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Over the service life of an engine, the main journals become eccentric. The process of line boring re-establishes the concentricity of the journal while keeping it in line with the other main journals. Here, Jack Merkel is line boring a V6 block with a set of Pro Gram Engineering caps torqued in place. These billet caps have about .040-inch extra material in the journal area to compensate for differences in blocks. Jack needed five passes with the boring bar to get all the way into the metal of the block. | 
This particular line boring setup is a military surplus model ("LBM") that was originally designed to be used in the field with a half-inch electric drill. |
This block will use a .030-inch over TRW forged piston (part No. L2481F-30, $469 per set) so Jack bores the cylinders out to 3.827 inches. The remaining diameter will be taken out during the bore honing process. | 
Here's a trick that will pay big dividends down the road. For some strange reason, Buick made the No. 2 and No. 3 main journal oiling holes 1/4 inch when the front oiling hole is 7/16 inch and the rear one is 5/16 inch. As a consequence, the oil delivery to the two center mains is restricted. For a stock motor, this is not a problem, but on a 500-hp mill like this it could lead to premature bearing failure. Merkel increases the size of the two center holes to 3/8 inch to improve the oil supply to the main bearings and connecting rods 2 through 5. | 
The advantage of the portable line-boring setup is that it allows the block to be bored with the cylinder heads torqued in place. Buick experts determined a long time ago that the webbing around the main journals distorts once the heads are bolted on, specifically around the center main journals. Shops not familiar with the Buick's boring needs may inadvertently create the potential for future bearing problems. |
Some Buick experts contend that the 3.8 Buick V6 does not need to be torque-plate honed, but as Jack Merkel demonstrat- ed to us with a dial-bore gauge and a torque plate, the bore diameter does indeed deviate between the thrust axis and the longitudinal axis, as well as the length of the bore. Merkel torque-plate hones all his blocks for true bore concentricity--the benefit is better power and longer wear for the rings, pistons and cylinder bores. | 
Here you can see the stock sized 1/4-inch main journal oiling hole on the left, and the larger 3/8-inch hole Merkel drills on the right. | 
Pro Gram Engineering billet steel caps (right, part No. B4.1V6C, $199.95) are approximately three times as strong as the factory cast-iron caps. They also fit into the block registers tighter than the stock caps, helping prevent cap walk in high-output applications. |
The boring process takes the cylinders out to 3.827 inches. The honing process will take the bores all the way out to 3.8315 inches. This is done in stages with the final half thousandth being taken out with a fine honing stone. The final bore diameter will produce with TRW forged pistons a piston-skirt-to-bore clearance of 4.5 thousandths. That's about 1 thousandths more than the minimum recommended by TRW but without the extra clearance, the expansion of this piston is great enough to cause scuffing at higher temperatures and boost levels. | 
This is why the main journal oiling mod is so important. The oil is fed to the mains past the camshaft bearings that further restrict oil flow. In this picture you can see the 3/8-inch drill bit intersect the cam journal and going to the passenger-side oil galley. In the foreground you can see where the galley comes out to the timing cover area. | 
Rod prep for Buicks is pretty much the same as for other engines with one important difference: the rod caps from the factory will exhibit a peened edge at the top of the rod bolthole. This is because the factory does not chamfer the hole before assembly. This creates a burr around the hole for subsequent rebuilds. You can see how the chamfered cap on the left allows the ARP rod bolt to seat properly on the cap. The cap on the right has not been chamfered so the connecting rod bold cannot sit flat on the cap. |
This picture from the top of the caps shows the chamfer that Merkel adds (cap on left). The stock cap is on the right. Merkel uses ARP 2000 rod bolts (part No. 123-6002) which have a higher tensile strength (190,000 psi) than ordinary bolts. | 
Weighing the reciprocating and rotating masses is straightforward engine building. The rods are the only part of the equation that count for both rotating and reciprocating weight. This means both ends of the rod must be calculated and entered into the bobweight formula (the reciprocating weight is obtained by measuring the total weight and then subtracting the rotating weight from the total weight). | 
The balancing process for a Buick V6 is pretty much the same as any other engine. The weights of the piston, rings, wrist pin, connecting rods and rod bearings are established and the values are written on a bobweight card. Bobweights are calculated using a formula unique to an even-fire 90* V6 and then attached to the recipient crankshaft. Merkel's Pro-bal computer balancing machine then tells him where to add or remove material from the crankshaft counterweights. The Buick Turbo V6 is an externally balanced assembly so the crankshaft must have the proper damper and flexplate attached to achieve a vibration-free balance. |
This interesting chart shows the different bobweight multiplication factors for the total reciprocating weight on a V6 bobweight card. While V8s are all 50 percent, V6s are all over the place, ranging from 35 percent for an Olds diesel to 50 percent for many others. The Buick even-fire V6 calls for 36.6 percent with rubber motor mounts and 50 percent for solid motor mounts. Some specialty Buick builders even call for a 52 percent over-balance, which would be used for a high-rpm solid motor-mount race engine. | | |
Once upon a time, in a decade long ago, Buick built a kick-ass little turbocharged V6 engine and dropped it into the handsome rear-wheel drive Regal. Rated at (wink, wink) 245 horsepower (in 1987), the mill was strong enough to push the barn door-like Buford down the dragstrip in the high 13-second range at about 98 mph. While this may not sound like much to brag about these days, in the mid-eighties, a high 13-second car was damn quick. As such, the blown Buicks were known to give the Corvette guys of the day fits, and contributed to more than a little inter-division rivalry inside GM. The turbo engine was so good that even Pontiac did the unthinkable by commandeering the V6 for installation in its 20th Anniversary Trans Ams.
