We've done a large number of those original LS-5's for the stick-appearing crowd, built right they will produce 500+ HP with keeping the 100% "look".
Stock heads, intake, exh manifolds, valve covers, and Q-jet carb. All 100% stock-appearing, but also an all-roller build, lifters and "real" roller rockers!
The photo below is one we did a while back, made excellent power considering the "restraints" on the build??
Thanks, Gary in N.Y.
P.S. I will take a 4.250" crank to pull it off, with some light-weight pistons and ring pack! We use Comp Cams for the hyd-roller setup! The heads get some SBC intake valves and some Mopar exh valves, both with .343" stems! Heads end up flowing 300/int and 200/ exh, no porting!
I also have a 70 LS-5--M/22, that I ordered. Did a frame off, Rebuilt the engine to basic stock specs. YES,, It will still give you a big thrill when you stand on it. Mine is close to stock from the oil pan to the 05 Q-Jet, Yours has an 04 Q-Jet.
With a fresh rebuild (0.30 over) the " Big Inch " LS-5 will give you SMILES of fun......:thumbsup:
Bob
To me the best thing you could do for that LS5 is put a Comp Cams 268H or 280H in there and it will make a lot more power than the GM cams did. Rework the Q-jet and tune the Ign and even with stock manifolds should go pretty good.
I would absolutely take Shevls' advice, put the original motor on a stand and build a good street motor, then you'll never worry about it. Good BB core motors are a relatively cheap starting point. Some day you'll be glad you did.
If you participate in "judged" shows you won't stand a chance with a non-original unit.
Every one of our 100% stock-appearing builds will pass in any shows!
Thanks, Gary in N.Y.
P.S. We can actually mill the decks (as much as necessary) in single pass on BOTH sides and never remove the original stamped numbers, it's easy to do for us!
Save the 512 block and stash everything original to the LS5 motor. Look for a 289 block (2 bolt is fine), cast crank, Hbeam rods and forged piston to produce a 496ci. Stick with a hydraulic roller and roller valve train. Easy 550+ drivable horsepower. Avoid the temptation to install too big of a cam and lose driveability. Search 496 build here on TC. lots to read up on. Then dress it as an LS5 in the car.
If your a numbers guy, keep original engine in the car. You would be surprised at the number of people that look at the numbers on the block at shows or even cruise nights. (if that is even a concern to you) There is always somebody looking at my LS6 for the numbers. Yes you can keep it on the stand but its just not the same to me as having the original engine in the car. I drive my car a lot and run it thru the gears, I don't baby it nor do I abuse it. I do enjoy the car like it is was intended for. My .02 cents
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