Skip White Performance - We have the best prices you will ever find for aluminum heads, rotating assemblies and strokers
Skip White Performance
1910 Brookside Lane
Kingsport, TN 37660

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 423-722-5152

SBC CHEVY 421 ROTATING ASSEMBLY SCAT 4340 CRANK & RODS -16cc RD Dh. 4.155 SMJ

$1,595.00

Available



Product Information

UPC371486739761
Product TypeShipped Product
Shipping Cost $76.50
Number of reviews 0

FULLY BALANCED SBC 421 ASSEMBLY WITH WISECO RACING FORGED PISTONS 4.155 BORE. -16cc RD D-CUP DISH, SCAT 4340 FORGED 3.875 STROKE CRANKSHAFT & 6.0 RODS FITS SBC 2PC REAR MAIN SEAL BLOCKS WITH 350 MAINS.
BALANCED IN HOUSE.

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The picture above is a file photo. See the detailed info below for the actual pictures and items included in this assembly.

WARNING!

This assembly cannot be used in a gm 400 block due to the crank main journal size. This assembly is made to fit in an aftermarket block with 350 main journals such as a Dart SHP or Little M, and various other brands. These aftermarket blocks are offered in both journal sizes, so be sure of the size you need before ordering. If you need this assembly to accommodate a block with 400 main journals, we do offer it in our other listings.

This setup uses our Scat 6 inch Competition Series rods and premium Wiseco pistons made from 2618 alloy. The rings that are supplied with the pistons are the Mahle 1.5, 1.5, 3.0mm. The Wiseco Racing Pistons have a fully machined crown/top. The pistons alone cost around $575.00 We consider the Wiseco Racing pistons to be the best pistons on the market.

We offer these assemblies with dish or flat top pistons, as well as other bore sizes. See details below for the actual specs.

GENERAL SPECS.

  • Crankshaft: Genuine Scat
  • Crankshaft Stroke: 3.875"
  • Crankshaft Material : 4340
  • Journal Diameter: 350 Mains. Be sure of the size you need!
  • Rear Main Seal: 2 pc RMS
  • Connecting Rods: Genuine Scat
  • Connecting Rod Type: Pro-Competion Series with ARP Cap Screws.
  • Connecting Rod Size: 6.000"
  • Wrist Pin: Full Floating
  • Connecting Rod Material: Forged 4340 Steel
  • Pistons: Wiseco Fully Forged High Performance
  • Piston Size: 4.155" (421 actual CID)
  • Dome Volume: -16cc RD Dish
  • Piston Material: Forged 2618 Aircraft Alloy
  • Piston Rings: Mahle High Performance
  • Ring Size: 1.5 1.5 3.0mm
  • Ring Fit: File Fit.
  • Ring Tension: Standard
  • Ring Material: Ductile Iron/Cast/Stainless/Moly
  • Main Bearings: King MB557SI
  • Rod Bearings: King CR807SI
  • Balance: In House on CWT balancer.
  • Damper: Pro-Race brand 6.75
  • Flexplate: 168 tooth heavy duty; 153 tooth is available. Manual Trans. flywheels also available.
Compression Ratio Chart

The calculations below assume your pistons are at zero deck. Let's say your compression calculates out to be 11.36, for example, based on having the pistons at zero deck (flush with the deck), but your pistons were going to be .005 in the hole, then the comp. ratio would only drop to approx. 11.23 and if left .010 in the hole, then it would drop to approx. 11.09 We do recommend having your block decked to allow the piston to set anywhere from flush (zero) to .005 in the hole for optimal performance. We used a 4.200 head gasket diameter, and a .040 head gasket thickness in our calculations to come up with our comp. ratio values.

Assembly

Cylinder Head Volume

58cc

64cc

68cc

72cc

421

Static Compression Ratio

4.155 Bore

11.36

10.67

10.25

9.87



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We do our own balancing with our brand new, 2013 model CWT 5500 Series Balancer. The CWT 5500 is the absolute ultimate for precision balancing. When we balance the assembly for this engine, it will be to very high specs, usually within 1-2 grams. We include a balance sheet with your setup.

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READ THIS LISTING COMPLETELY BEFORE YOU BUY ELSEWHERE!

