Ok guys I have a L98 block out of my 89. It is bored .30 over with splayed 4 bolt mains and the deck is o-ringed. I was going to do a turbo setup with it, around 12-15 pounds of boost. I am now considering going with a LS motor to do the same thing. Any pros or cons with the LS motor? Any major internal mods that would need to be done? Kind of testing the waters and getting opinions from the guys that have done this.

 

Would the sbc be EFI?

 

I am wanting to go that way with it. I took all the tuned port stuff off while ago and was running a carbed motor. I removed all the efi wiring harness as well so all that would have to be put back in.

 

I would run the sbc since you already have it.

 

I just wonder if I'll have alot more money in the sbc with all the internals, heads and injection system then going with the LS motor. I would have to build the sbc with everything since none of the stock parts will really work for what I want to do.

 

the only benefit of the LS motor is the stock heads/intake flow more than the stock L98 heads/intake. if you are planning on changing the heads on the LS motor, i would do the sbc and put whatever aftermarket heads on there along with a single plane.

 

There are a lot of additional advantages including the availability of aluminum engine blocks, 6 bolt main caps, lower intake profile, and ease of programability with the stock ECM.

Good news is that for the most part, a good head porting on any of the LS based motors will give you more flow that practically any SBC head - race included, so a strong LS engine won't necessarily need new heads.

 

No way, SB2.2 At 28" H2O: .600" 380/276 72.63%....

Here is a 358 SBC w/9.5:1 compression, and SB2 cylinder heads....;

http://www.youtube.com/watch?v=Y0jnkp9b8bM

 

Ok I have been out of the game for awhile since I dont really wrench anymore so what do the SB2 heads come off of or are they just aftermarket heads?

 

Expensive yes, but they flow ridiculously well....

http://www.raceflowdevelopment.com/RFD-heads-SB2-2.htm

 

Not sure if it was mentioned but the new LSX blocks have more head bolts for better clamping power. Not to mention they've been used in 2000+ HP turbo builds. It really comes back to how fast you want to go. If you're looking at throwing down some huge numbers dropping $2000+ on a block isn't that big of deal.

 

I would like to be around 700-800hp at the wheels or around that. More or less is not that big of a deal. This is just going to be fun car to drive and take to the track. Nothing really competitive. So I guess another question would be would all the internals need to be forged or just the rods and pistons. Looking for both answers on the L98 and the LSX.

 

if you count 2 3/8" bolts per cylinder as headbolts. some LSX blocks have real bad core shift.

 

He was referring to the actual LSX blocks, not LS(insert number here) blocks, I highly doubt you're commenting on actual LSX blocks.

 

Another nice thing about some current production and aftermarket blocks are they may have blind head holes so you can use head studs without fear of leaking coolant.

700-800 rwhp you'd want forged everything with ARP fastners. You'd also be looking at some low compression dish pistons for boost levels. Lower CR means more safe boost which means more power. You wouldn't want to go cheap or skip on anything. You would probably need more than 12-15 lbs of boost to do it though depending on the tune and which turbos you used. I'm pretty sure even Dart doesn't even recommend there SHP blocks to that power level for durability. I would think you'd be pushing an L98 block on borrowed time because for what you want you'd need around 900 crank HP considering drivetrain loss.

Are you looking at an actual designed kit like wrench rat twin kit or planning on doing the poweradders yourself?

 

Yes I am actually wanting to do a designed kit but if I had to piece one together that would not be a big deal. I know I am going to have to design the plumbing for the intercooler. I have talked with Banks about there twin turbo kit but I think I just want to do a single turbo since I have alot of room on the passenger side since my heater/ac box was removed completely. A twin is not out of the question but I know I will run into clearance and heating issuses on the driver side with the brake system. Again I can go lower in hp since I dont want to have to make a motor that is going to have to be rebuilt every so often. I want something that I can drive when I want but still have alot of fun with. Again I have my block 0-ringed already so I have been told I could do 20psi of boost but I dont really want to push it to the breaking point. Would hate to build this motor and blow it up, so if I am going to be pushing it with that HP I will just go down some.

Also I was looking at going with around 8.5-9.0 to 1 for compression.

 

I stand corrected - although SB2 heads are not even close to being anything near streetable and their power band is going to be a tad bit peaky. Nothing like having a 6k converter to get the motor up in its powerband?

 

That shouldn't be a problem for a splayed 4 bolt L98 block as you wouldn't have to rev it that high with a good amount of boost, especially if you stroke it to 383 or 396 (you are going to need a new crank, rods, and pistons anyway). I don't think that GM ever intended their L98 motors to have much more than 300hp or rev over 6000rpm due to the quality of the rotating assembly (the materials) and the 2 bolt block. Then again would you want to skip dumping money into a L98 block to get it strong, or would you go aftermarket block? Or would you go with an LS motor due to the 6 bolt bottom end and awesome head flow capability. Always a tradeoff!

 

im commenting on an actual LSX block not a LSx.

 

Ouch, thats gotta suck to get that with the pricetag they come with.

Though for the OP's goals, im sure a relatively stock LQ9/LQ4 block work fine.

I know theres one build floating around I saw a bit back, a stock LQ in a gto with an S375, only internal upgrade being valvesprings, and it made somewhere in the mid 800's...

 

Thats just to cover their butts. There are alot of guys running more power and more cubes out of those blocks than what dart recommends with no issues. its a good block.

You can make 700+whp on a 6.0 liter lq9/lq4 type motor fairly easily with mild ported stock heads, LS6 or equivalent intake, good cam, and 12 psi boost

My friends LS2 based motor with 317 truck heads, LS6 intake (i think), 230 deg cam, and twin 62mm turbos made 767whp on E85 on mustang dyno on 11 psi boost.

Pump gas will do over 700 on 11-13 psi easily. Thats on stock bottom end.

If you already have a decent sbc block and will upgrade the internals, that may be more reliable down the road but I think its a weaker block than the ls iron motors. It should handle 700whp but thats pushing alot of power on stock L98 block.

If you have to upgrade internals on both motors, i'd just go with the ls motor with iron block for better chance at reliability. You really only need stock ls crank upgraded rod bolts and forged pistons to handle that power. L98 will need stroker kit to make that power on 12-15 psi and a good set of heads.

 

So what do you guys think would be a safe amount of hp for a L98 block with all forged internals, 383 with a good set of heads?

Like I said I dont have to get that much hp but it would be fun.

 

I've seen guys push upwards of 800 hp on stock blocks but I've heard the 1 pc rear main seal blocks arent as thick in the lifter valley as the 2 pc older blocks so hard to say for sure. I personally didnt feel comfortable with 600whp on stock block so I went SHP and run mid 600's right now, but in a manual car its likely to be mid 700's. Converter eats up alot.

 

Yeah I see what you are saying. This will me a manual car also. I was looking around just pricing things and H-beam rods are stronger then I-beam correct. Any plus or minus to either?

And another question I have is what do you guys think of these copper head gaskets I see around? Would they help with the boost pressure to seal or not?

 

I run copper o-ring setup on my engine but im planning on running alot of boost. I would recommend Cometics for what you are doing.