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Discussion Starter · #1 ·
Just wondering if anyone has ever read anything about the efficiency of
a stock stroked LT1 vs. an LT1 that has been stroked. If all things
equal,which combination would be more efficient. I guess a few
points of interest would be the amount of HP per cubic inch and
how much would fuel economy be effected? ed
 

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Discussion Starter · #3 ·
Just an observation of what I have seen over the years is that fuel mileage is (or can be) as good or better.
Very interesting, so possibly the stock LT1 could be a better performing
motor, regarding fuel mileage, if it had a longer stroke. A little surprised
that GM wouldnt have produced it in the stroked form,since fuel economy
was an important element of the day. ed
 

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Not everyone will achieve this. Good tuning is what I believe to be one of the most essential factors, along with a compatible combination of goodies. :)
Exactly!!!

Just the amount of cubic inches.....by itself.....will not condemn you to poor gas mileage.

As mentioned, tune is important, as well as the parts used in the stroker motor.

For example.....at one point, my Impala had a high lift 224/230 cam with a 114 LSA (in my 396ci). My HP/TQ at the wheels was about 385hp/380TQ. But the cam had -4* overlap, my static compression ratio was 10.8:1 and my quench was about .041".

With 3.73 gears, I got 23MPG on the highway cruising at 70 MPH.....because all the components matched well.

BTW, Racy Roady.....you're driving the wrong car if you're concerned about MPG :roflmao:!!!

KW
 

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Discussion Starter · #6 ·
KW- About the fuel mileage on my Roady,on the highway I have acheived
about 25 mpg,yes it has a 2:56:1 rear gear,but I think thats pretty impressive for a big car. The Roady dosent see daily use,but at least two or three times a year we take it to our place in Maine,we usually have it loaded up pretty good with supplies ,clothes and whatever,so yes fuel mileage is important to me. Plus gas mileage is a good way to check how
well the car is running. ed
 

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KW- About the fuel mileage on my Roady,on the highway I have acheived
about 25 mpg,yes it has a 2:56:1 rear gear,but I think thats pretty impressive for a big car.......
Ed,

I'll be honest. I don't see how you can live with 2.56 gear. Those gears would drive me absolutely nucking futs :craz28: !

KW
 

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Discussion Starter · #8 ·
KW- I have a complete differential from a 91 Olds B-body wagon,It was a
trailer towing package car,so it has a 3.36:1 posi ,I know its a 3.30 something, that will eventually be installed in the Roady. When I had the trans re-done last year,I replaced the converter with an S-10 size unit.
so hopefully the combination of the new gear and converter will make the wagon a little more snappy. Then wait until I re-do the motor.Hopefully that will be sooner than later!
 

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Discussion Starter · #10 ·
Is that an 8 1/2" rear or a 7 1/2" rear?

KW
All B Body wagons from those years had 8.5 ring gears. Also the differential length is slightly longer in the wagons then the B body sedans.
Thats at least from reputable data that I have received. I have never
personally measured the ring gears or the differential length. ed
 

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Discussion Starter · #12 ·
I would say that a motor built with same quality light weight rotating assembly parts as stock and the same mild cam should achieve better MPG than stock, just from improving a motor from the 90s.

Throw as much efficient engine building practices into the motor and run a cam made for what you want. Should work quite well IMO.
Yep, My plan, to use good parts in the rotating assembly, good machine work practices,Align bore and finish hone the cyls with a plate for good
ring seal. Concentrate on reducing friction where ever I can and getting a custom cam that will concentrate on torque. The new motor along with my mild S-10 converter and the 3.36:1 rear that will be installed should make it a pretty efficient package and may even surprise a few cars at the traffic light. ed
 

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Engines have volumetric efficiency (VE).

A naturally aspirated (NA) stock engine has a rough VE of 85%. This is not always true but a rule of thumb.

So 85% of 350ci is 297.5ci.
A stock LT1 is consuming ~297.5ci of air.
This is why putting a better cam and heads on a stock bottom end of an engine gains more power. You are raising the VE.

So if you left everything stock on a stroked 383, at the same 85% VE you are consuming ~325.55ci of air.

Now you might think ah yes this engine is consuming more air therefore making more power and using more fuel. Wrong.

350ci is 91% of 383ci.
297.5ci is 91% 325.55ci.

All you did was increase the cylinder volume. You didn't raise the VE. What stroking an engine does it allows consume more air but you need the VE to go up to use that cylinder volume.
 
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