I just got this 1984 firebird trans am which comes stock with a 5.0 v8. I really want it to have an engine that has a lot more horsepower and is more modern. I want to put a newer chevy 405 in it and was wondering if anybody knew how hard this would be, how much it would cost and how long it would take. Thank you

Welcome aboard thirdgen.org.

"Newer Chevy 405"?

406 maybe? A 400 bored 0.030". Can you even make a 405 with an LSx engine?

405 horse LSx, maybe. I've heard of 4" bore block with 4" stroker crank in 402 and 408 versions.

A 0.030"-over 400 wouldn't exactly be "more modern".

maybe he means a big block 396

A 396 bored out 0.030" is a 402.

Isn't "more modern", either.

then im stumped, perhaps the thread starter should chime us in on what 405

Well i was actually just giving kind of a guestimate. I want it right around a 405 and i want it to be newer with newer technology. I just want it to be fast enough to beat almost anything on the road. lol

So you mean 405 HP? Gross at the flywheel (like crate engines are advertised - easy), net at the flywheel (like cars are rated - a little more difficult and more expensive), or at the rear wheels (a lot more expensive)?

Regardless of the answer to the above, it sounds like an LS1 is what would be best.

As to difficulty, read the LS1 swap sticky in the top section of this forum. It is more involved than a Gen I SBC swap (350, 383), and typically more expensive.

Cost - One of the more expensive swaps, especially if you don't do the work yourself. If you really want it to be faster than most stuff on the road and won't be doing the work yourself, budget between $15k and $20k.

Time - Some outfits get it done in a couple of weeks. I pulled the original engine and transmission out of my car in Feb '08, and I still don't have it running. At least the engine and transmission are in and most of the wiring is done. If I could work every evening and weekend on it, I'd guess I'd have it running before the end of July. But, that hasn't happened yet.