DARTMARK IV Iron Big Block - Technical NotesDeck Height.Bore.Main Bearing Size.Main Caps.Weight.Largest Recommended Bore.Camshaft Bearing Diameter.Camshaft Position.9.800" & 10.200"4.250", 4.500", 4.560" and 4.600" unfinishedStandard BBCAll 4 bolt - Steel or Ductile Iron4.250" bore 280lb / 4.600" 260lb4.625"Standard BBCStandard BBC or .400” RaisedCylinder Wall Thickness, min.Deck Thickness, min.300" @ 4.625" boreAdequate for all applications.Torque Specs - Main Caps1-52-41/2" bolts1/2" splayedDart’s inner head studs3/8" – 7/16" stepped100 ft lbs w/CMD #3100 ft lbs w/CMD #350ft lbs w/CMD #3Note: Be sure to check distributor to oil pump shaft clearance with distributor, intake manifold and oil pump installed onthe block before any assembly is attempted.Note: The tapered portion of the stud body should never contact the deck or bolt hole counter bore. If the stud body doesthread to deep and makes contact with the deck surface then you should use a small ball bearing in the bottom of the bolthole to space up the stud accordingly.NOTE: Due to the extended cylinder walls and variations in distributor and gear dimensions from numerousmanufacturers make sure to check clearance between bottom of distributor gear and block. If it is not adequate, machine.040" off the OD of the bottom section (w/o gear teeth) of the gear and chamfer the bottom end also.NOTE: Due to variations in lifter sizes and clearance preferences, most of our Engine Builder customers prefer the lifterbores sized on the small end of the specification. Sometimes these bores will need to be lightly honed.NOTE: Several aftermarket head bolt kits have four ¼" longer bolts for the end holes that are countersunk for the dowelpins. You need to verify that the bolts do not go into the block more than .850" from the deck surface or they will bottomout before they tighten on the head. If they are too long you should be able to grind off a thread or two.NOTE: The two oil filter adaptor attaching bolts should be 1 1/4" (1.250") O.A. length. This will allow 1/2" (.500") ofthread into the block. This is shorter than the stock Chevrolet bolts. This MUST be adhered to.NOTE: There is a drain back hole for the fuel pump cavity that is drilled through to the crankcase. The hole will have arough appearance and is located on the inside of the block about a 1/2" below the pan rail and directly under the fuel pumpboss. The hole is only there for drain back and it only needs to be open a minimum of .090".NOTE: The fuel pump pushrod bore is machined for a .500" rod. Be sure to check the clearance because of theinconsistencies in the diameters of push rods.SPECIAL NOTE: With a multitude of different crank, rod and piston combinations available it is important to checkclearance of all moving parts, especially crankshaft counterweight and connecting rod to block. All parts must be checkedbefore any type of machining or assembly is attempted. It is good engine building procedure to ALWAYS check the fit ofthe distributor before any machining or cleaning is done.NOTE: If you are using aftermarket cam profiles you must use the correct components for the application.8/27/2020B31
Standard BBC oil filter is used.Standard BBC timing chain, timing cover, gear or belt drive can be used on standard cam height Big M Blocks. .400” Raised cam (Big M²) blocks require raised cam timing cover P/N: 67240002 (includes gasket).Actual deck height will be .005"- .010" taller for additional machining requirements.Standard BBC oil pan can be used. Extra bolt holes are provided for stroker crank pan.Cam bearing OD should be deburred before installation.When removing main caps initially, the caps & block should be deburred before reinstalling. This will insure thatcorrect main size is maintained.Standard BBC head studs or bolts may be used. Studs should never be torqued into block.Head stud holes are blind. They do not go into the water jacket.A sealant/antiseize must be used on the head studs. Loctite # 620 is recommended.Block parts kits are provided with the Big “M" billet cap blocks