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Ask Anything - February 2014

RAT BLOCKS

Marc Nagley; Gun Barrel City, TX: I have two 454 four-bolt main blocks and would like to know which one would be the best for a buildup—something like the Blue Collar 454.

Block L: Casting Number 10114182
Block R: Casting Number 12550313

I also have a set of heads casting number 10114156. Would this set be good for my Blue Collar buildup? Several notes: Block R has six bolts for the timing cover and a mechanical fuel pump boss and a one-piece rear seal. Block L has a 10-bolt timing cover and a one-piece rear seal.

Also, will I be able to use the larger Manley valves, 2.19/1.88, and have the minor back cutting done to increase the flow with the above mentioned heads? The Ask Anything column is outstanding. I read it every issue. Keep up the good work. Wish I had half the knowledge you have. As the old saying goes, "You have forgotten more than most people know."

Jeff Smith: Well, Marc, we'll attempt to live up to your expectations! First, I had to check to make sure there really is a town called Gun Barrel City, Texas—and there is! My guess is that liberal Democrat Representative Nancy Pelosi (she is the House Minority leader) has never visited.

We'll go into more detail, but it appears these two blocks are very similar so choose the one that looks like it has been abused the least. Our pals at Jim Grubbs Motorsports tell us they rarely get a big-block Chevy in for machine work that does not need to be align-honed, so you might inspect both closely to see if one looks better. Try measuring the housing bore diameters of each main, but even that won't tell you if they are properly aligned. These are both Gen V blocks that are still the standard 4.25-inch bore that combined with a 4.00-inch stroke makes a 454. I am not aware of any real differences between the two blocks, except, as you mentioned, the 10114182 block has the 10-bolt timing cover. Most of the Gen V and VI blocks came with either a cast or plastic six-bolt timing cover. The most significant change for the GEN V/VI conversion was the one-piece rear main seal. This obviously requires a one-piece rear main seal crank that's not interchangeable with the older, MK IV two-piece rear main seal cranks. We found a cast, 4.250-inch stroker nodular iron crank from Ohio Crankshaft for $295 for a one-piece rear main seal engine that's incredibly affordable and adds a bunch of displacement for the same cost as a standard stroke crank. Another big change with these blocks was moving the main oil galley from the MK IV‘s position alongside the oil pan rail, to the Gen V placement parallel to the cam bore. This also creates a priority main oiling system, which is far better for higher-rpm lubrication to the mains and rods. Also, keep in mind that these blocks will require a specific Gen V/VI oil pan and gasket. Gen V blocks eliminated the mechanical fuel pump mount that was reinstated with the Gen VI version block.

Perhaps the biggest area of concern with the Gen V/VI blocks is the altered water jackets. Even more so because these cooling jacket holes in the block are different for Gen V and Gen VI. Both your blocks are Gen V and often a stock MK IV head like a stock iron casting may not work. The changed configuration of the upper water jacket holes creates a very thin area for the gasket to seal. Most current aftermarket big-block heads are now designed to accommodate both the Gen V and Gen VI (the Gen VI upper coolant holes nearest the lifter valley are different than the V) version blocks. Before purchasing a set of new heads, it would be wise to check with the manufacturer to ensure the head you choose is compatible with a Gen V block. We found several Fel-Pro head gaskets that will work with the Gen V block, including the PN 1047 gasket that is a 0.039-inch-thick composition gasket that is relatively affordable. I spoke with Fel-Pro's Greg West, who offered this great explanation: "The problem is with the head and block castings themselves. The oblong-shaped coolant openings located toward the valley side of the Gen V and VI blocks are cast holes and there can be quite a variation between castings, so they don't always match up to the corresponding coolant holes in the Gen IV heads. There is sufficient material on the gasket to cover the outer contour of both the heads and block, but the hole mis-match in the two castings doesn't provide enough land area to properly compress the gasket. I suggest laying pieces of carbonless paper on the deck of the block on the valley side. Tighten down the head on the block without a gasket. Remove the head and look at the impression left on the carbon paper around the water openings. If the impression on the paper around the water ports is less than a 1⁄4-inch, it is likely that water will leak into the valley."

Another feature of the Gen V/VI is that it is designed to accept a factory hydraulic roller camshaft. The front of the cam is stepped to accept a bolt-on cam limiter plate so you don't have to screw around with adjusting camshaft endplay with cam buttons. The lifter bores are also taller on these blocks to give more support to the hydraulic roller lifters. What all this means is that a hydraulic roller cam is much cheaper to install because you can use stock replacement lifters instead of the more pricey aftermarket retro-fit lifters.

Next thing to look at is the heads. If you are on a budget, you can retain the stock heads you mentioned. All the modifications are easy to do, but before you get too deep into these castings you need to know about the net lash valvetrain. Because setting lifter preload requires significant time on the assembly line, GM went with the net lash system, where a bolt tightens down the rocker to a set point that also preloads the lifter to its proper depth. For these newer big-blocks, GM used a small 3⁄8-inch bolt to retain the rocker arm instead of the typical big-block 7⁄16-inch adjustable stud. The problem is that tiny 3⁄8-inch bolt will not hold up against decent performance camshaft spring pressure. Plus, the net lash does not allow custom lifter preload, except through custom pushrod lengths. There is an alternative, however. Crane makes a conversion stud kit that uses a 3⁄8x16 lower portion stud that screws into the head with a 7⁄16-inch top thread that allows the use of big-block rocker arms. The Crane conversion kit is PN 99152-16 ($104, Summit Racing) and this would allow you to run roller rockers like the Crane Classic big-block rocker PN 13774-16 ($312, Summit Racing). If you stick with a mild hydraulic roller cam, the conversion rocker studs will work just fine. However, if you are considering running a big cam and spring pressure, that small 3⁄8-inch internal stud probably will not withstand a lot of spring pressure. With a bigger cam, have a machine shop do the compound angle drilling and tapping for a 7⁄16-inch stud. Just to cap this off, do a little more research because by the time you invest in machine work for larger valves, machining the rocker stud bosses for a 7⁄16-inch studs, a valve job, and the inevitable new guides, you will be quickly approaching the cost of a set of Edelbrock aluminum heads that are also considerably lighter. A pair of ready-to-bolt-on Edelbrock oval-port aluminum heads from Summit (PN 50459) will run $1,799.

More Info
Crane Cams; 866/388-5120; CraneCams.com
Edelbrock; 310/781-2222; Edelbrock.com
Federal-Mogul (Fel-Pro); 810/354-7700; Federal-Mogul.com
Ohio Crankshaft; 800/333-7113; OhioCrank.com

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