Bill Heath plans to return to Bonneville in 2010 with his 6.5L GM Diesel Racer. Some things just keep getting better with age.
The Heath Diesel land speed race team has raised its sites for the 2010 Bonneville Salt Flats events, hoping to top 160 MPH this season. Team 6265 has its goals set on wringing every last bit of speed from the current, nearly-stock engine configuration: this year’s effort represents a further refinement on the package but we still consider it Phase One. When we feel that we have gotten all we can from the truck in its current form, then we will move to Phase Two, which will include some changes in the fuel injection system. For now though, efforts are focused on making the best showing they can with the truck as it is.
|Ol' Dad (Bill Heath) posing with starting-line official at Bonneville in 2009.|
From the beginning, this rather ambitious project has been focused on one very important goal: to champion the truck and its diesel engine for all of its enthusiastic fans worldwide. The team feels the pressure to make a good showing, so a decent performance and meeting our goals is pretty darned important. During the early stages of the project the team calculated a projected speed based on frontal area, coefficient of drag and engine output eventually setting its’ sights on 130 MPH. It was reasoned that getting to 130 MPH in a full sized pickup would be a respectable accomplishment in any camp. The fact is, you just don’t see very many full-size, street legal trucks that will do 130, even down at sea level let alone at Bonneville’s 4,300-foot elevation.
One can only imagine our jubilation when, on its first official run across the salt, the team was rewarded with a very nice 141 MPH pass! And this was the average speed over the final mile. The actual top speed at the end of the 3-mile pass was 145 according to GPS! By the end of that event 6265 racer had managed to achieve a best average of 153 MPH with 157.5 as it max GPS-recorded speed at the three-mile marker. Yes, we were happy!
The 6265 racer is registered in DT class (diesel truck) which is a class that allows a wide range of performance upgrades with limits on engine displacement and fuel. And if water injection is used, only pure water is allowed. Chemical enhancements, such as methanol, propane and nitrous oxide are strictly prohibited. Team 6265 would appreciate ruling in this class that segregates trucks according to fuel system type. The more modern common rail equipped engines should compete with one another and distributor type injection pump trucks would compete with others in their own, separate class. At this point in time, however, this distinction is not made, so the 6265 truck must compete against all comers, even those with common rail, in spite of the vast differences in potential.
The limit on power imposed by the 6.5’s comparatively fuel-stingy Stanadyne DS-4 injection pump is a very real one and the team knew its only hope was to squeeze every last bit of power it could from what fuel is delivered. Toward that end, it would have to focus on doing everything possible to maximize diesel combustion efficiency.
The team has often referred to the racers engine as being ‘near-stock’. Near-stock in this case means using as many of the factory engine components as possible; however, in the interest of longevity, a few aftermarket upgrades are used. One is the crankshaft. Heath uses the excellent, cast steel replacement 6.5 crankshaft built by Scat Enterprises. This crank features the stock stroke length, so it has no affect on power output; however, in consideration of the engine’s relatively high power output and 5,000-RPM engine speed limit, the Scat crank is considered to be low cost insurance. The 6265 racer runs a higher-than-stock static compression ratio at 22.5:1. In addition, we force feed it with 31 PSI boost. This equates to fairly significant peak cylinder pressures and a great deal of both momentary / dynamic loading on the rotating assembly and its main-bearing support system. We are convinced of the superiority of the SCAT 6.5 crankshaft and likely would not attempt this feat with a factory unit. Even though the factory crankshafts just do not wear out, they can sometimes fail due to internal flaws. We find solid value in the improved material and manufacturing method used by SCAT in building this replacement crank.
Other upgrades include both the Heath Main Stud kit and ARP’s cylinder head stud kit. Heath prefers both of these upgrades in all engines.
Looking back to the Fall of 2008 when we first ran the 6265 racer, it was equipped with the original, numbers-matching 6.5 engine. Upon our return from that first event, engineers at Mahle piston wanted a chance to examine our racer’s pistons; they were anxious to see how well their little babies held up under the stresses imposed. According to their findings, these factory replacements weathered the storm quite well, having suffered no unusual wear or decline in structural integrity. A powerful microscope showed that sodium crystals had been imbedded in the tops of the pistons, which provided a degree of entertainment throughout the facility. Our pistons ended up as conversation pieces on a number of desks through the organization. They had paid their dues out on the flats and deserved a comfortable retirement.
Since that first outing with the 6.5 engine, we have been running the slightly smaller 6.2 and will stick with this combination. Based on our experiences with each both engines, we believe the 6.2 piston is superior to the one used in the 6.5. The 6.2 part is heavier, features more robust wrist pin bosses, a heavier crown and lower placement of the ring package. While we feel these differences are important in a heavy duty application such as this one, they would provide little if any benefit over a regular 6.5 version in normal applications.
Since we have the luxury of time during this build up, we are rocking this block. We fill our engine block coolant passages with one of the commercially available block fillers or just good, old-fashioned grout. The 6.2, as delivered from Diesel Depot had not had its coolant passages filled: there simply had not been enough time in the rush to prepare for racing last season.
We pour the block filler in after the interior passages are cleaned – clean as a whistle. We use a combination of hot tanking, sand blasting and or acid etching to achieve a rust scale-free and thoroughly clean bonding surface for the filler. Before we pour in the filler, the main caps are installed with the Heath Main Stud kit and torqued to specification. Then, one deck surface is leveled in preparation for adding the filler. Using a funnel through one of the deck holes, we pour the block to a level within about three-quarters of an inch of the interior deck surface structure. This allows necessary coolant circulation and distribution-communication between the block and the cylinder heads. As soon as the one side is poured, we work quickly to install a cylinder head with a used gasket. The head is torqued down with the fasteners that will be used in final assembly. In our case, of course, this means ARP studs. We torque the studs according to the factory recommended sequence, beginning at 20 foot-pounds. We increase the torque of these in 10-pound increments until we achieve 120 foot-pounds. As soon as the mud in this side of the engine has firmed enough to allow it, we rotate the block and level the opposite side the same way. When the block is poured and all trussed-up, it will sit for 60 to 70 days; the time we feel is necessary to gain a thorough cure.
|View of Scat crank laid into engine during assembly.|
|Scat crankshaft laid into block and ready for piston / rod assemblies.|
|Unfortunate view of grouchy old guy torquing main studs.|
When we get our block back from Rich, we thoroughly scrub it with soap and water to make sure it is clean as a whistle. Prior to assembly, all critical dimensions are measured to do our best to avoid errors.
First, we install new cam bearings with oil holes oriented per GM recommendation.
We use the Heath Main Stud kit in the racer. All 20 of these are screwed in to bottom then backed out 1/8-turn, before we lay the Scat crank into standard GM or Fed-Mogul bearings. The main caps are installed and torqued into place per kit-recommended procedure, which finalizes them at 105 foot-pounds on the inner rows and 95 foot-pounds on the outters.
Mahle recommends that this particular 6.2 piston, part number 027481, be fitted to its individual cylinder with a skirt clearance of 0.0025 inches. Because we will be operating at a higher-than-design combustion temperature and engine speed, we decided on setting the clearance on these at 0.0033 inches. We want the piston to be fitted as close as safely possible to keep the piston stable in the bore for best ring seal and to affect the best possible transfer of heat from the piston to the cylinder wall.
|6.2 piston and pin.|
|Piston, pin and rod all ready to go into engine.|
|View of connecting rod pin bushing prior to application of PKSX. Fine scratches on finish bore were caused by paper towel!|
|View of underside of 6.2 piston showing beefy construction.|
We use Techline’s Powerkote DFL-1. This particular, sacrificial type coating is designed to rub-off the pistons and work into the irregularities of the cylinder walls. The net effect is an excellent mating of the wearing parts. These sliding components settle-in together for a very nice, reduced-friction fit and one which creates the best possible ring seal. The thickness of the coating ranges from around 0.0015 to 0.002 inches when baked and cured. After the engine has been run-in and this sacrificial coating rubbed off, its thickness is reduced to zero over the original major diameter of the piston itself. Consequently, when we finish-hone the cylinder bores for each piston, we fit them as though there is no coating.
|The cylinder bore on right has had PKSX rubbed into its surface.|
|Cylinder head stud with proper amount of Ultra-Grey sealer applied.|
|Applying PKSX to piston ring frictional surfaces.|
|PKSX being rubbed into bearing shell frictional surface.|
|Rod bear shell before and after being treated with PKSX.|
|Piston / rod assembly with PKSX applied to piston rings.|
|Piston / rod assembly showing the rod bearing shell after it has been treated with PKSX.|
The reconditioning of connecting rods may well be the most critically important step in building a quality, higher performance 6.2/6.5. After checking for any cracks, the rod is outfitted with new bolts and properly resized on both ends. Perhaps the most important part of this process has to do with the proper finishing and accurate sizing of the wrist pin bushing bore. After fitting the rod with a new one, the pin bushing must be finish-sized to exactly the correct internal dimension and its bore centerline must be perfectly parallel to the bore centerline of the big end. Finally, it must be correctly located in terms of the center-to-center distance to the big end.
