STROKIN’ THE DART WINDSOR
Our current engine project begins with a 351W block and increasing displacement to a whopping 427 CID.
Text & photos by Mike Mavrigian
The Dart 351W iron-alloy block is available in either a 9.200” (standard Cleveland) or 9.500” deck height. We opted for the 9.5” deck.
This project will serve as an example of a street performance build, specifically targeted at the street rod/hot rod market. The basis of the build is a Dart cast iron 351W block. We’ll bore to 4.125” and accommodate a Scat 4.000” stroker crank, coupled with 6.200” Scat rods and JE pistons.
The Dart block replicates the original Ford 351W in terms of basic design and layout, but with several enhancements. Cylinder walls and decks are beefier, allowing much more custom machining latitude. The block also features priority main oiling system. The block material itself is much more rigid (high nickel alloy content iron block) and much more suited to high performance and/or racing applications. The main caps are machined billet steel, anchored with four bolts each (with splayed outboard center caps). The block also requires the use of a crankshaft that features Cleveland-sized (2.749”) main journals for added robustness. In short, Dart re-engineered the 351W block to meet today’s performance requirements. Basically, the Dart block makes the original Ford W block look like the skinny kid on the beach. Dart’s block is a brute, which basically blends the best from both the Windsor and Cleveland designs, along with Dart’s own performance enhancements.
Dart offers the block in either 4.000” or 4.125” unfinished bore sizes. This allows you to bore and hone exactly to your required bore diameter. Because the Dart blocks are CNC machined, all bores are properly centered and aligned. For example, cylinder bores centers and angles are already aligned relative to the main bore and decks; lifter bores are centered and are aimed 90-degrees to the camshaft bore centerline, etc. Aside from machining to achieve desired clearances and surface finish, there’s no need to correct any geometric issues (unlike dealing with a mass-produced OE block).
Even if bored to a max of 4.185”, Dart still provides adequate cylinder wall thickness for performance use. Decks also offer an extra margin of material to allow finish machining to suit the individual builder.
All five main caps are billet steel, and are deep-registered with no need for dowel sleeves.
The Dart block accepts all OE bolt-ons such as timing cover, water pump, fuel pump, etc.
The main bore is already exactly centered and aligned.
Lifter bores are machined on the tight side to allow the builder to achieve the oil clearance needed for a specific set of lifters.
The lifter valley features a very uniform and fine-cast surface finish for good oil return. Lifter feeds at the front and rear of the valley are threaded for 1/8” NPT. This allows you to install plugs/restrictors as desired. To restrict oil to the lifters you can either install restrictors at each end, or plug one end and restrict the other. Some builders prefer to plug the end they are feeding the main oil galley from and install restrictors at the opposite end. This provides priority main oiling before feeding the lifters.
As I grind/smooth the block exterior in preparation for paint, I’ll pay close attention to the cast Dart logos, since I don’t want to erase them.
This cross sectional view shows the cylinder wall thickness and clean water jacketing. (photo courtesy Dart)
Cross section of block front. (photo courtesy Dart)
Cross sectional view of the block rear. (photo courtesy Dart)
Our crankshaft is a forging from Scat, their part number 4-351C-4000-6200. This crank provides the Cleveland-sized 2.749” main journals, along with 2.100” rod pins, which allows the use of smallblock Chevy rods and rod bearings (this is a convenient feature, as a wide selection of rod lengths are readily available in SBC applications). This is a beautifully crafted component. All dimensions measured spot-on-the-money. Aside from potential material removal or addition during balancing with bobweights, I don’t anticipate the need for any additional massaging. Nice job, Scat.
Main journal oil holes are already neatly chamfered to induce oil entry during crank rotation.
Scat’s part number is very legibly etched into the face of the front counterweight for easy identification.
Our Scat rods are forged I-beam units with a center-to-center length of 6.200”. Both biog and small ends are closely weight matched, so no additional grinding will be necessary during balancing. Scat always does a nice job, and there are no surprises here.
