Just wondering what you 402+ci LS1 guys with street engines are getting for mileage. I stopped thought about things and realized:
I have a couple brand new LS1 cranks and a 320 mile crate motor I can sell.
ported L92's cost about the same as a decent set of CNC LS1 heads.
the intake set with injectors and throttle body cost less than the LSx alone.
I can build alot more streetable and I have all the supporting mods.
oil pump/lifters etc cost the same.

So the only thing I will really have to shell out that I wasnt expecting is a rotating assembly. I figure I can put one together and balance it for about $1700. Now if I keep a pretty mild cam in an LS stroker, with some 3.73's instead of something more steep like 4.10's with an M6, what do you think the cruising mileage would be?

I was told I will get around 27mpg with a decent heads/cam/intake setup. I am at 33 right now with an M6, cam and exhaust only. If I can get something fairly close then building a bigger engine would be worth it to me. For the most part I wont be beating it too bad.

 

Well my theory has always been, if fuel mileage matters leave it alone.

The very minute that I went heads cam on my 'bird I quit checking mileage.

 

I think gas mileage in an engine you plan to modify is still fairly important if you're going to drive it regularly. An engine setup that produces 15mpg vs. one that produces 8-10mpg city may steer somebody away from that decision. I think this is especially important if you haven't done the modifications yet and you're just pushing the idea around. It's just basically shopping around, much the same way you would compare gas mileage of one vehicle vs. another to aid in your decision to purchase it or not.

 

My 408 gets around 26-27 mpg highway.

I don't think 25 mpg on most LSx builds are out of the ordinary, unless you're going with a huge cam with alot of overlap.

 

Well here's the deal. I have the chance to buy a 4.125 bore 6.0 block. I'm thinking of doing it for the money involved. I could put a 4" crank in it and it would make for an easy 427 cubes. Aside from the shortblock, the rest is money that was to be spent anyway, which would have went on 346 cubes.

If I do it, which is still an if, it would be with a fairly mild cam. That way I have a nice comprimise of driveability and power. To get the same power with 346 cubes I would have to go a little bigger than I would like on the cam, and from what I gather, I would get roughly the same mileage. Nice thing is, more power is just a cam swap and a tune away.

 

God...you've got more cubes and obviously more power than my LT-1 and yet still get better gas mileage. LSx's suck!

 

Well, I have 3.42 gears in the car. If I had something like 3.90s or 4.10s, I'd probably get around 24-25 mpg.

Mike

 

Still, 24-25 with 530 hp to the wheels! I might be getting a hair better than half that with my mods and 3.73's and I'm getting 25 on the highway. LSx's suck!

 

think that sounds a little low as I hear people talking more like 28.. maybee need a tune


also, what do you guys think a stock LS1 say 2002 fbird would get if the only mods I did were a big cam + good flowing intake / exhaust??

think it could still hold something like 26,27 mpg?

 

Well I'm a little bit out of my element in this section of the forum. I'm referring to my 97 LT1. 25 seems to be about as high as I've seen, especially with the gears. I haven't had the car out on the highway since the LT install so I can't give the new mileage numbers. I was just jealous of the LSx's gas mileage figures, even with such high HP numbers.