big block chevy info



big block chevy info

Postby grumpyvette » November 14th, 2008, 10:10 am

the real basics, (off ebays site)-------------------------------------------------------------------------------
"
This guide is intended to help you sort out the more major differences among Big Block Chevrolet engines produced since 1958. Chevrolet has designed and produced several different "big block" engine families. Within each family, there can be evolutionary changes, and special parts designed for competition use which may not be directly interchangeable with the regular production items. I don't intend to cover every possible variation. For practical purposes, all big block Chevrolet engines use a cylinder bore spacing of 4.84 inches although note the one exception below.

Early engines were designated as Mark I, (Mk I) Mk II, Mk III, and Mk IV. Later engines continued the numbering system as Generation 5 (Gen 5), Gen 6, Gen 7. There are some conflicting theories as to the reason for the change from "Mark" to "Generation". My first guess: "Gen 5" sounds much more modern, hi-tech, and trendy than "Mk V".

Mark I: The original "Big Block Chevy", also called the "W" engine perhaps because of the layout of the valves and therefore the shape of the valve covers--although another possibility is that GM chose the "W" prototype for production rather than the competing "X" or "Y" prototypes, and therefore it's a convenient coincidence that the valve layout is in the shape of a "W". It should be noted that this engine became "Mark I" only after the Mark II was being designed years after the "W" was introduced. Whatever the origin of the name, this engine family was installed in vehicles beginning in 1958, as a 348. In 1961, it went to 409 cubic inches, (as immortalized in the Beach Boys song "She's so fine, my 409") and for one year only (1963) a few well-connected racers could buy a car with a 427 cubic inch version called the Z-11. The 427 version was all about performance, and had special parts which were not directly interchangeable with the 348/409. While production of the 427 was severely limited, both the 348 and 409 were offered in passenger cars and light- and medium-duty trucks. The truck blocks were somewhat different from the passenger car blocks, having slightly different water jackets and of course, lower compression achieved by changes in the piston in addition to more machining of the top of the cylinder. A novel feature of this engine is that the top of the cylinders are not machined at a 90 degree angle to the bore centerline. The top of the cylinder block is machined at a 16 degree angle, and the cylinder head has almost no "combustion chamber" cast into it. The combustion chamber is the top wedge-shaped section of the cylinder. Ford also introduced an engine family like that in '58--the Mercury/Edsel/Lincoln "MEL" 383/410/430/462. The "W" engine ended it's automotive production life part way through the 1965 model year, when the 409 Mk I was superseded by the 396 Mk IV engine.

Mark II: This is more of a prototype than a production engine. It is the 1963-only "Mystery Engine" several of which ran the Daytona 500 race, and in fact won the 100-mile qualifier setting a new record. It is largely the result of engineering work by Dick Keinath. Produced mainly as a 427 but with a few 396 and 409 cubic inch versions, all in VERY limited numbers. Even though it was intended as a NASCAR-capable engine, it had 2-bolt main caps. This engine was never installed in a production-line vehicle by GM, it only went to racers. And even though it was available in 1963, it has very little resemblance to the 427 Mark I "W" engine of the same year. The Mark II was a "breakthrough" design using intake and exhaust valves that are tilted in two planes--a canted-valve cylinder head, nicknamed the "Semi-Hemi" or "Porcupine" because it is "almost" a hemi head, and the valve stems stick out of the head casting at seemingly random angles. The engine was the subject of an extensive article in the May, 1963 Hot Rod Magazine. Because of NASCAR politics, Chevrolet was forced to sell two 427 Mark II engines to Ford after the '63 Daytona race, (to "prove" that it was a production engine, and therefore eligible to race in NASCAR events) and so this engine is not only the grandfather of the Mark IV and later big block Chevies, it's also the grandfather of the canted-valve Ford engines: Boss 302, 351 Cleveland and variants, and the 429/460 big block Ford. The bore and stroke of the 427 MK II is not the same as the 427 MK IV.

Mark III: Never released for production. This was rumored to be the result of GM/Chevrolet's proposed buyout of the tooling and rights to the Packard V-8 engine of the mid-to-late '50's. The Packard engine was truly huge, having 5" bore centers. The former president of Packard wound up at Ford after Packard folded, perhaps because of that, Ford was also interested in this engine. Ford wanted to make a V-12 variant from it just as Packard had once envisioned. One way or another, neither GM nor Ford actually went forward with the purchase.