We’ll be using JE forged pistons at a 4.125” bore size. Our flat-top pistons are currently on order, but a set of inverted dome pistons are shown here as an example of their Ford Windsor offerings. Piston sets include pins, locks and rings.
Our hydraulic roller bumpstick is a steel billet from Lunati. Valve lift is 544” intake and 560 exhaust. Duration @ 0.050” is 232 intake and 242 exhaust, with an intake centerline of 108 degrees and an exhaust centerline of 116 degrees.
Lunati’s tie-bar roller lifters feature undercut oil retention spaces. The tie bar prevents lifters from rotating within their respective bores.
Lifters feature heavy duty roller bearings and axles suitable for extreme pressures.
Our Clevite main bearings are part numbers for Cleveland-size mains.
Our Clevite rod bearings CB-663 HN are actually SBC bearings to accommodate our 2.100” rod pins and SBC rods.
Victor MLS (multi-layer steel) cylinder head gaskets will provide precise combustion and liquid sealing. MLS gaskets feature a special sealant coating and should not be unpacked until you’re ready to install.
The Moroso steel kick-out road racing style oil pan is powder-coated black.
I chose Moroso’s cast aluminum rocker covers, since I intend to treat them to a CNC engraving (this will be done at Innovators West, my favorite valve cover engraver).
The Race Pumps fuel pump will bolt up to the stock block location and will be mechanically activated by the cam, but the pump’s design produces a strong hydraulic pumping of fuel. The Race Pumps adjustable pressure regulator and the pump are machined from billet aluminum, feature a beautiful anodized finish, and each comes packaged in soft velvet-like jewelry bags.
Instead of using an adjustable piston ring compressor, I’ll use this billet aluminum tapered-ID compressor from ARP. Made specifically for a 4.125” bore, this will allow insertion of the ring-laden piston into the cylinder with ease.
Threaded fasteners are from ARP. For the sake of appearance, I opted for their polished stainless steel fasteners for those locations that I felt were applicable.
While all of the parts have yet to be selected, following is a rundown of our block, crank, rods and cam. I’ll get started on the block prep soon. Since this build is intended to focus on the custom rod market, one of the aspects of the build will involve a serious approach to the aesthetics. I’ll smooth-out the entire exterior surface area of the block to a glass-like finish and follow up with a very detailed painting. The visual aspect will be key, so I’ll choose an appropriate block color and I’ll enhance the overall package with complimentary colors and finishes with regard to all viewable components. It’ll be a showpiece. Our block features a 9.500” deck height. Considering our 4.000” stroke, 6.200” rods and the 9.500” deck, in order to achieve zero deck, pistons would require a theoretically ideal compression distance of 1.300”. CALCULATING PISTON CD BLOCK DECK HEIGHT – ½ STROKE – ROD LENGTH = PISTON CD 9.500 – 2.000 – 6.200 = 1.300 PISTON CD However, since we plan to use off-the-shelf pistons (as opposed to ordering a custom set), we decided on JE’s P/N 232474 pistons. Bore size is 4.125” (which will provide us with our desired 427 CID when combined with our 4.000” stroke). However, these pistons are available with a 1.280” compression distance, which will place the pistons 0.020” below deck in our 9.500” block. According to JE’s specs, this piston at zero deck will provide about 12.2:1 CR with 64cc chamber cylinder heads. The –0.020” piston-to-deck placement will help us to drop CR for a pump gas scenario (we’d like to end up with no more than 11.5:1 CR). Once we mock up and measure, we can always fine-tune by CNC milling a slight relief (inverse dome) on the pistons. With our camshaft duration (@0.050”) at 232 degrees intake and 242 exhaust, this should provide us with a real stump-puller, with a compression ratio that will work with pump gas. CALCULATING DISPLACEMENT BORE X BORE X STROKE X 0.7854 X NUMBER OF CYLINDERS 4.125 X 4.125 X 4.000 X 0.7854 X 8 = 427.65 CID
