The Stovebolt Site Forums The Shop Area Engine Shop 292 Rookie,Help!

I just came by a 65 292 to replace my tired 65 230.I do have concerns about gas mileage stories my buddies have told me.I am putting an OD automatic in at the same time.3.73 rear,235/75 tires,tonneau? cover. Rebuilt carb.This is a low mileage complete chassis that has been in a quonset hut for 20 years! Am I foolish to hope for 20 mpg on the hwy at 65-70?Prairie driver.I would really like to leave the engine stock-looking at least.Thanks,Tom.

Don't overdo it on the high gearing. The engine will lug down every time you open the throttle, and put the metering system in the carburetor into full-power mode, and actually decrease gas mileage. Once the power valve opens up, fuel mileage goes down the tube. Let it wind up a little, and light-throttle operation should be pretty economical. Lug it, and you won't like the mileage at all!
Jerry

Thanks,Jerry. I went to a farm auction looking for some parts and got the chassis for a song. I pre-lubed the engine and it runs smooth and quiet.

Tom,

I've read Jerry's posts and he seems to really know what he's talking about. I'm chiming in because I have a '66 Chevy shortbed stepside truck with a 292 and overdrive. My overdrive is a 4 speed manual shift. Like you I have 3.73 gears and I have 235/70R15s. Overdrive ratio is .73 so I turn about 2600 rpms at 80 mph, about 2200 at 70.

I get nowhere near 20 mpg. But I have a cam that's bigger than stock, headers and a 500 cfm 4 barrel. Problem with me is that it's really hard to keep it at only 70 with the torque of the 292. You might as well throw you on a nice sounding exhaust while you're at it - I have a Flowmaster muffler with dual outlets. Sounds near-v8ish, really deep at idle and normal acceleration.

I think 20 mpg is feasible for you, with the right setup. Jerry was right about lugging. Mileage will really suck if you lug or gun it. The right sized carb makes all the difference in the world too. I probably get about 15 mpg when I run 70 and use ideal acceleration techniques.

-ftyler

Thanks,Ftyler.I'm really excited about finding this 292.

Ftyler,

i have a 54 gmc 1/2t that i have a 292 for. it presently has a shot 283 sbc and th350 in it. i have a 292, but i would like to get a 4-spd OD like the one you have, i do have a bellhousing and flywheel, etc. for the 292. what years/models were the 4-spd OD's in? they are 4 on the floor aren't they?

thanks,

rotty

Hey,

I believe those transmissions were an option for 1981-86 Chevrolet light duty trucks. I believe the option code is MY-6. I don't know if they were diesel only (6.2L) or available for all models. But you can find them every now and then on Ebay. That's where I found both mine.

-ftyler

I owned a '74 GMC one ton dually flatbed with a '62 292 and a 4:11 rear. I got around 12-14mpg loaded or not, didn't seem to make any difference.

60 mph was comfortable top speed, the stock 292 does not like rpms much above 2500. As I recall, I'm too lazy to look it up, torque peak is between 1200-1600 depending on the year. Not surprisingly, this is a big truck engine designed for low speed pulling. Friction losses at high rpms with this engine are high. It is hard to lug this engine at normal highway speeds in a light vehicle. You have to learn not to push the throttle more unless the truck will accellerate. When you reach the point of no more accelleration you are wasting gas by using more throttle.

All these observations are based on a stock engine with a single barrel carb.

I did have headers on it because the stock manifold cracked, it does not seem to be a very good design. I may have overtightened the manifold bolts, very easy to do. Headers last forever and make the most wonderful sound you ever heard, especially at idle or slow speed. A nice rumble.

You may get 20 mpg with a light weight truck but I doubt it.

I have a 51 Chevy truck, 261 engine, 3.40 gears. it has an A883 4 spd OD like FT is describing, the overall gear ratio in OD is around 2.50, the engines turns 2000 rpm at around 65-70 mph.I have a vacuum gauge,the engine pulls 10-11 inches of vacuum at 70 mph, dips down to about 8 inches to cruise up mild hills. The engine has a 2300 type Holley 2bbl with a power valve opening of 6.5 inches of vacuum.So the enrichening circuit remains closed during normal cruising.Downshifting to 3rd direct at 65 mph gives 2600 rpm and 14 inches of vacuum and a lot of noise,lol..Since carburetor main metering circuits are responsive to air flow through the venturi and not engine vacuum as seen under the throttle plates, the low rpm ,higher load should give better fuel mileage.I haven't checked the fuel mileage on this truck yet, but my 261 powered 37 Chevy PU has a 390 Holley 4bbl, 3.36 gears and a 3 spd OD, runs 70 mph at 2 grand, when driving at 60 mph,1800 rpm, the truck gets about 21 mpg, 2-3 mpg more than when it had a regular 3 spd with the same 3.36 gears.My daily driver 94 S10 4.3 has 2.73 gears and a 5 spd OD,60 mph is 1400 rpm, gets 26 MPG on the highway at reasonable speeds.I know the S10 is fuel injected, but the throttle body injection is similar in operation to a carb.
This works for me cause the Holley power valves are a known value and come in a variety of vacuum openings so you can tune the carb to your siuation.AFB's and Edelbrocks use different color metering rod springs to vary the enrichening opening vacuum signal.
Supposedly the lower vacuum also results in less piston pumping loses and a more effecient engine.

FTyler & T'dup,

thanks for the info on the 4 spd OD's.

rotty