BakedPotato65

I have a one-piece seal, 4-bolt, 96-00 Vortec block I bought from Summit that I will be using to build a 383. I've been looking around for rotating assemblies that are already balanced that come with a flywheel, not a flexplate since I have a 4-speed Muncie. It has been pretty hard to find a kit that comes with a flywheel, but I found a SCAT kit on CNC Motorsports' website that has the option for a flywheel.

Here's the link: https://www.cnc-motorsports.com/scat...ons-54721.html .

I'm planning to have something like 460hp 480tq, 500hp/tq max, for this 383 and the car will be street driven only. It just needs to be fun and torquey getting around town and have a head turning idle. The rotating assembly I'm looking at has a cast crank, 4340 rods, and hyper pistons, I'm assuming these parts will hold up just fine for a street driven, under 500 hp/tq engine. But just to be sure, I came here to ask you guys of what you thought about this kit. I've read around and saw that the SCAT cranks are stronger than other cast cranks such as Eagle, and I saw one guy that said he had 750hp with a cast SCAT crank with no issues. So I'm assuming this kit will be fine for my application, no need to look into a forged crank. I just need a kit that's balanced with a flywheel because I don't want to have to deal with finding a good machine shop to get things balanced, so I'm leaning towards buying this kit.

Let me know what you think of this rotating assembly,
Thanks a lot

drwet

I would not build a performance engine with a cast crank again. This is the crank from my 383 that failed last summer. It is a factory 400 crank and I realize the Scat is likely a much higher quality piece, but it sucks when your crank breaks.

JoeMinnesota

I agree with drwet... I built a 390hp/425tq 383 some years back with a stock cast crank, hypers, 5.7 Rods, all balanced with a 4-sp and Ultradyne hydraulic. After a couple of seasons of street driving with one trip to the 1/4 mile annually, we pulled the motor apart before moving it to a weekend bracket car. It still ran good, but when checked the crank had developed a couple of hairline cracks and had to be scrapped. It was never spun past 6200-6500rpm and was not high compression; 99% street driven. I just wouldn't build a stroker without a forged crank again.

Opinions will vary on this. That was my experience.

jb78L-82

I agree with above^^^^. I would not build a 355/383 with cast crank or hyper pistons with anything over 400 Gross HP. I would not use cast anything with an approximately 500 gross hp engine! When I rebuilt my OEM 350 L-82 into a 355 with 10.2 compression, roller cam, and AFR aluminum heads back in 2014, I spoke to my builder who has done many engines in the 355/383 size and he advised against any cast crank and using hyper pistons. I am so glad I took his advice and reused/reconditioned my OEM L-82 forged crank and forged JE racing pistons/rings. The motor makes 425+ Gross HP and is street driven with occasional blasts to 6,000 RPM.

BROKEN RODS

I have sold a lot of rotators not a big fan of Cast cranks but have not had any problems with street and strip using the Scat 9000 series cranks.

That kit from CNC is an economy kit those rods are not for stroker build you would have to grind on the rods or get a reduced base circle cam. I would stay away from HYPER pistons and go with a better piston.

I have always used 6.000 rods and you can get a crank that you can internally balance using 6.000 rod with a one piece seal crank. I like the Scat Procomp rods with the 7/16 bolts

I like the Mahle pistons they are a little pricey but best money can buy. They use a 1MM 1MM 2MM ring pack.

Once you get the kit from CNC you still have to go through both ends of the rods possibly one the piston bosses in pistons. Mahle come spot on so far never had to clearance those out.

Here are some prices on parts you that you can search for. GET a true stroker kit with rods that are a stroker rod.

Scat Crank 9-350-3750-6000 is about 250.00 internal balance
Scat Rods 2-ICR-6000-7/16 is about 238.00
Mahle pistons flat top 930200630 about 735.00 1MM 1MM 2MM ring pack
Rods and mains 30.00 to 40.00

Balancing should be around 225.00 to .275.00

Polish the crank is around 45.00

Size both ends of the rods around 120.00

Good luck which ever way you go.

BakedPotato65

Ok, I guess it would probably be best to do everything right the first time and get forged everything seeing all the things that could go wrong with cast components. I assume the bottom end of an engine should be the most expensive part of the engine since it takes such a beating. I saw that a 4340 crank is good up to 1500hp, that's probably more than enough for a less than 500hp/tq engine. Thanks for the input

Alright, I looked around on CNC's website to find a kit with 6 inch rods and forged everything. I found this kit: https://www.cnc-motorsports.com/eagl...ons-55192.html . Seeing that it has a 4340 crank, 5140 6in rods, and forged Mahle pistons, I'm guessing this kit would be more than enough for what I'm planning power wise. It would probably be worth waiting and saving up a little more money and get a good assembly. I just hope that if I do get this kit, I can call CNC and have them balance a flywheel with the assembly so everything is good to go.

