My last foray into big-block Chevy building was about a year ago when my students at UNCC needed a real budget motor for their drag race Camaro (see "Budget Big-Block," Feb.-March, 2005). Starting with a donated 454, we managed to build a flat-tappet, stock-headed 475-incher that made close to 500 hp and proved enough to propel the car to a best of 6.62/101.8 mph in the eighth. [That's deep into the 10s for you quarter-milers. -ed.] It was now time to move on to something a little more removed from the near-stock spec of the 475. After the success of their first big-block Chevy build, three of my students, Bruce Greer, Nathan Bornitz, and Dusty Kennett, were hot to build something a little more exotic without fatally rupturing a typical working guy's budget. It should be able to pull double duty, both on the dragstrip and, with the help of a small splash of race fuel cut with pump gas, be able to run fine all night on the street. What they wanted was a Street Beast.
T&L Engines of Busch engine fame had volunteered to do our machining and help out where possible on this project. This proved to be very much in our favor as T&L also produces a line of custom big-block Chevy crate motors. These are all based on about half a dozen dyno-proven combinations ranging from 468 to 640 inches. The plan was to have the students spec out the Street Beast in its entirety, then have Lloyd McCleary, the boss at T&L, critique the proposed spec. Basically, the Street Beast had to be affordable, reliable, street drivable and, of course, fast. If I taught my students right, they should be able to come up with the best compromises to meet all the aforementioned criteria. This chart is what they jointly came up with:
With torque and horsepower targets of 620 lb-ft and 650 hp, this spec looked good to me, but I told the guys to check it out with Lloyd as he builds motors like this every week. Here was his take on it: "The Dominator carb, with its intermediate circuit that fills in between slow cruise and flat-out makes the Dominator an ideal big-block Chevy carb and the cubes can definitely use this carb's big cfm to their advantage. The Dominator gives away virtually zero to the smaller 4150-series Holley down low, but it certainly makes more at the mid and top end. Good choice, as is the manifold. The Dart Iron Eagles have the same chamber and port configuration as Dart's aluminum version and they make good power right out of the box. Basic porting will probably help to the tune of 20 or so hp. Valvetrain: great combination choice here with the beehive springs as the pivotal pieces. This should be a 50,000-mile valvetrain. The cam spec itself shows some serious research has been done here as most big-block cams are, to a certain extent, inappropriately spec'd for the job. For many crate motor builds, the day is only saved by the engine's big inches. The rest of the parts look to be compatible with the goals in mind. This should be a good engine as it is very similar to ones we have built. Bearing in mind the goals, I would say build it--as is."
With Lloyd's approval in hand, our team was ready to start and the first job was finding a suitable block that would go 125 thousandths oversize to give us the 482 inches.
Selecting The Block
First, it should be said that had the budget stretched a little more, we would be looking at a Dart block for this project. Maybe next time, but for now it had to be an OE block. Since T&L builds big-blocks and has cores on hand, the first place we looked for a block was there. Most big-blocks are good to hop up, but a little more selectivity is needed if it is to be bored .125-inch oversize. This is where the sonic tester comes into its own. The blocks here had been visually inspected to see they were OK for use and then cleaned. A block was picked at random and the job of testing it for cylinder wall thickness at the top (1 inch down the bore), middle, and bottom was started. Here we had a measure of luck as the first block tested met our requirements. From here, the block went directly on to T&L's boring machine. Various fixturing was used to ensure the bores were correctly positioned over the main bearing centerline.
When all was ready, the bores were hogged out to within about five thousandths of finished size and the whole operation moved on to the hone. With a deck plate in place, the block was finish-honed to size with the finish required for the Total Seal rings to be used.
