jas2730

iTrader: (7)

http://www.summitracing.com/parts/SCA-910442/

Seems like a no brainer. Put a $100 + into my stocker or grab this up and drop it right in. Did some research it's supposedly pre balanced and ready to bolt in. Just wondering if there are any horror stories out there.

AlkyIROC

Nothing wrong with SCAT parts.

jas2730

iTrader: (7)

Yeah, Your right. I'm just getting paranoid these days thinking everything's somehow coming from china and will last two weeks. Lol!

Jeffs82TA

iTrader: (1)

by what you have listed as a 89 IROC that crank won't fit your car since it is for a 2 piece RMS

jas2730

iTrader: (7)

Under engine it says ( in the making). I'm using a pre 87 350 as my base.

LilSki

iTrader: (1)

86 is first year for 1 piece RMS.

As for the crank I put the 1 Piece RMS version of that crank in my vortec build and it hasn't blown up yet. Heck I didn't even get anything balanced I just threw it in and it runs smooth as silk.

jas2730

iTrader: (7)

I stand corrected. I'm using a pre 86 block. Yeah, that's what I was looking at. The fact that it's already balanced will save me some cash so I went ahead and bought it. Thanks guys for easing my mind.

jas2730

iTrader: (7)

Okay so I put this crank in and everything checked out okay until I started putting the pistons back in. I kept my stock pistons and rods but when I put #1 and #2 in they started binding up against each other to the point where I can't turn the engine over. Is this even possible? Anyone have any advice?

AlkyIROC

Rods can only go on the crank one way. There's a chamfer on one side of the rod. It goes against the fillet on the crank. The side of the rod that doesn't have a chamfer goes against the other rod.

Bearing clearance. Providing you're putting the rods on the crank properly, how much bearing clearance do you have? You should put the bearings in the rod and torque the cap on. Measure the ID of the bearings from top to bottom then measure the OD of the rod journal. The bearings should have a few thousands of an inch more diameter.

Bearing caps go on the rods bearing tang to bearing tang.

Don't forget, when the engine is upside down on a stand, the #1 piston is on the opposite side. #1 is always the most forward cylinder.

jas2730

iTrader: (7)

I have plenty of clearance and everything is installed correctly. It rotates freely until I put two on the same journal. The sides of the rods bind up against each other.

AlkyIROC

Is the chamfer on the rods to the outside against the crank? Does the crank use normal or narrow bearings?

jas2730

iTrader: (7)

Yeah, they're pointed away from each other and I stamped everything during disassembly. I bought the crank from summit and they sent me the matching bearings for the crank. I'm at my wits end with this. I don't want to sink another dime in this thing. I could have bought a 383 crate motor for what I have in this thing!

TTOP350

iTrader: (8)

I have a scat 400 stroker crank (cast). I pulled it out for a freshen and I'm gld I did.
Its cracked in 2-3 places

AlkyIROC

I seem to say this a lot whenever someone thinks it's easy to slap together an engine. It's always cheaper to buy a prebuilt engine even if all you want is an OEM replacement engine. Parts are cheap. Machine work to make sure it all goes together properly takes time and money. Never assume parts you buy are ready for assembly when you open the box. It's always nice to say "I built it" but it's never cheaper.

My 588 is no different. I could easily have purchased a longblock race engine for far less than what I paid to build mine but it wouldn't have had the parts I wanted to use in it.

86LG4Bird

iTrader: (1)

Use your stock crank, ESPECIALLY if it only requries $100 to shape it up.
ANY aftermarket cast crank is a serious downgrade in reliability from the GM OEM cast cranks. Junk.

grumpyvette

not always TRUE! SCAT CAST STEEL CRANKS ARE A TOUGHER MATERIAL than most cast iron factory cranks

http://forum.grumpysperformance.com/...php?f=53&t=204

hpete

Hi-po cranks have a larger fillet radius than stock cranks, Summit probably sent you the wrong bearings. You'll have to call them to straighten things out. Btw cast steel is way tougher than any cast iron regardless of who casts it.

TTOP350

iTrader: (8)

I broke 3 400 GM cast cranks and then cracked the scat cast crank after I upgraded heads and cam. I now have a steel crank.

