The New Evolution Big Block Chevrolets Always Get Bigger

TITLE: THE NEW EVOLUTION
SUBTITLE: Big Block Chevrolets Always Get Bigger
CREDIT: By John DiBartolomeo

It might seem like ages now, but it really wasn't all that long ago when the thought of a 500-cubic inch engine was BIG and required quite a bit of engineering to build. Today that's certainly not the case as the aftermarket has geared up to take over where the factories have left off.
The basis for any engine build-up is the block and Brodix's 5-inch bore center aluminum casting was chosen for this project. By moving the bore centers outward, it allowed for a larger bore with increased thickness between cylinders. Surprisingly, the overall length dimension remains the same as any standard big block Chevrolet.
The basis for any engine build-up is the block and Brodix's 5-inch bore center aluminum casting was chosen for this project. By moving the bore centers outward, it allowed for a larger bore with increased thickness between cylinders. Surprisingly, the overall length dimension remains the same as any standard big block Chevrolet.


Evidence of this is everywhere you look, as 800-cubic inches has even become the norm in some classes. When it comes to the sportsman categories, there's an abundance of 565, 582 and 632 inch Chevrolets listed on the tech cards of some racers. Every one likes to go faster and in these cases, bigger is better. Because this particular powerplant is to be run in a Super Comp dragster, one might ask "Why faster when you're only governed by the 8.90 index?"
Moving the bore centers outward requires the same be done with the cylinder heads and Brodix's PB5000 heads match up perfectly. The use of larger intake valves is another by-product of the 5-inch bore centers. An engine is merely an air pump so the more air you can get into it, the better it will run.
Moving the bore centers outward requires the same be done with the cylinder heads and Brodix's PB5000 heads match up perfectly. The use of larger intake valves is another by-product of the 5-inch bore centers. An engine is merely an air pump so the more air you can get into it, the better it will run.


Obviously driving the finish line is a necessary part of the class as one doesn't want to cross too far ahead of their opponent and cause a break-out. In that scenario, the faster car sometimes has an advantage. Miles-per-hour appears to be the key in any of the super categories as it allows the driver to have the whole race run without having to look backward and see his competition. Add in the growing proliferation of the Top Sportsman and Top Dragster classes where it takes a fast car to qualify, and it appears engine sizes are expanding to keep up.

A big inch engine requires a big cylinder bore and one of the most obvious limitations to accomplishing this is the relatively close bore centers. As a point of reference, a standard big block Chevrolet engine has a bore center of 4.840 inches. The use of a 4.600 inch bore (common for a 565) only leaves roughly .250 between the cylinders. Going to a larger bore reduces that number which can cause issues.
The manifold used is for this project was a single 4-barrel cast unit. Although it wasn't designed for this cylinder head/block combo, a raw casting was purchased to which quite a few hours of work went into.
The manifold used is for this project was a single 4-barrel cast unit. Although it wasn't designed for this cylinder head/block combo, a raw casting was purchased to which quite a few hours of work went into.


While in the past, the OEM factories were the only ones producing their own castings, the aftermarket found the ability to produce their own castings with virtually unlimited potential. They've now been able to make changes which has produced a much needed "better mousetrap."
A build-up of this magnitude requires hours of assembly, checking and disassembly. Everything must be put together to check for clearance problems. The Jesel cam belt drive must have felt like it was installed and removed hundreds of times.
A build-up of this magnitude requires hours of assembly, checking and disassembly. Everything must be put together to check for clearance problems. The Jesel cam belt drive must have felt like it was installed and removed hundreds of times.
By spreading the bore centers, it's given engine builders the ability to utilize larger cylinder bores. Larger cylinder bores equals bigger inch engines. It also allow for a much freer flowing cylinder head because the larger intake valves used aren't crammed in there.

However, bigger inch engines can still require a bit of "engineering" to build. The theory would be to attempt to assemble a big inch engine utilizing relatively standard over-the-counter parts. Could it be done? Possibly, but Steve Williams and John Reedy of K&N Engineering were willing to give it a try.

