When it comes to making horsepower, cam choice is critical. We ordered a custom spec, Comp
If it were just opening new parts boxes and bolting-up the pieces, there would be no reason to call it engine building. Rather, it would be the simple task of engine assembly. Most of us who have a few years of wrench-turning under our belts are familiar with bolting together an engine assembly-especially with familiar mills such as our Mopar big- and small-blocks. Put together an engine in near stock form, and the process comes down to carefully assembling the pieces. The factory did the engineering homework, leaving us to make sure the package comes together according to the specs. Ditto for package combinations in various engine kits. The supplier (hopefully) has worked out the parts' combination, so all we need to do is screw everything together. Dip deep into a wide range of aftermarket catalogs and dream up a radical combination of your own, however, and the responsibility for making it work falls on your own shoulders. This is where the term "building" enters the equation.
The further away from stock form we go, the more keyed-in the builder has to be, not only to churn out mucho horsepower, but also to ensure that the thing will make it past the first turn of the crank.
The roller grind can achieve much higher velocity than a flat tappet, meaning the valve wi
Last month, we assembled our 440's basic bottom end. Although our bottom end included trick aftermarket Eagle rods and Arias pistons, that much of the job did not differ greatly from a stock rebuild. The clearances were set, and as long as the machinists did their job, we were home free.
This month, we will complete the lubrication system, the cam and cam drive, finish the heads, and set up the valvetrain. The question remained of whether we would assemble a fairly conservative package, or build something radical. As we weighed the possibilities, we decided to go radical. The goal-build as hairy a factory iron head 440 combination as we would dare, and cheat with every trick we know, so we could drive it on the street. Probably not "drive to the grocery store" street, but rather 8 inches of choppy vacuum at 1,100 rpm, four-speed, 4.56-geared; Cuda street. Yes, our 'Cuda would continually ask with its lopey idle, "Wanna drag?" We'll spill it all in the next few issues, and run a dyno test on this baseline package to show how we did.
The roller uses the high-performance three-bolt cam gear nose. Lube up the journals and ca
Most roller cams are ground on steel billets, which means a common steel distributor drive
For rockers, we opted to step up to a 1.6:1 ratio, for brutally quick valve action with ou
The Competition Cams high-ratio roller rocker setup is a bolt-in, but doesn't include new
With a shaft-mount system bolted in the stock location, the valvetrain geometry is fixed a
Actually measuring the effect of changing the pushrod length showed that lift varied by up
Providing the spin for the cam is the Milodon geardrive. It offers accuracy, reliability,
The Heart of the Matter
OK, it's down to the brass tacks now-cam selection. No other component on your parts shopping list sets the scene in the same manner as the camshaft. The cam choice will largely define the running characteristics and temperament of the final engine combination. How much power that can ultimately be produced, as well as the rpm capabilities of the engine, will be made or broken by the cam selection.
For the big-block Mopar, there are three choices-flat tappets in either hydraulic or solid, or solid roller. Each of these has its advantages and disadvantages relative to one another, but for ultimate power production, there is really only one choice-solid roller.
Setting up the geardrive begins with removing the stock front-cover locating dowels (we ha
With the solid roller getting the nod in the cam department, it came down to specifying a bumpstick for the task at hand. We wanted to get more scientific in our selection process, rather than flipping the pages of various cam manufacturers' catalogs. We turned to a relatively new service in the aftermarket industry, Cam Masters (see sidebar "Cam Do It," p. 45), to run the numbers.
Having the numbers, in terms of overlap, duration, lift, lobe separation angle, and installed centerline is only part of the picture. Actual lobe design and dynamics play a vital role in determining valvetrain stability and longevity. Cam Masters does not grind the cams, but at the back of every manufacturer's catalog is the lobe specifications section.
Generally neglected by the weekend warrior, these are the pages where the top level professional engine builders mine for info in selecting lobes to build custom cam combinations. We dug into the roller cam lobe specs section of the Competition Cams catalog to find our lobes. To gain longevity, we were after lobes with less aggressive dynamics than the Pro drag racing designs, but much hotter than a typical street roller. So, we focused our attention on the endurance race oval track lobes section.