only. These kits include: cam bearings, freezeplugs, timing cover dowel pins, oil pump dowel pins, head dowels, transmission dowels, oil galley plugs and a rearcam plug. These kits are sold separately when using the Sportsman series PN# 32000022.Press-in cam plug dia stock 2 7/32" 2.218".Standard BBC distributor is used.When a mechanical fuel pump is used, a standard length BBC push rod is used.Oil galley from filter to main galley is 5/8". The main oil galley is stepped 9/16" - 1/2" - 7/16" to insure an adequateoil supply to the main bearings.Lifter bores are lengthened .350" for greater lifter support.Roller Lifters should be Gen VI type which is .300" longer than Mark IV.Solid & hydraulic lifters should be Mark IV type.Timing cover and Oil pump dowel pins are .246” O.D. in dart blocksWe recommend using Fel-Pro# 1037, 1047 or 1067 head gaskets with the Big M block.DRY SUMP SYSTEMIf a dry sump oiling system is used you must plug the oil inlet hole in the rear main cap or in the block, underneath the rearmain cap.Block has threaded inlet for dry sump oil feed in rear of block.Stock oil filter can be used with a dry sump system.PRIORITY MAIN OIL SYSTEMOil is directed to the main bearings first, then to the cam bearings.The lifter galley is fed only from the front.The lifter galley is threaded for 1/4" NPT restrictors.INSIDE HEAD STUDSWhen installing Dart’s Inside Head Stud & Shoe Kit be sure the shoe and the 7/16" end of the inner head stud slide into themachined pocket in the block. Thread the stud into the cylinder head before the head is installed. Sometimes you may haveto bottom tap the stud hole in the head to get full engagement of the threads on the stud. Install the shoes and nuts beforetightening any head bolts or studs because you may have to tilt the head up at the top to slide the shoe and washer on andstart the nut. Torque the 3/8-24 nuts to 50 ft lb with CMD#3 after torqueing all other head studs or bolts.“STROKER" OIL PAN GASKETWe install the extra bolt holes at the main cap for blocks that have been ground for extra rod clearance. The recommendedoil pan gasket set for stroker cranks is Fel-Pro# 1863. This has the side rails trimmed for rod clearance and has bolt holeson the main cap center lines.8/27/2020B31
Dart BBC Big M² Block Tech SheetPart #Material:Bore:Bore & stroke:Cam bearing bore ID:Cam bearings:Cam bearing O.S.Cam bearing press:Camshaft position:Cam Drive:Cam Plug:Cubic Inch:Cylinder Wall Thickness:Deck Height:Deck Thickness:Dist. Tap Hole Valley:Fuel Pump Boss:Fuel Pump Pushrod:Freeze Plugs:Head Bolt Pattern:Inside Head Studs:Lifter Bores:Main bearing size:Main bearing bore:Main caps:Oil system:Oil Galley, main:Oil Cooler Holes:Oil Galley, filter main:Oil Filter:Oil Pan:Rear Main Seal:Hyd. Roller Provisions:Serial No.Starter:Stud & bolt holes:Tapped Holes:Timing chain / gears:Timing Cover:Torque Specs:Weight:Block Prep Option:31213344 – 31223655Superior Iron Alloy4.250", 4.500", 4.560", and 4.600"4.625" x 4.750" (max recommended)2.120" Std.Coated, grooved, w/3 oil holes PN# 32210030 .010", .020", .030" available *Call for Part numbers.002"Standard or .400” (Option / Big M²)Timing chain, Gear drive & Belt driveStandard BBC 2.215" P/N: 32520000632" (Max Recommended).300" min @ 4.625" bore9.800", 10.200" & 10.400” on Big M²Adequate for all applicationsNoneMechanical pump provisionStd. BBC or .200” for Raised cam/Big M² - P/N: PR200FPStd. Press in cup plugs 1 5/8 “dia.Std. BBC Big M Bolt PatternP/N: 64210240 (Not included)BBC .8427" - .8437" .300 Taller Gen V, VI styleStd. BBC2.937" – 2.938"Steel Billet or Ductile Iron (Sportsman) 4 boltWet or Dry Sump - Main Priority OilingStepped, 9/16" – 1/2" – 7/16"None (Can use aftermarket inline)5/8"Stock oil filter locationStd. BBC bolt pattern & Stroker pattern at mainsSTD 2 pc seal / Felpro# 2918 or 29182NoneOn main caps / Front passenger side below deckMounts in standard locationBlind tappedStd. English Thread & PitchStd. BBC or .400” Raised cam/Big M²(Cloyes 9-3647TX3, 9-3647TX9 or 9-3147A)Gen IV / V stock 10 bolt cover or Dart .400” Aluminumcover P/N: 67240002 (Includes Gasket)All ½" bolts – 100 ft lbs w/CMD #3 high pressure lube4.250" bore (280lbs) – 4.500" bore (260lbs)4.600" bore (250lbs)Available for additional fee (Call)8/27/2020B31
