aftermarket heads for a BBC

Discussion in 'Cams, Heads and Valve Trains' started by Grumpy, May 2, 2016.

  1. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    knowing what you intend to do with an engine, once its built,
    and having a realistic idea about your personal skills and your budget limitations would go a long way towards pointing, YOU, OR ANYONE ELSE, to the best cylinder head to select.

    big block chevy engines have a reputation for dropping , or sucking valves and busting valve train components
    ,mostly due too the fact that many guys don,t have a clue how too,
    nor do they bother too,

    verify clearances or valve train geometry,
    simply , checking and using quality components with properly matched clearances,rather than selecting the least expensive part you can find listed, goes a long way toward reducing problems.
    and use of the correct valve spring load rates,and carefully installing and checking the valve train geometry, and ideally buying ALL matched components ,IDEALLY FROM A SINGLE, HIGH QUALITY ,NAME BRAND SOURCE,
    or from the cam manufacturer of your choice,
    would greatly reduce the potential for sucking, or dropping a valve(s)
    you can,t simply slap in a radical cam in your BBC engine using stock valve train components, with a reasonable expectation of maintaining long term durability

    ID bet fully 30% of the valve train parts sold in this hobby,are sold as replacements for failed parts that were damaged due to the installer failing to carefully read and follow directions and check clearances

    Im 68 years old and Ive been building and racing cars and engines since I was in my teens,Ive probably built an average of 3-4 BBC, and or SBC engines a year
    (with more than a few mopar, caddy, Buick, Pontiac engines along the way)
    mostly for the local muscle car guys and myself over the last 45 plus years and I can assure you both research and experience maters, I look back at what I built during my 20s and remember the frustration I felt not knowing what was required and thinking about all the mistakes I made back then I have constantly tried hard to help the newer guys avoid many of the pit-falls I learned from.

    yeah reading links sucks but it takes far less time and wastes FAR less money than blindly and randomly jumping into an engine build ignoring the potential problems and knowing what your doing and why and how its done never hurts
    before you spend a good deal of money porting and un-shrouding any iron cylinder heads, keep in mind aluminum heads are easily repaired in a skilled and experienced automotive machine shop thats equipped to do those repairs but damaged iron cylinder heads are either much harder to repair or good door stops

    a couple known dependable engine builders
    Last edited: Oct 24, 2017
  2. 87vette81big

    87vette81big Guest

    I have never heard of Big Block Chevies Swallowing or Dropping Valves Grumpy.

    Small Block Chevies Yes.
    Dirt Track Racing and pushing 8,000 + RPM's with 6.14 - 7.38 gears in the Ford 9" inch or Winters Quick Change Rearend.

    The only common mishap with BBC Drag Racing here in Illinois is Blown Headgaskets.
    Lots of Nitrous Oxide used. 500 -750 HP Shots.
    Last edited by a moderator: Jul 13, 2017
  3. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

  4. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member
    New Big Block Racing Heads from MBE

    Written by Jeff Huneycutt on December 2, 2016

    We take a look at MBE’s new clean-sheet cylinder head design for Big Block Modified racing

    When it comes to oval track racing, the Big Block Modifieds will likely never have as many racers as you commonly see in the Late Model, or IMCA Modified ranks. But that doesn’t mean the Big Block racers don’t fight just as hard and put on every bit as good a show. And you’d better believe they deserve equipment that’s the highest quality just like everyone else.

    And even though racers have 467 cubic inches of big block power to help get them around the track, Mod racers are just like anyone else in racing–they are always looking for more horsepower. To help them get exactly that, MBE Cylinder Heads & Manifolds has created a new cylinder head for Big Block Modified racing that is a clean-sheet design and looks to hold a lot of advantages over its existing competition. Not only does MBE’s owner, Matt Bieneman, have a history working NASCAR developing cylinder heads, the company currently owns several records in drag racing, so whenever MBE comes up with a new head design it’s usually worth a look.

    The great weakness of the Chevrolet Big Block cylinder head is that intake ports #1 and 5 are straighter than #3 and 7 (and the same holds true for #2 and 6 versus 4 and 8). The straighter ports flow significantly better than the other two, and had porters over the years have struggled to make all the ports flow more evenly.

    The problem with unequal flow between ports is it makes the engine impossible to tune optimally. If you tune for the engine’s four best flowing ports, the other four will need less jet to keep from going rich. Obviously, you can’t have a single carburetor provide different amounts of fuel to different intake ports, so you never will be able to get all eight ports perfect. You can either tune to maximize the good ports, try to make the most out of the bad ports, or shoot for something in the middle.

