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GreaseDog
05-04-2012, 05:34 PM
My buddy is looking at putting a Gen III engine in his 74Firebird. He wants to stock to 400 ci, since the car is a Formula 400 clone. What block and heads should we be looking for to start this build?
907 Chevy
05-04-2012, 08:57 PM
My buddy is looking at putting a Gen III engine in his 74Firebird. He wants to stock to 400 ci, since the car is a Formula 400 clone. What block and heads should we be looking for to start this build?

Forget the 400cid limit and build this...

http://www.popularhotrodding.com/tech/1112phr_racing_engine_design_6l_ls_chevy_motor/viewall.html
GreaseDog
05-04-2012, 11:02 PM
It's a Formula 400 clone... Not a Formula 425 clone...
Zero260
05-05-2012, 07:56 AM
Wtf, no small block? lol

Whats the budget?

If he goes with a 6.2li block, it can be dry sleeved to 4.125. 6.2" rods with a 3.75" crank will give him the 400 cubes.

Any other block is going to have to be sleeved. And I'd find a ls1 or l33 block for that.

No cheap head option with a bore that big. I'd probably look at some ls7 style heads.

A lsx 400 in that car would be cool. Not sure if its worth all the money. He could boost a 6.0 pull out for a lot cheaper. Just saying...
GreaseDog
05-05-2012, 10:53 AM
Not looking to keep the bore and stroke the same necessarily, just the overall cubes. Looks like we can come close with a 3.9" crank in a stock 6.0 block,i came up with 398ci.
Zero260
05-05-2012, 01:54 PM
I've never seen a build with a 3.9" stroke and a stock bore. Definately different. What kind of power is your friend wanting to make?
Doober
05-05-2012, 02:56 PM
A 4" stroker crank would give 402 with a 4" bore. Low end torque would be really good too thanks to the longer stroke.
GreaseDog
05-06-2012, 06:08 PM
no idea what kind of power output we're looking for, but it should be stout.
Doober
05-06-2012, 06:25 PM
With the flow capabilities of an LS head I figure lots :D
RPMbagged97
05-06-2012, 07:22 PM
A 402 is very common in the boosted LS engines. I dont know why he is so worried about the cubes matching, when you can just make up any number and nobody will know the difference by looking at the outside. It could be a anything from a 4.8 to a 6.2 and it will look the same from the outside.
GreaseDog
05-06-2012, 08:11 PM
A 402 is very common in the boosted LS engines. I dont know why he is so worried about the cubes matching, when you can just make up any number and nobody will know the difference by looking at the outside. It could be a anything from a 4.8 to a 6.2 and it will look the same from the outside.

same reason we're kicking around the idea of a 390ci Windsor stroker for the '67 Fastback Mustang... stick badges on it that say 390ci, and when people ask if its a 390, you can honestly reply "yes". they don't need to know that it's not a 390 Y block.