So this might sound dumb to many of you but I am thinking of building a FF Cobra and putting in an LS motor. I currently have a nitrous 408 Z06 (for the HP wars) and this cobra would be a car to cruise to the lakehouse in, etc. I would want a V8 because everything else sounds bad, lol!

What is the best combo to run for good mileage and longevity? I am thinking of a smaller displacement engine, destroked, small bore, etc but something that can rev up if need be to have fun (some twisty roads along the way). No FI, no big cam, no nitrous, etc.

Can I build a 327? low 220's cam.... Thanks.

 

Just put a stock crate motor in. 5.3 liter = 325ci

 

why not go with a LS3, just a small cam in it and upgrade the valvetrain to spin to ~7000 rpm? you would be a lot happier with bigger cubes, anyone would, in a light chassis it will get upper 20's on the hwy anyway, thats pretty good for what could be an easy 450 whp car. the only reason to go small cubes is for sanctioning body rules or a lot of boost. All the aluminum motors weigh the same, might as well get the most out of it. Throw a lightweight flywheel on it and rev it to the moon! youre going to beat on the smaller motor harder to get the car moving in the twisties, big cubes for longevities sake

 

If it was me, I'd buy a GM crate motor. You can get an LS1, , LS3 or LS6, complete with intake, injectors, ignition, water pump, etc., from Scoggin-Dickey for between $5600 and $6700. It's an incredible deal. See this page: http://sdparts.com/catalog/crate-engines

The 5.3 is the same stroke as the 5.7 and 6.0, smaller bore. Better economy but hard to get valves in it to breathe up top. The 4.8 uses the same bore as the 5.3 with a shorter stroke.

Me, I'd go with the LS6. The 5.7 seems to be the "sweet" combo on this engine. Yes, the bigger ones make more power, but there's definitely an economy hit. In a Cobra replica I think the 5.7 would be plenty.

GMPP also offers complete electronics kits to hook it all up for about a grand, and also complete front drive accessory kits. Both are intended for street rods and swaps into muscle cars, so they will be perfect for you.

 

LS2 block, 4.8 crank, lightweight pistons and rods, and some heads optimized for flow at high RPM would be a blast... I seriously considered it for my 67 camaro, i wanted that Z28 302 screamer feel.. anyways..

LS2 block, 4.8 crank, 4.8 sized rods (6.278)
3.27 stroke X 4.006 bore = 329 CID

it's still low displacement (fuel economy), and the big plus over a standard 5.3 is the ability to run much bigger heads and valves.. and the short stroke long rod makes it rev up very quickly.. everything can be done with off the shelf parts, too, since the deck heights are all similar

 

The 2004 CTS-VR race car ran a 4.13 x 3.27 bore x stroke, and made 500hp at 7200...

high compression of course

 

Thats a cool idea, what heads and intake would you run on there?

Interesting, that would be a fun ride for sure!

 

If you want to spend a lot of money building an engine go the larger bore with 4.8 crank, but why bother? In any case I'd use an (aluminum block) LS1. Do you really want the extra 80 lbs or so up front?

For a 7000+ runner, buy a used LS1 from a Camaro, have a good valve job done on the 241 heads, or on some 243s if you can score a reasonably priced set, put in good rod bolts, run an Edelbrock or GMPP single plane, and have it and the valvetrain done by someone who regualrly does successful 7500+ rpm LS hydraulic valvetrains using stock lifters and rockers on carbed engines.

The Ford headers might work with minimum modifications. The primaries might be a bit small on Ford headers (because they don't make enough power ). Is FF offering LS engine mounts yet?

With a cam in the 220s power above 6500 might be restricted. I'd let my cam guy choose duration, etc based on the power band, idle characteristics and driveablility you want.

OK, if you just like to spend money, start with the 3.900 bore LS1, add the 4.8 crank, get some [***] 243 heads (can't use a non-sponsor name), ported manifold and HR valvetrain and have a 7000++ 5.1L that will pull you socks off. It's about 5 grand+ more than the easier 5.7 L that I described. Is it worth it?

Good luck, and have fun!


Jon

[EDIT] Higgs, I like your screen name. Are you hypothetical also?

 

I was planning a FF Cobra build (before the recession) with a stock LS1 and 243 heads. It is lightweight, revs high enough, reliable, and very cost-effective. Plus it has plenty of power for a car that light.