I run the car and spin the motor hard

jas2730

iTrader: (7)

I got it turning again! I put a breaker bar on it and gave it some motivation and it loosened up. I then rechecked all my clearances and bearing positions, relubed everything and after I was able to spin it by hand. I installed the remaining pistons with no issues. I guess I just needed to walk away and sleep on it. I find that works well when I get all hot headed.

jas2730

iTrader: (7)

I looked into that before ordering. The rep assured me that the crank required std bearings. Which was backed up when I checked my clearances.

grumpyvette

http://forum.grumpysperformance.com/...php?f=53&t=852

http://forum.grumpysperformance.com/...php?f=53&t=247

http://forum.grumpysperformance.com/...hp?f=53&t=2726

http://forum.grumpysperformance.com/...php?f=52&t=399

http://forum.grumpysperformance.com/...php?f=52&t=181

you need to read thru this, its obvious somethings very wrong

jas2730

iTrader: (7)

All good now. Thanks.

redneckjoe

thank you for the link. its very informative.

novaderrik

it doesn't matter how strong it is if the machine work is all jacked up.. i've read many reports of Chinese cranks (yes, Scat cranks are Chinese..) being machined too narrow on the throws where the two rod journals sit side and causing things to bind up.. this is easy to check with a feeler gauge between the rods- i forget how much clearance there is supposed to be, but too little and it might bind up once things get up to temp.

most people that get one of these aftermarket cranks are spending money that they don't need to spend.. i was told my a very good machinist that has been building small blocks since the mid 60's that a properly machined stock cast crank will last up to about 500hp and well over 7000rpm for extended periods of time in a stock 2 bolt main block if you put studs on the mains and get it balanced. he's built a lot of winning engines for the various stock car classes over the years so i'll trust what he says..

86LG4Bird

iTrader: (1)

Anybody that has ACTUAL experience building and running engines will tell you the same thing. People that come on here telling you that cheap aftermarket cast cranks, from China or anywhere else, are anywhere near as good as the GM stock cranks are going by stuff they've read that has no connection to what is actually happening out there and is just outright wrong. 500 hp bracket motors over here with stock cast cranks spinning 7000 are not cracking. And after about 50% of the aftermarket cast cranks (Scat, Eagle, and others) either outright failing or showing cracks in their bi-annual teardowns, the builder will either change their mind or turn away any customer that still wants to go that route.

grumpyvette

its the quality of the machine work and balancing plus attention to details like bearing clearances and the damper used that has a HUGE effect on durability , Ive built dozens of engines with SCAT cranks both CAST STEEL and 4340 FORGED STEEL, with ZERO issues the mere fact that there is a problem, encountered with bearing clearances, while checking with micrometers or plastic-gauge, or excess resistance to rotation or a clearance issue found with the rotating assembly components or of needing excess force to spin the engine indicates MAJOR assembly issues, that must be corrected before you proceed further with assembly.
the links posted go into most of the potential things that need to be checked BEFORE, and During the assembly process.
Even a forged 4340 crank will quickly fail if you don,t balance and assemble an engine with those factors set up correctly,and the FACT is that a forged steel or CAST STEEL crank is made of stronger material than a cast iron crank, thats not in dispute, its the engine builder thats responsible to make sure the clearance work, , parts selection,and balance work and parts matching process is correctly completed.
get cheap, assemble a random bunch of miss matched components , forget to do the clearance work, install a damper thats not correct and ANY crank assembly will eventually fail.
theres a reason why a forged crank is usually selected for a race engine, its FAR MORE DURABLE
why cast cranks and high stress and high rpms are a bad idea
and NO! THESE ARE PICTURES OFF THE INTERNET, IVE NEVER BUSTED A CRANK, BUT I AM AWARE IT HAPPENS and TEND TO AVOID USE OF CAST IRON CRANKS, OR STOCK CONNECTING RODS IN RACE APPLICATIONS

TTOP350

iTrader: (8)

Buuuut when pushed past those numbers, a GM crank WILL fail. Not if, its when. At 7K rpm I would have a issue with a stock crank. I have 3 (GM400 cranks) that I scrapped and have friends pushn them to failure also.
For a 500 hp, 6500rpm street car, I can see using a stock GM crank if it will pass all the tests a machine shop can throw at it.
I'm forged aftermarket now.

AlkyIROC

Cast cranks are fine as long as you're not using a power adder. It's even better if it passes a magnaflux test. I had a stock cast 400 crank in my old 383 and spun it to 7000 rpm. The stock rod bolts and cast 350 pistons failed before the crank did.

The crank and rods in my 588 are billet steel.

RBob

iTrader: (1)

What Grumpy said, some people can even break forged cranks as shown in the pictures. Note the parting line in the picture above, forged.

RBob.