"We were sort of at a point with the older 4.84 bore center engines," says Reedy, "where we wanted to go to the next evolution of the big block Chevrolet. We wanted to install a bigger intake valve but we were limited by the placement in the cylinder head."
Our block came directly from Brodix completely bored and honed for pistons and rings, while the crankshaft bores were line honed and ready to go. However, bearing clearances still need to be checked and double-checked.
Our block came directly from Brodix completely bored and honed for pistons and rings, while the crankshaft bores were line honed and ready to go. However, bearing clearances still need to be checked and double-checked.


The introduction of Brodix's aluminum engine block with a 5.00 inch bore spacing allowed them to accomplish that fact. The original plan was to build a larger bore engine with the same stroke (4.25) that they had been using. However, the shortest deck block Brodix could supply was a 10.7-inch deck height. A standard height Chevrolet block has a deck height of 9.80. The extra height would cause the piston to have a tall compression height, which is the distance from the centerline of the piston pin to the top deck of the piston. This makes for a heavy piston as well as causing it to pivot around the piston pin and rock in the bore.
The pistons used came directly from JE ready to install except for some slight deburring of the domes. As is the case with the today's components, the aftermarket is aware of what you're attempting to accomplish and as such, usually work with one another to offer components which fit together with little or no problems.
The pistons used came directly from JE ready to install except for some slight deburring of the domes. As is the case with the today's components, the aftermarket is aware of what you're attempting to accomplish and as such, usually work with one another to offer components which fit together with little or no problems.


The connecting rods used in K&N's other engines was a rather standard .400-inch longer than stock. By lengthening the stroke to 4-1/2" (4.500) and using a connecting rod measuring 7.200 center to center it allowed for a fairly standard (if there appears to be such a thing with this type of engine) 1.25" compression height.

With the basic foundation laid out, Reedy and Williams set about to gather components which came fairly easy. "The aftermarket really understands this type of build," Reedy said. "Their tech people knew somewhat of what we were trying to accomplish, so it was easy to explain to them and have them supply us with what components they felt would work."
With camshaft recommendations from Tim Cole of Comp Cams, a large 60mm journal cam made its way west. The Brodix block utilizes a billet rear cam plug held in place by a spiral-lock. Because of this, the cam was roughly 1/4" too long in the back which necessitated trimming.
With camshaft recommendations from Tim Cole of Comp Cams, a large 60mm journal cam made its way west. The Brodix block utilizes a billet rear cam plug held in place by a spiral-lock. Because of this, the cam was roughly 1/4" too long in the back which necessitated trimming.


The block and cylinder heads were the first things to come from Brodix. The block came through completely bored and honed to size, ready to install pistons. The aluminum block was also line honed by Brodix for the crankshaft and had the cam raised one inch to clear any crankshaft stroke.

The aluminum PB 5000 CNC-ported cylinder heads also came from Brodix completely machined with Stealth valves. The five inch bore centers of the block require heads which have the combustion chambers moved to center over the bores. By moving the bore centers, it also allowed for a larger intake valve, which was part of the original plan.
The camshaft was ground on a rather wide 116-degree centerline which will help with high rpm power. Degreeing the cam in requires installing the T&D rockers which actuate light weight springs attached to the valve.
The camshaft was ground on a rather wide 116-degree centerline which will help with high rpm power. Degreeing the cam in requires installing the T&D rockers which actuate light weight springs attached to the valve.


While the block and heads are fairly standard, the one piece of the puzzle missing was an intake manifold. Reedy said, "Most of the people who purchase this combination from Brodix will usually choose to utilize a hand-built sheet metal manifold with two carburetors. We didn't want to do that. We want this to be a single four-barrel engine so that we can run a single throttle stop."