The case is installed finger-tight, and the cam cover plate is removed. The outer gear is
On the intake, we went with the NC series 4149-a Busch Grand National oval track lobe-which is super-aggressive on the opening and easier on the closing. Specs come in at 292 degree-rated duration (260 at .050 inch) and a lobe lift of .421 inch. With the recommended lash of .024 inch, that results in a theoretical valve lift of .650 inch with a 1.6:1 rocker. On the exhaust side, we chose Competition Cams' High Tech .420-inch Exhaust Series, again an oval track lobe, designed to be easier on the valvetrain than Comp's most aggressive designs. Specs on the exhaust are 296 degree-rated duration (258 at .050 inch) and a lobe lift of .420 inch, giving a theoretical lift of .646 inch with 1.6 rockers. As spec'd out by Cam Masters, the lobes were ground 107 degrees apart. There's no way we are claiming maintenance-free 100,000 mile reliability with these radical lobes, but with careful attention to keeping the valvetrain weight to a minimum, and holding spring load as light as possible, consistent with proper control, we expect to achieve respectable life.
Backing up our roller cam, we went with Comp's PN 829 roller lifters. Although Comp lists lifters for the 440 in various pushrod heights-even some with offsets for increased pushrod-to-head clearance-the standard height, non-offset PN 829s are ideal for our iron-head 440. Built with a roller wheel made from an exotic steel nickel alloy of a much higher grade than the ball bearing steel commonly used, we weren't worried about durability in our application. The Comp lifters have been proven in full race engines at 10,000-plus rpm with valve-spring pressures of as much as 1,000 psi over the nose. If they can live under that kind of punishment, handling the requirements of our 440 should be child's play.
Slide the case over to the right, to get rid of any lash between the gears with the newspr
Once the case is locked down in position with the correct gear clearance, the stock dowel
The supplied tapered 51/416-inch dowels are driven in with a brass drift to finish the job
Degreeing in or phasing the cam begins with finding top dead center. A dial indicator is s
Max Gain Valvetrain
Although we respect the stock, Chrysler-stamped steel rocker system with moderate hydraulic cams, we had already gone off the deep end in terms of cam selection, so there was no looking back when it came time to select the balance of the valvetrain. It's a fact that intake flow is the limiting factor in producing a max power 440 when using factory cast-iron heads. Even with our best ported heads (see "Going With the Flow, Part 2," Feb. '99) moving 34 percent more air than stock, extracting as much horsepower as we can depends on packing the largest charge possible into the cylinder. The most obvious way of doing this is to open the valve longer by adding cam duration. Our cam, within a 292 degree-rated duration, pushed the valve events as radical as we dared go, and beyond. Drag race rollers could be had to push this duration up another 20-plus degrees if you please, and make more high-rpm power, but power would just begin to turn on at a stock 440's redline. The alternative is to open the valve as fast and as far as possible in the 292 degrees we chose.
While some competitive engines were factory fitted with higher ratio rockers, Mopar big-blocks were factory fitted with 1.5:1 rated rockers. This combo worked well with the stock head and cam combination. With our modified heads producing excellent flow in the high-lift range, getting airflow there fast would pay off in horsepower.
Next, the indicator is set up to read cam lift off the No. 1 intake lobe, and the outer ha
To fire the valve open as quickly and as far as possible, we went to Comp's 1.6:1 shaft-mounted, aluminum roller rocker kit. With the radical roller cam, anything less than a needle bearing fulcrum to handle the required spring loads, and the roller tip-to-control guide wear just wouldn't cut it. The Comp kit contains shafts hardened to 57 on the Rockwell scale (stock shafts are a no-go), and the required spacers. The stock hold-downs are modified and reused, or, if you're handy, machine your own billet versions.
Valvespring choice, as previously mentioned, was a critical decision point, in terms of balancing the control of high spring loads with the longer cam and valvetrain life of a lighter spring. Generally, the recommended valve springs are spec'd to handle the maximum rpm a given lobe is likely to encounter. Although we were using radical oval-track lobes, our iron-head 440 will never come close to the 9,000 rpm for which these spring combinations are spec'd. With a maximum anticipated engine speed of 7,000 to 7,500 rpm, based on our airflow and engine displacement, we calculated a more livable spring rate of 180 psi seat pressure, and 480 psi over the nose would do the job. This also would dramatically increase the valvetrain life. Again, the Competition Cams catalog was tapped, and its PN 953 dual-valve springs were ordered.