Mark IV: The engine that most people think of as the "big block Chevy". Released partway into the 1965 model year as a 396, superseding the older 409. It is a development of the Mark II and using similar but not identical canted valve (semi-hemi/porcupine) cylinder heads. It was later expanded to 402 (often still labeled as a 396, or even a 400,) a 427, a 454, and a few "special" engines were produced in the late '60's for offshore boat racing as a 482. There was a 366 and a 427 version that each had a .400 taller deck height to accommodate .400 taller pistons using four rings instead of the more usual three rings. These tall-deck engines were used only in medium-duty trucks (NOT in pickup trucks--think in terms of big farm trucks, garbage trucks, dump trucks, school busses, etc.) The tall-deck blocks all had 4-bolt main caps, forged crankshafts, and the strongest of the 3/8 bolt connecting rods. All-out performance engines used 7/16 bolt connecting rods, along with other changes. This engine family was discontinued in 1990, with the Gen 5 appearing in 1991.
BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
Image
mark iv blocks
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mark v blocks
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(keep in mind that ALL '91 and later Gen.V and Gen.VI big blocks come with 4-bolt main caps. The two-bolt big blocks are no longer in production
MANY BUT NOT ALL aftermarket head designs have been modified to work on both the early MARK IV 1965-90 and later MARK V & VI blocks 1991-later.)

BTW, , on BIG BLOCKS the oil pumps and oil filter adapters are different due to the block oil filter recess and rear seals being different
GEN 4 or MARK IV
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GEN V and VI
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Gen 5: General Motors made substantial revisions to the Mark IV engine, and the result was christened "Gen 5" when it was released for the 1991 model year as a 454. There were 502 cu. in. versions, but never installed in a production vehicle, the 502s were over-the-parts-counter only. Changes to the Gen 5 as compared to the Mk IV included, but are not limited to: rear main seal (and therefore the crankshaft and block) were changed to accept a one-piece seal, oiling passages were moved, the mechanical fuel pump provisions were removed from the block casting, the machined boss for a clutch bracket was eliminated, the cylinder heads lost the ability to adjust the valve lash, and the coolant passages at the top of the cylinder block were revised. The changes to the coolant passage openings meant that installing Mk IV cylinder heads on a Gen 5 block could result in coolant seepage into the lifter valley. Frankly, the changes (except for the one-piece rear main seal) were all easily recognized as cost-cutting measures which also removed some quality and/or utility. All told, the Gen 5 engine was not well regarded by the Chevy enthusiasts because of the changes to the coolant passages and the lack of an adjustable valvetrain. As always, the aftermarket has provided reasonable fixes for the problems. The Gen 5 lasted only until 1995 Gen 6: GM recognized that it did not make any friends when it designed the Gen 5, and so they chose to revise the coolant passages again when designing the Gen 6, allowing the older heads to be used without coolant seepage problems. The boss for the clutch bracket returned, but was generally not drilled and tapped. The non-adjustable valvetrain remained, as did the one-piece rear main seal. Some but not all Gen 6 454 (and not 502) blocks regained a mechanical fuel pump provision. Production engines installed in pickup trucks got a high-efficiency cylinder head, still canted-valve, but with a modern heart-shaped combustion chamber of about 100cc. The intake port has a "ski jump" cast into it to promote swirling of the intake air flow. All production vehicles with a Gen 6 used a 454 version, but over-the-counter 502s are available. The Gen 6 is sometimes referred to as the "Gen Fix" because it fixed a number of issues that disappointed enthusiasts when the Gen 5 was released. As an added bonus, most if not all Gen 6 engines use hydraulic roller lifters.

Gen 7: A very major revision of the previous engines resulted in the 8.1 liter/ 8100/ 496 cubic inch Gen 7 in 2001. The block gained .400 in deck height so it is the same height as the previous "Tall Deck" truck blocks, wider oil pan rails, and the cylinder heads have symmetrical port layouts instead of the previous 4 long/4 short port layout. Very little interchanges between the 8.1 liter engine and the previous Mark IV/Gen 5/Gen 6 engines. The head bolt pattern and even the firing order of the cylinders has been changed. There are some things that remained true to the previous Mk IV/Gen 5/Gen 6--the bellhousing bolt pattern, the side motor mount bolt pattern, the flywheel bolt pattern, and the exhaust manifold bolt pattern are the same. Note that the bolt holes are threaded for metric fasteners. The 8.1 is internally balanced, so you could install a flywheel/flexplate from a 396/427 Mk IV provided you use the correct bolts to suit the 8.1 crankshaft.

