Steven89Iroc

I'd like some help as to what the rotating assembly should consist of in this engine I'm about to start on. I asked in gen tech but didn't get much help.
First, just to give an idea of where it's going, the BBSDesigns street/strip turbo kit (with .63 a/r stg III turbine sides) is going on this engine.

Now, think of it this way. I want to run 15 psi on a stock L98. I also want it to have the ability to rev to 6000, and I have $2000 to spend on the engine (not counting the block/crank or heads because I already have them). I'm not neccesarily concerned with a horsepower number, whatever 15 psi will be is plenty for this setup (with too much torque anyway), though I estimate it should be around 450hp and 600 lb/ft at the crank.

Now, what are the cheapest bottom-end parts I need to accomplish this?
I'm pretty much set on the Speed-Pro D-cup forged pistons. They have a -21.1cc dish, so 8.5-8.7:1 CR is about where I'll end up with the stock 64cc redone heads. Everything else in the rotating assembly I'm not yet sure about, and this is where I seek advice. So, that $2000 has to include machine work, gaskets/seals/bolts etc., rods, pistons, crank, etc. (not heads, I have a set that are already rebuilt, not cam, and not intake, those are stock). Could the stock crank with ARP bolts handle this, somewhat reliably?

You might ask why I'm using stock heads/cam/TPI, well it's because I only have $2000. Later on I'll top it with an HSR, then later down the road I'm going to build an all-out turbo engine, so for now stock parts are getting boosted.

Any and all help is appreciated. Thanks alot.

unknown_host

iTrader: (1)

Hey you should know me from 3GO .

I would go with a Probe forged piston over the Speed Pro, newer better piston and right around the same price. You can score a set of Eagle H beam rods off ebay for right around $330. As for a crankshaft, I would look into a scat 9000 instead of reusing the stocker. The Scat 9000 series cast cranks are under $200 and I have a few friends running serious horsepower on these for several seasons. Hope this helps .

PS, if you go to www.cnc-motorsports.com you can score the whole rotating assembly I mentioned for right at $900.00 if I am not mistaking.

Seth

Steven89Iroc

Yep, I know you.

I'll look more into the Probe pistons, it's a possibility. I'm not too hot on the idea of H-beams because of the extra weight, and the fact that I don't think I'll make enough power with the stock heads/cam (even with an HSR) to warrant using them. A decent set of 4340 I-beams should do me fine and be cheaper as well, no?
I've read mixed reviews on Scat and their products, and coming from what I know, I don't want to deal with them. :/ Are there any other decent-cheap crank options?

I did see those rotating assemblies from CNC Motorsports, but like I said, I want to stay away from Scat products.

Thanks for the help so far.


OBTW, if anyone is wondering why I only have $2000 for the engine but $3500 for the TT kit, it's because it's already paid for and should be on it's way as soon as Puerto Rico gets power back so Edgardo can send off the turbos to be ceramic coated.
I planned on boosting the stock engine until I built one when I get out of the Navy, but this one drank some water forcing me into building a cheap-ish engine now, and I'm not putting it together without boost-friendly(er) internals (just a little backround).

unknown_host

iTrader: (1)

Makes sense. You can find bad press about Eagle too if you really look around, I remember a year or so ago Car Craft published a picture of one of their Eagle rods that they were running in a mopar motor they built for an article, it broke in 3 different places. If you dont like scat, we can work around that .

I called cnc-motorsports a while back and asked them about the difference between the probe and speed pro forged pistons. They said the speed pro design hasnt been updated in years, and that the probes weigh significantly less and are a better all around piston.

Another good connecting rod is the GMPP powdered metal connecting rod, like what came in my crate motor and in LT1 motors. GM says they are good to 500 horsepower and they cost in the $230.00 range.

I have no experience with Eagle crankshafts so I can't help you out there. Good luck man.

Steven89Iroc

Thanks for the good luck.

The Probe pistons sound like they are better, but the biggest dish I can get is -13.8cc, and they cost $485. Too much compression and too much money. :/
The Speed Pro "turbo" pistons have a -21.1cc dish (which is perfect), and Summit has them for $320 for all 8. I'm sure they'll work plenty good for this application.

I just saw Cola 1-piece seal 4340 350 cranks on Ebay going for $350 with no bids, and a buy-it-now for $400. That 'might' be a bit too much for me, but hell, it's only one more month's play money. I've never heard bad things about Cola, everyone says they're the best. I still don't know if I'll 'need' to spend $400 on a crank at this point though.

I'm still looking at rod options, I'd like to go with 4340 forged if funds permit. I've seen a lot of no-name or small name 4340 I-beams on Ebay for around $300, would anybody here trust something like that?

Anybody else want to chime in?

unknown_host

iTrader: (1)

http://www.cnc-motorsports.com/produ...407&CtgID=7124

20.3cc dome, comes with rings for $359.99

And the GMPP PM rods are a forged I beam rod.

Good luck getting other replies .

Steven89Iroc

Damn, that sounds much better, I might just do that.

They're forged, but not 4340. I'm just thinking that if I can afford 4340 rods, why not?

I know huh. What's up with that? Back in the day (like 1998, heh) tons of people used to answer questions here.

For the record, I am one of the strongest advocators of the search function, and I'm a searchin' fool. The questions I ask here, I haven't been able to track down specific answers to.

MrDude_1

given your budget, i would go with the powdered rods if i were you.

id also go with less dish on the piston.. shoot for around 8.7 to 9...

Steven89Iroc

The PN of the Speed Pro pistons I'm looking at is L2441F30 (you can find it here, enter the PN in the search http://www.21cgt.com/FMWebCatalog/default.htm )

They have a D-cup dish of -21.1cc's, which comes out to 8.35:1 with stock heads, stock deck height (which I found was .035", is this accurate?) and a .031" head gasket. I want to use a thinner head gasket, or get the block decked if it needs it. Depending on how much is taken off, I could end up with around 8.7:1 which is what I want.
To throw a twist in, the heads I bought have been milled, but the seller didn't know how much. I have to figure it out to know for sure, but it shouldn't have been more than .010" I think. My plan is to get a straight edge and dial indicator, and measure the distance from the head surface to a common point inside each chamber (all 8), then do the same with stock heads and subtract the difference. That should tell me with fairly good accuracy.
These pistons weigh 565 grams.

Now, the Probe pistons listed (except .030 over) have a -20.3cc dish, and I don't know if they are D-cup shaped, but I don't think so. I've heard D-cups are better for combustion efficiency, so that's a minus.
This would bring the compression up to 8.41:1 with everything else being the same (compared to 8.35). That's not a big difference. Again, deck height, head milling and gasket thickness can bring this up some.
These weigh 498 grams, or 67 grams lighter than the Speed Pro's, which is a slight plus, but I'm not going to be revving to 7000 (with this engine), so the weight shouldn't make a huge difference.

Now, either of these should work well, but it sort of comes down to which is more important, weight or dish shape. That I'm not sure about.

If you guys are sure I'll be okay with the powdered rods then I might do that. It's just what, like $70 more for 4340 rods on Ebay?

If I use powdered rods, will there be any point to using anything other than the stock crank with ARP main studs?

Steven89Iroc

If I'm going to be running a consistant 450hp and 600 lb/ft, I think I might want something rated for more than 450. :shrug: