SBC 421 DART Short Block Kit - Forged Wiseco Pistons and Manley Forged Crank

The photos above and below are file photos. Actual appearance may vary.  All parts are brand new, first line, unblemished, and balanced. This short block kit is not assembled .

What Comes With It

A brand new Dart SHP block that has been decked, bored and honed to specs, Dart coated cam bearings, Manley fully forged crankshaft and 4340 Scat rods, Wiseco forged pistons, high performance rings, King bearings, and a heavy duty 168 or 153 tooth flexplate and a Pro-Sport SFI damper.

The assembly is fully balanced. See details for all the actual specs. In the lower section of this ad is information on the various upgrades we offer in our other listings.

Our short block kits are custom built to your specifications (piston configurations, compression ratio, rod setups, and upgrades). Contact us for custom builds.

This is a file photo. Actual appearance may vary. Freeze plugs not included.

Block Specifications

• Dart SHP Block
• 2pc rear main seal
• Splayed center caps

The block is bored to size with our new Centroid touch probe machine. Few machine shops have a machine of this accuracy.

We also deck the blocks to an RA finish of approx. 15 or better. The decking procedure is also done by our Centroid CNC machine.

We often find many brand new blocks to have a sloping deck of up to 4 thous. When we're finished decking the block it is within approx. .001 accuracy from end to end. Many machine shops fail to catch this as the machinery they use does not allow for such accuracy.

We then plate hone the block with our new Sunnen SV10 diamond hone machine. This is also a very advanced machine that hones the block with a finish unlike conventional machines.

The final step is to clean the block in our high pressure block washer. You should always re-wash your block before assembly. This is to assure that the block is free of contaminants.

Pictured below is the rotating assembly that comes with the short block kit.

Crankshaft Specs.

• Crankshaft: Manley
• Crankshaft Stroke: 3.875"
• Crankshaft Material : 4340 Fully Forged
• Journal Diameter: STD SBC
• Rear Main Seal: 2pc RMS

Connecting Rod Specs.

• Rods: Genuine Scat
• Rod Type: Scat Pro-Competition, I-beam, Bronze Bushed.
• Rod Length: 6.00"
• Rod Material: Forged 4340 Alloy.
• Rod Bolt/Cap Screw: ARP 2000 Cap Screws.

Piston & Ring Specs.

• Pistons: Wiseco Fully Forged. High Performance for street/strip use.
• Piston Size: 4.155"
• Piston Material: Forged 2618 Aircraft Alloy
• Piston Rings: Mahle High Performance, Moly, Standard Tension.
• Ring Size and Fit: 1.5mm 1.5mm 3.0mm File Fit.
• Ring Material: Ductile Iron/Cast/Stainless/Moly

Bearing, Damper, and Flexplate Specs.

• Main Bearings: King MB557HP High Performance
• Rod Bearings:  King CR807HP High Performance
• Balance: In House on CWT balancer.
• Damper: Pro-Race brand Pro-Sport Series 6.61" SFI damper
• Flexplate: Heavy Duty 168 tooth or 153 tooth. Manual Trans. flywheels available.

Important note

Many customers have asked us what size they should bore their block at to allow for a proper piston to wall clearance. The required clearance is built into the piston already. For example if these pistons show a given size such as 4.030 then that is exactly what you will bore the block to. The actual size of the pistons when measured at the skirt, 1/2 inch above the tang will show to be approx. 4.026. The needed clearance is built in. Should you be using these pistons in a marine app. where the boat receives it's water from the lake, then an additional 1.5-2.0 thous. would be added to your final bore size, and some forced induction apps may also require a slight increase in bore size.

These pistons are totally suitable for use with mid level nitrous or blower setups. Extreme level builds that are making hp numbers in the 1000 hp range will require a set of custom made extreme duty pistons.

Our Wiseco Forged pistons are custom designed with an increase in compression height. This has many advantages. Here are a few facts about compression height and deck height.

Our custom made pistons have a compression height that is .010 taller on bbc pistons, and .015 taller on sbc pistons, as compared to most all of the catalog pistons on the market. We find this to be a very valuable feature.

Since our pistons sit at a taller than normal compression height, we only have to remove approx. .005-.010 off the deck surface of the block. Our goal is set the piston at zero deck (flush with the deck surface). This maintains the deck's thickness, making it much stronger than a block that has been cut down .025. The engine will also run a bit cooler with a thicker deck. It's well known that the deck dissipates much of the built up heat an engine generates. This also allows for future deck re-surfacing without compromising the integrity of the block. On our bbc engines, we actually leave the piston about .003 to .005 in the hole to allow for possible piston rock. Our sbc engines will have the pistons setting right at zero with the deck.

The pictures below are file photos of our Wiseco pistons. Actual appearance may vary.

Manley 4340 Fully Forged Crankshaft. (File photo)

The material used in this crankshaft is manufactured from an exclusive Space Age material that was designed for high strength and fatigue resistance. The Manley cranks are the best value you will ever find. The Manley crankshafts are the best way to build a strong bottom end for, street rods, dirt and circle track racing, and drag strip racing. This crank is suitable for use up to approx. 800+ hp.

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. Also be sure to check your main and rod journal size.

SCAT Competition Series Rods w/ARP-2000 hardware

Our choice of rods are the SCAT COMPETITION SERIES rods with ARP-2000 cap screws.

The Scat Pro-Competition 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 2000 cap screws. The ARP 2000 rod bolts are a superior rod bolt compared the ARP 8740 rod bolts, and usually cost approx. $89.50 more. As of this date, 7/5/24 the ARP 2000 rod bolts will be included in all of our 421, 427 and 434 engine builds.

If you do a search on the Scat Pro-Competition 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 appearance in the pictures. These rods do look impressive. The style is reminiscent of an Oliver premium rod.

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

Our Scat rods are bronze bushed, and unlike Eagle I beam rods, these are fully forged 4340 alloy.

Genuine ARP 2000 cap screws.

We have noticed some engine builders using low cost generic rods, bolts, and crankshafts in their engines. These non-branded, (no-name) products are often poor quality in many ways. You will notice many of the low end engine builders fail to mention the actual brand of the rods or cranks used in their engines. 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. Besides the obvious issues such as incorrect sizing and machining that is difficult to correct, the questionable alloy these items may be produced from and the potentially incorrect heat treating methods used, could prove to be disastrous. Little can be done to verify this and nothing can be done to correct it. Failures of such critical parts will usually result in catastrophic damage to the engine. As you may have noticed, this is why we specify the brand name and series of every part used in our engines.

See our tech article on ARP Hardware

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.

Before the engine is assembled, we strongly suggest checking the rods on a Sunnen machine for sizing on both ends. We recommend this with any rod regardless of cost or brand. It is not uncommon to find some of the rods requiring a slight bump through the hone for perfection in sizing and roundness. We also offer this kit with a proofed set of rods. This is an excellent choice for those wanting to build the engine on their own.

MAHLE File-Fit Rings Included

King Main and Rod Bearings Included

Be sure to double check your clearances when your motor is assembled.

Pro-Sport harmonic SFI damper, 6.61 diameter, included.

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, and are often out of spec. The timing marks were also poorly marked on some of the balancers we have come across. You don't want a balancer coming off or one that is improperly weighted. Another problem with low grade dampers is the elastomer bonding can lose its adherence to the inner and outer structure. This problem is referred to as a slipped damper. We have only encountered this once in 10 years with the Pro-Race brand dampers. Damper failure rates are much higher on engines using a non-SFI damper coupled with hp ratings exceeding 450 and turn 5600 rpm or higher.

We know of several competitors including these balancers with short block kits. The Pro-Sport SFI 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.

Flexplate Included

This flexplate will resist cracking. One good telltale in identifying a low quality 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 much thicker than an OE plate, and are either zinc dichromate or black powder coated. We would never use the thinner OE style 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 crank has a dowel pin installed in it. You must align the flexplate or flywheel to the dowel pin. The assembly was balanced with this pin installed.

Balanced In-House

We do our own balancing with our new state of the art CWT 5500 Series balancers . The CWT 5500 is the ultimate for precision balancing. We now have three of these in our machine shop. Every rotating assembly we sell is balanced within 2 grams or less at no extra charge. A balance sheet is included with your assembly. Race balance upgrades are available.

Rust Warning

If you are going to store your rotating assembly or short block kit for any length of time, it is very important that you protect these parts by spraying a light coat of rust preventive substance on all bare metal parts. This is especially important for those storing these parts in a high moisture or humid environment. Very light surface rust is easily removable and will cause no harm, but heavy rust can damage these parts and be very costly to fix.