This assembly uses a Scat 4340 Forged steel crankshaft and 4340 Scat Competition rods, Mahle plasma moly rings, King bearings, ProStreet damper, and SFI approvable 168 tooth flexplate. See our other listings for various piston bores in flat or dish style.

The Scat 4340 Crankshaft is one of the best values you will ever find in crankshafts. The HP King bearings are included with this assembly.

The picture below is a generic file photo of a Scat crankshaft. You will receive the correct model packaged in the original Scat box.

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We recommend that you check the thrust clearance on the crank before assembling the engine. This is recommended on any crankshaft, regardless of brand or cost.

Our choice of rods are the 6 inch SCAT COMPETITION SERIES rods with ARP-8740 cap screws.

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The Scat Pro-Comp extreme duty I-beam rods should not be mistaken for ProComp rods. These rods are made exclusively by Scat, and have nothing to do with the ProComp company. The critical sizing and installation of the ARP cap screws is performed on a Sunnen machine in the USA by Scat Industries. These rods are excellent for those wanting the extra security offered by a rod with 7/16 ARP cap screws.

Take notice of the design of these rods. They are far superior to conventional style I-beam rods. We are now using this rod in all of our Stage 4 and up SBC engines. We also use this rod in our big block 540/555 engines, making approx. 700+hp

If you do a search on the Scat Pro-Comp rods, you will find a vast amount of info on many car forums. All of the info is 100% positive. These rods are run in engines that not only produce high horsepower levels, but also run at continuous RPM. Notice the general appearance in the pictures. These rods do look impressive. The style is reminiscent of a steel billet rod.

The fact that these rods are incredibly strong and well made, coupled with the fact they are light weight and offer better clearance than any H-Beam rod on the market, made it an easy decision to use them in all of our high horsepower street/strip engines.

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We have noticed some sellers using generic rods and crankshafts in their rotating assemblies. These non-branded (no-name) rods and cranks are often poor quality in many ways. You will notice many sellers fail to mention the actual brand of these products. Upon further investigation, you will find such parts not to be a branded name product. They may label these parts with a name, but one that is totally unrecognizable in the industry. Our experience in years past with such rods and cranks has been disappointing, to say the least. Failures of such critical parts in your engine may result in catastrophic damage. Machine shops are sometimes able to correct some of the problems with these low quality rods and cranks, but at great expense to the customer. As for the questionable alloy these items may be produced from and the potentially incorrect heat treating methods used, little can be done to verify this and nothing can be done to correct it. As you may have noticed, this is why we specify the name brand and series of every part used in our assemblies.

Many of the inferior "no-name" rods on the market will also have "no-name" rod bolts in them. We have seen these bolts before, and they are very low quality. They don't have ARP's rolled thread design, and they don't torque down with the same characteristics as a genuine ARP bolt. It's not just a matter of having a different brand bolt in the rods; these bolts are low quality in many ways. They have been known to fail in engines to a much greater degree than a high quality rod bolt, and this failure usually causes catastrophic damage in the engine. Beware of rods that don't mention the rod bolt brand. As far as we're concerned, ARP bolts are the only brand we would ever use or accept in a set of rods.

KING HP MAIN AND ROD BEARINGS ARE INCLUDED.

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WISECO FULLY FORGED PISTONS, RATED AT 800+ HP. THESE PISTONS ARE VERY RESISTANT TO THE DAMAGE CAUSED BY DETONATION COMPARED TO NON FORGED OR HYPEREUTECTIC PISTONS. WISECO PISTONS ARE 100% MANUFACTURED IN THE USA. THEY ARE ONE OF THE HIGHEST RATED PISTON BUILDERS IN THE COUNTRY.

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Having high quality forged pistons will be your only hope should the conditions arise for detonation to occur. We sell nothing but forged pistons made from 2618 alloy, as I find it comforting to know that my customers will have an engine with a tremendous safeguard built into it. Support rails, wrist pins, and pin locks included.