You are now in the ballpark as far as timing (and maybe dead-on if you were careful) is co
Reliably putting a lid on a spring for high-rpm duty required a top-quality retainer. Since we wanted to minimize the valve spring pressure, lightening up the valvetrain was one of the major criteria. Light, yet strong, titanium retainers fit these requirements perfectly. We went with Comp's premium lightweight PN 720 Timetal 62 alloy 10-degree retainers. Locking them to the valve, we specified the 10-degree Superlocks, which are available with a specially machined recessed groove for increased clearance to the lash caps. All in all, it was a bulletproof combination.
Rounding out the valvetrain are the pushrods. In a highly modified engine, the chances of the required pushrod length being the same as stock are slim to none. With Comp's adjustable roller rockers, a pushrod with a cupped seat at the rocker, and a ball end at the lifter is required. For stock or mildly modified engines, Comp lists replacement pushrods by application. In the case of modified engines, factors such as block and head deck height, rocker arm design, cam base circle diameter, lifter pushrod seat height, and valve stem length all affect the required pushrod length. The best approach is to purchase a special adjustable length pushrod from Comp, and then determine the required length on the engine for the best geometry. We set our engine up with an adjustable pushrod, and mailed it over to the guys at Comp Cams for sixteen custom ones made to the same length. Comp stocks a wide range of pushrod lengths off the shelf, or they will build them to specs to match your combination. To keep the theme of a lightweight valvetrain, we went with Comp Cams' 31/48-inch Lite Hi Tech .065-inch wall pushrods. Made from super strong 4130 steel hardened to over 60 Rockwell, these pups are good for 9,000-plus rpm-totally worry-free in our 440.
With the geardrive installed, we could button up the bottom end. The Milodon tray wouldn't
Milodon makes this trick adjustable oil pump pressure regulator, a bolt-in replacement for
Valve setup consisted of Manley 1.81-inch exhaust valves-modified with a radius margin-and
Our heads were expertly ported by Dave Vizard's righthand man-Head Porter Gilbert Mink-to
The cam can't do its job unless it is effectively hooked to the crankshaft. In a stock rebuild, cam drive considerations are fairly straightforward-just pick the chain drive of a quality that suits your performance level and wallet, bolt it in, and go. With our roller cam and our intended initial dyno mule application, we had a few extra considerations. A flat tappet cam has a taper built into the cam lobes, which provides a slight rearward force on the shaft, and keeps the cam in contact with the thrust face between the block and cam gear. With a roller cam's flat interface at the lifter's contact, this force is no longer there, meaning some method must be employed to keep the cam from sliding forward out of position. The usual approach is to use a thrust button or roller at the nose of the cam, and, if the stock timing cover is used, the face should be reinforced to eliminate flexing of the thin, stamped cover.
Since we could foresee testing cams in future dyno evaluations, we wanted a drive system that provides absolute dead-on valve timing accuracy, easy cam phasing adjustment (advance/retard), and easy access to the cam while valuable dyno time is ticking. The only drive system we know of for the Mopar big-block that provided all these requirements, and has an advanced thrust control system built in, is the Milodon Pro Gear Drive.
Gilbert also cut the new 30-degree intake seats for the huge Manley intake valves, and 45-
Basically the same system, which is the standard in top drag classes, the Milodon drive is a single idler system, with its fixed idler running in a sturdy aluminum cover. This setup is the real thing-a far cry from the cheaper, floating dual-idler geardrives. With a single fixed idler, the gear lash is precisely set, minimizing timing irregularities. It's a fact of life that even the best chaindrive systems will stretch over time, changing and varying the cam timing. With the Milodon drive's hardened gears, once the timing is set, it's set to stay.
With Milodon's geardrive, a separate O-ringed camshaft cover plate allows access to the cam without the usual drill of pulling the damper and disturbing the gasket seal at the oil pan when pulling the timing cover. By simply removing the access cover, the cam can be removed, or the cam phasing adjusted by means of the drive's Vernier two-piece cam drive gear. Behind the cam gear is a needle-roller thrust-bearing pack, and at the front, a thrust face is built in, holding the cam in position. The whole package is a bolt-in deal, requiring only that the front-block dowel pins be redrilled to set the clearance between the gears. The only caveat is that the added thickness of the aluminum cover means the water pump must be spaced out about .200-inch (spacers are part of the kit) for clearance. This means the stock water pump pulley will no longer line up. Sure, it'll give us that distinctive "come and get me copper" geardrive whine, but that's music to our ears.