Do you think it would be any cheaper to buy parts separately instead of as a kit? Or is it best to have everything come as a complete kit.

REELAV8R

I'm going to be the odd one out here. the crank shown by Drwet looks to be an OEM crank and a cast OEM crank is not up to the task of 400+ HP for very long, so I would expect one to fail quickly if pushed too far.

However a Scat steel crank is far superior to an OEM cast crank and can easily live with your 460 HP engine. Whether you use hyper or forged pistons is going to largely depend on your piston speeds you anticipate seeing and HP levels.
I have been using the Scat steel crank and hyper pistons at 440 HP on a 350 with no issues. Scat I believe told me it was good to 550 HP/TQ. You can give them a call and ask.

BROKEN RODS

Those Sir rods are not a stroker rod and are bottom of the barrel, I deal with a of of companies and Eagle I will not deal with to many problems over the years, I have seen to many times where you break down the Sir rods re torque them back up and they change there size. Do a search.

5140 is not a 4340 rod LOL

That 9000 series crank I have put in some marine builds over the years no problems to date if I was ever going to have a problem it would sure show up in a marine build.

The kit I have specked out has been proven many times over and over with zero problems, The only thing I have found the rod journals were on the low side and had to use a .001 under bearing which is no big deal.

Scat seems to be quality parts compared to Eagle I have seen the difference between the two.

If you just looking for the best price then go with the cheapest kit out there, If you looking for quality parts you may have to spend a little more.

You have a brand new block you should have it zero decked, Bored and plate honed for the best ring seal.

On the 383's i have machined and built using the one piece rear seal use the kit I talked about, Dart SHP 180 runner heads 72CC chamber, GM hot cam 234/242 installed at 108 intake center line, with the GM lifter and spider kit, Which makes for a nice set up, It has the nicest sounding idle, and it seems to pull really good.

Pete at CP Motor works is a good friend and he has seen the same problem with Eagle cranks as I have.

Good luck which ever way you go.

cv67

x2 on Scat 9000 they can take some abuse;not a fan of sir rods either
bottom line have all parts checked. The engine is only good as the machinig and assembly

I dont trust any prebalanced kit, spend the 200 & take it, your balancer clutch etc to get them double checked, ck runout and straightness.
Better to find out up front rather than have a vibration or bearing issue later. Even a cam thats not straight can give you fits and a motor that shakes like crazy

BROKEN RODS

I have been through some prebalanced rotators they are not even close some times. Interesting a balanced rotator comes all balanced rods are still in plastic wrappers, pistons are still sealed in the there box never been opened..

My own builds I use a forged crank but some customers that assemble their own want cast cranks and so far Scat cranks have worked out well.

BakedPotato65

So if I were to buy the parts you listed above, Scat 9000 crank, scat rods, and Mahle pistons, these parts would be good for a max of 500hp/tq for a street driven car that will probably never go past 6000 rpm? Will the rods have enough clearance for the cam or will I have to take it to a shop?

Also, for the rod and main bearings, are the main bearings different for a 1-piece rear main seal than a 2-piece? And is there a certain brand to buy from for main and rod bearings, Summit brand bearings are pretty cheap and have good reviews also, but I don't know if better ones are worth the money.

Thanks

cv67

Id use what the mfr or your machinist recommends, those parts will hold up to 6k no problem. Scat way better than those SIRs.....think youd be fine with the 9000 crank but if you can afford the forged even better.

BROKEN RODS

I would highly recommend those rods for your build they have plenty of cam to rod clearance and no need to run a reduced base circle cam. Those rods have the same cam to rod clearance as the Callies rods and look very similar to the Lunati Pro Mod rods.

The Summit rod and mains are made by King and are an aluminum bearing which is are great bearings. I use the King HP bearings which are aluminum and they stand up great in my Drag and circle track builds. Like I said the rod journals always seem to be on the low side and require .001 under and I use the Sealed Power which is an aluminum bearing. If you need that number send me a PM.

Those Mahle pistons are top of the line with there ring package but make sure you have a qualified shop finish hone your block with torque plates using the same hardware and gasket you will be using in the end build. Having the cylinders round once the heads are bolted on is key to ring seal. Not doing this would be a big waste on money. Believe me.

Depending on the casting you may need to clearance the pan rails. I have seen a few blocks where the rods hit one cylinder in the inside towards the cam rare but it does happen.

Yes you will have new parts and I can guarantee you will need to size both ends of the rods which is normal. Always break the rods down retorque check the big end they are always to the low side or under. The pin end always needs to be pin fit. plus you need to check for bend and twist.

The crank will look good but its a ground finish, Take a penny tip at a 45 degree angle and drag it across the journal you feel what I am taking about.

I am building a SB 427 3.875 stroke by 4.185 bore right now and those are the rods are what I am using. Its not an all out build but a street build that should be in the 525 horse range but have about 560 or better torque. Heads are only AFR 210's with a HYD roller and I am using the GM lifter and spider package. Air gap intake and 10:3 compression custom dish pistons.