I have had a chance to compare Mark IV, Gen 5/6 and Gen 7 head gaskets. It seems to be possible--but very difficult--to install IV/5/6 heads on the Gen 7 block. GM did this on one show vehicle, it IS possible. You must move three head bolt holes in the block; and as the holes only move about 1/2 their diameter it would be difficult to plug the existing holes, re-drill the new holes, and still have enough strength in the deck surface. There are cooling system differences as well that must be addressed. I have NOT done this conversion; but I do have comparison photos of the head gaskets.

Specifications:
(sorry if this table loses it's formatting: I don't know how to fix it. It looks "ok" at full screen width on my computer)

Engine family Displacement Bore Stroke Rod length

MK I 348 4.125 3.25 6.135

MK I 409 4.31 3.5 6.010

MK I 427 4.31 3.65 6.135

MK II 427 4.31 3.65 6.135

MK IV 366 3.938 3.76 6.135 (Only offered as a medium duty truck engine)

MK IV 396 4.094 3.76 6.135

MK IV 402 4.125 3.76 6.135

MK IV 427 4.250 3.76 6.135 (Offered in passenger car and medium duty truck versions)

MK IV/Gen 5/6 454 4.250 4.0 6.135

MK IV 482 4.250 4.25 6.405 (very rare, made only for offshore boat races. Used tall-deck block)

Gen 5/6 502 4.466 4.0 6.135 (Over the parts-counter only; not installed in production vehicles)

Gen 7 496/8.1 4.25 4.37

Specials: GM has sold many special-purpose engines, partial engines, blocks, cylinder heads, etc., "over the parts counter" that were never installed in production line vehicles. It is very difficult to track all the various items--suffice to say that heavy-duty "Bowtie" blocks and cylinder heads in various configurations--Mark IV, Gen 5, etc, have been produced. Oldsmobile used the Big Block Chevy as a baseline when designing the first of the Drag Race Competition Engines (DRCE) so that the early DRCE engines have an Olds Rocket emblem cast into the block, but it's Chevy parts that fit inside. There are special high performance blocks and heads, in either iron or aluminum, produced by GM and by aftermarket suppliers to suit almost any racing need.

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.

Please check out my guides to GM small block engines , and Olds, Pontiac, and Buick big block engines, Mopar V-8 engine families, Ford V-8 engine families since 1932 or HEI distributors , too.

http://www.dragzine.com/tech-stories/en ... ine-block/
"
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: big block chevy info

Postby grumpyvette » November 15th, 2008, 2:46 pm

if you thought that was good read thru this series

http://www.idavette.net/hib/vette_bbfh.htm

Image
and this article

http://maliburacing.com/patrick_budd_article.htm

more info

http://www.circletrack.com/techarticles ... index.html


http://www.s-series.org/htm/tech/GMPerf ... 99-104.pdf

IF YOUVE GOT DEEP pockets
aluminum's FAR easier to repair once damaged as TIG welding ALUMINUM is far simpler than nickle brazing cast iron, aluminum dissipates heat faster, aluminum,s far easier to machine, and if your doing some mods you can weld stuff too aluminum far easier
but the cast iron blocks USUALLY got an edge in stiffness
the big problem is COST,

http://www.brodix.com/blocks/5inchblock.html

http://www.brodix.com/blocks/4.500block.html

http://www.dartheads.com/products/engin ... ig-blocks/

http://www.dartheads.com/products/engin ... locks.html

http://www.cnblocks.com/

http://sdparts.com/details/gm-performan ... s/19170540

http://www.jegs.com/p/World-Products/Wo ... 3/10002/-1
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: big block chevy info

Postby brain55 » February 17th, 2009, 11:22 pm

I am currently having a Gen VII, 8.1L engine rebuilt for my 2001 K3500 GMC Sierra. I have learned a few things so far.

First of all, even though this engine is 8 years old now, there are very few aftermarket parts available.

One of the first things my machinist noticed was that it has low tension oil rings from the factory (which may explain the 2 qts. of oil it used every 3000 miles since the day I bought it).

It has torque to yield head bolts which are not reusable (ARP is just now working on making bolts available for this) I'm hoping are are going to be available before my machinist needs them or I will be buying 2 sets of the factory bolts, since this engine has to be bored with torque plates. We had to buy factory rod bolts, ARP doesn't make these yet either.