GM specifies a pin-to-bushing clearance ranging between 0.0003 to 0.0012 inches. This specification means no tighter than 0.0003 inches with service wear limit of 0.0012 inches. We insist on a fairly tight fit-up and shoot for a range of 0.0003 inches to 0.0005 inches. This tighter clearance specification provides for the greatest contact surface area between pin and bush, resulting in the best possible load bearing surface. With the correct bore-surface finish and clearance at 0.0004 inches, the pin / bush will support a tremendously large load and, because the surface is large, the supporting film of oil will remain intact and will not be so easily squeezed out. Think of this way: if there was zero clearance between the two parts, pin and bushing, the load of the pin against the bushing would, at least in theory, be a full, 180˚ of contact (1/2 of the full circle) a relatively large load bearing surface. However, when the pin is more loosely fitted into the bushing bore, the contact surface will be substantially reduced.
Mahle supplies the pistons with a 0.0004 inches clearance to the pin and we leave that alone, preferring the Mahle factory finish and size. In addition, the surface finish of the bushing is critical. For best performance and durability, the pin bushing must be bored to dimension and not honed. The pin bushing is to be bored to its final inside diameter using a proper boring machine, such as the Tobin-Arp. We are convinced that these pin bushings cannot be successfully honed to size. While a honed finish has been accepted as the way to go in general automotive practice, it will not cut the mustard in this or any similar heavy load application. Here is why: the honing stones will load with the relatively soft material to cause a course and too deeply scratched load-bearing surface and one that will imbed hone-stone material. These scratches or gouges and ridges that accompany each of them cause point-contact-welding and lubrication breakdown failure between the pin and bushing. The wrist-pin will ride atop these ragged ridges and the oil film will squeeze out from between these ridge-points and the pin, resulting in melting and rounding off of the ridge tops between the two unprotected parts. When the ragged ridge-tops, formed by the hone process have been melted and rounded over, the bushings’ net effective inside diameter will be much larger, which greatly increases the pin to bushing clearance and which, in turn, substantially reduces the pin to bushing contact area. The engineers refer to this as “high point contact welding and lubrication breakdown”.
The specialized boring process will create a load-bearing surface in the bushing that, in cross-section, is wavy and not ragged. This smooth, wavy, contoured surface provides a substantially greater load-bearing surface interspersed with oil retaining channels. The combination, having a machined surface versus one that is honed and having the correct working clearance between it and the pin, provides an excellent load-bearing package; one that will stand up to the forces we apply in a run down the Salt.
We have set the piston deck clearance (height above the gasket surface) at 0.0060 inches. This setting is achieved for each cylinder. We use a standard thickness (0.0440 inches compressed) Fel-Pro gasket in conjunction with the 0.0060 inches deck clearance to achieve a piston to cylinder head squish clearance of about 0.0380 inches less any piston rocking.
|Measuring piston-to-deck ‘clearance’. We set up to have the piston up out of the hole 0.006 inches.|
|Squirting oil in cylinders during asssembly.|
Our cylinder heads are the regular 6.5 versions casting (number 10137567). They are modified by the fitting in of 1982 J series 6.2 intake and exhaust valves. These larger valves measure 1.96 inches and 1.63 inches and require that the valve seats be machined in order to accept them. The seats, as well as the approach and departure angle cuts used, exactly duplicate the GM design for these original 6.2 heads. The valve bowls and runner passages are untouched, as-cast, factory stock. We leave these as-cast for two reasons. First, in consideration of our goal of maintaining the engine as closely as possible to its factory configuration, porting the heads was not an acceptable alternative. Second, the factory intake runner is a pretty decent design in terms of flow and, more importantly, it has an excellent swirl generating quality. In our diesel, the ability of the intake port to generate a strong swirling motion of the intake airflow is far more important than its ability to produce some big flow number on a test bench. GM engineered this cylinder head to create an exceptionally strong swirl quality. As the piston heads down the cylinder bore, the incoming air sweeps around the circumference of the cylinder. By virtue of a strong momentum, this circular motion of the air will continue even as the valve closes and the piston comes back up toward top dead center. This intake-port-generated swirl contributes greatly to the all-important turbulence of combustion-space air charge. Turbulence during the combustion process helps to assure that oxygen reaches the greatest number of fuel particles. We reason that since we do not have a huge volume of fuel to play with, we must take full advantage of what we do have. It is all about the efficiency of combustion.