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All of our Wiseco forged pistons are custom made for us and will sit flush in the block at a deck height of 9.015. If you have a virgin block, the deck height is at 9.025 and most machine shops will only have to shave approx. .010 to remove any warping and put down a fresh finish. This puts the block right at 9.015, creating a zero deck with these pistons. Having the pistons sit flush with the deck creates a very good quench/squish zone. Most other catalog pistons sit .025 below stock deck height, (9.00). Their reasoning for this: should the block have been decked multiple times, then the pistons will not be sitting too far above the deck surface. Most of our customers have a block that is at standard deck height and if you were to use a standard catalog piston then you would have to butcher the block .025 to accommodate them, and if you failed to cut the block down to achieve a zero deck then you would end up with a very poor quench/squish zone. By cutting the block to 9.00 you now have lost a considerable amount of strength in the deck area, and this can also cause the engine to run hotter than it would with a thicker deck, not to mention your block is somewhat at it's end limit for future decking. Should you have a block that is at 9.00 it is a very simple task for us or any machine shop to deck the piston tops and bring the compression height down.

The Wiseco pistons are rated very high in the performance industry. They normally offer three levels of pistons, starting with the Pro-Tru Street version made with 4032 forged alloy. The next level up would be the Pro-Tru series that are much more expensive and made from 2618 aircraft alloy. The highest level pistons they offer are their professional line made for very high level racing. Those are normally in the $700-$1100 price range.

Our custom made Wiseco pistons are very close in comparison to the middle version as they are made using the 2618 aircraft alloy and have fully machined crowns. Wiseco has their own foundry on location. We know of no other piston company with their own foundry. Our pistons are custom designed to address the needs of the high performance street rod industry.

You may have noticed that our Wiseco custom made pistons are referred to as Racing Pistons on the package. This does not mean that the pistons are for racing only. This is a generic term, referring to their ability to be used in high performance applications as well as for street rod use. These pistons are 100% suitable for street or strip use and designed as such. A true all out racing piston would not be suitable for street use for many reasons, but these pistons are perfectly designed for use on the street, as well as for drag racing.

These pistons are also suitable for use with nitrous or blower setups, but for those not running forced induction, the forged pistons offer very high reliability. The 2618 forged piston is stronger than any other alloy used in the piston industry. For the slight increase in cost, this setup is the best value on the market.

Notice the detailed gas porting and ring grooves in the Wiseco piston.

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One more feature that makes our Wiseco Racing pistons different than many others is the alloy used to make them. Many of the forged pistons that are in the lower cost range use a forged 4032 high silicone alloy. This is certainly a cut above the regular hypereutectic pistons on the market but it is still one step down from forged 2618 aircraft alloy, at least in respect to resistance against the effects of detonation. Our pistons are all custom made with 2618 aircraft alloy only. They also have a redesigned skirt that virtually eliminates piston rattle when cold. We use such a high quality piston in our engines because of its resistance against the effects of detonation.

Pistons that are non-forged or forged made from high silicone 4032 alloy, can fragment from the effects of detonation. This can then allow the connecting rod to destroy the block, crank, and cylinder head. Those types of pistons are fine for stock or mild engine builds, but should never be used in engines built to high horse power numbers. The forged 2618 alloy piston is much more resistant to extreme heat and is also very strong in general.

Our Wiseco forged pistons will clear most any valve size on the market.

Item Code


Vendor Name

Wiseco

Product Type

Race Series for street/strip use

Product Model

Custom built for SWP

Engine Displacement (cu.in.)

421

Engine Family

CHEVROLET - Small Block V8

Material

2618 Fully Forged Aluminum

Base Bore (in)

4.155

Stroke (in)

3.875

Rod Length (in)

6.000

Compression Height (in)

1.080

Top Type

Reverse Dome

Net Head Volume (cc)

-16cc

Deck Thickness (in)

0.350

Weight Without Pin (g)

422 Approx.

Wrist Pin Diameter (in)

0.927

Wrist Pin Length (in)

2.500

Wrist Pin Weight (g)

118

Pin Lock Type

Spiral

Ring Set #

40564CP

Top Ring Groove Size

1.5mm

Second Ring Groove Size

1.5mm

Oil Ring Groove Size

3.00mm

Top Ring Land (in)

0.255

Second Ring Land (in)

0.170

Bottom Ring Land (in)

0.090

Quantity

8.

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MAHLE PLASMA MOLY RING SET INCLUDED. 1.5mm 1.5mm 3.0mm file fit.