The rockers on these heads are not adjustable. ARP does make rocker studs with the correct metric threads so I am going to upgrade to full roller rockers and they will be adjustable too. Crower is going to regrind a cam for me to get some added bottom end torque.

I expect to be towing a 14,000+ lb trailer daily with this truck, which is why I choose the have an engine built for it after 165,000 miles. I will update this with more info as I get it.

Brian
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Re: big block chevy info

Postby grumpyvette » February 18th, 2009, 6:07 am

thanks for posting that info,
and please keep us up to date on your progress, and any part numbers for components as you find them.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: big block chevy info

Postby brain55 » March 10th, 2009, 7:36 pm

Just a quick update.

My original plan was to have a core rebuilt and then just do an engine swap, in-out-no problem. Well, as I am learning with this engine, nothing is easy. My engine builder's core supplier went through 5 blocks and was not able to come up with a good block. So plan B, I took my truck over to a shop he recommended to pull my engine so he would have something to rebuild. As expected he was able to see that the 2 qts of oil this thing burned every 3000 miles went right past the rings. The piston tops and combustion chambers were completely gooey with oil.

The one good thing so far is that the bore will clean up at .020" oversize. That brings us back to the next ordeal. Nobody makes a standard tension oil ring for this engine. So we sent the pistons to Total Seal today so they could cut 3/16" oil ring grooves in them instead of the 4mm stock width. So we should get those back next week and then he can send everything off to the balancers.

In the mean time he can work on the heads. I hope that that goes smoothly. We ordered ARP's screw in rocker studs with the correct metric threads for the head and Comp Pro-Magnum full roller rockers so I will have adjustable valvetrain now. I hope GM didn't do anything screwy with the rocker geometry and standard 1.7:1 rockers will work.

When this is all said and done I will post part numbers. I don't want to put anything down untill I know its going to work.

Brian
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Re: big block chevy info

Postby grumpyvette » May 19th, 2011, 4:56 pm

related links with lots of info


http://www.chevyhiperformance.com/techa ... index.html

http://reviews.ebay.com/Big-Block-Chevy ... 0001563647

viewtopic.php?f=51&t=2692


http://www.carquest.com/common/download ... 3_4886.pdf

Issue:
General Motors (GM) 7.4L (454 CID)
engines use two types of engine
blocks: the Mark IV and Mark V. The
Mark IV is found on 7.4L engines in
model years from 1965 - 1990, and
the Mark V is found on 7.4L engines
in model years from 1991 and later.
Often, installers will attempt to adapt a Mark IV cylinder head for a Mark V block.
This conversion can be made if attention is paid to the coolant circulation because
the Mark IV and Mark V have different coolant flows, and were
originally designed for different head gaskets. If the conversion is not performed
correctly, the engine will overheat, causing premature engine wear and damage.

Resolution:
CARQUEST Gaskets by Victor Reinz® has designed two Nitroseal® head gaskets
to specifically allow for this conversion. The installation requires that CARQUEST
Gaskets by Victor Reinz® part number 4918 be installed on the right cylinder
bank to maintain proper coolant circulation, and part number 4923 be installed on
the left cylinder bank
for the correct coolant flow.

Application:
Ask for CARQUEST Gaskets by Victor Reinz® part numbers 4918 (right bank)
and 4923 (left bank), or part number 4886 for conventional Mark V applications
and part number 3884SG for conventional Mark IV applications.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: big block chevy info

Postby grumpyvette » May 12th, 2014, 7:20 pm

Big Block Chevrolet Gen V and Gen VI Oiling SystemSolving the mystery of the Gen V and Gen VI Priority Main Oiling system
Priority Main Oiling System
The Generation V and VI big block Chevrolet blocks feature a priority main oiling system where the main oil supply passage is located adjacent to the camshaft tunnel. Drilled passages which intersect this large oil tunnel carry oil directly to the main bearings. If you are facing the front of the block with the engine in the upright position, this main oil supply tunnel is located in the 2 o’clock position just below the right hand lifter oil supply line.

Oil Cooler Plumbing
Located along the oil pan rail just ahead of the oil filter pad are two drilled and tapped (3/8” NPT) oil passages for routing oil to an external oil cooler. The hole located closest to the oil filter pad (#2) is for the outgoing supply line to the oil cooler. The front passage (#1), which is farthest from the filter pad, is the return line from the oil cooler.