The Turbo Buicks quickly became a favorite of the street racing set, as they were quiet and stealthy, had prodigious torque on tap and a hard-hooking factory four-link suspension. Basically, all the key elements were in place to make them the perfect weapon of choice for the urban street brawler. Many a big-block musclecar was humbled by the upstart buzzin' half-dozen. In a short time, the mill proved itself very responsive to minor bolt-ons, being just a few key parts (and traction) away from high- to mid-twelve second timeslips.
Buick's turbocharged V6 made not only incredible power, but it also proved itself as a durable piece, able to shrug off startling amounts of abuse with nary a complaint. While it was strong, it was not completely immune to the ravages of detonation. As the years passed, the casualties began to mount. A bad load of gas here or an over boost situation there made history of untold numbers of head gaskets, or in worst-case scenarios, hard parts such as pistons. When the worst happened, many turned to their local machine shop for assistance in rebuilding the engine. While a few had good luck with the local rebuilds, scores more did not. Soon it was discovered that GM had hundreds of new old stock replacement engines in inventory. This seemed to be the perfect solution, as the factory engines had certainly proven capable of taking their lumps. Alas, GM's supply of crate engines ran out in the mid-nineties, leaving Buick performance fans again in search of a viable solution.
Enter Jack Merkel Performance Engines. "I saw that there was no one filling the demand for 10- and 11-second street car engines," said Merkel. "I spent a lot of time fixing other peoples' mistakes in these engines, and decided I could do a better job." Merkel has recently moved into the same building as Ron's Custom Auto and is the primary supplier for Buick engines to RCA. While there is no direct connection between the two, there is a shared dedication to the turbocharged Buick V6 powerplant and a wealth of engine-building knowledge resulting from this closeness. Merkel offers a wide range of services ranging from stock rebuilds to custom crate engines such as the one we are about to detail for you here.
While it is true that almost any competent machine shop has the ability to properly rebuild a Turbo V6 engine, the trick is whether they will do it correctly or just apply the usual Chevy small-block conventional wisdom to the rebuild. A shop doing the latter is asking for trouble. Merkel: "If you build a Buick V6 like a small-block Chevy, be sure you pack a large shovel. You're gonna need it to pick up the pieces." Finding a machine shop that understands the special needs of a Buick is a daunting task, to be sure.
Jack Merkel Performance Engines performs many mods for the unique needs of the Buick turbo V6 engine. Due to its rather unorthodox oiling system, the engine has some unique bearing clearance needs. "Common small-block Chevy thinking manifests itself by allowing too much bearing clearance. This works fine for the SBCs, which commonly spin 6-, 7-, or even 8-thousand rpm. But the Buick motors usually spin 5200-5600 rpm max. They have very high cylinder pressures at low rpm and can produce in excess of 600 lb.-ft. of torque under 3000 rpm. If the main bearings are hemorrhaging oil pressure at low rpm, the rods are going to be in an oil starvation situation. They will overheat and this will cause a spun bearing," explains Merkel.
Another key element in the machine work phase of the buildup is the act of balancing the rotating assembly. "V6s are notorious as rough running engines," said Merkel. "I have found that the crank is usually close but the rods can be all over the place." According to Merkel, it is not at all uncommon to see connecting rod weight variances in the 5-8 gram range. While that might not sound like a lot, it makes all the difference to engine smoothness and longevity. "It makes a tremendous difference in the way the car runs. You can really tell a difference at high rpm, as well as with the car just idling in gear," said Merkel. "It is a lot smoother."
What follows is the first of three parts that will take us to a completed Buick V6 capable of running low 11s. We will deal with the basic machine work on the block and rotating assembly in part 1, concentrating on those tricks that are unique to the Buick V6. Part 2 will focus on short-block assembly and special oiling issues unique to the Buick V6, and part 3 will deal with the induction. Follow along as Jack Merkel takes us through the machining steps of building serious Buick power!
SHORT-BLOCK SHOPPING CART*
ARP rod bolts - part No. 123-6002... $122.77
ARP main studs - part No. 123-5401... $64.95
Pro Gram Engineering billet main caps - part No. B4.1V6C... $199.95
TRW forged pistons - part No. L2481F-30... $469 per set
Speed Pro plasma moly rings - part No. R10499-30... $140.47
Fel-Pro two-piece neoprene rear main seal - part No. BS-40613... $22.23
Federal Mogul main bearing - part No. 107M... $94.29
Federal Mogul rod bearings - part No. 6-3755APA... $32.57
Federal Mogul cam bearings - part No. 1755M... $14.36
Federal Mogul core plugs - part No. 381-8073... $9.24
Comp Cams custom grind cam - part No. 206/206... $200.00
Speed Pro timing set - part No. 220-3129... $71.01
Federal Mogul high volume oil pump kit - part No. 224-518-V... $44.86
Federal Mogul oil pump thrust plate - part No. 224-518TP... $14.69
TOTAL SHORT-BLOCK LABOR
(including machine work) $1900.00
total short-block cost: $3299.00
* Note that some items which appear in the shopping cart will not be discussed until the next installment. Also, the total short-block turnkey cost is less than the actual total.