Multi-time NHRA national event and divisional event champion Steve Williams says, "We've always run the cast-style aluminum manifolds and I firmly believe they are more consistent because they will hold heat. When you're out there round-robin racing, consistency is what plays a key and properly maintaining the same intake manifold temperature day and night does play a role.
After cutting the manifold to remove the distributor pocket and front water passages, K&N fabricated adapter plates to match the manifold to the cylinder heads.
After cutting the manifold to remove the distributor pocket and front water passages, K&N fabricated adapter plates to match the manifold to the cylinder heads.


"A sheet metal manifold might tend to make more horsepower, but we're not sure yet about its consistency. We're going to do extensive dyno testing with this combination so we'll know for sure."

What transpired was the use of a Brodix PM1917 manifold which matched up fairly well but required a little bit of tweaking. "The center ports lined up fairly decent," says Reedy, "and the outer ports just needed to be moved out about 3/8". Brodix leaves these manifold fairly small so that the inside edge of the outer ports lined up perfect and I just moved the outside wall out to match the heads. They also sent us the manifold without bolt holes and we fabricated spacer plates to move the manifold up in order to line it up better with the cylinder heads."
With the manifold and adapter plates mounted to the heads, the valley plate can be seen here. Typically, the lifter galley on a Chevrolet engine is covered by the intake manifold, but in this case, a valley cover was fabricated and mounted to the manifold adapter plates. The cover makes it a snap for changing lifters without removing the intake.
With the manifold and adapter plates mounted to the heads, the valley plate can be seen here. Typically, the lifter galley on a Chevrolet engine is covered by the intake manifold, but in this case, a valley cover was fabricated and mounted to the manifold adapter plates. The cover makes it a snap for changing lifters without removing the intake.


One other part of machine work on the manifold was the removal of the front crossover water passage and the distributor casting. The water passage didn't line up to the heads and the exit point of the water will be through the front of the cylinder heads. A front-mounted Jesel distributor drive was intended to be used, so that the rear part of the manifold which mounts the distributor was also unnecessary. By machining these areas off of the manifold, it made the manifold simply just a spider of runners and plenum area, but that still required a valley plate to close off the lifter galley of the block.
The columns of steel they're calling pushrods these days help to maintain positive valve control. Manton Pushrods fabricated these to dimensions we provided after measuring for the proper geometry using an adjustable pushrod supplied with the T&D rockers.
The columns of steel they're calling pushrods these days help to maintain positive valve control. Manton Pushrods fabricated these to dimensions we provided after measuring for the proper geometry using an adjustable pushrod supplied with the T&D rockers.


Reedy says, "This engine is intended to be campaigned for hundreds of runs without disassembly, but most racers will want to change lifters from time to time as a precautionary measure. Steve felt that if we could design this with some type of valley cover which could be removed, it would speed up the process of changing lifters. This would alleviate having to remove the intake manifold, which is a common occurrence with a big block Chevy."

In that regard, a lifter valley cover was fabricated and attached to the intake manifold adapter plates. It bolts right in and uses silicone RTV sealant to keep it sealed. Brodix has been working on a combination such as this so it might only be a matter of time before it's readily available.

With the rest of the parts coming in quite rapidly, it was time to mock up the engine. This isn't the type of engine in which you simply order the parts and bolt it all together. It's imperative for the components to be rough-assembled and checked for proper clearances.
Because of the large diameter of the pushrods, the cylinder heads needed extra clearance. We say it was a simple matter to hand grind the area, but in reality, there wasn't much simple about it other than to spend the time and do it properly.
Because of the large diameter of the pushrods, the cylinder heads needed extra clearance. We say it was a simple matter to hand grind the area, but in reality, there wasn't much simple about it other than to spend the time and do it properly.


One of the first interferences in an assembly of this nature is the connecting rods hit the inside of the block due to the added stroke. This goes back to understanding the needs of your customer and the Brodix block is cast extremely large in that area. Reedy said, "There was absolutely no clearance problems there as I think you could put in a five-inch stroke crankshaft and it would clear." When it came to the piston department, Brodix had already worked with JE Pistons on a set of slugs which matched the cylinder head combustion chambers. In that regard, it was very simple to merely supply JE with the measurement of how deep off the deck of the head the valves were, along with the camshaft specs.

