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Positive thinking ...
We are still asking:
What did you
get done on
your Bolt today
????


The question, initially posted May 23, 2005, was:
"Whatcha do on your Bolt
this weekend?"

After 51,906,997 views, 7378 replies over 185 pages, this thread in General Truck Talk is a happening! And it's not just weekends anymore.


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So ...


What did you get done on your Bolt today????


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Re: gas mileage
Superfly #747231 Sun May 15 2011 08:03 PM
Joined: Dec 2003
Posts: 1,570
D
Shop Shark
Way too many of you guys are looking at a particular engine to get good MPG and performance.My friends,its all in the gearing,with my 350 and 700R4 setup the 700R4 has a very low first gear that will kick **** on take off.Then with the overdrive 4th gear it is very economical.No reason why a 383 should not run economical too.Course with any setup ya gotta drive with a little common sense.At 73 yrs. of age I drive my truck at a very reasonable pace.Then there are the other days when some young jerkoff wants to race it from a stoplight.Sometimes I accomidate them and guess what.Yeah Old yeller leaves them sitting,and they wonder what in the hell happened,youi know like how in the Hell did that old pickup beat me back there.Those are the fun days.So for performance and economy look to gearing first,then worry about horsepower.

Last edited by dale937; Sun May 15 2011 08:05 PM.
Re: gas mileage
dale937 #747257 Sun May 15 2011 08:58 PM
Joined: May 2011
Posts: 39
L
New Guy
Very good point. It takes the same amount of energy to get and keep the truck down the highway regardless of engine displacement. Pick the engine you want. Then, set cruise rpm to accoumplish this task with the best vacuum and least throttle imput to maintain the desired speed in the conditions you drive in most. With carbuteted engins keep out of the power valve our your licked from the beginning. Electronic Fuel Injection is why modern LS1 vettes can cruise 70 at almost idle and get away with it. The combination of EFI and low cruise RPM with close ratio gearing in the higher tranny gears is the key to best mileage.

Re: gas mileage
Longbed61 #747477 Mon May 16 2011 02:05 PM
Joined: Aug 2006
Posts: 486
J
'Bolter
Someone mentioned on another site that the optimum compression ratio for best fuel economy was not the same as that for best power but they didn't elaborate. I'm not a member of that board so I thought I'd ask you guys what you recommend. I'm primarily interested in a 250 and a 283 because those are the two engines I have to work with. Any insight will be appreciated.


'64 swb stepside (gone)
'57 1 ton
'53 phone truck
'59 swb
'46 1 1/2 ton
'68 swb gmc
Re: gas mileage
jfnar #747479 Mon May 16 2011 02:12 PM
Joined: Dec 2010
Posts: 302
S
'Bolter
google stoichiometric ratio...that would be the definition of a perfect burn to achieve best gas mileage but may not be the best power output. wrap your brain bowl around this.....

A stoichiometric mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air/fuel mixture is approximately 14.7; i.e. the approximate mass of air is 14.7 mass of fuel. Any mixture less than 14.7 to 1 is considered to be a rich mixture, any more than 14.7 to 1 is a lean mixture - given perfect (ideal) "test" fuel (gasoline consisting of solely n-heptane and iso-octane). In reality, most fuels consist of a combination of heptane, octane, a handful of other alkanes, plus additives including detergents, and possibly oxygenators such as MTBE (methyl tert-butyl ether) or ethanol/methanol. These compounds all alter the stoichiometric ratio, with most of the additives pushing the ratio downward (oxygenators bring extra oxygen to the combustion event in liquid form that is released at time of combustions; for MTBE-laden fuel, a stoichiometric ratio can be as low as 14.1:1). Vehicles using an oxygen sensor(s) or other feedback-loop to control fuel to air ratios (usually by controlling fuel volume) will usually compensate automatically for this change in the fuel's stoichiometric rate by measuring the exhaust gas composition, while vehicles without such controls (such as most motorcycles until recently, and cars predating the mid-1980s) may have difficulties running certain boutique blends of fuels (esp. winter fuels used in some areas) and may need to be rejetted (or otherwise have the fueling ratios altered) to compensate for special boutique fuel mixes. Vehicles using oxygen sensors enable the air-fuel ratio to be monitored by means of an air fuel ratio meter.



