Best LS Block for Forced Induction?

**topgun1851** · 02-18-2008, 04:12 PM

Which LS series bare block (not internals) is the best for forced induction? I’m aiming for 700rwhp with no more than 15psi, but I’m thinking 10psi may do it. I’m debating between the LS2 and LS3. I’m hearing the LS7 is questionable being boosted due to the large bore size. Is the LS9 the same as the LS3 block but with different internals? What is up with the LSX? So which LS should I go with and would I be safe to bore it out?

rapter34 · 02-18-2008, 04:28 PM

im guessing the best would be if you got an iron block instead of aluminum.

**cailey37** · 02-18-2008, 04:56 PM

I know that the rumor is out there about the LSX blocks having some issues but I'm not too convinced just yet. I say if you can get your hands on one have it sonic-tested and make sure that everything is good to go and if it comes out good, build away. They are rated at 2500hp and have an additional head bolt on each cylinder to help with boosted apps. Your only other alternative is the Warhawk Block but it's like 3x the cost of a LSX. If it were me I'd buy a LSX block. In fact, my next motor build will be one.

**Frost** · 02-18-2008, 05:28 PM

That's a little overboard for 700rwhp.... a stock ls1 block is fine even past 800rwhp.

**cailey37** · 02-18-2008, 05:54 PM

Originally Posted by Frost

That's a little overboard for 700rwhp.... a stock ls1 block is fine even past 800rwhp.

Yea but with the boost required to get you there you will lift the cylinder heads. Trust me...I know...I run mine at about 15-16lbs of boost and with cometic head gaskets and arp bolts it still gets lift. An extra bolt on the cylinder head wouldn't hurt plus the LSX is going for about $1800. Just make sure you sonic test it.....supposidly, Bill Heard Chevrolet has four of the LSX's on hand......

**C&Cbird** · 02-18-2008, 08:50 PM

I know several people use the iron 6.0 block for boost also.

**Frost** · 02-18-2008, 09:46 PM

Originally Posted by cailey37

Yea but with the boost required to get you there you will lift the cylinder heads. Trust me...I know...I run mine at about 15-16lbs of boost and with cometic head gaskets and arp bolts it still gets lift. An extra bolt on the cylinder head wouldn't hurt plus the LSX is going for about $1800. Just make sure you sonic test it.....supposidly, Bill Heard Chevrolet has four of the LSX's on hand......

I have over 8000 miles of HARD around the block, showing off, etc at 17psi on pump and meth with my HKE stock-inch forged motor. The setup made 600rwhp at 10psi well before the tuning was refined (AFR 10.3-10.6:1, 16deg timing) and never went back to the dyno. The tune settled on 17psi and 19deg of timing and has NEVER pushed a bit of water at all and has been driven hard. GM MLS gaskets, ARP 12pt studs, TEA stg 2.5 ported OEM castings. My buddy David made 852rwhp with a similar setup and ALL PRO heads, NicD just made 800-something on his stock-inch LS1 with AFR 225s and only 16psi. This is just naming a few.

If you are pushing water at that level and are at 9:1 or under, you need to back the timing down in the higher gears (possibly all, but it needs to taper down by time-in-boost), you can do that with your BS3.

**C&Cbird** · 02-18-2008, 10:10 PM

I noticed a difference between the two, he said he has head bolts, you have head studs. That will make a difference.

**Frost** · 02-19-2008, 05:19 AM

Studs are standard fare at that level of boost. Regardless, the question is about the block. Iron blocks are heavy, I wouldn't use one until I needed one.

**cailey37** · 02-21-2008, 09:34 AM

I've known people that have their blocks machined out to accept 1/2" studs.....costs a couple hundred dollars but well worth it from what I'm hearing.

**TNTramair** · 02-21-2008, 10:22 AM

you get mixed reviews from people all the time with differant set ups in referance to pushing water. there are guys running 20+psi dont push a bit of water and on the flip side, people running 14-17psi push water....from 346 to 427ci so i personally dont think it has all that much to do with the block/heads or headgaskets your using...possibly tuning/timing issues???

mine wont see over 15psi as its just a cruiser and i dont wanna go all out. im running a TSP402 with GM mls gaskets, ARP head studs and L92 heads off the shelf. ill have to wait and see if i run into any water issues after its run for awile but im pretty confident it'll be ok.

**Redphoenix1998** · 02-21-2008, 10:42 PM

I know that the stock LS1 block can handle up to 950 hp and the largest bore size with stock sleeves is 3.905 fromn 3.898. Iron is definately a stronger choice but studs for the mains and heads, a girdle, MLS gm gaskets, a good crankcase ventilation system and you should be good to go.