While in previous engines we have used only the factory camshaft, this year, we are building our engine with one especially designed to enhance power output in the upper RPM range. This new cam is designed to improve power output in the 4000 to 4500 RPM range, right where our engine spends the majority of its time. Certainly, we have been happy with the factory grind, but think we can do a bit better.
We use factory stock timing sprockets and chain rather than any aftermarket arrangement. These pieces are bulletproof and work great. Our efforts to date have been with the factory parts and in fact we have gone fastest with old, high mileage parts that are still within factory specifications for chain free play. Just for your information, the specified looseness of chain is 0.5 inches for new parts with 0.8 inches as the service limit. Our 2008 engine ran with parts that had been in service for 288,000 miles and which measured 0.6 inches free play.
Lower Volume Oil Pump
The 2010 engine will be outfitted with a standard, lower volume original-equipment Melling brand oil pump along with factory pump pickup and oil pan. The later model, higher volume 6.5 oil pump does not work well in this application because of the extraordinarily high RPM we spin the engine up to. The big pump will pull the pan dry and over supply the engine’s upper regions in our application, however, in normal pickup truck RPM ranges this big pump works fine. We are also reworking the rocker arms to reduce oil flow into the rocker arm chambers. The factory upper engine oiling is a little too free-flowing for our use of the engine and again, this is because of the high RPM.
Fel-Pro’s Cylinder Head Gaskets and ARP Cylinder Head Studs
We use Fel-Pro’s regular cylinder head gaskets in conjunction with ARP cylinder head studs. Over the years we have determined a specific procedure for fastening the heads onto the block. Of course we do not risk using anything less than perfectly true and flat sealing surfaces on the block and the heads, nothing fancy, just straight and square. Since they have worked out well, we will stick with the Fel-Pro gaskets until we find something better. Cleanliness is critical, so we wipe-clean both sealing surfaces with acetone prior to doing the assembly. Before installing Fel-Pro’s head gaskets onto the locating dowels and even though Fel-Pro says it it is not necessary, we coat these with gasket sealer. While we have used this gasket both with and without sealer, we have seen some minor water seepage with bare gaskets, so err on the conservative side and apply the sealer. For many years, we have successfully employed the Permatex Copper Coat but will use the Hylomar Universal Blue Racing Formula gasket and jointing compound on this year’s engine. We believe this to be a superior sealer in this higher stress application, although I have no hesitation in using Copper Coat on our regular engines. 2054, 2055
After the heads are set onto the block, each stud is installed after we apply Permatex Ultra Grey to the coarse-thread end of the stud. These need to be sealed as they screw into wet places, however the sealant must be applied sparingly. We use a finger tip to roll the sealer into the threads, loading them level to their major diameter: no more, no less. These are then run into the block and fully seated before they are backed off about 1/8 of a turn. When all are installed, we use a little brush to coat the threads with ARP’s special lube.
Next, on go the washers which are lubed on both surfaces. We thread-on the nuts, which are run down by hand. Then we run the screw back out to the top of the stud before we run them back down to the washer a final time. This last step is intended to distribute the lube onto the threads of both the stud and the nut in order to assure the lowest friction when tightening them up. We then, per factory torque sequence, pull the nuts to 25 foot-pounds. The torque is increased in 10 pound steps till it reaches 115 foot-pounds. We go over all the nuts a couple of times at each step to assure good even loading of the gasket. After the engine sits overnight, we go over them all again at 115 foot-pounds. This procedure takes some time, but we never have a problem even at the elevated cylinder pressure our land speed engine experiences.
We run the racer without an oil cooler, making some changes in the bypass valves to accommodate the lack of a cooler. Why no cooler you may ask? That’s easy: we do not need one. In fact, we would like to have a far greater oil temperature at the start of the run but we are limited to only being able to idle the engine while in the staging lanes. I would much prefer being able to do our full throttle pass right at the end of a 30-mile highway drive. Oil temperature at the end of the pass is still not very high, at least not high enough to warrant oil cooling. We use a fully synthetic 5-30 oil, one not specifically designed for diesel. Our oil does not need to be able to deal with soot accumulations, as we don’t drive it more than about 1,000 miles between engine dismantling and inspection. We use the lighter weight to facilitate flow and protection at less than operating temps as well as to reduce power loss associated with oil-friction.
