Has anyone used a scat rotating assembly for a stroker build?
 

I am on the fence of jumping from 454 mag stock internals on full rebuilds or making the jump to a scat stroker rotating assembly. Scat sells them both balanced and unbalanced, I would prefer to use the machine shop as little as possible due to time and it seems like every time I take even simple things in to the machine shop I end up with a huge bill. I am looking at the kits from summit that have the scat 9000 crank which is the only cast crank I would trust, scat forged I beam rods w/ARP bolts, Icon forged dome pistons that will bump me to 9.6-1 on 934 heads, rings and bearings are all included for 1306 unbalanced or 1483 balanced w/freight. Some people say don’t trust the balance, some say they have had them checked and were spot on, some say they were messed up. The only thing I see that I am loosing from going 454 to stroker is the forged crank, these engines are going in a 38 stinger that is likely never going to be a speed demon of any sort due to size and weight, hoping to get 500-550hp when done so I don’t see the scat cast crank being an issue. I am mainly worried about the balance on these kits, the parts all seem to have a good reputation based on my research and discussions with marine engine builders. Has anyone else used these kits?

First Scat has come a long way from the old days and has passed eagle and a few others when it comes to cranks. Most of their other stuff imho has always been good (just like Howards Cams). As for balancing, take it to a shop. With the internet you are not trapped with your local guy. They (Summit) can balance what they send you but you will still need your Harmonic Balancer and Flywheel done to do it right. Here is my build sheet for a Mark IV stroker. Current Build Sheet SuperNova19.com

I have seen several of your posts on that build searching through the forums. I don't think summit balances these, I think scat does. Part of me thinks who better to balance it than the people putting these kits together. To my understanding these kits are internally balanced so that you use a neutral balancer and flywheel. I was originally looking at the skip white kits that had the balancer and flywheel but their kits did not offer a piston that would get me into the right compression ratio. The last time i checked the back log at my machine shop, they were a good month or so out with back log :(

I hear ya but I still would rather for the balancer to have everything at once. Maybe the rods are heavy and all they would have to do is drill the flywheel instead of balancing all the rods to the new weight. Maybe your flywheel is not perfect? Who knows but I would not trust OEM parts to be perfect. As for the "balanced kit", all their parts in this range are "balanced" like all the pistons will be within a gram or so in a set (I forget exactly what the tolerance is). Each rod's weight will be within so many grams and etc etc. A balanced kit may be just balanced parts picked off a shelf and not balanced to each other as a rotating assembly. Also I stroked a 427 tall block that is a internally balanced when I started. They drilled both the balancer and the flywheel to clean it up.
Last, are you sure you 454 is internally balanced? That don't sound right to me.

I would call Scat and get a rundown as to what process their balanced kit goes thru....

Balance Rotating Assemblies - Chevy High Performance Magazine

I emailed scat and got the run down. They balance them whithin 5-7 grams which in my mind is not good enough considering the cost vs doing it local so I guess I am buying the unbalanced kit and going local. thanks everyone for the help!

I used two 4.25 on 540 builds a few year ago, Smith power balanced the rotating assemblies, Bob Smith said dont bring me another one.....LOL.....maybe they have improved ??

On a side note, please make sure you put your rod bearings in right when it comes to after market cranks. Make sure you don't need "narrowed" bearings.

I would use a Crower instead of a Scat. And for surely never use a Eagle branded in any marine engine. Just saying

why?

quality for one.

And then I can ask WHY Scat ?

Anyone that does that should not be balancing engines. Same with drilling on a damper.

There are many Scat stroker kits out there in marine builds. Keep it under 700HP and you should be fine. And always have your machine shop check the balance.

Might have been misinformation. Thought we were talking about forged cranks...

i have used scat and eagle rotating assembly,s and individual parts,the eagle crank journal size was all over the place requiring mix&match bearings,the scat cranks were spot on sizewise.i would have no problem with 1000 hp with either 4340 crank&h beam rods with arp 2000 bolts but i do my best to talk people out of the eagle cranks for the mentioned reason.

Maybe I should have explained a little more. A 427 Tall Block is internally balanced but once you stroke it with Kiekhaefer rods there is no way to internally balance it without turning the crank into Swiss cheese. To be honest about it we actually used a 454 external flywheel and drilled it because if we used a 427 neutral flywheel we would have had to add to much metal to it and that "heavy metal" is expensive.

i have never seen a stroker aftermarket crank that did not need narrowed bearings,the journal radius is bigger for added strength.on a side note i recently took a 557 apart that someone else built,it had clevite p main bearings and they were shot,luckily the crank was good with a polishing.

yes it does cost a little more to do things right but the end result makes it worth it.