PRO RACE BRAND HARMONIC DAMPER, 6.75 DIAMETER INCLUDED. THESE ARE VERY HIGH QUALITY ITEMS. YOU SHOULD NEVER USE AN OLD DAMPER/BALANCER.

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We have noticed others using a low grade knockoff brand damper/balancer, and we have encountered them in the past. They are substandard in appearance, but they are usually out of spec. We don't have anything against knockoff products if they meet our standards and offer a good value. We think it is great that many of the name brand companies are getting their just rewards for what we consider nothing short of offering overpriced goods. Take our word on this, you don't want a balancer coming off or one that is improperly weighted. The timing marks were also poorly marked on some of the balancers we have come across.

We know of several competitors using these balancers. The ProStreet brand is far superior to most any we have ever seen. They were once known as a knockoff product, and have become one the best values on the market, without comprising quality whatsoever.

HEAVY DUTY FLEXPLATE INCLUDED.

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HEAVY DUTY FLEXPLATE. This flexplate will resist cracking and warpage, leading to imbalance in the engine. One good telltale in identifying a cheap flexplate is the lack of welding on each side where the plate mates to the ring gear. They usually have a pale grey color to them, as they are not coated, and will rust quickly. Ours are welded on both sides, and are approximately 30 thousandths thicker than an OEM plate, and are either zinc dichromate or black powder coated. We would never use the thinner plate on an assembly like this.

We do offer this assembly with a manual flywheel. See our other listings. In most cases we do have both sizes, 153 and 168 tooth, available.

WARNING: the flexplate and crank have a dowel pin hole. You must align the flexplate and crank dowel pin holes, but do not use a dowel pin. The flexplate was aligned to the crank when we balanced the assembly, and must be installed the same way.

YOU SHOULD NEVER USE AN OEM STYLE FLEXPLATE ON AN ENGINE. THEY ARE NOT SUFFICIENT TO HANDLE 400+ HP. MANY SELLERS OFFER THE LESS EXPENSIVE THINNER FLEXPLATE, OR WORSE YET THEY DO NOT BALANCE THE ASSEMBLY WITH THE ACTUAL FLEXPLATE THAT IS SHIPPED WITH THE ASSEMBLY. THEY USE ONE PLATE OUT OF A BATCH OF PLATES, ASSUMING THEY ARE ALL THE SAME.

WE FOUND NO TWO FLEXPLATES TO BE REMOTELY CLOSE IN THIS RESPECT. THE MASSIVE WELDING ON THESE PLATES AROUND THE RING GEAR ON BOTH SIDES AND ATTACHING THE WEIGHT IS VERY INCONSISTENT AS FAR AS BALANCING IS CONCERNED, SO WE DO SEND THE ACTUAL PLATE USED WHEN BALANCING AND SERIAL NUMBER IT TO MATCH THE REST OF THE ASSEMBLY.

Many rotating assemblies we see are not using the most suitable parts. We hope you value the fact that we have put together an above average assembly. Please read the full listing.

You can easily replace your flexplate to an exact match, should you ever need it. You would have to send us your damaged plate to match it. Many people have plates that have lost several teeth due to a starter issue. If this ever happens, just send us the plate and we can reproduce it, and we also compensate for the missing teeth when matching up the plate on the balancer.

We offer this assembly with selected upgrades. Listed below are some of the most requested ones. Many not only improve performance, but further enhance the reliability and longevity of your engine, along with resale value.

SFI Certified Flexplate: This is a very low cost upgrade and may be required when racing your car at certain tracks. The flexplate that comes with this assembly is a heavy duty plate, but the SFI certified plate is one step up in quality and safety. This SFI plate is made in North America. We noticed these have much less run-out and warpage than we see with many other plates on the market. Plates with too much run-out and warpage can cause a host of problems for your transmission and starter, and affect balancing. The low cost to upgrade to this is well worth, it in our opinion.

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SFI damper: Offers an extreme level of safety against breakage, and is very resistant against slippage of the elastomer damping material. SFI dampers are not only made from a better grade of steel, they are also constructed differently and have a much better appearance. They usually last much longer than a non-SFI damper. Many drag strips require this on engines producing high horse power levels. The SFI certification is laser etched into the side.

