Inliners International Forums General Discussion Engines the best outta my 292?

i have a stock 292, except for HEI, 1 barrel, etc etc.
i've read that the 292 gets such bad gas-mileage, is that it doesn't breath? or something like that.

soooo..i am wondering if you guys could point me in the right direction as to getting the most outta this engine. ANY replys are welcomed.
thanx for your time. Sam.

good question...you should get many responses with this question.....Bottom line- the Chevy Inline 6 head has a poor design so very little efficiency can be found...but, yes there is a way to change this-Until you modify head for better airflow-NO matter what cam, ignition, exhaust system, CR, carb or rear gear ratio you use- you will not increase efficiency of engine performance for performance or MPG....this is basic physics.... see what responses you get here - and again very good question....

Lee

Well I have a 292 that breathes well. It has a 500 cfm 4 barrel carb on top of an Offy intake; and a set of 36" long tube headers. It doesn't get good gas mileage, even when cruising at 60 mph (which is only 1900 rpms for me).

The engine also has a cam ground to optimize low end torque. Still no improvement on gas mileage. I guess one thing to consider is that my engine is in a '66 shortbed truck. But the mileage probably wouldn't be much better in a car either. Bottom line - this engine was built and tuned for work, not mileage. And in that respect it doesn't disappoint!

-magic mike-

ok, i know i'm not gonna be up there with the rice rockets on gas mileage..but hey. a bit over 10 is nice! lol. but yes. what sorta head work would help? and as for carb...i really would like 2x1 when the time comes. or 3x1 if i get real tricky. but yes. thats in the future. right now i just want to get it up and running as best as possible. thanx again.
Sam.

One other consideration for gas mileage is the rear axle ratio and tire size. Numerically high axle gears won't be as economical as lower numbers in the same vehicle. Low profile tires have to turn faster to maintain the same road speed as taller tires. There is no argument that something around a 26.5 inch tall tire spinning off of a 3.73 or stiffer rear gear will give you impressive acceleration from a stop light but mileage would be better with a taller tire and a final drive under 3.00, whether you get it directly or from an overdrive trans. The overdrive trans gives you the best of both worlds, enough gear to launch the vehicle and economy at cruising pseeds. If an overdrive isn't an option for you then you have to decide how the vehicle will be used and which way to go with gear and tire combos.

Although the 292 seems to have a reputation for poor mileage compared to a 250 you have to remember that the bigger the horse, the more they eat. Another factor might be that the stock head design works better on the 250 than on its bigger brother. Sure a 283 to 305 V - thingy almost always gives better mileage in the same vehicle but the efficiency of the head design, intake and exhaust systems help.

concerning MPG increase, this is the goal we all look for....your budget will probably determine what steps to take...here are my suggestions(I have had 5 different street Chevy Inline 6's over 25 years-3 250's and 2 292'2 and also now a 292 drag truck).....I have tried MANY different combinations, some,NO!!, All worked because the engine started up and ran, but some combinations worked best-this is the trick finding the best with the components you have added....try these steps 1st-make sure you have a 292 stock intake if you are not adding a Clifford or OFFY aftermarket- the 292 intake manifolds are bigger than the 250 intake manifold-i learned this from MANY roundtrack racers who were restricted to stock intake manifolds for racing and only used the 292 intake manifolds....2nd-update to a better exhaust system-use a STRAIGHT thru muffler...straight thru mufflers help scavange cylinders of exhaust the BEST, without getting as much of the exhaust out of cylinder you will "dilute" incoming fuel mixture and will not have a good fresh intake charge for an efficient combustion...3rd-add headers-this along with a straight thru muffler will help in engine efficency....4th add a better/hotter coil for a hotter/stronger spark-also open gap on spark plugs-try .045....
these above steps are the basic Performance Bolt-On's that will help....if you are willing to go to more intense steps , you will need to add a different cam and have head work done- the head was never designed for much performance but it does work-with better valves (tulip exhaust valves-but will need to have longerr pushrods)and better intake valves.along with various steps to head work you can increase the efficiency of these heads and engines quite alot...with my 3/4 ton 1971 C 20 I get 22+ mpg at 70 mph on Interstate and 10-15 around town(depends on if i drive easy or not)-I have a 4:10 rear gear and use the New Process MY6 833 3 speed with OD trans and have 33" tall rear tires-with the tires and gear and OD -my final drive in OD is Approximately 3.00....I have a highly modified head and a Jacobs Pro Street ignition also-so it took a while to narrow down this combination....with patience and at least a small budget you can start to increase your MPG's....
what are you using for exhaust now?

I have a 292 as well, mine in a ´67 Chevy Longwide. I´ve hade similar problems. My pickup gets about 8-9 MPG on the highway. I´m not sure what rear-end ratio I´m running, but I know that the tranny is a 4 speed w/ granny gear. I´m wanting to swap my manifold and carb for an Offey and Edelbrock 4 barrel. This should help my engine breathe as well, right?

What is bigger on the 292 intake manifold?

hello..the ports are bigger on a true 292 Intake manifold(the Ports are bigger)...Clyde Norwood -owner of PES- told me of this years ago and many round track racers told of this too-only thing is, there r very few of them out there now-most 292's had 194-250 intake manifolds just like we find 194-250 exhaust manifolds on the 292....Interesting isnt it?
Go find the "old timers"-not only for more of this fun info but to become enlighten and to make an older person feel wanted and needed.......
Lee