The heads then were taken to M&R machine in Glendale, California-which handled all our bas
The heads were assembled with a $20 lever-action valvespring compressor from Harbor Freigh
Running dual springs means the spring seats must be machined for clearance (arrow A), and
One of the most critical measurements you will make is the valve-to-piston clearance. Clea
Lube It Or Lose It
Last month, we detailed our lubrication plan, and modified the stock internal block passages leading to the new Milodon high-volume pump. With the front cam drive and cover installed, we were ready to button up the bottom end. We weren't straying too far from factory issue in the lubrication system, shying away from exotica such as external pump feeds or swinging pickups. Putting a lid on the lubrication system came down to a windage tray and pan selection. We went with the Milodon tray. Similar in concept to the excellent factory offering, this tray offered more complete coverage of the spinning crank at the front of the crankcase, and two more rows of louvers/baffles to aid in drain-back.
With that part complete, it was just a matter of choosing a sump for the task at hand. Hard-learned lessons have taught us that any kind of potential for street use virtually excludes the traditional drag race asphalt plows. The Milodon wide sump street pan fit our need for increased capacity, with much less of a penalty in terms of ground clearance than a full deep sump, drag-type pan.
While thumbing through the Milodon catalog, we spotted a nifty adjustable oil pump pressure regulator, which we couldn't resist. It allows the dialing-in of the oil pump relief valve with a turn of an Allen screw.
The above method will indicate how much lift you can handle, but won't give you a clue of
If you followed our series on porting Mopar big-block heads, you've got a handle on the porting tricks we employed. For our initial dyno testing, we are running a set of 915s, ported exactly as described in "Going With the Flow, Part 2," (Feb. '99). We chose the 915s, which share the same basic intake ports as the 906, because they are the only late-model heads that offer the combustion advantages of closed chambers as described in "Going With the Flow, Part 1" (Jan. '99).
To recap, getting big improvements in high-lift flow from the 915/906 intake is no picnic. We found the later 346-452 heads to be much more responsive to porting and large valve modifications on the intake port. Unless the earlier head is precisely reworked-preferably with a flow bench at hand-the modified smog heads will outflow them hands down. Ultimately, we were able to best the late castings with the early port (albeit with much more development time on the flow bench) by close to 6 percent at max lift. For us, it required more than twice the porting time just to equal the flow of the ported late casting, and four times the porting time and constant progress checks on the bench to gain that 6 percent edge. Our ported 915s moved 34 percent more air at max lift than the stock port, with no welding, brazing, sleeving, or epoxy.
Pop the heads back off, and with a razor, slice sections of the compressed clay, then chec
The exhaust valves on our test heads are common oversize replacement Manley units in a 1.81-inch diameter, modified with a radius margin for better flow. On the intake side, things are a bit more unconventional. Looking at the heads, flow guru David Vizard's first question was, "What size valves are you running?" "2.14," we told him, "it's what everyone runs." The next question was, "Why? It looks like a 2.25-inch valve would drop in." After the ensuing session at the Serdi seat machine for a 30-degree seat in the 2.25-inch diameter, we were testing the head with a Hemi-sized 2.25-inch valve (a big-block Chevy unit). Top-end flow picked up a few cfm, but lift from right off the seat through the mid-lift ranges was fattened up over our already great numbers by up to 10-12 cfm.
We arranged for Manley to make us a custom set of cut-down big-block Chevy 2.25-inch valves, with the keeper groove at the stock Mopar height. A peculiarity in valve manufacturing is that the tip must be indivi-dually hardened to a much higher level than the rest of the valve to withstand the rocker's action. Our special cut-down and regrooved valves from Manley would, of course, lose the hard tip, which is not a problem if a lash cap is installed. We ordered the semicustom valves with a tip length .080-inch shorter than a stock Mopar valve, so we would have a stock length with a .080-inch-thick lash cap in place. With the improved low to midrange flow, we set up our test 915s with the custom 2.25-inch Manleys.
We wanted to know the exact compression ratio of our combination, as well as equalize the
Ironically, after slaving over the math to determine if the .080-inch-shorter tip length would enable the lash caps to clear the Comp Cams locks with the recessed lash cap groove (it's quite close), we found that the added .080-inch lash cap thickness actually would have worked fine with a stock-length tip when using the Comp rockers (the geometry is actually slightly better). Next time, we'll specify the standard tip length and run lash caps on the intake and exhaust.