Thoughts on what the competition offers

Many short block kits we see on the market are not using the most suitable parts. We hope you can value the fact that we have put together an above average short block kit. The failure rate with the parts we use is near non-existent. It was through trial and error in years past that taught us where to draw the line with low cost parts. We are out-priced by many others selling short block kits that include parts with high failure rates. Many of these parts also pose a great problem due to the fact they require additional machining and can end up costing you a great deal more money and time. If you're going to have a machine shop build your engine, we strongly advise you get an opinion from them on the parts you're going to be bringing to them. Rest assured they will find no problem with the quality of our parts. We have also seen sellers offering parts that are not compatible with what most people are building. We have seen several sellers offering no-name brand rods with an assembly. These type of rods also have no-name bolts in them. It is our strong advice to avoid this grade of rods. The low grade dampers and flexplates are also another problem. Another area of concern would be balancing. Not sure how much attention these sellers are giving in this area. We spend up to two hours balancing an assembly, and using the very best up to date balancing equipment on the market. If the assembly is not balanced properly, it will hammer the bearings out of the engine, not to mention there is nothing worse than an engine that lacks a smooth feel and sound when under load.

Upgrades!

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.

Note: The upgrade prices below are subject to change. Refer to the actual ugrade listing for the exact price of these upgrades. The changes are usually very small if any.

SFI Certified Flexplate: Cost of this upgrade is $24.50, 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.

SFI Rated Billet Steel flywheel upgrade/option for manual transmission. Upgrade to a SFI billet steel flywheel 168-tooth or 153-tooth for manual transmissions. We highly recommend the SFI billet steel flywheel for those running hard. These are fully cnc'd and far superior in many ways compared to the regular cast iron flywheel.

Cost for the SFI billet flywheel option can vary depending on availability. We carry two lines of the SFI plates, PRW and Ram. The Ram plates are a much higher grade product. We have this upgrade/option featured in our other listings. There will be a Chevy 153 tooth and a Chevy 168 tooth size available. Be sure you know the size you need.

Crank polishing: Cost for the crank polishing upgrade is $39.50, 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.

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. This is due to the fact that Clevite A series bearings use a slightly harder aluminum alloy.

Upgrade to Clevite "H/HN" Series - FORGED bearings is $45.00 (Use only on 4340 forged crank.)

We have these Clevite bearing upgrades featured in our other listings. You can see these and other upgrade options in our ebay store under the "UPGRADES" category, or simply do a search with the key word, "Upgrade" in the search bar when shopping in our ebay store. Before you finalize your purchase of this assembly you may add any of these upgrades to your shopping cart.

Rod to cam clearance and sizing : Cost of this rod to cam clearancing and sizing upgrade is $89.50, We know exactly where and how much to cut the rods on our vertical milling machine 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.

The clearancing we will do assumes the use of a reduced base cam. We do not recommend a full base circle cam in this assembly.

We do the rod to cam clearancing on a vertical milling machine as pictured below as part of this upgrade. By doing this procedure on a milling machine the rods are cut precisely at the correct angle to clear the cam. This also keeps the amount removed identical on each rod. It would be very difficult to do this by hand on a grinder as is commonly done. After we clearance the rods on the milling machine we go over them on a wire brush machine to clean up the edges, and remove any stress risers. This is a very critical procedure. Those who lack the experience and choose to do this on their own risk destroying the rod and or the bolt, or at least removing too much material and weakening the rod and or bolt.

Race balancing : Cost of this race balancing upgrade is $125.00, 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 Rod Upgrade : Cost of this Scat H-Beam rod upgrade is $89.50, 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.

H-Beam rods will require the use of a reduced base circle cam.

Block prep package : Cost of this block prep package is $265.00, This upgrade includes notching the block on our Centroid cnc machine to allow additional clearance for the crank if necessary. We also de-burr the block, hone the lifter bores to spec, chamfer the top of the cylinders, and lifter bores, and install the special Dart cam bearings and freeze plugs. The block is then thoroughly cleaned in our block washing machine. We find this upgrade essential for those lacking the proper equipment or knowledge to perform this correctly.

SBC Short Block Kit Assembly upgrade: Cost of this SBC Short Block Kit Assembly upgrade is $575.00, This upgrade includes everything in the Block Prep Package plus assembling the short block kit. If you choose this upgrade, DO NOT also include the block prep package in your cart.

Preparing the block in our Centroid CNC machine for precise notching, if necessary.

The blocks are washed in a dedicated block cleaning machine.

Pictured above is the final rinsing and drying to remove the cleaning solvents.

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.

Transmission Choice

Please read our tech article on Choosing a Chevy Transmission

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