    So Bieneman and his crew at MBE came up with a port package that not only flows exceptionally well, but also keeps all four intake ports in each head equal within a percent of so of flow. Of course, that required some serious work to achieve that feat while allowing the new heads to still work with conventional intake manifolds and exhaust headers.

    In fact, it is so different that MBE couldn’t find an existing casting that would fit the company’s needs as a starting point. Many head porters will select a raw casting from a manufacturer, weld up areas where they need more material, cut away where they want less and call it a day. The other option is to cut a cylinder head completely from a chunk of billet aluminum. But that’s extremely costly and out of the range of many race teams.

    So MBE went out and had its own high-quality aluminum casting made just to its specs. A custom casting is an investment, but it means less work must be done to bring the head into ready-to-race condition. And since other cylinder head specialists can’t get their hands on this casting, MBE can keep its advantage all to itself.

    We paid a visit to MBE’s shop in Mooresville, NC, to get a closer look for ourselves. Check out the accompanying photos to see what we found.

    MBE’s new 18-degree Big Block cylinder head is designed to eliminate some of the greatest weaknesses inherent in the original design. Besides straightening the valve angle from the stock 24 degrees, MBE also significantly reworked the intake ports so that all four are practically identical in terms of flow.
    In order to get where they needed to go, MBE invested in its own casting which allows the spring pockets to be raised a full half of an inch and the intake ports, in turn, can move up 0.330 of an inch. The new casting also allows for the intake valves to be moved 0.060 of an inch toward the center of the port. This helps unshroud the valve and contributes to this head to flow 8 percent better than MBE’s previous head (which was already a leader in the class).
    The Big Block Mod heads will work with standard intake manifolds, but here you can see just how much the raised intake ports pick the manifold up off the engine’s China wall. You will need to take steps to keep the area between the top of the block and the bottom of the intake sealed, but MBE also has a cast intake made specifically to get the most out of this head.
    Here, you can see the extensive machining work done to cut weight from the top of the head. You can also see the 16 fastener locations for the one-piece rocker bar. None of the fasteners extend into the ports. This not only helps flow, but keeps the valvetrain more stable for better valve spring life and improved valve control at the redline.
    The combustion chambers are sized at 83 cc’s. That’s small for a big block chamber, but Bieneman says they’ve worked very hard to get the chamber that small while maximizing efficiency. The small chamber means you can cut down the dome that’s usually used on Big Block Modified racing pistons. A flatter piston top makes for a faster moving flame front when the spark plug ignites the air/fuel mixture and more complete burn. All that adds up to more power.
    A diamond-hard DLC coating on the valves helps stave off wear, even if dirt and grit gets past the air filter. The valves as sized at 2.300 inches for the intakes and 1.800 for the exhausts, and the stems are 5/16 and 11/32 of an inch respectively. The larger exhaust valve stem is a pretty cool trick MBE discovered in its drag racing programs. Big block engines produce a lot of heat, and the larger stem helps the exhaust valve move the head from combustion through the guide and into the head where the water jackets can carry it away.
    To help engine builders make the most possible power from the heads, MBE also offers valves, springs, lifters and even a camshaft. And because the raised intake ports can cause sealing issues, they’ve even worked with Cometic to produce a custom set of gaskets.
    Here’s a look at the extensively worked ports. On the dyno MBE says the extreme flow the heads are capable of means an engine can produce over 700 lb/ft of torque from 4,500 all the way to 6,700 rpm with peak power around 930 horsepower.
    Both T&D and Jesel have one-piece shaft-mount rocker setups to work with this Big Block head with the rockers constructed from either steel or aluminum. Intake valve lift can be as high as 0.930 of an inch!
    MBE doesn’t want to give too much away when it comes to the proprietary valve job they use, saying that they have thousands of hours invested into research. We do know that the intake is a five-angle valve job, but MBE is keeping the angles and widths to themselves. They also use a single-point CNC cutter because of the machine’s adaptability. We’re also told that when used correctly, it can hold the valve seats to within 0.0002 of an inch concentricity.

