LSX376-B15 or TMS 370/408 fully forged?

[vhawk]

I blew up my engine and I need a new one now.


Which one one would you choose (B15 is ~2k cheaper)?


I am planning to run it with a base AGP TT kit and stock driveline to make 600-650whp until I upgrade my driveline and fueling. After that I might shoot for 800-1000whp.


One of my concerns is that 408 will produce too much power for my clutch and tranny to survive even with weakest 4.5lbs springs. Will it?






LSX376-B15 specs:


Part Number: 19299306
Engine Type: LSX-Series G en IV Small-Block V-8
Displacement (cu in): 376 cu in (6.2L)
Bore x Stroke (in): 4.065 x 3.622 (103.25 x 92 mm)
Block (P/N 19260095): LSX cast-iron with 6-bolt,
cross-bolted main caps
Crankshaft (P/N 12603616): Forged 4340 steel
Connecting Rods (P/N 12607475): Forged powdered metal
Pistons (P/N 19259381): Forged aluminum
Camshaft Type (P/N 12638426): Hydraulic roller
Valve Lift (in): 0.560" intake / 0.555" exhaust
Camshaft Duration (@0.050 in): 210° intake / 230° exhaust
Cylinder Heads (P/N 19201805): LSX-LS3 rectangular port; with
“as cast” 68cc chambers and
6-bolt attachment
Valve Size (in): 2.160 intake / 1.550 exhaust
Compression ratio: 9:1
Rocker Arms (P/N 12569167 int): Investment-cast, roll trunnion
Rocker Arms (P/N 10214664 exh): Investment-cast, roll trunnion
Rocker Arm Ratio: 1.7:1
Recommended Fuel: 87 octane
Maximum Recommended RPM: 6,600
Reluctor Wheel: 58X
Balanced: Internal





TMS 370/408 fully forged specs:

Blueprinted GM block Seasoned core

ACL coated racing main bearings

ACL coated racing rod bearings

Thompson Motorsports single piece racing cam bearings

K1 forged crankshaft with reluctor 3.622" or 4.000"

Manley H-Heavy 4340 forged connecting rods with ARP 2000 rod bolts

You choice of Diamond or Wiseco shelf piston with GFX file fit rings

Steel ring set

Frankenstein Thompson Motorsports edition M311 heads

11* CNC ported aftermarket casting 6 bolt heads

Extreme duty stainless intake and extreme duty solid exhaust valves

Billet Rocker Rails

.660" platnum springs

Thompson Motorsports custom ground Camshaft

Thompson Motorsports custom length Chromoly pushrods

Stock replacement bolts ARP HEAD STUDS ADD $366 OR $400 FOR 6 BOLT

Melling Select High pressure oil pump

Billet adjustable timing set

Thompson Motorsports high RPM lifter set

Trunion Upgraded Rockers

GM MLS head gaskets

GM lifter trays

Thompson motorsports Professional assembly and 12 month unlimited mileage warranty

[Greenhornet2]

I don't know enough to give you an opinion on which engine. As fars as what your driveline will hold it depends on what you are doing. Stock will hold up to 800-1000whp on the street as you will spin. Go to the track with stickies and you can break stuff at 500whp and it gets easier the more hp and harder launch you go with. Eliminate wheel hop and preload the driveline before launch helps. Shock, and wheel hop kill things.

[RupertPupkin]

No dog in the fight, for I’m in the same boat as searching for a short block for my FI build. I did see TMS with a 408 w/ rotating assembly for sale for 4250$. Plus your heads are what 2500$-ish. Idk if it’s going on still, but I emailed them yesterday. That warranty is always nice..


Too much power... lol

[Greenhornet2]

I would say, save your money on heads stock ones are good and cost/hp is really high on aftermarket, FI really doesn't need heads until you're for a lot more than 1khp

[vhawk]

I am not sure my heads and cam are still alive and I would not trust local shops to check, repair and assemble everything back because they have very little experience with Camaros :( They are also willing to ask about 1k for assembly.



So I think I need a complete long block.


Maybe I could ask TSP to put cheaper ls3 heads, those would be 1k cheaper.

[Vegas Bound]

I have a LSX376 B-8 and make 757 rwhp through a PD blower and 4L80e. Using accepted ratios, that's close to 900 hp at the crank. No issues for years.
If you are planning on going TT, save some money and get the B-8.

