racer7088

You can keep the skirt further up in the bore with a tighter rings stack in an NA app. piston. It's almost as if you made the cylinder longer.

With a power adder you have to lower the rings so the skirt is also lower too then at BDC. Now it's like the cylinder got shorter.

The stroke plus the ring stack determines where the skirt actually stops or is at in the cylinder at BDC.

Randy WS6

iTrader: (69)

Im running 255cc Dart Pro1's cnc by TSP 2.100 int & 1.60 ext. valves, 58cc chambers and the cam I have (for now) is a Crane .650/.650-250/266-112

PREDATOR-Z

How about the new GM iron LSX block?

Would a 4.125 bore/4.125 stroke be reasonable in that one? Nitrous would be used.

SLED28

iTrader: (7)

Yes and Yes! SHould be able to make 850rwhp with nitrous Predator

PREDATOR-Z

What are the rpm limits of such a motor, like can it be "reliable" at 7000>7200 rpm?
I know reliable is a loose term but I'm contemplating a setup like :

LSX block
AFR 225s
Lunati pro billet rods with matching nitrous pistons.
cam specs of my design
12:1 SCR
Wilson equal runner intake (alum)
100 mm TB

SLED28

iTrader: (7)

Yes it is reliable at 7000 rpms. Those parts would go 8000+ no problem.

racer7088

The sleeves are longer in the LSX PREDATOR but the pistons need to have a certain amount of ring land real estate if LARGE NOS is going to be used regularly.

SLED28

iTrader: (7)

If large nitrous is used, say 300+, I don't even recommend a 4.125 stroke. Stick with the 4.00" crank. Like I said I have made 850 on a iron 422, the LSX combo will do the same on a 4.125 stroke

PREDATOR-Z

No it wouldn't be for crazy shots. On average I would say 200 in dual stage.
Target is firm 9s on juice.
This will be mostly race but with some street manners. Cam will have in the neighbourhood of 53>55 IVC, 1 or 2* intake biased for rev capability after peak, overlap in the 16>20* range, race weight ~ 3200lbs
TH400, reverse manual, gears 3.70> 4.10 range. (Stall based on cam).

On the heads I might go with Katech 2.100 lightweight valves, new Comp high lift 918s, titanium retainers, basicaly the lightest moving valvetrain my pocket can afford.

Crank, nothing crazy at the power levels i'm shooting for, I would rather put the $$ in the rods, pistons and valvetrain.

Since it is an iron block, I'm tempted to cryo the setup. I've never done it on LS motors but I've had good results on 2J motors and FI SBCs. Problem is, it is relatively labor costly as whole motor needs to be fully assembled, blueprinted, then dissasembled and Cryo'd. Otherwise good luck filing anything after that

blu00rdstr

In the table below, take a look at the note for the pistons for longer stroke, '*Requires oil-ring support rail'. The oil ring doesn't overlap the pin with a stock stroke. These particular pistons have a thick .260" top ring down space. I'm sure there are lots of builders who held their breath and had good luck with moving the rings up or with oil rings that had a gap of material under them. I'm sticking with the stock stroke, the thick top ring down, and no oil ring overlap of the pin.

Randy WS6

iTrader: (69)

I run a 4.100" crank in my stock sleeve length LS2 block. Runs grate.

See5

iTrader: (53)

Seems like LS2/L92s/LS3s with their shorter sleeves ought to be limited to 4" stroke. Even at that, the piston is getting low in the sleeve. LS7s @ 4.125 are fine due to longer sleeve.
415s are "safe" with L92/LS3 stock blocks. Is the incremental displacement beyond 4" stroke worth the "issues"?

Beaflag VonRathburg

iTrader: (176)

LS2 and L92 blocks have longer sleeves than iron blocks. People have been using iron blocks for large crank combinations for a long time. It's about setting up the pistons correctly and proper clearancing. Other than those two issues I see no problem with using a larger crank in one of those blocks.

z34_nut

iTrader: (7)

I do not personally like the Eagle crankshafts. At my shop I use a Hines Balancer. Every time we throw a late model Eagle crank to spin, it requires at least 4 pieces of heavy metal. This is a sever problem with cost, and speed of assembly. They can cost up to $700 for the customer easily. Also, the pre balanced assemblies we've received are out 10-20 grams from one end to another.

Scat, and Callies are the only two cranks that I have balanced that do not require extra material. Scat offers a 4.00, 4.125, and 4.250. Their Crankshafts are well worth the money, come with the reluctor pre installed, and heavy metal pre installed as well. The actual pre measured bob weight is about 1850. Most rotating assemblies are less then this.

I think by reading my post you can see what crank I prefer.

racer7088

Hahahahaha WTF! I've balanced no less than 600 Eagle cranks with no heavy metal! What the hell are you doing! What BWs are you running!!! Maybe your balancer is not working?

z34_nut

iTrader: (7)

Apparently you are balancing to the finest specifications.

Every late model engine shop in my area knows about this situation. When a customer shows us an eagle crank that isn't pre-balanced, we cringe.

Here, talk to a sponsor here on the site.

Rick @ Synergy. Strange, his engine shop has the same problem.

racer7088

The SCAT LS1 stuff just came out but I hope you are right and they are better than their previous Billet LS1 crank stuff. A lot of SCAT's stuff won't go internal in other cranks but their LS1 stuff that just came out hopefully will or at least is supposed to. I will have one soon and I will finally see if they have the rest of that crank right as well.

racer7088

I bet they do! Hahahahaha! Maybe I get all the good ones!

z34_nut

iTrader: (7)

I just balanced one of Scats new 4.00 cranks 3 days ago. It was perfect, but it helps that our bob weight was only 1630.

z34_nut

iTrader: (7)

I'm not sure, but depending on how accurate your balancer is, you can see an insane difference if your using a cheaper balancer. Our Hines "Eliminator" balancing system is extremely accurate, the employee I have behind the machine has 30 years experience, and is one of the best in the country hands down. I know its not my balancer.