    a couple known dependable engine builders
    Last edited: Jun 20, 2017
    Strictly Attitude likes this.
  5. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    theres always a big factor in the selection of engine components ,
    for most of us and thats obviously the COST VS potential power gained.
    what many guys fail to look at is the valve lift vs flow numbers, and intended application,
    I does you darn little good to purchase a killer BBC, set of 360 cfm rectangular port cylinder heads that flow 400- 450 cfm at .800 lift if ,
    your cam selected max's out a .650 lift, its not designed to maintain valve control at over 6000 rpm, and your intake port flow stalls at 390 cfm
    especially on something like a 9:1 compression 454 BBC, with a typical 750 quadrajet carburetor on a Stock style low rise dual plane intake,
    yet I see similar mis-matched components rather frequently , usually from guys that got KILLER DEALS on lightly used race engine parts they picked up at bargain prices at swap meets.
    look over the parts your selecting very carefully and use some logic in matching components, if you realistically won,t be running the engine over 6000 rpm, and your displacement is under 427-454 cid, your very unlikely to benefit
    be aware that head bolts enter the block coolant passages,
    so if you failed to dip the bolt threads in sealant when they were assembled,
    through the heads coolant can seep up along the head bolts,
    into the area under the valve cover

    btw read this


    both of these work great at sealing head bolt threads,IF you forgot to use thread sealant on the head bolt threads, why, not try to eliminate one potential area of concern,why not pull each head bolt one at a time and clean its threads dip the clean bolt in the can of sealant and re-install and re-tighten the individual bolt to the required torque, before removing the next bolt, I've done this in the past when guys failed too seal the bolt threads and its worked and there was no head gasket issues later, the only thing you have to loose by trying this is the cost of a can of thread sealant and an hour or two of your time, and of course you'll more than likely need to re-adjust valves as the rockers will need to be removed at some point in the process..
    lets do some MATH
    lets assume you want to build a kick ass 540 BBC

    a 540 has a 4.25" stroke and 5200 f.p.m. in piston speed would be a reasonable upper rpm limit (7350 RPM )if you intend to maintain reasonable long term durability.
    now that would MANDATE a solid lifter cam (ideally a roller solid lifter) valve train to maintain valve train stability in most cases.
    at 7350 rpm a 540 will in theory use 1723 cubic feet of air PER MINUTE
    thats 215.4 cubic feet of air per minute per cylinder, if divided equally but each cylinder draws
    67.5 cubic inches per cylinder x 3675 intake strokes,
    thats about 1723 cubic feet of air per port, per minute, and 3675 intake strokes per minute
    thats .469 cubic feet per intake stroke ,
    (theres 144 cubic inches in a cubic foot) and a cylinder in a 540 has 67.5 cubic inches.
    theres 8 cylinders that need 67.5 cubic inches of air volume 3675 times per minute.

    but remember an intake port and intake valve ,flows air during about 250 degrees in a 720 degree cycle, thats about 35% -40% of the time,the engines intake valve is effectively open and flowing air, and remember the exhaust scavenging,
    has a huge effect on intake flow rates.
    lets look at an intake port that flows 400 cfm which you might need to allow a 540 to flow enough air because even if the heads potentially flow 400 cfm the intake manifold or some other component may not fully keep up!
    flow rates are measured on a flow bench at constant flow rates,
    but theres 61.25 intake strokes per minute, per cylinder.
    in theory a port that flows 400 cfm will flow about 160 cfm during the 40% of the time its open in the 720 degree cycle. thats 160 CFM x 144 cubic inches,
    23040 cubic inches
    /61.25 intake strokes per minute= 376 cubic inches of rated flow capacity

    376 cubic inches x 61.25 intake stroke per minute =23039 cubic inches


    Last edited: Aug 11, 2017
  6. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member


    by Molly Koecher

    by Tom Dufur

    The big-block Chevy’s canted valve heads are largely responsible for the tremendous power capability of the Rat motor and its continued popularity. The original head design is often referred to as having a 26-degree valve angle, although this intake valve angle of inclination is only one of four angles needed to numerically describe the big-block’s valve angles. The exhaust is tilted 17 degrees relative to the deck surface, and both are inclined 4 degrees laterally. This compound arrangement of valve angles gives the big-block head its characteristic “valves pointing everywhere” appearance when the valve covers are removed and is responsible for the early “porcupine head” nickname when the big-block made its debut in the mid 1960s.

    [​IMG]Aluminum aftermarket cylinder heads offer tremendous airflow potential to maximize power potential.