Careful examination reveals that these two passages intersect the same return line that feeds oil back to the main oil tunnel. This requires that a special fitting be used in the #2 supply line to prevent oil from short circuiting the oil cooler.

Part number SD1540 provides the necessary diverter basket to prevent the supply oil from entering the return line before going to the oil cooler. This fitting has a dash 10AN thread to allow the use of aftermarket components to plumb your external oil cooler. The front passage #1 will require a 3/8” NPT by dash 10AN adapter (#FCM2185), which is available from Scoggin-Dickey.

Understanding By-pass Valve Locations
Factory assembled 454, 502 engines and short blocks have two by-pass valves installed in the block. These factory installed by-pass valves (#25013759) will open at an 11 psi pressure differential. One by-pass valve is installed in the center hole on the oil filter pad (#4). This hole is the oil return passage from the oil filter. The second by-pass valve is installed in the adjacent hole (#3). The egg shaped hole (#5) is the high pressure oil supply passage from the oil pump.

For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-pass in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.

If you intend to use a remote oil filter, a high pressure by-pass valve part number 25161284 must be installed in position #3. This valve will open at a 30 psi pressure differential. A plug will be installed in position #4 to prevent oil flow thru this passage. Oil should be returned to the block in the 3/8” hole located just able the oil filter pad. An oil filter block off plate kit (#SD3891) can be purchased from Scoggin-Dickey for Gen V and VI blocks to plumb your external oil filter.

If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure by-pass valves (#25161284). One will be installed in location #3 and the second in location #4. Happy oiling!
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: big block chevy info

Postby grumpyvette » April 16th, 2015, 3:04 pm

By David Reher-Morrison Racing Engines

The road to high technology is often a two-way street. People who are involved in motorsports maintain that racing improves the breed, from the invention of the rearview mirror by Ray Harroun, the first Indianapolis 500 winner, to the disc brakes and low-profile tires that are commonplace on cars today. But the improvements that are made on everyday automobiles and trucks can pay dividends for racers, too. The extended lifter bosses in the sixth-generation (Gen VI) big-block Chevrolet V8 are an example of production engine technology that has benefited hardcore drag racers.

GM engineers lengthened the lifter bosses in late-model small-block and big-block V8 engines to accommodate hydraulic roller lifters. The switch from flat tappets to roller lifters was primarily intended to reduce friction and to improve fuel economy on the highway. It had the additional benefit of allowing faster, more aggressive camshaft profiles that boosted horsepower in high-performance street engines like the LT1 and LT4 small-blocks.

When the first Gen VI big-block with tall lifter bosses arrived in our shop, we were dismayed. There weren’t any commercially available solid roller lifters that would fit the extended bores. Our first impulse was to machine the tops of the bosses to accept the shorter lifters we’d used for years, but then we realized that would be a big step backward. We recognized that the longer bosses would stabilize the lifters in their bores – a real advantage in big-block Chevy engines with angled pushrods.

Crower stepped up with a redesigned roller tappet with a longer body and a raised tie bar that cleared the taller lifter bosses. Now “long body” lifters are available from many performance camshaft companies.

When we overhauled the first race engines built with Gen VI blocks, we discovered that lifter bore wear was dramatically reduced. With the old short lifter bosses, the tops of the bores were often bellmouthed after a season of racing. That’s because the big-block Chevy’s sharply angled pushrods subject the lifters to strong side loads. This sideways thrust is especially apparent in engines with Dart Big Chief and Brodix Big Duke spread-port cylinder heads because they have more severe pushrod angles than conventional siamesed port heads.

When Richard Maskin was developing the aftermarket Dart Big M big-block, I recommended that he use extended lifter bosses because of our positive results with this design. In fact, we now use Big M blocks with tall lifter bosses for almost all of our Super Series engines. I was surprised to learn recently that Dart also offers Big M blocks with the lifter bosses machined down to standard height. When I quizzed Maskin about this, he told me that many racers still want to use their old short-body lifters.

In my opinion, short lifters are the wrong approach. If a racer is going to spend the money on a brand-new block, he should take advantage of the latest technology that’s available. Yes, a set of long-body lifters costs more than a set of standard lifters, but the benefits they offer in longer service life and improved reliability are well worth the relatively minor additional expense. It’s false economy to save a few dollars on lifters when you consider the thousands it can cost to repair an engine after a catastrophic lifter failure.

