will need about 440cfm to satisfy the equation,and will need premium gas with an anti-detonant, while the 360 will need a 520carb, and burn shunk-pee.
That's why I say "stuck with a 273".
If a turbo is on the table, well then, with a rearrangement of parts,she'd start to be bad-azz. Hyup, I could see that making 400 pretty quick. But say goodbye to the 5-speed.And along with that the great hi-way mileage. But you could keep the 2.76s,lol. And I would go automatic.