    Big-block Chevy factory heads are offered in aluminum and cast iron, with either open or closed combustion chambers, and with oval or rectangular intake ports. In the aftermarket, most performance heads are aluminum rectangular port, open-chamber designs reminiscent of the original LS6 casting, although you can also buy aftermarket oval port and cast-iron heads.

    Factory heads are classified as either high-performance (rectangular port) or standard passenger car (oval ports). Late-model trucks feature an even smaller oval intake port, frequently referred to as the “peanut” port, on heads that appear to be nearly round at the port entrance. Rat motor heads feature a unique combination of siamesed intake ports mated with symmetrical combustion chambers and equally spaced exhaust ports.

    As a result of this arrangement, each siamesed pair of intake runners features non-symmetrical left-hand and right-hand ports. The port on the right side of each pair (as you face the intake flange surface) is longer and directs the inlet charge more to the center of the chamber, and is referred to as the “good” port; the one of the left, obviously referred to as the “bad” port, dumps the air/fuel mix toward the cylinder wall and usually doesn’t flow as well as the right port. This minor idiosyncrasy of the big-block’s design has never been a real problem in terms of limiting the engine’s power potential, until extremely high airflow levels are reached on large-displacement or very-high-RPM engines. On engines approaching or exceeding the 1,000-hp mark (normally aspirated), the use of race-only spread port or Big Chief–style heads serves to even out the port volume, shape, and airflow in all eight intake ports.

    Why didn’t the Chevrolet engineers just make it a mirror-image design like the small-block V-8? Because the big-block has six head bolts around each bore (if you count the hidden bolt bosses on the bottom of two of the intake ports), and that dictates where the intake ports must be placed. Also, it’s possible that the resulting siamesed exhaust ports might run too hot for long-term reliability with the big-block’s higher power levels and resulting increased exhaust flow.

    Oval or Rectangular Intake Ports

    Much has been said about the differences between rectangular ports and oval ports, and the only fact that everyone agrees with is that each design has its own strengths and weaknesses. All factory high-performance engines featured the larger rectangular port heads, which have higher airflow rates than production oval port heads. However, the larger volume of the rectangular ports produces rather sluggish flow velocities at low speeds, and smaller oval port heads are often a better choice for a daily driver or street and strip car.

    [​IMG] [​IMG]
    Stock iron oval ports from a “206” casting head. Note Stock iron rectangular ports from a “990” casting head. distance from the ports to the center bolt-hole above Note that the tops of the ports are almost even with the the pair of runners. bottom of the center bolt-hole.

    When reworked by someone who really knows what to do, oval port heads are capable of providing very good performance up to 600 or more horsepower. However, most high-performance street and full-race big-blocks can still take advantage of larger rectangular port heads. When I refer to the port size as larger or smaller, I’d like to think in terms of port cross-sectional area, but that dimension changes constantly throughout the length of the port, so the most common way to measure port size is to determine the volume in cubic centimeters, just as with the combustion chamber.

    [​IMG]Big-block head bolt torque pattern. Stock head bolts get torqued to 70 ft-lbs in three steps of 40, 55, and 70 ft-lbs. Use thread sealer on all bolts that go into the water jacket, which means all blocks except Bowtie and aftermarket. Aftermarket studs usually get torqued to 60 ft-lbs, but check with the fastener manufacturer for specific torque recommendations.

    While intake port volumes are a valuable guide in cylinder head selection, remember that port volume is not necessarily proportional to port flow, and that just because one design has 340-cc runners and another has 320s, that doesn’t mean that the larger head flows more air or makes more power, although that is usually the case.

    In fact, if two heads with different- size runners have the same flowbench numbers, you are generally better off with the smaller runner head, especially if low-RPM throttle response and drivability are important. Also, when comparing port volume of spread port cylinder heads, remember that because these heads have raised runner locations, they are longer than conventional cylinder head intake ports, and the port volume is greater due to the extra length. A 400-cc raised-runner intake port may actually be smaller in cross-sectional area than a 380-cc conventional intake port. Be careful when comparing apples to oranges.

    There are aftermarket oval port heads with about 290-cc intake runners, and small rectangular port heads with around 300-cc ports. I’ll bet you a year’s supply of donuts that the power difference on the dyno is minimal, and you could never tell the difference from the driver’s seat.

    The GMPP head (PN 12363400) with 300-cc rectangular intake ports (left) performs very similarly to the oval port head (PN 12363392) with 290-cc intake ports (right), if both have the same compression ratios. The oval port head has 110-cc chambers, and the rectangular port head comes with 118-cc chambers.