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Crank polishing: Extends bearing life, reduces oil temp, frees up a slight amount of average horsepower. This is a very low cost upgrade, and in the world of mass production, most cranks do not come with a true polished finish. This is why most machine shops have a machine to do this. The difference is dramatic between a crank right out of the box and one that we have polished. Bearing companies claim that cranks that have better finishes on the journals will survive the break-in better, and have much longer bearing life. We do a two-step process and bring the RA numbers down in the single digit range. We have the most advanced crank polishing machine on the market.

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Clevite Bearings: We find the Clevite bearings to be a somewhat better product overall. Clevite is what we now use in all of our engines. This is not to say that King bearings are faulty in any way, but under certain conditions, we have seen fewer problems develop with Clevite bearings during break-in. We have sold King bearings for many years and do not hear of problems from our customers, but our experience on the dyno has shown the Clevite bearings have a better surface appearance upon tear-down after many dyno passes.

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Rod to cam clearancing and sizing: We know exactly where and how much to cut the rods for correct cam clearance, and sizing the big end and wrist pin bushing on the Sunnen machine saves a trip to the machine shop. All rods, regardless of brand, should be checked for sizing on a Sunnen machine, and corrected if needed. You will seldom see a complete set of rods that have perfect sizing on both ends right out of the box.

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Race balancing: This is for those who want the engine to operate virtually vibration free at high rpm. Extends engine life and frees up a few more horse power. This is a somewhat labor intensive procedure and is not required, but the feel of an absolutely vibration free engine at high rpm is desirable by many. The standard balance job that is included with this assembly at no extra charge is certainly sufficient. With a race balance job, all pistons and rods are match weighed to within 2/10's of a gram or less, and the final balance is brought down to around 1 gram plus or minus. An ultra smooth engine at high rpm has a noticeable feel and sound to it. If you do not opt for this upgrade, the assembly will still be fully balanced. We spend a good hour and a half doing the regular balance work, and it will certainly meet your needs.

Scat H-Beam Rods: Recommended for those running hard. The Scat Competition rods that come with this assembly are sufficient for most street rod uses, but the Scat H-beam rods will most likely offer more security against rod breakage under hard use. The H-beam rods have a 750+ HP rating.

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ARP-2000 rod bolts: This is one upgrade that we find to be very valuable. The rod bolts are most likely to fail under hard use, moreso than the rod itself. When a rod bolt fails during high RPM, total engine destruction is usually the result. The ARP-2000 rod bolts are a very good upgrade, in our opinion. We actually have few, if any, problems with the regular ARP-8740 bolts, but those who run hard always upgrade to the ARP-2000 rod bolts. The ARP-2000 rod bolts also torque at a higher number, and this increased clamping force is also a factor in keeping the big end of the rod stable and true to size. The ARP-2000 bolts are installed in the rods and this upgrade is only available with the Competition rod upgrade.

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The upgrades above are all available in our other listings. Some of these are often requested by those building an engine without a machine shop. We find most of these upgrades very valuable for those wanting to take longevity and durability to the next level. They are all bottom end related, and that's an area worth investing a few more dollars into, in our opinion, especially if you’re planning on running long and/or hard. These upgrades are also valuable for your build history on your engine, and would certainly increase the resale value of your engine, should you ever sell it.

PLEASE GIVE US A CALL AT 423-722-5152 or 877-383-5152 FOR TECHNICAL INFO. OUR HOURS ARE 8am-8pm EASTERN. 10am-3pm ON SAT.

BE SURE OF THE COMPRESSION RANGE AND BORE SIZE YOU WANT BEFORE PURCHASING.

A note from Skip White, company president.

We have built this assembly for many people that are into street/strip use and mid level drag racing, and have yet to experience a failure. Every part in this assembly meets our satisfaction. I can promise you that many assemblies offered by other sellers pale in comparison to ours. This is the best value you will find on the market.

Many people have asked how is it that we can sell this assembly for such a low price. To answer this; we buy our products at master WD (warehouse distributor) level for all of the items in this assembly, and we are selling direct to the public. We are a volume sales based company. Our profit is based on sheer volume, with a very low markup. By selling large volumes, we have to purchase large volumes of products. It is this large volume purchasing that allows us to buy products at a much lower price and we simply pass these savings on to our customers.

Skip White

Call for tech info at 423-722-5152.

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