There are also instances in engine design when the racers have the right idea. One of the major shortcomings of the production big-block Chevrolet V8 is its four “missing” head bolts on the intake side of cylinders No. 2, 3, 6 and 7. While the other four cylinders have six head bolts arranged symmetrically around each bore, there is a 4.550-inch span between the upper head bolt holes on these four cylinders which have only five fasteners. Since the four missing bolt holes would be located underneath the intake ports in a stock big-block head, I can only assume that these bolts were eliminated because of the difficulty of installing them on an assembly line and servicing the cylinder heads in the field.

When the first aluminum versions of the Chevy big-block V8 were released for Can-Am road racing in the late ’60s, they featured four bolt bosses in the lifter valley. These bosses engaged studs or bolts that threaded into holes underneath the intake ports to provide the clamping force that is required to seal the head gaskets in a competition engine. Today most big-block cylinder heads have provisions for these studs, even if the bosses aren’t drilled and tapped.

Unfortunately, these lifter valley head bolt bosses were never incorporated in production cast-iron blocks. When we built our first big-block racing engines with Mark IV blocks, we dimpled the deck surfaces with a centerpunch in an attempt to hold the gasket in place. Later we fabricated steel head lugs and mounted them in the lifter valley with bolts and dowel pins. The first option really wasn’t very effective, and the second was expensive and time-consuming.

We see evidence of seepage past the head gaskets in almost every competition big-block Chevy V8 that does not have these four additional head fasteners. When the power level reaches 850 to 900 horsepower, the head gaskets are almost certain to fail in the long span between the upper head bolts.

In the past, the most practical solution was to machine the block for O-rings and use soft copper head gaskets. This is an expensive proposition, however, when your goal is to build affordable engines for sportsman racers. Fortunately, GM’s CNC-machined Gen VI competition cylinder case, some Merlin blocks and all Dart Big M blocks now incorporate head bolt lugs in their lifter valleys – a real improvement over production castings. Among these alternatives, the Big M block is the most affordable choice for sportsman racers.

It doesn’t take much clamping force to solve the big-block’s head gasket problems. We use a 3/8-inch stud torqued to 45 ft./lbs. on our Super Series engines. This has proven to be so effective that we have eliminated O-rings on all but our most powerful big-block bracket engines.

There is a common misconception that more torque on the head fasteners improves head gasket sealing. We use imprint paper to measure the load on the head gaskets, and we have learned that less is better in many instances. The length of the fasteners (bolts or studs) and the distance between them affects the clamping force they produce on the gasket. On our Pro Stock DRCE engines, for example, we torque the outer row of studs to 55 ft./lbs., the valley bolts to 42 ft./lbs. and the long center studs to 70 ft./lbs. We have found that these different torque specifications produce the most uniform loads on the head gasket and keep the head as flat as possible on the block’s deck surface.

Racing is about finding solutions to problems, whether it’s seeing the guy behind you with a rearview mirror or keeping the lifters and head gaskets alive in a big-block V8. In most instances, it’s not rocket science, but simply common sense.
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Re: big block chevy info

Postby grumpyvette » April 16th, 2015, 3:09 pm

By David Reher, Reher-Morrison Racing Engines

“There are some basic skills that must be mastered to build an engine successfully.”

I traveled backward in time last week. It happened while we were rebuilding a big-block Chevrolet engine. This particular engine won the 1982 NHRA Pro Stock championship, and overhauling it was like firing up a time machine.

We’re creating a replica of the championship-winning Reher-Morrison Camaro that will be displayed in the Hendrick Motorsports museum in Concord, N.C. I consider it an honor to have one of our race cars alongside Rick Hendrick’s stable of NASCAR champions. We’re out front with the fact that it’s not the real car – the original is under the care of a collector in West Texas – but the motor is the real deal.

In its time, this was the baddest big-block Chevy in the country. Today there are better parts and more advanced technology in just about any bracket racing engine we build at Reher-Morrison.

I’m looking at this killer engine from 1982, and shaking my head. The genuine GM aluminum cylinder heads still have “X” marks on the castings that signify they were made with cores we’d shaved at the Winters foundry. It’s got stock-diameter lifters, without a lifter bushing in sight. Aluminum rods as big as clubs, stud-mounted rocker arms, and spindly pushrods – that was the state of the art 28 years ago.