    Open or Closed Combustion Chambers

    [​IMG] [​IMG]
    Cast-iron late-1960s “206” head with bathtub-shaped Cast-iron high-performance rectangular port “990” head

    98-cc closed combustion chambers with open 118-cc combustion chambers. Note the lazy-D
    shape of the chambers.

    Big-block heads all had closed combustion chambers, or bathtub-shaped chambers, when the engine was introduced in the mid 1960s. In 1969 the open combustion chamber was introduced and it offered better air/fuel flow and a better combustion burn in the chamber. The only drawback to the new chamber design was that it was large, around 118 cc compared to closed chamber heads, which had about 101 to 109 cc, so high-dome pistons were needed to achieve the same compression ratios as the closed chamber heads. Note that domed pistons designed for open chamber cylinder heads do not work with closed chamber heads due to insufficient clearance. While introduced on high-performance rectangular port heads, the open combustion chamber was soon being used in common oval port heads to lower the compression ratio for use with unleaded gasoline, and the reduced quench area was found to be helpful in reducing exhaust emissions.

    [​IMG] [​IMG]

    Mark IV, Gen V and Gen VI Heads

    All production big-block heads have similar characteristics, including 7/16-inch rocker studs (except Gen V and Gen VI) and the same seven-bolt valve cover pattern. Early cast-iron and all-aluminum heads used 3/4-inch-reach gasketed spark plugs, while most 1970-and-later iron heads switched to the smaller taper seat “peanut” plugs. Aluminum heads have two additional threaded bosses under the intake runners for additional clamping and better head gasket retention when used with engine blocks equipped with corresponding bosses in the lifter valley. The only OEM blocks with these bosses were the rare ZL1 aluminum blocks, but many modern aftermarket blocks have this added feature. Mark IV, Gen V and Gen VI heads all have the same head bolt pattern, but they are not interchangeable due to different water jacket cooling passages. Most aftermarket aluminum heads feature a universal water passage design allowing their use on Mark IV or Gen V/VI blocks, but you need to check with the manufacturer to verify this feature.

    [​IMG]Gen V and Gen VI heads have different water jacket passages than Mark IV heads, and do not work on Mark IV blocks. (Photo Courtesy GMPP).

    All production big-block heads have stamped steel pushrod guideplates under the rocker arm studs for either 5/16-, 3/8-, or 7/16-inch pushrods, but Gen V/VI heads switched to a non-adjustable valvetrain. Although Gen V/VI heads retained the original valve cover bolt pattern, their matching cast aluminum valve covers were equipped with a durable rubber O-ring in place of the traditional valve cover gasket. All production heads use the same intake and exhaust bolt patterns, which include a bolt-hole between each pair of intake ports. The boss required for this additional bolt-hole intrudes on the port entrance, so it is deleted on most aftermarket heads because it is not necessary for a good gasket seal.

    [​IMG]All production big-block heads had an exhaust crossover passage between the two pairs of siamesed intake ports. The casting cavities above and below the center exhaust crossover are blind cavities that don’t connect to anything. Some aftermarket intake manifolds don’t cover the upper opening, which does not cause any problems.

    All OEM big-block heads had an exhaust crossover passage for intake manifold heat and automatic choke operation, as well as supplying exhaust gas for EGR-equipped (exhaust gas recirculation) vehicles from the early 1970s on. High-performance engine builders try to keep the intake manifold as cool as possible for maximum intake charge density, so performance intake gasket sets usually include metal plates to block off this exhaust crossover passage, and most aftermarket heads delete the exhaust crossover provision entirely.

    All OEM Rat motor heads were equipped with steel valves that have 3/8-inch diameter valvestems, and the overall length of the intake valves is 5.218 inches while the exhaust valves measure 5.350 inches. Aftermarket heads typically come with 11/32-inch-diameter valvestems, and frequently use longer than stock valve lengths that allow installation of taller valvesprings that are better suited for use with high-lift camshafts. The smaller-diameter stems not only lighten the valves for better high-RPM performance, but also offer a slight improvement in airflow. OEM intake valve head diameters were either 2.06 or 2.19 inches, and exhaust valve heads measured either 1.72, 1.84, or 1.88 inches. All production heads and most aftermarket heads come with traditional 45-degree valve seats; however, some high-end aftermarket heads are available with 55-degree seats, which offer improved high-lift flow at the expense of some low-lift flow.

