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  #1  
Old Mar 21st, 06, 03:15 PM
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Default Lunati Sledgehammer Rotating Assembly

Anyone ever run a Lunati Sledgehammer Balanced Rotating Assembly? It comes with a Sledghammer 4340 crank, Forged I beam rods, and TWR forged pistons. I was also looking at the Eagle Balanced Competition Assembly which includes Eagle's 4340 forged crank, 4340 h beam rods, and SRP forged pistons. My speed shop said that Eagle cranks have to be machined even when new, so I don't know if I would be better off with the lunati assembly. Would that be overkill. I'm going to building a 350 and the cam i plan to use develops 420hp but delivers power up to 6200rpm. I don't plan on using NOS, but who knows in the future. The local speed shop recommended using a forged assembly for durability since the engine would be spin higher then 6000rpms. I'm not sure if my block is a 4 bolt or 2 bolt, but I will have it converted to a 4 bolt with splayed bolts if its a 2 bolt. I'm hoping it's a4bolt since its 3970010 block. What would you guys recommend for a crank, rods, and pistons?
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  #2  
Old Mar 21st, 06, 04:50 PM
Larger Dave Larger Dave is offline
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Cool Re: Lunati Sledgehammer Rotating Assembly

I'd invest in an aftermarket block also, that way no matter what you throw at the engine it will stay together. And if you're thinking of a 4 bolt conversion then the difference in price will be about $500 to $700 more for the aftermarket over a stock block but well worth it.

The Lunati crank is nice, and I have used Eagle products with out a problem as well. I am quite fussy and I have checked all dimensions without ever noting any excessive variation in either product.

I favor buying the Lunati Sledgehammer balanced rotating assembly because you get all the parts balanced and ready for assembly. You know they will work together because the manufacture has done a lot of your home work for you in terms of parts interference (skirts clearing counter weights, etc.)


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Old Mar 21st, 06, 06:50 PM
Eric68 Eric68 is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

That crank and rod combo is WAY WAY WAY overkill for the power level and RPM you plan to run. You could run a 2 bolt GM block with cast crank and decent rods and be fine at 420 HP. In fact, I have used a GM cast crank, GM X rods with ARP bolts, and old fashioned TRW forged pistons and abused the SNOT out of a 400 HP 355 for several years with no ill effects at all.

Personally, I would look at a factory 4 bolt block, an aftermarket cast crank, aftermarket I-beam rods, and forged pistons. That would IMO be overkill for what you are doing, but the extra beef is there in case you ever decide to spray it a little or get more agressive with the combo.

Personally, I would look at a cast (nodular) aftermarket crank (like the Scat 9000 or Eagle) and a bushed pin I beam rod with decent ARP bolts in it (like the Eagle SIR or the Scat 3/8 capscrew rod). A good forged piston like the SRP would be fine too -- much better than the heavy TRW pistons, and a lighter piston will be easier on the other parts too.

I ran an Eagle cast crank and Eagle SIR rods in my 383 for over 5 years with good luck. I didn't spray it, but the car did go high 10's on the motor before I built my new 410" combo.
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Old Mar 21st, 06, 07:15 PM
JimM JimM is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

I built the bottom end Eric describes (except I think he means the 7/16 capscrew rods) in a 2 bolt main block with studs. I have no doubt it will live a long and happy life.

I think the key is the 6" rods and superlight SRP pistons. My pistons only wieghed 440 grams, and it balanced with a 1680 gram bobwieght, it's REALLY light.
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Old Mar 21st, 06, 07:35 PM
greg moreira greg moreira is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

Just some insight....I wouldnt depend on too many pre balanced assemblies from anyone to show up perfectly ready to run. I guess if your not picky, itll be close enough to work, but if you want it right....lots of em need to go for another spin if you know what Im sayin. I cannot comment on the sledgehammer pre balanced units, but I wouldnt be surprised if a picky machinist could do it better. Just generally speaking, I havent heard many people say that any companies pre balanced is deal is done as well as it could be.

And I agree....with what your doin, youd do good with the scat 7/16's 6 inch I beam 4340 steel rods. Very nice stuff for the money. They make a nice crankshaft too. Their 9000 series are nice pieces, or you could spend a couple more bucks on one of the steel ones(which still aint too expensive...a little cheaper than the lunati). Then, have a good shop balance it up right.