The crower 4.25 crank is over 2000 dollars and they do not appear to have a 1 piece rear main available. the kits I am looking at are around 1300 complete. Yea, I get the crower is probably hands down a better product and I would absolutely consider it if I was building a 1200hp engine. I will be lucky to get to 525, that crank is simply over kill for this application

Callies Compstar is a nice piece about 700 bucks

Am I crazy for wanting to use the scat 9000 crank? I get it is cast but they have a great reputation for not having issues, I personally believe they are stronger than a standard cast crank but maybe i am wrong. If it was any other cast crank I would not use it. I had a discussion with Eddie Young a couple of years ago on them and he said he had a customer running them in a pair of 750hp blower engines with no issues and that I won’t have any issues in my HP range. The callies crank is an option, its 718 but it does add a decent chunk more cash to the build since I lose the package price discount having to piece the parts together, about 700 per side. These engines were supposed to stay 454 mags/460s so this nearly doubles the original budget to gain 29 cubes per engine

A cast crank It's rated for 550-600HP in a vehicle by the manufacturer. In a boat I'd strongly advise against it. I didn't realize you speaking of a cast crank, skimmed thread...

If it was any other cast crank I would agree. The scat 9000 crank is supposed to be good till at least 700hp

no cast crank is good to 700 hp.it,s physics.

4.25" stroke doesn't apply to same 'rules' as a 4.00" stroke. 4.25" has a lot more journal overlap.

Last few who wabted cat 4.25" strokes I warned wished they would have listened.

Bad luck or was my opinion worth something ? :)

Do your homework. Listen to you rown voice after you do due diligence. You are a big boy.

I was once told that I was wasting my time building gm stock cast internal 454s up to 450+ hp. Allot of those folks also argued that I couldn't use a truck long block lol. Allot of folks tell me not to assemble my own engines. Out of all of the marine engines that I built off of that recipe which was a L29 454 gen 6 cast engine, I lost one. That engine failed at 5000rpm by snapping a valve head off the stem, falling into the combustion chamber and shattering the piston. The rod broke through the cylinder wall and bent the rod almost 180 degrees around and the cast crank doing this at 5k was still perfect and went into another engine. Had that valve not failed, I am certain that engine would still be going today. I built another long block to that engine and was back in the water 2 weeks later for less than 1000 bucks, most of that went the the machine shop to assemble my heads in a hurry and that motor is still in my 27' to this day. In that boat, it was either full throttle or idle so it was abused plenty lol

From all research I have seen, on people who actually have used the scat 9000 in lots of race builds and marine applications, the scat cast steel crank will hold fine under 600hp in a marine application. If we were talking a cast crank form the 80s or any aftermarket cast crank besides the 9000 I wouldn't even be talking about this. The 9000 is newer technology in casting and scat seems to have their stuff together on machining them correctly. Do I think forged is batter? Absolutely, do I need it? That's the debate. Its easy to say throw another 1000 bucks a side at these but then I realize I still need drives, transom assemblies, hydraulic helm.... (replacing king cobras) I guess I'm getting frustrated at this point, this is one of those deals where I was thinking hey, 1500 a side to gain 29 cubes seems reasonable cost wise and then like any other performance build, it is going to spiral out of control. I was going to do this build on my 27 so I did a ton or research and then found my 38 so I never built it. I already have 2 perfect forged 454 rotating assemblies sitting in the garage, 2 brand new sets of 454 030 merc pistons, I have all of my heads, valve train, cams that will not be changing so I am going to see maybe 30hp per side which in my big pig of a boat is going to probably only amount to 1-2mph. I am old and lame and usually have 4 kids on the boat so my boat stays at 3000-3500rpm almost all of the time and do short bursts to top speed once in awhile when its just adults hot rodding around. I can probably still see 500hp with theses engines as a 454/460 so I guess there is that. Once these go together, they are what they are and will not be getting anything more done to them, I have too many other projects that need time and money. I think it is time to reevaluate this idea.

hello..REGALMAN4925

MY 2CENTS........
I RECENTLY BUMMED MY 510S TO 547S
I HAVE SCAT CRANK EAGLE RODS JE PISTONS
MY HEAVY BOAT LIKES TORQUE THAT U GET WITH THE ADDED STROKE
IT IS A INTERNALLY BALANCED CRANK JUST AS THE 4.0 CRANK WAS..
THEN OF COURSE MY ENGINE SHOP '' DYNAMIC SPEED'' BALANCED THE ENTIRE ASSEMBLY

AFTER READING YOUR LAST BLOG,,,SOUNDS LIKE YOU MADE UP YOUR MIND..........GOOD LUCK


REMEMBER THERES NO SUBSTITUTE FOR CUBIC INCHES EXCEPT CUBIC DOLLARS..!!!!!!!!!!!!!

Saw it mentioned, I would not put HP in a marine application without one. You can get away with a lot more in Automotive because it comes off a load. Not marine!