    Aftermarket Cylinder Heads

    The vast majority of aftermarket heads are rectangular port aluminum with open combustion chambers, similar to the fabled LS6/LS7 production heads. However, they are much more than mere copies of the Chevy part, and many offer such advanced features as non-stock valve angles, larger valve head diameters for more flow, more robust valvesprings for high-RPM operation, and your choice of various intake port sizes to match your requirements. Some offer raised ports, usually by .100 inch on the intake ports and as much as 3/4 inch on the exhaust ports.

    [​IMG]Many aftermarket heads, such as this Edelbrock Performer RPM 454-R, are rectangular port aluminum with open combustion chambers, similar to the fabled LS6/LS7 production heads. (Photo Courtesy Edelbrock)

    Note that if you plan to use exhaust headers designed for stock heads in a stock engine compartment, you need to check for possible header interference with raised port heads, or have custom headers made. Typical material specs call for the use of either A355 or A356 aluminum alloy, usually hardened to T-6 specs, and most offer beefier construction with thicker-than-stock deck surfaces and port walls, allowing additional modifications by knowledgeable cylinder head specialists.

    In addition to GMPP, there are an abundance of manufacturers offering high-performance heads for the big-block Chevy including Air Flow Research (AFR), Brodix, Carl Foltz Engineering (CFE), Dart, Edelbrock, Pro-Filer, Racing Head Service (RHS), Raptor (Reher-Morrison Racing Engines), Sonny’s Racing Engines (SRE), Trick Flow Specialties (TFS), World Products, and probably more by the time you read this. Contact the manufacturer of your choice for more specific information before making your final head selection.

    [​IMG]Modern competition heads usually have heart-shaped combustion chambers to minimize chamber volume and increase the quench area.

    Spread Port Heads

    As good as the original Chevy head design was, things really started to heat up when GM engineers got involved in the Pro Stock wars in the 1980s. Because of the Corporate Engine policy, GM competitors were allowed to use any GM family engine in their race cars and the big-block Chevy was obviously better suited to all-out racing than any other GM big-block engine. Pontiac engineers took advantage of this break to create a head for the Rat motor with a superior port design, shallower valve angles, and smaller, more efficient combustion chambers.

    [​IMG]The quench or squish area of the cylinder head is the flat surface that hangs over the bore. As the piston comes to TDC the air/fuel mixture is rapidly expelled, creating turbulence in the chamber, which greatly increases combustion efficiency

    The Pontiac Super Duty Pro Stock cylinder head (PN 10045427) featured intake ports that were spread apart to even out the flow differential inherent in the original Chevrolet siamesed port design, and the shallow valve angles required substantially raised intake ports to straighten the airflow path from the port entrance to the valve seat.

    From there, Oldsmobile engineers took their shot at creating the best possible drag race head, and introduced the Oldsmobile Pro Stock head (PN 24502585). The Olds Pro Stock head evolved into the GM DRCE, the development of which was spearheaded by a young Warren Johnson, soon to be the dominant NHRA Pro Stock racer of the 1980s and 1990s.

    [​IMG]D-shaped exhaust ports decrease the flow differential between the floor and the roof of the exhaust ports, and they help to combat reversion.

    Not to be forgotten, Chevrolet engineers also developed a spread port head, the Chevy Symmetrical Port Head (PN 10051128), with similar design parameters: evenly spaced intake ports and shallow valve angles with miniscule combustion chambers.

    Today, the latest version of the Olds DRCE is the spec cylinder head for all GM-powered vehicles in NHRA Pro Stock competition, while the Pontiac Pro Stock head has been widely copied by aftermarket manufacturers, resulting in the Dart Big Chief head (paying tribute to the Pontiac Indian tribe), the Brodix Big Duke head, and Edelbrock’s Big Victor head, with more development sure to follow. If you want to make 1,000 hp or more without power adders, “Big” heads are the way to go.

    Even though these “Big” heads all share some common design parameters, they are not identical and most require specific matching components such as pistons, intake manifolds, and shaft rocker arm assemblies. All spread port big-block Chevy heads require shaft rocker arms because the pushrods must be relocated around the revised intake port location, and the large amount of rocker arm offset eliminates the use of traditional stud-mount rockers. Most accept the original Pontiac-designed eight-bolt valve covers, although the Edelbrock Big Victor head features a unique valve cover bolt pattern to relocate the bolt-hole bosses for improved rocker arm clearance and valvetrain geometry. This is one of the reasons that fabricated aluminum sheet-metal valve covers are so popular these days—they can be quickly produced one at a time or in relatively small batches to fit whatever bolt pattern you want. Besides, they look racy!

