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Jabes1 · 04-15-2013, 04:58 AM

Not much accomplished in the last few days just laptop rodding...

I'm going for driver on this build, focusing on function more than form at the moment. I've been hypothesizing about my power plant and mpg's a lot lately. I'm not expecting 31 mpgs, but just to get it as efficient as possible.

Rear tire diameter: 29.74 inches
Source: http://mcgrefer.com/sizeinfo/2754520

Engine RPM calculator source: http://www.csgnetwork.com/multirpmcalc.html

Ive been looking into changing out my torque converter to a Hughes towing converter, this one to be exact http://www.summitracing.com/parts/hu...make/chevrolet. 'Ive also been looking into pulling a rearend out of a junkyard so I can swap rearends and not specifically gears in the rearend. 'been looking at a 3.08 and 2.73 ratios. The Engine RPM calculator Im using gives some interesting numbers. Im running a pretty well warmed over TH400 with a Gear Vendor behind it and the ability to split gears and .70 overdrive. Currently it has a 1800-2400 rpm stall converter that isn't helping me achieve my goals. I don't think this is completely accurate, because the RPM calculator doesn't account for converter slippage.

3.08 Ratio: (without GV)

Tire Height (29.74)
MPH 75
Transmission Final Gear Ratio ( 1.00)

Engine RPM: 2610...

3.08 Ratio: (With GV)

Ring Gear and Pinion Ratio (3.08)
Tire Height (29.74)
MPH 75
Transmission Final Gear Ratio (.070)

Engine RPM 1827

2.73 Ratio: (Without GV)

Ring Gear and Pinion Ratio (2.73)
Tire Height (29.74)
MPH 75
Transmission Final Gear Ratio (1.00)

Engine RPM 2313

2.73 Ratio: (With GV)
Ring Gear and Pinion Ratio (2.73)
Tire Height (29.74.)
MPH 75
Transmission Final Gear Ratio (0.70)

Engine RPM 1619

I realize I'm working with a flying brick... I think it may be possible to run the 2.73's without loosing mileage. If I push the speed up to 80mph the rpms sit at 1727, give or take 2-300 rpm slippage it puts me at around 2000 rpms. I'm running a TPI fuel injection setup which we all know is great for low rpm torque due to its long individual runners, so I don't see it lugging the engine much. I may have to swap cams as the one I have in it may also be working against my goals, but with a tight, low stall converter I may be able to pull it off. Any thoughts suggestions or comments?

04-15-2013, 04:58 AM	#17
Jabes1 Registered User Join Date: Jan 2013 Location: Apple Valley, CA Posts: 275	Re: 74' by Jabes... Not much accomplished in the last few days just laptop rodding... I'm going for driver on this build, focusing on function more than form at the moment. I've been hypothesizing about my power plant and mpg's a lot lately. I'm not expecting 31 mpgs, but just to get it as efficient as possible. Rear tire diameter: 29.74 inches Source: http://mcgrefer.com/sizeinfo/2754520 Engine RPM calculator source: http://www.csgnetwork.com/multirpmcalc.html Ive been looking into changing out my torque converter to a Hughes towing converter, this one to be exact http://www.summitracing.com/parts/hu...make/chevrolet. 'Ive also been looking into pulling a rearend out of a junkyard so I can swap rearends and not specifically gears in the rearend. 'been looking at a 3.08 and 2.73 ratios. The Engine RPM calculator Im using gives some interesting numbers. Im running a pretty well warmed over TH400 with a Gear Vendor behind it and the ability to split gears and .70 overdrive. Currently it has a 1800-2400 rpm stall converter that isn't helping me achieve my goals. I don't think this is completely accurate, because the RPM calculator doesn't account for converter slippage. 3.08 Ratio: (without GV) Tire Height (29.74) MPH 75 Transmission Final Gear Ratio ( 1.00) Engine RPM: 2610... 3.08 Ratio: (With GV) Ring Gear and Pinion Ratio (3.08) Tire Height (29.74) MPH 75 Transmission Final Gear Ratio (.070) Engine RPM 1827 2.73 Ratio: (Without GV) Ring Gear and Pinion Ratio (2.73) Tire Height (29.74) MPH 75 Transmission Final Gear Ratio (1.00) Engine RPM 2313 2.73 Ratio: (With GV) Ring Gear and Pinion Ratio (2.73) Tire Height (29.74.) MPH 75 Transmission Final Gear Ratio (0.70) Engine RPM 1619 I realize I'm working with a flying brick... I think it may be possible to run the 2.73's without loosing mileage. If I push the speed up to 80mph the rpms sit at 1727, give or take 2-300 rpm slippage it puts me at around 2000 rpms. I'm running a TPI fuel injection setup which we all know is great for low rpm torque due to its long individual runners, so I don't see it lugging the engine much. I may have to swap cams as the one I have in it may also be working against my goals, but with a tight, low stall converter I may be able to pull it off. Any thoughts suggestions or comments? Last edited by Jabes1; 04-15-2013 at 05:12 AM. Reason: Accidently hit enter and wasn't finished.