"They've got a program which tells them just how far to cut the reliefs for valves based on the cam specs," says Reedy, "and that made it a snap as we did very little to the piston dome with the exception of just knocking off some of the sharp edges."
With the short block assembled and the Moroso dry sump oil pump and vacuum pump, ATI Super Damper, MSD crank trigger and Meziere water pump attached, we're ready for cylinder head installation and finish assembly. Next issue: Dyno time and the search for 1,200 horsepower (or more).
With the short block assembled and the Moroso dry sump oil pump and vacuum pump, ATI Super Damper, MSD crank trigger and Meziere water pump attached, we're ready for cylinder head installation and finish assembly. Next issue: Dyno time and the search for 1,200 horsepower (or more).


The pistons were also cut for .043 thick top gapless moly piston ring from Total Seal. The second rings are also .043 thick and are back cut to relive tension. The 3mm thick oil rings were ordered with ten pound tangential tension. The light tension helps in the friction department, but also requires the use of a vacuum pump to aid in sealing. Because of the aluminum block, the cylinder bores do have a tendency to move around a little and the gapless Total Seal rings help to maintain ring seal better than a standard-type ring. While Total Seal has been the leader in piston rings for quite a long time, the real beauty about ordering rings from them is, once again, they understand their customer's needs. You speak directly with an engineer/salesman who can assist you to be sure you receive the correct rings for your particular application.

For the camshaft selection, Tim Cole of Comp Cams knew exactly what this engine required and supplied a large 60mm journal billet cam. Because of the type of billet rear cam plug in the Brodix block, the cam itself was roughly 1/4" longer then it should have been. All that was required was to simply slip the cam in a lathe and turn .250 off the back of the cam.

With all of the mock-up done and the final assembly all but completed, the next step in this evolution will be some extensive dyno testing. Wiiliams said, "Because this is a relatively new combination, we're not going to put this in one of our cars until we're sure it makes the horsepower and torque we think it should. We also have a couple of new single four-barrel carburetors to try; some of them pretty revolutionary."

Stay tuned to Part 2 in our next issue for "625-cubic inches of dyno testing."

TECH SPECS-625 CUBIC INCHES
Block: Brodix 8B 5000 5" bore center Exhaust Valve: Stealth 1.860 inch
Deck Height:10.700 inch Pushrods:Manton 9/16"
Bore Dia:4.700 inch Valve Springs:Comp Cams #26028 - 346lb @ 2.20 on seat
Bore Spacing:5.000 inch Valve Spring Retainers:Del West titanium w/7-degree locks
Oil Pump:Moroso 4-stage dry sump pump Rocker Arms:T&D 1.85 ratio intake/exhaust
Crankshaft:Crower lightweight billet Camshaft:Comp Cams 60mm roller 4/7 swap
Stroke:4.500 inch Cam Lift:.975 intake/.950 exhaust
Bearings:Clevite V-series Cam Duration:287° Intake, 308° Exhaust @ .050, 116 lobe center
Rods:Crower Maxlight Billet steel Cam Drive:Jesel #KFD-76100 belt drive for 1.0" raised cam
Rod length:7.200 inch Cam Lifters:Crower .937" diameter, .180" intake offset
Pistons:JE pistons 1.25" compression height 16:1 C.R. Intake Manifold:Brodix PM1917
Top Ring Width:Total Seal .043 inch gapless .170 wall Carburetors:Braswell 2.50 Throttle Bore & APD 1250 Holley
Second Ring Width:Total Seal .043 inch .170 wall napier Damper:ATI 7"
Oil Ring Width:3 mm, 10-pound tension Vacuum Pump:Moroso 4-vane
Cylinder heads:Brodix PB 5000 CNC-ported w/80 cc chambers Ignition:MSD Digital 7 w/crank trigger
Head Gasket:Fel Pro Multi Layer Steel Distributor:Front drive Jesel
Intake Valve:Stealth 2.520 inch Ignition Wires:MSD Super Conductor