Thread: Chevy 292 straight six

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So I'm looking to buy a 292 that is stock bore but has 1.94 intake and 1.60 exhaust and a comp cams .488 lift with 212 duration and 113 lobe separation. My question is what kind of gas mileage would I get with a stock intake and exhaust and a t5 world 5 speed with a .67 over drive. I have a 1973 c10 daily driver with a 250 straight six that's getting weak and would like to go this route due to its a good price for the motor. Any help would be great.

Thanks

Do you know what gear ratio in the rear end? sounds like a good idling and torque maker and with o/d trans should see upwards of 20 mpg. but most all depends on axle ratio.

Gotta love those straight six builds! Here’s some additional information you may find useful for the ½ ton models:
Short bed has 117.5” WB and weighs 3,280 pounds
Long bed has 131.5” WB and weighs 3,836
Rear end rations were 3.43:1 and 3.73:1. The six cylinders most likely came with the 3.73:1. I’m assuming you have a three speed manual, which had a 3.50 low gear. If you have the truck 4-speed second gear ration is 3.58.

The 250 CI motor produced 105 horsepower and 185 on the torque. The 292 (stock) is 120 horse and 215 ft/pounds of torque so you’ll notice an increase by default. The larger valves and cam selection should help this one breath a bit better and I’d be surprised if the head wasn’t shaved a whisker to square it up so you may have a bit more compression than stock.

I have personal experience with a 1969 (similar size – probably less aerodynamic than the ’73) with the following modifications:
Offy 4 barrel manifold like this one - http://www.summitracing.com/parts/of...Fe87MgodpgEAGA

4 barrel Holley – 450cfm like this one - http://www.summitracing.com/parts/hl...48-1/overview/

Split manifold headers like these - http://www.summitracing.com/parts/he...del/c10-pickup with a crossover pipe, 2-1/2” exhaust through Flowmaster 40 series all the way to the rear bumper.

5 speed (Richmond? I think) with a 3.76 first and a 1:1 final to a 3.08:1 Positraction rear end with 33” overall diameter tires at 35-40psi.

Few other things – aftermarket oil pan with windage tray to keep oil away from the crank, MSD electronics and an aftermarket (Mallory) pointless distributor, K&N 3” tall air cleaner.

Around town (mostly empty – driver and ½- full tank of gas) 11-13 mpg. Maiden voyage from Portland to Seattle, about 400 miles of 55-60 mph freeway carrying two, 200+ pound people, yielded a surprising 21 mpg. Overall 12-16 seemed to be average. No difference whatsoever between regular and premium fuel - although I'd dump a few left over gallons of race gas (110+ octane) in her from time-to-time and I'm pretty sure I heard a sigh of satisfaction!)

The 3.76 first with the 3.08 rear end does not produce neck-snapping acceleration, but it’s fine for drivability and pulling a light motorcycle trailer.

Enjoy,
Glenn