*UNDER CONSTRUCTION*
1953 Chevrolet 3100 1/2 ton-previously abandoned resto.

My Project Bolt

I hate when people leave their brains at home. Seriously when did critical thinking and customer service go out the window? How about common sense and striving to go the extra mile? Idiots, surrounded by idiots it tell you.
Re: gas mileage
Silverado_9c3 #747485 Mon May 16 2011 02:48 PM
Joined: Aug 2006
Posts: 486
J
'Bolter
Not sure I follow all that but how does air / fuel ratio affect compression ratio? To clarify my original question, I'm looking for the best compression ratio for gas milage on a carbureted engine burning regular gas. I suspect the stock CR gave the best milage on the fuel of that day but might not be the best on today's gas. Don't plan to use any fuel additives, just plain regular gas. Thanks.


'64 swb stepside (gone)
'57 1 ton
'53 phone truck
'59 swb
'46 1 1/2 ton
'68 swb gmc
Re: gas mileage
jfnar #747504 Mon May 16 2011 04:03 PM
Joined: Feb 2000
Posts: 4,439
J
'Bolter
I would try for 9.0 to 1. Thats a good number that will run on 87 octane with killing the pistons or bearings. You can get away with more with a good timing curve, and carb calibration, but you will give up some performance for fuel mileage. At 9.0 to 1 you can achieve mileage with out giving up much.
Some of the new cars are in the 11 to 12 to one range, but the computers are able to control all the inputs and compensate as needed, your carb won't!

For the 250, a simple piston swap will get you there, for the 283, I have no idea.

Joe

Re: gas mileage
Joe H #747567 Mon May 16 2011 09:56 PM
Joined: Aug 2006
Posts: 486
J
'Bolter
Thanks Joe, that's what I'm looking for. I'll do some research on heads for the 283, possibly from a 305.


'64 swb stepside (gone)
'57 1 ton
'53 phone truck
'59 swb
'46 1 1/2 ton
'68 swb gmc
Re: gas mileage
jfnar #747575 Mon May 16 2011 10:55 PM
Joined: Mar 2010
Posts: 926
Y
yar Offline
Shop Shark
jfnar, the compression ratio you pick depends on whether you are using iron or aluminum heads. Before you laugh, a "valve job" that puts used heads in like new condition (bronze guide liners, 3-angle valve seat regrind, centerless grind valve stems to restore roundness, grind valve faces, new springs, new valve seals, resurface gasket surface) can actually cost more than new heads. And with performance heads you also get nice bowl blending and screw in studs.

Iron heads at 9:1 will not tolerate 87 octane gas on a hot day if you are running a carburetor unless it is jetted way too rich for clean running and good power. My street roadster has 9:1 aluminum heads and it took some very careful carburetor and distributor calibration to avoid pinging on 89 octane.

There is a HUGE variety of small block Chevy heads out there with combustion chamber volumes from under 60cc up to 76cc. That range, in addition to the similar HUGE variety of pistons, will let you pick any compression ratio you want.

Supposedly one of the biggest bargains out there is vortec heads but there are some good versions and some ones to avoid.

If you're building an engine from scratch you can make it be anything you want it to be. Have fun!


Ray
Re: gas mileage
yar #747653 Tue May 17 2011 04:30 AM
Joined: Dec 2009
Posts: 46
5
56srw Offline OP
'Bolter
i talked to the shop my truck is at and was told 273 was the gear ratio in the rear end he installed, he has driven it on the highways and said it was running good and smooth, i get off the boat in 9 more days and i will see what it is like, i am sure it wont take my 2 porsches off the line anymore, wife and son will like that, i was just wanting to get it to cruise the highways a little better, will see soon

Re: gas mileage
56srw #747683 Tue May 17 2011 08:34 AM
Joined: Dec 2004
Posts: 1,899
B
Shop Shark
Point of clarification...

Are you rear gears 2.73:1?
Are you using a TH350 or 700R4?

If using the 700R4, the 2.73 gears will be absolutely worthless.
Well maybe not worthless, but you won't be able to use the OD unless you are going down hill with a tail wind.


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