[dreksnot]

TMS. Iron block for sure as you're likely to keep wanting to bump the power more, then more. Fuel systems definitely first choice to improve over heads. Driveline is essential to be able to put the power down without breaking stuff. Or, just power-up and you'll be replacing those items one-by-one as they get shredded.

[vhawk]

Originally Posted by Vegas Bound

I Using accepted ratios, that's close to 900 hp at the crank. No issues for years.
If you are planning on going TT, save some money and get the B-8.

Isn't it closer to 1000 because the blower takes some power to spin itself?


900x0.85 = 765, so it's only for the tranny losses accounted.


I've been thinking of B8 but from what I read here and other forums it wouldn't hold more than 14psi and it starts pushing water at that boost level.

[Vegas Bound]

Originally Posted by vhawk

Isn't it closer to 1000 because the blower takes some power to spin itself?


900x0.85 = 765, so it's only for the tranny losses accounted.


I've been thinking of B8 but from what I read here and other forums it wouldn't hold more than 14psi and it starts pushing water at that boost level.

No, it's 900ish. Blower, accessories, trans, driveline account for about 15% loss. I have 17 lbs of boost. I do have plans to swap for 6 bolt heads in the future. My current build is 7 years old with no issues yet.

[caper]

not sure on the engine, but my trans is fully blown out, never been on the track, no stickies...just 700rwhp...wasnt much good left in the trans.

[Vanishing Point]

I started with an LSX B-8, overtuned it, bent a rod, rebuilt it as a forged 409. As it fried things, I replaced the tranny, rear end, pumps, injectors, E-85, pulleys, on...and on... and very soon a new Kong blower.

I never planned on getting in this deep. It's an addiction. You’ll want more. If I ever do this again, I realize that now. Just go all in on whatever component you’re doing. B-15 won’t be enough. Build it while it’s out of the car and make it cheaper by doing it right the first time. If that means you have to wait longer for the finances on the next mod, so be it. You don’t want to half step the next mod either. May seem like it costs more and takes longer going all in, but that’s cheaper and faster than going half in on everything, then replacing it all in later.

And building it solid enough not to break is the cheaper option than over tuning a lesser set up.

That’s just my opinion, based on how I am, and from what I see, how many others are as well. But maybe you can stop with lower power. If you want an LSX, you’ll probably be eventually going all in. Be honest with yourself, and make the decision that best suits you, whatever that may be.

[dreksnot]

Originally Posted by Vanishing Point

I started with an LSX B-8, overtuned it, bent a rod, rebuilt it as a forged 409. As it fried things, I replaced the tranny, rear end, pumps, injectors, E-85, pulleys, on...and on... and very soon a new Kong blower.

I never planned on getting in this deep. It's an addiction. You’ll want more. If I ever do this again, I realize that now. Just go all in on whatever component you’re doing. B-15 won’t be enough. Build it while it’s out of the car and make it cheaper by doing it right the first time. If that means you have to wait longer for the finances on the next mod, so be it. You don’t want to half step the next mod either. May seem like it costs more and takes longer going all in, but that’s cheaper and faster than going half in on everything, then replacing it all in later.

And building it solid enough not to break is the cheaper option than over tuning a lesser set up.

That’s just my opinion, based on how I am, and from what I see, how many others are as well. But maybe you can stop with lower power. If you want an LSX, you’ll probably be eventually going all in. Be honest with yourself, and make the decision that best suits you, whatever that may be.

up

[Greenhornet2]

Originally Posted by vhawk

Isn't it closer to 1000 because the blower takes some power to spin itself?


900x0.85 = 765, so it's only for the tranny losses accounted.


I've been thinking of B8 but from what I read here and other forums it wouldn't hold more than 14psi and it starts pushing water at that boost level.

Power at the crank is power at the crank it doesn't matter what losses the are. Turbo 900 crankhp same as pd blower 900 crankhp the engine is stressed more to get the pd blower there yes but the output is the same. The turbo may only need 9 psi to get there where as the PD needs 12psi if that makes sense. Stock stuff will hold about 14psi before pushing water by the arp head stud kit will help that, not sure what the limit is with those then there's doing larger studs too. I'd just get a short block at that point do the stud kit and buy a set of ls3 heads.

[bct10985]

There is a lot more to it than just boost pressure.