DART BLOCK TECH
Deck height……….9.500” Bore……………….4.125” unfinished Main bearing size…Std. Cleveland 2.749” Weight…………….195 lbs Maximum bore……4.185” Camshaft journal dia….Std. 351 Camshaft position…….Std. 351 Cylinder wall thickness (min)…..0.250” @ 4.185” bore Deck thickness (min)……0.675” Main cap torque specs….. 1-5 ½” bolts 105 ft lbs 2-4 7/16” bolts 65 ft lbs 1 & 5 3/8” bolts 35 ft lbs NOTES: Standard 351W timing chain, timing cover, gear or belt drive may be used. Actual deck height will be 0.001” – 0.005” taller for additional machining requirements. Standard 351W oil pump fits correctly even with the 4-bolt front main cap. When initially removing main caps, the caps and block should be deburred before reinstalling. This will insure that correct main size is maintained. Press-in 1 ½” freeze plugs and 2 3/8” cam plugs are provided. Use 351W ½” head bolt or studs kit. Head stud holes are blind and are not open to the water jackets. A sealant/antiseize must be used on the head studs. Loctite #620 is recommended. Studs should never be torqued into the block. They should be lightly snugged. It is preferred that a bullet nose (0.375” OD x 0.150” deep) be machined onto the lower end of the head studs to allow stud bottoming into the block in order to center the studs before tightening. CAM BEARING NOTES: Cam bearing OD should be deburred before installation. All Dart cam bearings are coated for cooler operation and increased reliability. Camshaft bearing bores are 2.200” ID on all five cam bores. The cam bearings feature five different IDs to fit the stock Ford cam journals, but all bearings feature common ODs. Position Brg # Part # Cam OD Front # 1 B384 32210051 2.081” 2 B385 32210061 2.066” 3 B386 32210071 2.051” 4 B387 32210081 2.036” Rear 5 B388 32210091 2.021” Complete set 32210041 Cam bearing sets for cams with common 2.081” size on all journals are available from Dart or Durabond #351RHP. Cam bearing sets for 2.051” common journals are also available from dart or Ford # M-6261-C351 PIPE PLUGS All front and rear oil galleys are tapped ¼” NPT. These are straight thread, not a tapered thread. When using a ¼” NPT tapered pipe plug, the diameter of the plug determines how deep the plug enters the threaded hole. If the plug is too shallow it can be threaded with a ¼” NPT tapered pipe die to the desired size. Various length plugs are available from Pioneer for adjusting the depth of the plug: PP584…………0.325” OA PP625…………0.333” PP567…………0.375” PP507…………0.460” NOTE: Due to variations in lifter sizes and clearance preferences, lifter bores are sized on the small side of the specification. Sometimes these bores will need to be lightly honed. The lifter bore diameter spec is 0.8747 – 0.8757”. Most lifter manufacturers recommend 0.0015 – 0.002” clearance. Always check lifter to bore clearance. SPECIAL NOTE: With a multitude of crankshaft, rod & piston combinations available, it is very important to check clearances of all moving parts, especially crankshaft counterweight and connecting rod to block clearances. Because the Dart cylinder barrels have been extended for increased piston skirt support, with stroker kits you may need to clearance the bottom of the bores for rod clearance. Be careful if you need to add counterweight clearance at the oil pump area. Be sure to leave enough material to seal the oil pump mounting flange. Also, always check the fit of the distributor before any machining is done. Some oil pans, including stock pans, will not clear the 4-bolt front and rear main caps. You need to use a pan that is specifically made for 4-bolt end-caps. Most manufacturers should stock pans for this block (Moroso, Canton, etc.). At the rear of the pan rail where the pan gasket and the rubber end-seal meets, there is a 1/8”-deep machined section in the block. Most engine builders fill this void with silicone. This void can also be filled with a piece of metal ½” x ¾” x 1/8” if preferred. This metal piece can be siliconed in place or a 1/8” hole can be drilled and tapped, securing the piece with a flat-top screw. On blocks with 2.749” mains, there is no provision to mount an oil pump suction screen. If using a suction screen, you must use a 2-bolt 351W stud kit, ARP # 154-5409. When using a dry sump system or a wet sump with external oil pump, you must block off the oil pump outlet hole in the block next to the front main cap. Dart recommends drilling and tapping for a 3/8” NPT plug. The oil filter inlet hole can be blocked using a –12 AN plug utilizing an O-ring style washer for sealing. The recommended inlet is at the rear of the block, on top of the bellhousing area. This will provide true priority main oiling, as it delivers oil directly into the main oil galley and feeds the main bearings before it feeds the lifter galleys. This increases the oil flow to the mains and drastically reduces the oil pressure requirements. This is a ½” NPT thread and is placed at a 2-degree angle to help the fitting clear the cylinder head, although some minor clearancing may be required. If this method is used, the –10 AN feed hole at the front of the block also must be plugged. If the front external oil feed is used, you must plug the ½” NPT feed at the rear of the block. The oil feed hole at the front left corner of the block features a –10 AN thread, not a tapered pipe thread. If you do not plan to use this hole, install an O-ring boss plug. This –10 AN plug is available (Aeroquip #FCM-3726, Russell #660290 or Earls #981410ERL). You can drill and tap this plug if desired (for an oil pressure tap), or use a –10 AN male to –4 AN male union reducer (Aeroquip #FCM2188 or equivalent). LIFTER VALLEY RESTRICTORS The lifter feeds at the front and rear of the lifter valley are threaded for 1/8” NPT plugs. There are two lifter feed passages under the ½” NPT crossover plug (the one coming from the main oil galley, towards the passenger side). The threaded portion is between the main oil galley and the passenger side lifter oil galley. This restricts both left and right lifter galleys. Because it restricts both sides, the orifice size in the 1/8” NPT plug should be large enough to feed both sides. These restrictors are located at both ends of the block. To restrict the lifters, you need to either install restrictors at both ends, or plug one end and restrict the other. Some engine builders prefer to plug the end that feeds the main oil galley and install restrictors at the other end. This provides priority main oiling before feeding the lifters.. HYDRAULIC ROLLER LIFTERS Having dual lifter galley feeds at each end of the lifter valley is very useful, but it does interfere with the OEM Ford sheet metal hydraulic roller lifter retainer that Ford and some aftermarket camshaft companies furnish in their kits. You cannot use an OEM style lifter retainer or OEM style roller lifter in the Dart block. You must use a tie-bar style hydraulic roller lifter. Note: the block will readily accept flat tappet hydraulic or solid lifters as well if you don’t plan to use a roller cam. OUR DART BLOCK SPECIFICATIONS Material………………..superior iron alloy Bore……………………4.125” unfinished Bore & stroke………….4.185” x 4.250” max recommended Cam bearing bore ID..…SVO 2.203 – 2.205” Cam bearings…………..special coated, grooved, w/3 oil holes Cam bearing O.S. ……...+0.010”, +0.020”, +0.030” Cam bearing press……...0.002 – 0.003” Cam journal OD………..Standard Ford SB (can be bored for 55mm) Cam plug……………….2.375” dia. cup plug Cylinder wall thickness…0.250” min @ 4.185” bore Cubic inch displacement.. 