    The big-block Chevy V-8 engine has been part of the automotive scene ever since it’s introduction in 1965. Its impact on the streets and race tracks of America were immediate and blatant. With time, the engine evolved and gained size, making it even better with age. Now, some four decades-plus later, there are a wide range of factory-based and aftermarket options for the legendary big-block Chevy engine. Which options are best for any specific purpose can be challenging to figure out, but this book makes it easier. In addition to identifying and reviewing all of the factory components, this book also takes a close look at all the major hard parts offered in the high-performance aftermarket.

    The trick to building any high-performance engine is to properly team together the proper components, and How to Build Killer Big-Block Chevy Engines shows readers exactly how to do so.
    found this gasket over at summit..
    using the correct head gasket too match the heads and cylinder heads your using on any big block chevy engine, is critical to prevent coolant loss, and maintain proper cooling
    head gaskets are rarely completely round, nore are combustion chambers
    you,ll want to place a head gasket you,ll use on the heads and mark the area inside the opening as the only areas you can change,
    (notice the gasket fire ring is NOT a perfect circle like many people assume)
    ideally you,ll want to un-shroud the valves while opening up the combustion chamber volume,
    but not extend the combustion chamber past the front edge of the gasket fire ring,
    as that usually causes gasket failure

    you might be amazed at how much material can be removed ,
    too noticeably increase air-flow and un-shroud the valves,
    and how little it might effectively change,
    the combustion chamber volume and compression.

    laying a head gasket on the head and use machinist blue dye to show the areas inside the gasket fire-ring



    Brand Fel-Pro
    Manufacturer's Part Number Q8180PT2
    Part Type Head Gaskets
    Product Line Fel-Pro Head Gaskets
    Summit Racing Part Number FEL-8180PT-2

    Bore (in) 4.370 in.
    Bore (mm) 110.998mm
    Gasket Material PermaTorqueMLS
    Compressed Thickness (in) 0.039 in.
    Compressed Volume (cc) 9.700cc
    Lock Wire No
    Quantity Sold individually.

    According to summits apps page

    The gasket your have fits

    Engine Type V8
    Liter 6.5
    CID 396
    Engine Size 6.5L/396
    Beginning Year 1966
    Ending Year 1970
    Engine Family Chevy big block Mark IV

    Engine Type V8
    Liter 6.6
    CID 402
    Engine Size 6.6L/402
    Beginning Year 1970
    Ending Year 1972
    Engine Family Chevy big block Mark IV

    Engine Type V8
    Liter 7.4
    CID 454
    Engine Size 7.4L/454
    Beginning Year 1970
    Ending Year 1990
    Engine Family Chevy big block Mark IV

    it may be the result of a crack in the head or block or just an intake or head gasket leaking, issue, as stated change oil and filter ,
    and if the problem returns you darn sure better track down the source before repairs get exponentially more expensive
    some cracks won,t leak until the engine heat of the engine thats been running for awhile expands the metal.
    if its not up too operating temp, theres no leak.
    its not un-common for intake gaskets to leak coolant,
    into the lifter gallery if they were not correctly installed or damaged, or intake manifolds to leak coolant,
    if the coolant passages are corroded or improperly machined,
    or too find coolant leaks if the wrong head gaskets were used.

    Coolant Routing Mk IV/Gen 5/Gen 6
    There are two different ways that coolant can be routed through the engine: series flow and parallel flow. Both ways work just fine. There may be a slight preference for parallel flow, but it is not a big deal. Series flow has the water exiting the water pump, flowing through the block to the rear, it then transfers through the head gasket and into the cylinder head through two large passages on each cylinder bank at the rear of the block. The coolant then travels from the rear of the head, forward to the front of the head, into the intake manifold water passage and out past the thermostat and thermostat housing. The water cools the block first, then it cools the head. The coldest water (coming out of the water pump) is directly below the hottest water (having already picked up the heat of the block and the head) as the hot water transfers into the intake manifold. By contrast, parallel flow has the water exiting from the water pump into the block, where a portion "geysers" up into the head between the first and second cylinder, another portion "geysers" up to the head between the second and third cylinders, another portion geysers up to the head between the third and fourth cylinder, and the remainder transfers to the head at the rear of the block. The coolant temperature inside the engine is more even that way. The differences in coolant routing is having (or not having) the three additional coolant transfer holes in each block deck, and three matching holes in the head gasket. The heads have passages for either system, and are not different based on coolant flow.

