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Old 11-02-2011, 11:58 AM
luckyusaf luckyusaf is offline
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Default Which LS engine has the best horsepower to gas mileage ratio?

I am building a Pro Touring 66 Chevelle and wanting to put in an LS9 or LSA engine. After doing some more research there are not a lot of classics out there with these engines. I am curious as to why? Is it the cost factor? I want 600+ horsepower but honestly my main concern is fuel economy/gas mileage as this build is for my daily driver. I know the new vettes and CTS-Vs get decent mileage considering the horsepower they are pushing. To better some up my question...Which LS engine has the best horsepower to fuel economy ratio?

66 Chevelle
LS ?
Bowler 6L90E
Schwartz Performance Chassis
Moser 12-Bolt
RideTech Adjustable Coilovers
Wilwood 14" Rotors/6-Piston
Forgeline ZX3P 20x12/19x10
BF Goodrich Rubber
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Old 11-02-2011, 03:02 PM
rfrankb4 rfrankb4 is offline
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I think the main reason you do not see more of them is just the expense. For what you want that being good power and good fuel economy with a budget to support a LS9 it would be a good pick.

It seems to me that most people spending that much money want all out power and go with RHS or LSX blocks.

As to the 6l90 trans the main reason you do not see more of those is that they are far more difficult to tune and are significantly deeper as I recall forcing the engine to be moved higher up for pan clearance.

Your build would be undeniably cool and likely a great driver as the LS9 is very well engineered for reliability while still making 600+hp all with good fuel economy.

That said it seems a little silly to be talking about fuel economy when you are going to be around 35k in engine, trans, swap components, custom headers (going to need custom to get 2" primaries on the 66s unfortunately or even 1 7/8th)...

That is probably 20k more than a used LS2/3/6.0 and 4l80e that would have equivalent fuel economy. Or 15kish over the above with a maggy on it. sure you get better reliability but 15k buys a hell of a lot of gas. (thats an optimistic 400 thousand mile break even point if there ever would be a break even point between a cheep 6.0/4l80 and a LSA/6l90)

Last edited by rfrankb4; 11-04-2011 at 07:04 AM.
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