Night Hawk

What would your L98 motor rebuild (in detail) consist of to get you the most powerful motor using the absolute least amount of fuel over stock. Would there be anyway to actually rebuild a L98 to make more power AND be more fuel efficient, if so definatley tell me as I do a lot of interstate driving and my 1988 L98 GTA is in need of a motor rebuild.

zippy

boy, very good question. a rebuild like that just takes using modern equipment and technology. long rods, higher compression, fast burn heads, strong ignition, etc. good start would be 6 inch rod 355, around 10.5 or 11.0 to one. good head would be fast burn for it's efficient chamber which allows higher compression and has great swirl for complete combustion. the large rods decrease rotating mass and also allow for better combustion. lightweight piston choice would help with total seal type rings. could also use vortec heads for the fast burn type chamber, but the fast burn aluminum heads save weight. beef the ignition way up and smoothen the intake ports to make everything flow easy. headers with low restriction exhaust and converters to help keep piston stroke resistance low. good cold air intake at the air cleaner end with low restriction all the way. cam choice will be ok to go bigger, but carefull on duration numbers. roller rockers with high ratio help since high lift only increases air speed. many other tricks, but just a few to start with. anyone else??

Night Hawk

Lets add in the fact that this motor will idealy like to run on 87 octane pump gas...therefore reducing the compression aspect, keeping it under 10:1 compression I would say. The car also has 3:73 gears.

Ed Maher

I just want to add that in an ultimate efficiency build-up, iron heads are the way to go. They keep more heat in the combustion chamber, which means more energy is in the power stroke, and less is wasted into the cooling system.
...ed

Night Hawk

How much more efficient are the iron heads...are we talking fuel efficiency, like would I notice a MPG drop if I put on aluminum heads?

FastBroker

You'll see more mileage increases from less throttle input. Just use about 9.5:1 CR with a mellow cam. Call COMP cams and have them recommend you a total setup for what you want. They are great guys. Post what they tell you here???

Biochem

Dude, if you're looking at getting 50 mpg, then get a Metro! If you want an engine that is hovering around the 400HP mark, passes emmissions, and still gets 25mpg on the highway, then look at my sig..

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

zippy

there was a test done a while back in either car craft or chp on one like this. they used 87 octane and ran either just under 11.0 to one or right on, don't remember which. aluminum heads are going to be more efficient. can just increase compression a touch to make up for the lower efficiency of aluminum, but the extra weight savings makes up for the milage. this is why about all new vehicles have them. also allows higher compression to make up for some of the efficency difference.