If money werent a problem would you prefer the ls3 427 stroker from BlueprintEngines that uses around 8psi to make 800hp or would you go with a lsx376 plus magnuson at 14-15psi to make similar hp/tq?

 

I'd do the LSX376 without question as it's a way better foundation to build on should you decide to go bigger. If the LS3 427 was re-sleeved to a 4.125 bore than I'd maybe go that route for a mild FI build but the LSX block is a triple digit capable contender.

 

You'd only need 11psi theoretically on the LSX376 to match the 427 on 8psi. LSX376 with a 2650 instead of the 427 with older 2300 is the way I'd go.

 

What kind of differences in power band and drivability are there when you have one engine relying more on displacement and compression vs the other relying more on higher boost? As for what @01CamaroSSTx said are there issues with those LS3 strokers having durability problems?

 

 

Generally more cubes will drive better with more responsive part throttle....but if the method of boost is a roots/twin screw type blower then torque is not a problem even off idle.

 

Ask 100 people if 4.125 stroke in a stock sleeve LS3 is a good idea or not and you'll get a 100 ideas why yes or no! I personally wouldn't be too keen on it but what do I know, not much. That thing is $23k if you really want a big c.i. engine and are willing to spend $23k you might contact a reputable builder and see what a Dart or LSX blocked 441 would cost, pick some good heads, put a Maggie 2650 kit on it and it shouldn't be over $23k...might not have show car looking billet accessory drive on it though.

For the 376, yeah with 10-12psi and if you have decent rear gears, it pretty much feels like you're in a top fuel dragster unless your car is real heavy. I have a stock long block LS3 with a non-intercooler TVS2650 on it running avg 11-12psi, 4.11 gears, th350 trans, 31" tires, and it is berserk from the tiniest throttle input from idle. My car is only around 3k lbs though so Im sure any heavier and it would get a lot tamer. My cam is a summit comp ground something like 234/246 113, I think a decently big cam in an LS3 is pretty decent just by itself.

But if you're looking to spend money, like I am always dreaming of, here would be a really nice setup:
Dart 441 (I'd confirm the pistons are 2618 first but Ive been eyeballing this for a while ): $6400 Dart 441
AFR or TFS LS3 heads: $2800
Holley Term X: $1000 <--what a deal!
Maggie or Edelbrock 2650 setup: $7500
Accessory drive: $800
Cam/pushrods/lifters/rockers: $1300
good balancer: $300
​​​​​​really good oil pan and pump: $700
Bosch 210 injectors: $650
Coils and wires: $300

Damn that adds up, over $20k!

For that kind of money, a LSX376 + Maggie or Edelbrock blower kit is a bargain and it would be pretty amazing if anyone was ever disappointed with that it would be surprising! LSX376 long block is a bargain esp coming with those pretty damn nice heads, the Blueprint deal is kind of sketchy, no brands given on the rotator, etc.

 

Thanks for the info. So you think the lsx376 + maggie2650 should put 750+ to the crank? I would have an engine builder build me something but cant seem to find one around here. Should I get a ls3 instead to have an aluminum block? I know these are vague questions, Im just trying to get 750-800 hp and be streetable without breaking the bank.

 

Yeah with a big cam would probably take 7-8 psi and with the cam that comes in it more like 12 psi, very rough estimates!

If you really really don't think you'll want more than 750-800 chp then I'd do the LS3 crate engine to save 100 lbs. Probably more like 150 lbs, I think the LSX blocks are about 40 lbs heavier than regular LQ4/LY6 blocks....might want to investigate that.

 

What car is this engine going? Trans and rear gear, tire? Just wondering!

 

70 Nova build in progress. Planning for t56 and ford 9" 3.89 ratio, 315s, torque arm suspension. Are there any LS3 crate long blocks I should know about? Been searching and not finding much,

 

Ah nice manual!
https://www.jegs.com/i/Chevrolet-Per...20382/10002/-1
https://www.summitracing.com/parts/nal-19432422

There are a few part numbers for the stock LS3 long block, search Jegs, Summit, Pace, SDPC, GMPartGiant, seems to be 4999 with free shipping but you'll have to check to see who has one in stock! Lots of out of stocks!

Kind of the deal of the century but will need a bit to finish it, coils, manifold, accessory drive, etc, can use mostly cheap factory stuff!

 

I was looking at those but wasnt sure if they can handle boost and 800hp. Im not looking to necessarily save money, I want it to be built right, but if that will do then I am all for it. Nice that its aluminum block too.

 

I would go with the lsx376. Its a 6 bolt block with far more potential IMO

 

Hmmm. Money no object.... FOMO.... You buying this end of Jan?

 

Gonna buy as soon as I decide what I want. Car is not ready for an engine yet, so not a huge rush, but looks like some of these crate engines take a while to get.

 

If I wanted to get the LSX over 800hp, what do I do? Cam it, port the heads and turn the boost to 15psi? Should get me around 1000hp?

 

Turbo is the best way, Ive done a lot of turbo setup and a couple of TVS setups and turbo is way easiest to make crazy power. Ive made a hair over800/800 WHEEL hp/tq with a cammed LS3 on 16psi with, one setup was a single PT7675 and other setup was two S257 turbos.

You can make a ton of power with a TVS but the belt becomes more and more of a pain as you start getting up to 800whp....with turbos its just super easy. Not trying to talk you out of a TVS but just giving options! If you want more and more power with a TVS start off with an 8 or 10 rib setup. The other thing is blower really does make less power per pound of boost, it becomes really obvious when you do both on the same engine a few times! Come to think of it this poor LS3 I have has been put through the ringer and no issues haha Ive had a few setups on it TVS2650, single PT7675, twin S257, single S594, I'd say with the S594 it saw 1100chp/950whp quite a few time and no issues, other than bent a rod when the S594 spiked to 28psi a few times accidentally because of crimped off wg line, my fault totally. That was probably using 1300chp worth of fuel after looking at the logs. Actually that killed a crank bearing too, full disclosure, stock long block LS3 does not live at 7500rpm and 28psi, at least not with my tune. It will live on 16-18psi forever with a good tune, and thats 800whp/wtq. That'll take a 3500 raceweight car to 150mph in the quarter.

I jump between setups ALOT, always looking for the best street driver that makes mind blowing power, I think the conclusion for me is always 376 or bigger, LS3 headed, bigger than you'd think cam, and single S476 sxe with 87mm turbine. That would make an easy 1000whp through a manual if you ever wanted to go that nuts, but would still be super responsive and work just fine at 600whp. B15 if you really want to drive around with 1000whp or LS3 if you are ok limiting yourself to 800whp and can run decent fuel.

You'll get a million opinions on what is best. One thing I'll say that isn't an opinion, this is a fact, 800whp/800wtq with a drag radial on concrete is f'ing fun as ****, never gets old in a 3500 lb or less car haha.

 

I’m not looking to go down the turbo rabbit hole. So you’re saying for 800chp I could use the GM LS3? Even with the nodular iron crank? Would I want to cam it as well? Other option would be to buy a new ls3 block and find a builder. If I started from scratch like that would I wanna leave it at 6.2 or stroke it up some?

 

Sounds like everyone has provided the right advice for 800hp and you don't want to take it.

A stock bottom end 5.3 with a turbo will make 800hp all day long (with the right turbo) but the real question is who is tuning it and what ecu ? If you don't have a good ecu and good tuner, it doesn't matter what you build.