    Be aware that gaskets that DO have the three extra holes between the cylinders often have restricted coolant flow at the rear--instead of having two large coolant transfer holes at the rear, there is only one, and it's the smaller of the two holes that remains. This is important because if you use a parallel flow head gasket on a series flow block, you can have massive overheating and there's NOTHING that will cure the problem except to replace the head gaskets with ones that don't restrict flow at the rear of the block, or to drill the block decks to allow the coolant to flow into the head between the cylinders. Here's why they can overheat: A series-flow block doesn't have the openings between the cylinders, no coolant can flow up to the head there. The gasket may only have the single, smaller opening at the rear, so the amount of water that gets through that opening is greatly reduced from what the block designers intended. The result is that the coolant flow through the engine is only a fraction of what is needed.

    Most, but NOT all Mk IV engines are Series Flow. ALL Gen 5 and Gen 6 engines are Parallel Flow. A series flow block can be converted to parallel flow by drilling 3 holes in each deck surface, and then use parallel flow head gaskets. You can use the parallel flow gaskets as templates for locating the additional holes. It's really easy: Put the parallel flow gaskets on the block, mark the location and size of the three extra holes. Remove the gasket. Grab a 1/2" drill and a drill bit of the correct size, and pop the extra holes in the block. There is NO modification needed on the head castings. Some blocks have one of the holes already, but it needs to be ground oblong to properly match the gasket. Again, very easy with a hand held die grinder and rotary file.

    I'd assume the intake gaskets are the source until proven otherwise.
    but be aware that miss matched head gaskets, to the heads and block combo in use, can cause several issues

    don,t assume the worst, just logically and step by step track down and correct the issue using FACTS.
    The Gen V was first installed in the 1991 year models.
    The earliest casting I've decoded was a very late (Nov/Dec?) 1989 date.

    The Gen VI was first installed in the 1996 year models.

    The cams for the Mark IV and Gen V are interchangable for flat tappet lifters.
    The Gen VI where the first equiped with Roller Lifters, but the main difference is the machined flats on the lifter bores of this block - you can still install an earlier cam without rollers.
    The cam retainer plate holes are verticle on a Gen V~VI, rotated 90deg from the Mark IV's horizontal orientation.
    The '91 on trucks with Gen V's had manual transmissions and use a bracket for the pivot, the later medium duty trucks have a hydraulic clutch.
    The Gen blocks use longer main cap bolts than the Mark blocks.
    The crank on the Gen engines uses one long key in the keyway slot for the cam drive gear and the damper - the Mark cranks have two short keyway slots and two seperate keys, one for the cam gear one for the damper.
    As he stated, Gen cranks are one-piece seal, Mark are two-piece.
    The Flex plates are interchangeable - but Flywheels, for truck and marine applications, are not interchangeable on Mark and Gen engines.


    Last edited: Oct 10, 2017
  7. Grumpy

    Grumpy The Grumpy Grease Monkey Staff Member

    These Fel-Pro head gaskets illustrate the different coolant circulation patterns in early versus later big-block Chevrolet engines. See text for details.
    These Fel-Pro head gaskets illustrate proper Mark IV big-block Chevy head gasket selection. For improved cooling, most (but not all) 1971–1990 Mark IV Chevrolet big-blocks use parallel-flow coolant circulation. They have three cooling holes on the block-deck’s exhaust side (A through C), and small single coolant holes at the rear of each deck (D and E). Any big-block Chevy head gasket with the appropriate bore size and thickness can be used—although a gasket with only the small water passages at each end (top, Fel-Pro Performance 1037 or Fel-Pro marine PN 17046) is recommended (only the gasket’s rear hole is “active” on each side). Prior to 1971, most (but not all) Mark IV Chevrolet big-blocks had series-flow cooling. At most, the block decks have only one lower coolant hole (C on the passenger side; A on the driver side), and there are double coolant passages at the rear of each deck (D through G; only the rear holes are “active”). Series-flow blocks must use Fel-Pro PNs 1017-1, 1017-2, 1027 (shown, bottom), 1057, or 1093. Although all big-block Chevy Mark IV heads and the performance gaskets shown here have the extra lower holes, they are nonfunctional without the extra holes in the block. Parallel-flow blocks can be converted to series flow by adding the missing holes using the appropriate gasket as a template.

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