As far as eagle, they have also proven themselves to be good for the money. Just fine for your application in my opinion. Tons are using them(like Eric for example). Just one disclaimer.....of the guys I know that build a LOT of engines(like for a living)...a good few of them who have used both eagle and scat prefer scat. Here is why. Both of these companies make good, but cheaper stuff. So, you cant expect either company to send a perfect product every time. But, the guys that see enough to make a fair comparison say that scat will show up in good shape a little more often than eagle.
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Old Mar 21st, 06, 08:13 PM
JimM JimM is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

Like Greg said, don't trust a "pre-balanced assemby" and don't just use this stuff out of the box. I bought mine from the machinist who did my block prep, same price the stuff gets mail order, but it was CHECKED and balanced by him (for a fee of course). he had to hone the small ends and the piston pin bores, and I think a lil work on the crank, and the balance job. He checked everything for size, and honed each hole to match it's piston.
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Old Mar 22nd, 06, 03:56 AM
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Default Re: Lunati Sledgehammer Rotating Assembly

I came across this assembled short block from Golden Engines. They are a little over an hour from me. I was thinking of upgrading to the forged pistons.


http://www.golenengineservice.com/ht...rt_blocks.html
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Old Mar 22nd, 06, 04:23 AM
Busted Knuckles Busted Knuckles is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

I'm with Eric. We just built a stroker for my son with Eagle cast steel crank, SIR rods, SRP pistons and vortec heads. We'll be using a ZZ4 cam and running it off of the factory computer in his truck. We're looking for about 400hp and 450ft/lbs at the flywheel. I believe in buying good parts but a 4340 crank and what are probably Lunati Pro Mod rods in that package is overkill for what you're building. Myother project is a 406 for an '81 Corvette. That one gets the good stuff ($$$) because I intend to drive it like a 4-speed Corvette was intended to be driven. Just my .02
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Old Mar 22nd, 06, 06:39 AM
TexasPerfProd TexasPerfProd is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

I agree that the kits you mention are both pretty much overkill for the slightly over 400hp goal. On the other hand you can never build one to strong as long as the pocket book allows. Personally you could build this with a cast crank a decent set of prepped rods w/ARP bolts and be ok. But a middle ground strength crank and rod option might be a 5140 material not as strong as the 4340 stuff but stronger than the stock stuff.
I agree that these rotating assemblies that are offered without all the rotating parts are at best partially balanced. We computer balance our rotating assemblies only if the balancer and flywheel/flexplate are purchased at the same time for this reason. You must have the entire rotating mass to completely balance the engine.

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Old Mar 22nd, 06, 06:44 AM
Eric68 Eric68 is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

And to add to what I was saying before . . . IMO one the most common causes of a blown engine isn't the bottom end. It often starts with the valvetrain and a parts collision -- like a valve hitting a piston. If that happens even the best bottom end will come unglued. Other common causes are bad machine work (bearing clearances), bad assembly, wrong/incompatible parts.

I would back off a notch on the bottm end and put the money into a good quality top end.
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Old Mar 22nd, 06, 07:01 AM
rlovell383 rlovell383 is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

I also agree with Eric68. Its nice to have a fancy bottom end but if cheaper stuff does the same job just as good.......Why? There is no power to be found below the heads, you can take the saved money and invest in porting/cam/blah blah, and make more power. As far as parts selection. I've personaly balanced and clearanced many of both the scat and eagle parts and have found the scat products to be superior in every way. Journals are much more consistent, they balance easier, they have less runout and you arent giving your money to china. You get what you pay for. Get as light a piston as you can afford and the engine will live a long time.

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Old Mar 22nd, 06, 07:50 AM
JimM JimM is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

Just to throw another set of numbers... my bottom end cost $1270, for an internal balanced scat 9000 crank, the good 6" rods, srp forged pistons, and rings and bearings.
The machine work was close to that much, including bore and torque plate hone, add studs and line hone, check EVERYTHING and corrct to blueprint spec as required, and balance it.

That adds up to $2500 for a pile of parts ready to put together. It was the cheapest I would dare to do this, and I'd trust it to 6500 and 500 HP.
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Old Mar 22nd, 06, 08:17 AM
robert68 robert68 is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

Jim - You can't be including the cost of the block in your example, can you? If "DenRS" spends another $1500 on an aftermarket block then you're at $4K pretty quickly. For his described application wouldn't a ZZ4 short block handle 400-450 hp easily at about half the price. I don't claim to know very much so please correct me if I'm wrong - Rob
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Old Mar 22nd, 06, 08:36 AM
JimM JimM is offline
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Default Re: Lunati Sledgehammer Rotating Assembly

I used my original 327 block, and the machine shop cost also included tanking it, freeze plugs, clearancing for the stroker, checking the decks (shop was instructed NOT to machine the numbers off) etc etc.

There are a bunch of places selling low cost engines and short blocks, and lotsa people running them with no issues. lotsa people doing really low budget builds in their garage, too. I've certainly done my share of dingleball honed, plastigage checked engines in the past.

I'm old now. I have the money to do it right, tho I didn't feel the need to overbuild, either.

A GMPP short block, long block, or comeplete engine is a good solid motor, but I don't think they are fully blueprinted, either. They do come with a solid warantee, a lot to be said for that.
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Old Mar 22nd, 06, 03:23 PM
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Default Re: Lunati Sledgehammer Rotating Assembly

Thanks for the info. I think I'll look at new cast steel cranks, forged I beam rods and forged pistons and getting the whole thing balanced. I'll price out the block work and see if I'm better off getting a new gm 4 bolt for $650 or using my own.
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