Steven89Iroc

I'll try to keep this as short as possible, but I have a lot to say and ask, so please read through.

My IROC-Z bent some rods when it inhaled water, so it's time to build an engine. I had already ordered the BBSDesigns S/S twin turbo kit to put on the stock L98, but since I have to have an engine apart I'm going to put in some low compression forged pistons and rods (at least) so I can run more boost reliably. I'm somewhat short on funds, so I'd like to make this cost efficient.
Unfortunately I can't afford the AFR's/HSR/turbo cam I want right now, so it's basically going to be a stock L98 built for more boost. (Later on I'll build a badass engine from the ground up.)

I already bought another complete L98 out of an '88 IROC that was running upon removal, but it has 113k on it so it's definately getting rebuilt no matter what. I'm going to have it bored .030 over, as well as magnafluxed/cleaned and decked if it needs it etc., so I figure $500 in machine work. I figure another $500 for misc. rebuild items (gaskets/seals/oil pump, etc.) As for heads, I already bought a stock L98 set that was completely redone 1000 miles ago so they're good to go.

Now, I have a several options (damn sbc's, hehe), and I'm not sure which I should do. What I want out of it is 15 psi capability which should be ~450hp and ~600lb/ft with TPI and these turbos/fuel/tuning, etc., and capability to rev to 6,000 reliably because I might swap to an HSR sooner than later (call me crazy, but I actually want less low end torque because it'll never hook with 600 lb/ft anyway, and more upper rpm power is always better, maybe over 500hp).

I suppose the first question should be: How much power will the stock crank and 2-bolt mains (with ARP bolts) handle? Because if it isn't more than 500hp and 5500 rpm, then I might as well get Eagle 5140 SIR I-beam rods which are rated at 500 (okay, so boost cushions rods a little better, but we won't get into that now). However, if it will handle more, then I should get some stouter rods. Scat 4340's are pretty cheap still, and should hold more power.

I guess what I'm asking is, what will be the weak link if I have 5140 forged rods and Speed Pro forged D-cup pistons (coming to 8.5:1 compression)?

If that setup won't hold 500/6000 or so, then I might just go overkill and get some decent-cheap 4340 rods ($250 on Ebay), and a decent-cheap 4340 crank ($350 on Ebay) along with the same pistons ($320). I've heard that a properly done (ARP, forged crank) stock 2-bolt main block can hold 600hp. Is this true? If so, that setup will be fine for whatever I can throw at the current application.

Yet another option is to just get a rotating assembly from CNC Motorsports, one like this. http://www.cnc-motorsports.com/produ...390&CtgID=9015
That should support ~600hp, no? It seems like a feasible option. OBTW, I'm not going 383 so don't bother asking, it's 350 for now.

I have more questions but I don't want to overdo it, so I'll ask later.

Please help me out here. Thanks alot.

ljnowell

Get the forged internals, spend the money to get splayed mains installed, and proud of your completely solid nearly invincible bottom end.

Steven89Iroc

That simple, huh? Do you think that rotating assembly from CNC would be that strong? I can't afford anything better than that right now.

How much is it usually to machine for splayed mains, and how much are the caps? Like I said I don't have tons of money so I can't go "all out" just yet, unless it isn't very expensive. If that'll all support a reliable 600hp and 6500rpm, then it would work for my "Stage II" setup, all I'd have to do is add the good heads/intake/cam to the package to get there. (TPI crap being "Stage I").

Most of the money for this current build is going to come from selling my '92 RS for $1500, hopefully I can sell it quick. Any more than the $1500 will come out of paychecks (I have a few hundred per month extra). Forged/splayed boosted TPI sound like a plan?
What does everyone think? More insight please.

Steven89Iroc

Well upon searching for information on Scat, I found this: https://www.thirdgen.org/techbb2/sho...ight=scat+4340 ...and decided to stay away from Scat products.

If nothing else, somebody with some experience please tell me if I'm going to be safe running 15 psi on the L98 with 5140 rods and a stock crank (and of course the Speed Pro D-cup pistons).

ljnowell

http://cgi.ebay.com/ebaymotors/ws/eB...918850857&rd=1

There is a good example of splayed main caps. If it were me, and I were going to boost the engine, I would go with a forged crank, but I know people who havent. The scat/eagle thing is definately enough to make you wonder. But there are other companies out there.

Steven89Iroc

Well damn, that's not too bad for the main caps. I wonder how much machine work is.

Oh I definately want a forged crank, but it seems that any reputable 4340 cranks are $600+ which is understandable, I just can't swing it right now with the rest of the stuff I need to buy. All the cheaper cranks are from no name companies, and I don't want to chance it with something like that. I did mention the forged crank on Ebay for $350, but IIRC that was a Scat as well. If I can find a reliable forged crank for that much or less then I might be able to do it. Otherwise, I have to stay stock.

jims87camaro

how fast to you want to go? how much are you willing to spend to get there? if it means that you wait until you have enough cash to purchase the bullet proof bottom end, then i would hold off on buying anything at this point.

the stock crank may be spec'd to handle X amount of power, but i don't know what that number is for certainty. i've heard of guys with 600 ft lbs on the stock crank, but i am not sure that is something i would do. i am headed in that direction and i am going forged.

Steven89Iroc

Well I've pretty much laid out my budget and requirements. I don't have forever to wait for money, at least not long enough to buy completely bullet-proof pieces. That's why I plan on a 'Stage II' build when I'm out of the Navy and back home.

I'll try to simple it up a little to help myself out.

I want to run 15 psi with two T3's on a stock L98. I also want it to have the ability to rev to 6000. I'm not neccesarily concerned with a horsepower number, whatever 15 psi will be is plenty for this setup (with too much torque anyway).
Now, what are the cheapest bottom-end parts I need to accomplish this?
The Speed-Pro D-cup forged pistons are for sure, I'm using them. An 8.5-8.7:1 CR is also for sure. Everything else in the rotating assembly I'm not yet sure about, and this is where I seek advice.

Thanks for the help so far.