468 CID max recommended Deck height……………..9.500” (also available as 9.200”) Fuel pump………………mechanical pump provision Freeze plugs…………….Standard Ford press-in cup plugs 1.500” OD Head bolts………………1/2” blind holes Lifter bores………………Standard Ford 0.8747 – 0.8757” (honed to size) Lifters…………………...Standard Ford (rollers need tie-bar style lifters) Main journal size………..2.749” (standard 351 Cleveland) Main bearing bore……….2.9415 – 2.9425” (honed to size) Main thrust width……….0.913” – 0.915” Main cap bolts…………..#1 ½” (2) 3/8” (2) #2, #3, #4 ½” (2) 7/16” splayed (2) #5 ½” (2) 3/8” (2) Main cap press………….0.003 – 0.004” Main caps……………….Steel billet, 4-bolt Main cap register………..Deep stepped register on each side (no need for dowels) Oil system………………Standard wet sump or SVO dry sump Priority main oiling with external pump (wet or dry) Oil filter…………………Standard filter Oil pan…………………..Standard 351W pan Rear main seal…………..Standard one-piece seal (FelPro #2921 or 2942 or equivalent) Serial number……………Right front and main caps Starter……………………Standard Head stud/bolt holes……..1/2” standard SVO with blind holes Timing chain/gears………Standard components Timing cover…………….Stock 351W style Main cap torque specs……1-5 ½” bolts – 105 ft lbs 2-4 7/16” bolts – 65 ft lbs 1 & 5 3/8” bolts – 35 ft lbs MEASURING & MACHINING THE DART BLOCK Decks are CNC machined to standard deck heights. Measure before machining. Main journals are finished line honed to the low-to-middle of the specification. Measure and hone to suit your preference. Crankshaft and rod clearance should always be checked before any machining is started. You need a minimum of 0.060” clearance for rotating counterweights and rod big ends. Due to variations in OD dimensions of the numerous lifter manufacturers, lifter bores are finish honed on the tight side of the tolerance to leave room for lifters that are larger in diameter than standard. HONING PROCEDURES (Recommended by Dart) Honing oil……………Sunnen MAN 845-55 Speed & feed…………CK-10 (C&E) Pulleys CV-616….185 RPM / 50 stroked per minute Honing……………….1. Rough 0.003” from size Sunnen C30A-25 2. 220 to size Sunnen C30A-55 3. 280 3 strokes Sunnen C30J-65 4. 400 3 strokes Sunnen C30J-85 Re-honing……………1. 220 3 strokes Sunnen C30A-55 2. 280 3 strokes Sunnen C30J-65 3. 400 3 strokes Sunnen C30J-85 Note: RA should be 26 – 28 Shoe assembly technique: Titanium or hard shoe (P/N CK-3570) from Sunnen on one side of honing head. Delrin (engineered plastic) attached to brass show holder & trimmed to size on other side. DO NOT use bronze shoe.
OUR PART NUMBERS TO DATE
BLOCK Dart Iron Eagle Ford Windsor 31385135 CRANKSHAFT Scat 4-351C-4000-6200 CONNECTING RODS Scat I-beam 2-ICR6200-7/16 PISTONS JE Pistons #232474 CAMSHAFT Lunati hydraulic roller 51012 RRN1-232-242 Valve lift 544 intake / 560 exhaust (with 1.6:1 rockers) Lobe lift 340 intake / 350 exhaust Duration @0.050 232 intake / 242 exhaust Centerline 108 intake / 116 exhaust Timing @0.050 tappet lift 8 BTDC 44 ABDC 57 BBDC 5 ATDC LIFTERS Lunati 72335LUN OIL PAN Moroso 20507 OIL PICKUP Moroso 24507 VALVE COVERS Moroso cast aluminum 68450 FUEL PUMP Race Pumps billet hydraulic pump 1700 FUEL PRESSURE REGULATOR Race Pumps adjustable 5011 FASTENERS ARP Head studs……………..….254-4703 Intake manifold…………...454-2103 Oil pan studs……………...454-1904 Balancer bolt……………...150-2501 Alternator bracket bolt……450-3301 Thermostat housing……….450-7401 Valve cover studs…………400-7614 Distributor stud…………....450-1701 Cam bolt……………..……155-1001 Oil pump shaft………….....154-7901 SPECIALTY TOOLS ARP piston ring compressor……..900-1250 CYLINDER HEAD GASKETS Victor MLS 54293 GASKET SET Victor FS3428A MAIN BEARINGS Clevite MS-1010 H ROD BEARINGS Clevite CB-663 HN This first article merely serves as a prelude to this build. Stay tuned as we walk through each step. I’ll provide intimate details of each and every component as the build progresses.