While the block prep was being done, UNCC student Bruce Greer was busy on the mill prepping the dome on the Ross pistons. Some 250 thousandths was machined off to encourage flame front propagation over the piston crown. This reduced the crown from 36cc to 30cc. In conjunction with about 70 thousandths off the heads, this resulted in a quasi-streetable 12:1 compression ratio (using a 1-to-10 mixture of 112 Octane race fuel cut with 93 octane pump gas). Along with the piston prep, the rods were lightened, reconned, and balanced. This was handled by Dusty Kennett. For the record, stock big-block rods are, though a little on the short side, plenty tough if somewhat heavy. Fortunately, there is scope for some serious lightening. With Dusty's beam polishing, removing most of the balance pad on the small end and cap milling, some 90 grams were removed. After all the grunt work was done, the caps and rods were refaced at the parting line--equipped with ARP bolts and re-honed to size. The pin end was also made floating by honing it out. With the lubes used, a steel-on-steel rod end would still be good for 100K. When all machining and such was done, Dusty balanced the rods end-to-end to less than a gram.
For a crank, we used a barley worn stock cast iron piece that seemingly had rarely been taxed in its entire life. A check on the journals revealed that we would have to grind 10 thousandths off the mains to get clearances where we wanted them. With that done, the crank, rods and pistons were balanced with a Professional Products external balance damper in place.
Within the framework of our budget, our Dominator-carbed, 482-inch, 675hp big-block was a
The first move was to start sonic testing and recording all the numbers. As luck would hav
Nathen Bornitz, Dusty Kennett, and Bruce Greer (L to R) are all second-year UNCC Motorspor
Here our block is being precisely set up on the boring machine, ready to be punched out to
The lighter-than-usual Ross forged pistons come with a little extra on the crown so the en
Here the amount milled off the top of the Ross pistons can be seen. After milling, a .125-
After Dusty Kennett's cap milling, beam polishing, and pin-end lightening work, the stock
Bottom End Assembly
The bottom end assembly was pretty much Bruce Greer's department. The first move was to check all the bearing clearances to see that they fell within tolerances. Normally, this would have been done with an extremely high-dollar internal micrometer (there is no such thing as a cheap one) but, in an effort to keep this in the realm of reality so the average hot rodder can follow the same path, plasti-gage was used. The bearings were the Calico-coated ones. Sure, they are more expensive, but over the last few years they have more than proved themselves in extreme situations. The target clearances for our 482 big-block were 2 thousandths for the big ends and 2.5 for the mains. Judging plasti-gage closer than a couple of tenths of a thousandth does take a sharp eye, but with an eye glass and patience, it can be done. What was seen was a very acceptable 2.4 to 2.8 for the mains and between 1.9 and 2.3 for the big ends. Whether that was precisely so would still take a $600 mic, but the plasti-gage did tell us that our clearances were well within a working range.
At this point, we were ready to assemble the bottom end, but an oversight on my part meant that the Total Seal rings were still a couple of days away from arriving. Still, that did not preclude us from installing the cam. The cam's valve opening and closing points were established based on a computer modeling of our engine and then using Cam Master to predict the required events. Just for the record, this program is extremely accurate and for all practical purposes eliminates having to dyno test to get the best cam for the job. [You can also buy a copy of CamQuest6 from COMP Cams for $10. It runs on any Windows PC and allows you to spec several cams--showing you simulated dyno pulls--just by plugging in your other engine specs.--ed.] Using our Cam Master generated a COMP Cams Xtreme Street roller cam with an advertised 292 degrees on the intake and 298 on the exhaust. This was ground on a 107 LCA at four degrees advanced. Although we may be giving away a few hp to more aggressive profiles, these Xtreme street roller profiles have characteristics conducive toward long life. With the valvesprings selected (these were COMP's latest beehives intended primarily for big-block applications such as ours), we can now accommodate about 685 thousandths lift max. With 1.7 ratio rockers, the cam will deliver, after being lashed, just shy of 650 thousandths.
A point of interest is that the more accurately a cam is spec'd, the more important it is to time it in correctly. To facilitate this, a COMP Cams adjustable timing set (PN 8110) was used. This is infinitely adjustable over a range from +6 to -6 degrees. To establish where TDC was, the number one piston/rod assembly, less rings, was temporarily installed. Next, the cam and roller lifters, (PN 819-16) were installed and COMP's cam timing tools were ready to do the job. It took just one degree of adjustment to get the cam's intake centerline to the required 103 degrees. The last job to do was to install the nylon end thrust button, and the lower part of the 482's valvetrain was done. The next job would be selecting the pushrod lengths and that would come later in the build.