I hope I have helped you out as I see a lot of shops misleading people when it come to stroker kits that really work.

Are you on F/B ??

Good luck which ever way you go.

Black04Vert

I have a 383 in progress. Here's some info to take with a grain of salt:

To counter some of the suggestions here, there are some drawbacks to using forged everything. For instance, forged 2618 pistons have high piston-to-wall clearances compared to hyper. This can result in piston slap until your engine is warm. Forged 4032 has tighter piston-to-wall clearances and less thermal expansion with less chance of piston slap. A good quality hyper should be good to 600-650 though.

Forged rods seems like a safe bet to me. However, if your quench is poor or you are using iron heads you might consider using 5.7 rods vs 6.0+ to reduce your dwell and chance of detonation at the expense of a little weight and piston side loading.

The forums are loaded with folks blowing up cast cranks. Also, the "this crank is good to X horsepower" claims are probably also not taking into account that you will be using a manual which has potentially higher shock loads than an auto.

If you buy everything as a set then it's easier to get an internally balanced setup.

BROKEN RODS

I actually have a some 383 wit a 6.125 rods and to date detonation is not a factor, Longer rods and dwell time do require less timing. I also have noticed flatter torque curve with the longer rods.

My self I use 4340 cranks unless a customer does not have the money for a forged crank. I would say 98% of my builds I use forged cranks.

5.7 Rod 383's most cranks will not internally balance with out heavy metal and thats not cheap.

5.7 rod pistons for a 383 at BDC have way to much piston hanging out of the bottom of the bore.

BKbroiler

I can offer some real world 383 experience. My engine is internally balanced with an Eagle cast steel crank, reconditioned stock L48 rods with ARP bolts and JE forged pistons. This engine has withstood far more punishment than the occasional "spirited driving" would cause. I bracket race the car and I have about 240 quarter mile runs on it going a best of 12.15 at 110 mph. I have about 10K street miles on this setup over the last 9 years or so. No problems.

OldCarBum

If you haven't looked at the big picture for building your motor I would at this point so its all done right the first time.
Ask yourself what am I really going to use my car for?
1. What kind of roads will I be driving? Around town, light to light, cruising on road trips, on the interstate? Twisting foothill, mountain and coastal back roads?
2. Where do I want my power band to start, bottom, mid-range or top end?
3. What rear end gears?
4. What cam shaft do I need to make the power where I want it?
5. Compression ratio?
6. Do I want to rebuild this motor again in 6 months or ten years?
Then you can answer the questions you are asking?
Mainly a good cast crank will support the torque and horsepower you plan in your build, but for a few dollars more a good forged crank is better. Over kill? Maybe... But if you want a motor that will last I would go with the better parts.
Forged crank, forged pistons, long rods etc, and don't forget about good heads!
Have a good machine shop check and balance everything.
Don't forget about upgrading your valve train as those items are even more prone to failure, ie push rods, rockers, lifters, and the list goes on.
Even give thought to your oil pan choice. Stroker clearance, windage tray, crank scraper, baffling.
I'm going through this same process with my 496 build.
Quality and strength cost more for a reason.
Call SCAT on their customer service line and ask them to put a package together for you.
Tell them you want good quality within your budget and you don't want the economy stuff.
If you can't afford the better parts now, do like I am, save more money and get the better quality parts as you can afford them.

BROKEN RODS

Hate to inform you but how many SBC's that uses a 3.875 stroke or 4.000 stroke use a 6.0 rod and more stroke more dwell time along with the rod long rod and more then a engine with a 3.750 stroke, You can't get a 5.7 rod to work with a 4.000 stroke or 3.875 stroke so these engine are not going to live because they have 6.0 rod in them. Look at the LS engines 6.125 rods.

I really don't think a 3.750 stroke using a 6.000 or 6.125 rod is a problem, Longer rod less angulation, less friction, lighter pistons, less side loading, I like the piston moving off TDC slower you take more advantage of the burn time.

Some of my restricted circle track engines I use a 6.250 rods flatter torque curve and it carries the HP longer NOOOOOOOOOOO problems with detonation.

L88Plus

Why use a 1500hp crank in a 500hp block?
Scat cast crank, Scat procomp rods, pick your pistons and get after it.

cv67

tuning with an 02 sensor can take risk out of cast or hypers also keep temps from getting out of hand helps too

Yrs ago we did a cheapy 350 for a friends C10 "budget bomb"
CAT crank, rods, cheapest cast 11:1 pistons he could find
Ported a set of Edelbrock heads,he244/252 comp SFT. He abused the pee out of it but never blew we are all waiting. 160 stat good fan and tuning.
lots of ways to skin a cat. Lots poo poo those rods/crank but never had a problem just have em looked over.