Lifter galleysThe liftergalleys use ½”O-ring ANPlugs to seal inthe block. P/N:32892500Main oil feedThe main oil feedin the block uses a¾” O-ring AN plugto seal it. P/N:32892750Big M FrontBig M RearView1/8” NPT¼” NPTOil Pressure port –¼” NPTOil Feed – ½” NPT(in from remotemount oil filter)Front CrossoverThe Restrictor location is accessed from the front crossover (inside thevalley) by removing the ¼” pipe plug. The block is tapped for a 1/8”NPT pipe plug between the Main oil feed and the8/27/2020Lifter galley as seenin the picture here.If running a -12 oil feed line in the rear of the block, depending on thefittings being used you mayneed to add additional clearance to what isB31already there to get the fittings to clear the block.
½” NPT OilFeed(in Oilfrom½” NPTFeedremoteoil(in frommountremotefilter)mount oil filter)Restrictor LocationMain Oil FeedOil flow comes in from the oil pump pickup, passes through the oil filter, up to the main oil galley, it is thendiverted to the Main line (Crankshaft) bearings first (Priority main oiling) then flows to the Cam bearings andLifter galleys secondary.The Oil Restrictor location is accessed from the front crossover(inside the valley) by removing the ¼” pipe plug. The block is tappedfor a 1/8” NPT pipe plug between the Main oil feed and the Liftergalley.8/27/2020B31
IMPORTANTThis Block should be assembled only by experienced, professional enginebuilders.INSPECTIONUpon receiving this block it should be thoroughly inspected for shipping damage.Prior to machining and assembly please inspect the following items:Cylinder bores - Oil passages - Deck surfaces - All threadsMEASURING & MACHINING All initial measuring should be done before any machining has begun. Decks are CNC machined to standard deck heights. If you need a particulardeck height always measure before machining. Main journals are finish line honed to the low to middle of the specification.They should be measured for your preference. If you have need for a differentdiameter you must realign hone this yourself. Crankshaft & rod clearance should always be checked before any machining isstarted. You need .060” clearance for rotating counterweights and rods. Due to variations in OD dimensions of the numerous lifter manufacturers, lifterbores are finish honed on the tight side of the tolerance to leave room for liftersthat are larger than the standard.WASHING Final washing should be very thorough, paying particular attention to all oilgalleys. Use hot soapy water and rinse with hot water first, followed by coldwater which helps reduces rust.8/27/2020B31
Big M² block parts kitP/N: 320000228/27/2020B31
Here at Dart we are constantly improving upon our products to ensure that you are receiving the latest and mosttechnologically advanced products in the industry. Through our extensive R&D we have found that valvetrain oil is crucialin a high-performance engine. The following modification is not always necessary but if you are getting minimal oil to thepushrods and rocker arms this will help to correct oil volume to the valvetrain that may occur when using solid roller liftersin any block.Machining a small groove from the pushrod feed hole to the oil band / machined feed hole in your solid lifters (Front holeonly as shown in Figure 2 above) depending on your tooling & method. You can also do this with a cutoff wheel or a dremel.This allows you to use the restrictor provisions provided in your Dart block to fine tune the amount of oil going to the lifter oilgalleys, pushrods, rocker arms and valve springs.CAUTION!The use of lifters that are heavily lightened should not be used in Dart Blocks.The lightening holes will cause lifter oil to leak into the valley instead ofoiling the pushrod, rocker arm and valvespring.Please call our technical staff with any questions Mon-Fri 9am-6pm E/T (248)-362-11888/27/2020B31