Piston and Rod Assembly
After establishing which way they go on the pistons, the pistons were mated to the now full-floating-pin rods. A generous coating of high-pressure build lube is advisable to cover the time it takes for the engine oil to work its way into the pin/rod clearance space. Bruce Greer then gapped the Total Seal rings exactly as per the instructions contained in the box, and assembled them onto the pistons. The installation of the piston/rod assembly into the block was the next step. Here it is always advisable, especially when using Total Seal rings, to use a tapered installer. Usually, these are a fixed size and can only be used on one bore size, but Total Seal has adjustable ones that will cover over 1/8-inch adjustment.
After all the short-block components were in, the assembly was tested for turning torque. Typically, a big-block falls into the 30-35 lb-ft range. This one turned over at 16 lb-ft. [You may remember our winning big-block Chevy from the Engine Masters Challenge turned at 12 lb-ft, proof that low friction does matter. --ed.]That is a testament to the fine bore preparation done by T&L and to the care taken by the students to make sure everything was right on the money. The last item of importance on the bottom end was the crank damper. Here, a cost-effective unit from Professional Products was used. It got the job done without costing an arm and a leg.
Next month, we'll show you how to make big flow numbers with some cost-effective Dart Iron Eagle heads; we'll assemble everything, and put the Street Beast on the dyno.
The selection of lightweight pistons, plus the rod lightening, meant having to take quite
The final balance on the rotating assembly was to T&L's strict Busch Car engine accuracy.
For our bearing requirements, we used the Busch car tested and proven bearings from Calico
You may not be able to afford a $600 internal micrometer to test bearing clearances, but y
This double-roller timing set from COMP Cams is infinitely adjustable over a +/- 6 degree
Want to avoid nicking those freshly installed cam bearings as you load the cam into the bl
The solid rollers we used were the latest heavy-duty spec big-block items from COMP, PN 81
Our 286 x 286 Xtreme solid street roller was timed in to a 103-degree intake centerline. T
Roller cams need end float control. Here we used a nylon thrust button to do the job.
A considerable reduction was made in reciprocating mass. Firstly, the rods were reworked,
When installing pistons with Total Seal rings, the chances of inadvertent damage are incre
For damping out any crank-destroying torsional vibrations, a highly affordable Professiona
Here is our finished block and rotating assembly. Turning torque was a scant 16 lb-ft.
|Carb||1050 Dominator||Big-blocks like Dominators||$676 |
|Intake||Holly Dominator||Has already tested good||$190 |
|Heads||Home-ported Dart Iron Eagles||2.3/1.88 valves, small port||$1,410 |
|Cam||COMP solid street roller||286 x 286 on 107 LCA plus lifters ||$620 |
|Valvetrain||Beehive springs + matching hardware||High-tech perf., low-tech cost. Includes pushrods & rockers||$700|
|Block||Stock, 4-bolt||Sonic tester selected||$250 |
|Pistons ||Ross + 125||12:1 with heads milled||$660 |
|Rings||Total Seal||Our dyno tests show best||$<250 |
|Rods||OE items||ARP bolted, lightened and balanced||$280 |
|Crank||Stock cast - ground 10 under (labor)||For street/strip good for 700 hp||$150 |
|Oil Pump||Moroso competition spec||55 psi||$80 |
|Pan||Moroso Street/Strip||Does a great job for the money||$230 |
|Ignition||Performance Distributors HEI||Strong sparks to 7,000+ rpm, priced including plug cables||$360 |
|Fasteners||ARP||Best insurance||$80 |
|Gaskets||Fel Pro||Top quality||$120 |
|Damper||Professional Products||$70 |
|Block Machining||Bore & hone labor||$250 |
|Misc Parts||$180 |