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

    a couple known dependable engine builders
    Last edited: Jun 20, 2017 at 9:06 PM
  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.
  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 at 8:48 PM
    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

    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: Jun 18, 2017 at 7:49 PM

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