Our engine uses our regular; off the shelf highoutput (HO) Bosch fuel injectors. These injectors are combined with factory fuel injection high pressure lines and an out of the box new Stanadyne 5521 injection pump. The only modification to the injection pump is the addition of one of Tim Outland’s (Turbine Doc) Feed The Beast fuel inlet fittings. Tim insisted that we use this thing and I guess I can’t say it doesn’t work! We run an Air Dog fuel lift pump adjusted to seven PSI fuel pressure. The higher engine speed we run substantially changes the amount of fuel necessary to support it, stretching the limits of our regular heavy duty pickup truck lift pump.
The racer is outfitted with one of our regular production two-wheel-drive PMD Isolator systems as well as the latest version of GM’s electronic filter harness. It also uses a modified version of our Max E Tork GL4 program in its computer box. This particular Max E Tork PROM is custom engineered for our unique application. It is set up to allow the engine to operate to a maximum of 5,000 RPM. This specification differs from our regular offering that limits engine speed to 3,700 RPM. Its start-of-injection timing schedule is altered to suit the particular engine speeds and loads that this engine experiences. The maximum fuel rate is identical to our regular production program, which exercises the injection pump to its physical limits. The primary limiting factor in our combination is the DS-4 Stanadyne injection pump. However, in consideration of this limit, we are very satisfied with the power we have managed to get. This really is making the best of a bad situation!
The single most important performance improvements featured on our engine are the custom-made tube style headers and custom engineered turbochargers. The headers are built of heavy wall, drawn over mandrel (DOM), 1.625 od 1.45 id tubing. The 4 tubes are routed into a simple, 4 tube collector which mounts the turbocharger. The turbochargers were custom engineered for us by B-D Diesel Power’s John Todd. These turbos are designed to operated at high efficiency with an output of 31 psi boost at maximum engine speed.
We feed a greater than normal amount of pure water to the engine with a version of the Heath Water-Mist Injection system set up for the application. During a run across the salt, our engine consumes 0.65 gallons of diesel and 1.1 gallons of water. Intake air temperature stays very close to 130˚F and exhaust gas temperature hovers in the 1350 to 1400˚F range.
We are working on a new, cold air intake system for the racer. In previous outings, we were using a very simple set up comprised of two cone shaped air filters mounted directly to the turbochargers. These pulled intake air from within the engine compartment. The new setup will provide air at ambient temperature and also provide some benefit due to higher ram-air pressure.
Power is applied through a standard 4L80E and 9-inch Ford differential. The rear axle housing is from a mid 1970s Lincoln Mark IV. It happens to be configured with the correct flange-to-flange width and wheel lug pattern used on these half-ton two wheel drive GM pickups. We changed the pinion yoke to one found on a mid 1960s Ford pickup and had a high performance driveshaft made to replace the original. We needed to make sure the driveshaft operates safely at the 6,000 RPM it experiences, so we had one custom made for the truck.
Future plans call for a new Tremec TKO 600, five-speed gear box to replace the automatic. In addition to a reduced parasitic loss, this new box features a far more attractive fourth to fifth split. This will allow the engine to enjoy a greater and more favorable shift recovery RPM when it goes to fifth gear, making it better able to accelerate on up to maximum speed. We figure that the TKO600 will help us gain an additional three MPH.
In the interest of maintaining a nearly stock appearance and function, our racer retains a full factory interior with the exception of the seats. These were removed to allow installation of the required, SCTA approved roll cage and related safety equipment. The truck features power windows, power-tilt steering, cruise control, stereo, cup holders, carpeting, sound deadening, etc etc. In fact, I am able to listen to the track announcer’s FM station broadcasted information during the high speed run through the truck’s stereo system: it is that smooth and quiet at speed. This is no ordinary racer!
We plan to have our pit area set up and the truck inspected in time for opening ceremonies on Saturday morning August 14, 2010. We are joined there each year by a growing number of loyal supporters who, as honorary salt brethren, jump right in to lend a hand and to make these outings successful. The camaraderie we enjoy at these events is special, indeed. From the time we all meet for breakfast each morning until our busy, fun-filled race day comes to an end, we have a swell time. You are hereby invited to join in the festivities!