The Manley 2.25-inch valves feature an 111/432-inch stem diameter, which reduces weight and assists us in our goals toward a lightweight valvetrain. The exhaust valves are standard 31/48-inch stem units, which actually is a benefit for critical heat dissipation in an exhaust valve. The guides were replaced with corresponding 111/432-inch silicon bronze inserts on the intake, and 31/48-inch inserts on the exhaust. With extremely high-lift cams, a top-quality guide insert is mandatory, if any reasonable guide life is to be expected. For longevity, forget about cast-iron guides. Our silicon bronze guides were sourced from APT. Rounding out the head mods, the spring seats were machined to take the dual valve springs, and the guideboss cut down for positive stop guideseals (a must for oil control with the high-vacuum Total Seal rings installed previously).
The deck clearance is measured as part of the compression ratio calculation. Figure the ga
We were straying fairly far from the way Chrysler originally assembled the 440, so we had to perform a wide range of critical measurements to ensure that it would all work. Piston-to-head clearance, valve-to-piston clearance, pushrod length, and valvetrain geometry are some critical checks to be made. A mistake in these areas can mean disaster.
Another measurement that should not be overlooked is the actual compression ratio. A wide range of possible chamber volumes, block-deck heights, gasket thickness, possible piston modifications, and a host of other variables will affect the compression ratio. Piston manufacturers will toss a number out there, based on their own assumptions of values for those variables. This generally can serve as a ballpark guide, but will not necessarily give the ratio for your own combination. Throw in various widely published chamber-size specs, usually not production based, but theoretical drag racing NHRA minimum volumes, and it's easy to be totally off when estimating the ratio.
The only real way to figure the ratio is to measure it. The accompanying photo captions detail the setups we used for the various measurements, but how do you get the ratio? You've gotta do the math. If the word "pi" makes you wince, find a buddy who paid attention in high school math class. The basic formula for compression ratio is:
Total volume above the piston at BDC
Total volume above the piston at TDC
With the piston's flat area down exactly .500-inch from the block's deck, we can calculate
Total volume above the piston at TDC includes the chamber volume, gasket volume, piston deck clearance volume (which can be positive or negative depending on the compression height), minus any piston dome, or plus any dish. Some of these volumes (regular shapes) can be calculated from measurement, while others (irregular shapes) are best measured by displacement (CCing). We cover the procedures we used in the accompanying photo captions.
To get the total volume at BDC, add the swept volume (volume created by the area of your bore times the stroke) to the volume figured at TDC. Divide the number at BDC by your TDC figure, and you've got your ratio. Ours worked out to 12.66:1.
Rather than making a mess when pulling up the Plexiglas, and spilling checking fluid every
Cam Do It
Wouldn't it be great if we had an expert engine builder on hand each time we built an engine, carefully considering our individual parts combination, and coming up with an appropriate cam to get the job done? Unfortunately for most of us do-it-yourselfers, hiring a top pro to select our cam is virtually a pipe dream-until now.
Thanks to Cam Masters-which has developed a program based on sophisticated computer modeling-for less than $30, custom-tailored cam selection now is within easy reach of the average enthusiast.
The heads were bolted onto the block with Milodon's dead-soft, solid copper head gaskets.
Taking into account individual variables for your specific engine, such as compression ratio, bore, stroke, valve sizes, rod length, cylinder head flow curve (if available), rocker ratio, and planned fuel octane, you select the application of how radical you want to go, and the Cam Master program will deliver custom specs for your engine. The selection of performance level is overlap-driven, since after all, overlap is the biggest factor in how radical the combination will idle. We chose a hot street/strip grind (70-90 degrees of overlap in the Cam Masters model), and the Cam Master program worked out the optimal duration for the intake and exhaust lobes, lift, overlap, and the all-important lobe separation and installed centerline angles.
Cam Masters does not grind cams, but based on the specs the company calculates, it will find the closest match in an off-the-shelf grind from its extensive database of the leading manufacturer's cams, or point you to the correct lobes if a custom grind is desired. The program also will provide the part numbers for a matched set of components to complete the valvetrain. Cam Masters is a Warehouse Distributor for many of the major cam manufactures, so you can have the cam ordered with a single phone call, or take the numbers and go shopping yourself.