ls7 swap

[team39763]

I bet the aerodynamics really bring the fuel mileage down.  The weight will likely be less than a NBS (new body style) truck though. 
   Capt is correct on those prices, but maybe you could find some deals and cut some corners.  I bought a NBS radiator for $50(it does the job). You can buy used headers or manifolds for $300 or less, the rest of the exhaust won't be too bad if you don't get too crazy.  I ended up with the $100+ mounts, but my original mounts were like $30-$40 and that same company(carshopinc) now makes more than one configuration.  As far as the fuel system, you may be able to shave a few bucks off(not much) by running your own aluminum hardlines($30 @ Summit) and maybe an external Walbro pump.

[Captkaos]

I am not saying 100% highway of 25mpg it out of the question.  I would expect at least that for long trips.  My 305 got 22mpg on trips. (TBI) running about 62-65mph.

I am saying average is not going to be huge over the current 15mpg, maybe like 18 or 19mpg.
If you are looking for 25 in the city you are driving the wrong vehicle.

[78blackbeauty]

right now im saving for the swap. i have a job to get as and things but i need better mpg

[TexasRed]

Why not a used car?

[78 Chevyrado]

15-16MPG is really good for these trucks....  Just save for your swap.  anything else you pour money into will be a waste, MPG-wise.  Bum rides from people all you can.  been there done that.

[78blackbeauty]

im trying to get a used car for now but theyre kinda pricey up front

[Gandalf1969]

im trying to get a used car for now but theyre kinda pricey up front

Did you read my recomendations about planning the swap?  No offense but I assert that anyone thinking about a used car being pricey up front or doing this swap to get better mileage has not thought the cost of the project through.  It's not like you can put the engine in and drive it while you do the other mods.  Cooling, fuel, electrics, (LS7) oil system.... all need to be done to even get the truck back on the road.  Think it through - you may find your used car money sitting on an engine stand in your garage :-)   Consider that these engines are only getting cheaper also.

And what team39763 said is completely on the money - another LSx swap can be had for much less and get the same (as stock LS7) much cheaper.  Again, selling your LS7 you may end up with enough for your used car AND an engine package for your swap.  Put in a stock LS1/2/3/6 for now - get the other mods done to run the truck.  THEN you can do heads, cam, intake etc etc down the road.  That gets you your swap much quicker, your used car for DD and all for much more reasonable money IMHO.

YMMV.

[frotosride]

Ls7 is cool and all and does make a lot of power but as many have replied there is a big ls family that can do the same. My 1.5 cents...I've seen to many of those aluminum blocks cracked to ever want on in anything i want to punish..@ the last super chevy show there was one going for $400 except the huge chunk that was missing from #7 cylinder.. but hey it's your money.. like everyone has already told you plan, plan, plan....then do it some more. If you did wet sump would be easier to deal with and a little cheaper than buying all the dry sum parts in the long run.

[VileZambonie]

You just don't build a 73-87 chevy truck for good gas mileage. It's a lose lose situation if you're looking at it from an economical standpoint. The cost to try to squeeze mpgs by doing a swap like this eats up the cost of the savings if there is any. An LS7 swap isn't going to save you any money that's for sure. If you need good mileage try this...

http://seattle.craigslist.org/skc/ctd/1857446732.html