I have been following this board for a while now and am getting ready to purchase a cobra replica to put together. I am more than likely going to go the FFR route. My plan is to use a similar set up LS1 to the one that powers my Camaro. A cam and heads LS1 (more LS6 now) with all the bolt ons made 420rwhp and 400rwtq on a mild tune.
But one thing I have seen here is alot of misconceptions about the LS1/6 powerplant.
Oiling issues: this was a problem 98-00 motors. It can EASILY be fixed with a ported
oil pump for about 120.00. I would recommend a ported
oil pump on ANY motor that you plan on using. The extra
oil pressure never hurts anything.
Differences between the LS1 and LS6:
The only differences between the LS1 and the LS6 is that the LS6 came with higher flowing heads and intake. The cam was also slightly larger than the LS1. The heads are the key though, you can get as much as 20 more HP out of a good set of ported LS6 heads than you can with a set of LS1's. the PCV system on the LS6 is also far superior to the LS1.
The LS1 heads are a direct decendant of the NASCAR 18 degree heads. The factory heads flow fairly impresive numbers right out of the box, put after a good port job they can flow insane amounts of air. My MTI Stage 2 LS6 heads flowed 317 @ .600, thats alot of air.
Cubic inches:
ALL LSx based powerplants are 346ci. I have seen some pretty crazy ci sizes get thrown around. the new LS7 motor that MAY be used in the C6 vettes will more than likely be a 6.0 litre motor.
There is the C5R block that comes from the factory with a 4.125 bore that was built specifically for the Corvette Le Mans cars. You can buy them through ANY GM dealership at the meager price of 8,000.00 and thats just the bare block!
You can however bore and stroke your block out as far as 46x but I dont recommend that unless your car is a trailor queen. The are a number of companies out there that can provide blocks that already have been bored out. 2 of the big ones are MTI and ARE.
There are a number of aftermarket comanies that specialize in LSx performance now. And they make some great products, but you do have to pay for them. LSx parts are far from cheap. You can figure paying around double for LSx parts over standard SBC/SBF parts.
The only real "weak link" in the LS1/6 motors is the connecting rod bolts. but for a street car that isnt going to see much abuse its not a concern. the factory crank shafts can handle as much as 600hp before seeing issues with them.
the biggest "choke" point in the motor has been the intake manifold, the newer LS6 intake did have some good improvements but guys going into the BIG hp numbers are even running out of air with the LS6 intake. A company called Fuel Air Spark Technology (F.A.S.T) has developed a modular intake manifold that is supposed to show huge gains above the LS6 intake all the way across the powerband. this intake will be available late NOV./DEC.
If your looking for "crate" engines, I would honestly suggest EBAY. You can find low milage LS1 motors for reletively cheap prices.
I could go on forever about these motors. They are by far probably the best and most advanced engines available today in a factory production car. And tuning them is easier than any other motor out there today. I am not the knowlege guru about these motors but I have had a few of them apart and done alot of playing/tuning with them.
Here is a link to my little race car. Hopefully very soon there wil be a LSx powered FFR cobra right next to it!
http://www.imagestation.com/album/?id=4291599213