Seeing an artifact like that 1982 Pro Stock engine reinforces my belief that we are currently living in the Golden Age of engine development. Many of today’s off-the-shelf parts are superior to the handmade, high-dollar, top-secret components that powered yesterday’s record-setting Pro Stocks. In fact, I sometimes fantasize about racing one of our Super Series sportsman engines back in the day when the Reher-Morrison Chevrolets were battling Glidden, Johnson, and Iaconio for the top spot in Pro Stock. I think it would have been a powerful weapon.

My intention is not to wallow in nostalgia, but to point out the strides in materials and technology made by aftermarket manufacturers. There is a multitude of aftermarket blocks available in a variety of configurations. If a customer wants a block with a 55mm cam, I can order one from the manufacturer instead of boring out the cam tunnel on a mill in our shop. If a racer wants cylinder heads with a 14-degree valve angle, I can get them with a phone call instead of spending days building up the decks with aluminum welding rod. Life is definitely good for racers and engine builders these days.

Unfortunately the law of unintended consequences hasn’t been repealed, and there is a downside to this rich bounty of parts. As always, the devil is in the details. With so many manufacturers producing so many variations, finding compatible parts can be extremely difficult for do-it-yourself engine builders. Just consider the myriad differences among “conventional” big-block Chevy cylinder heads in valve diameters, valve angles, guide locations, and combustion chamber shapes. A piston dome that fits one head perfectly can be a total disaster with another head. The height of the valve seats, the location and depth of the valve reliefs, the profile of the dome, the lift and duration of the camshaft, the rocker arm ratio, and a dozen other design features all must be considered.

I’m told that GM has produced more than 95 million small-block V-8 engines. Replacement parts are available from any well-stocked dealership or auto parts store, and there is a reasonable expectation that every part will fit every engine. The market for specialized racing components is tiny in comparison, with no standardization among the various aftermarket manufacturers. Every manufacturer has a notion about how to make better parts – that’s what drives the performance industry. With this continuous development, it’s up to the engine builder to make sure that the parts will work together.

Building an engine is an enjoyable and rewarding experience for many racers. That’s how I got started in racing, and I’m grateful that eventually it became my livelihood. But for some people, engine building is an exercise in frustration.

I believe there are some basic skills that must be mastered to build an engine successfully. These include the ability to degree a camshaft, check piston-to-valve clearance, locate valve notches, measure valve angles, verify dome-to-head clearance, and align the intake manifold runners. There is no lack of information on these topics: Books and videos are available that describe these procedures in detail, and several schools teach the fundamentals of building racing engines.

High-tech parts can be enticing, but a successful engine builder doesn’t overlook the basics. For example, when you’re building for maximum power, compression ratio matters. Piston-to-valve clearance is a major factor in determining compression ratio because the valve pockets are typically the largest surfaces on the piston dome. If the valve reliefs are deeper than necessary, it’s easy to give up 10cc or more of dome volume. That can mean the difference between a 15:1 compression ratio and a 13:1 compression ratio – and two full points of compression will have a huge impact on performance.

What good is a set of the latest high-dollar CNC-ported cylinder heads if the compression ratio is under par? Few racers have the equipment and expertise to test cylinder heads, but anyone can check the compression ratio with a burette and a piece of Plexiglas. It’s a basic skill of engine building.

I’m continually amazed at the subtleties of engine building. Just changing from one brand of lifters to another brand can change the engine’s oil pressure by eight or 10 psi. How is this possible? Take a close look at the oil grooves in the lifters. An annular groove acts like a restrictor to reduce flow through the oil gallery; a straight hole allows more oil to move through the lifter body and consequently reduces oil pressure. An inexperienced engine builder would be looking at the oil pump to fix a problem that’s really caused by a difference in lifter designs. That’s just one example of the complexities of a racing engine that’s assembled with parts from dozens of suppliers.

Looking at the parts and pieces from that 1982 Pro Stock engine, it’s apparent that we didn’t know what we didn’t know. If we had understood the importance of valvetrain dynamics, the performance benefits of lightweight parts, and the impact of combustion chamber design, our engine would have been much different. We simply didn’t have the parts and the knowledge to build a more powerful engine; we did the best we could with what we had to work with.

The evolution of engine technology never stops. I’m sure that 30 years from now, some builder will tear down a 2010 Pro Stock engine and wonder, “What were they thinking?”
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IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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