Oldsmobile V-8 Engines. Bill Trovato

2.0000 .0010 1.9995 .0015 1.9990 .0020 1.9985 .0025 1.9980 .0030 1.9975 .0035 1.9970 .0040 1.9965 .0045 1.9960 .0050 1.9955 .0055

      Big-Block Chevrolet

       Connecting Rod (stroker applications)

Rod housing bore	2.3250 inches
Uncoated bearing	Clevite CB743 H
Dimension of bearing torqued in rod housing bore	2.2023 inches
Crankshaft Main Journal	Main Bearing
Dimension (inches)	Clearance (inch)
2.2000	.0023
2.1995	.0028
2.1990	.0033
2.1985	.0038
2.1980	.0043
2.1975	.0048
2.1970	.0053

       Connecting Rod (stroker applications)

Rod housing bore	2.3250 inches
Polydyne coated bearing	Clevite CB743H
Dimension of bearing torqued in rod housing bore	2.2010 inches
Crankshaft Main Journal	Main Bearing
Dimension (inches)	Clearance (inch)
2.2000	.0010
2.1995	.0015
2.1990	.0020
2.1985	.0025
2.1980	.0030
2.1975	.0035
2.1970	.0040
2.1965	.0045
2.1960	.0050
2.1955	.0055

      The second area of concern is surface finish. You cannot have a crankshaft journal too flat or too smooth. A common procedure is to rough grind the journal and then superfinish it until it is smooth. You have to be very careful when superfinishing because the abrasive belt typically removes more material in the center of the journal and less on the ends.

      Do yourself a favor; don’t shop around for this operation. You get what you pay for. Find a good crank grinder who is easy to deal with and pay him for his time. Typically, if you have a conversation with the crank grinder and let him know that you are willing to pay for the extra time spent on a quality job, it is usually received very well. And he will be very happy to spend the extra time required to give you a high-quality grinding job. The extra expense is usually pennies when compared to the consequences of engine failure.

Stroking

      One of the most popular Oldsmobile performance modifications is to increase the stroke of the crankshaft. This increased stroke not only increases the cubic inches of the engine, but has a few other advantages.

      In general, an engine with increased stroke makes more torque at a lower-RPM range, which makes this modification ideal for high-performance street engines. More torque and horsepower in the lower-RPM ranges allows the use of tighter torque converters and low-numerical gears, which makes this modification a popular choice for high-performance street cars. I have not seen an engine yet that didn’t like to be larger. An increased stroke makes more average horsepower and torque throughout the RPM range. I have never seen that to be a negative thing, whether it is a street engine or a race engine. Another advantage is that the rod-journal diameter is reduced, which allows the use of more popular (available and less-expensive) Chevrolet connecting rods, in addition to reduced friction and less weight.

       This finished 3.750 destroked 425 crankshaft is knife-edged, balanced, and, with reduced-diameter counterweights, ready to be bolted into Greg Finnican’s 394-ci DX Olds small-block.

      This procedure is done to the crankshaft by changing the rod-journal diameter to that of a smaller-diameter engine (usually the common Chevrolet). By removing the material on the part of the rod journal closest to crankshaft centerline only, instead of removing the material all the way around, the stroke of the crankshaft is increased. The stroke is increased by the amount of material you remove from the bottom of the journal.

      An example of a typical stroker Oldsmobile crank is a 455 big-block. The factory stroke is 4.250 inches, and the rod journal is 2.500 inches in diameter. If you want to increase stroke by .250, giving the crankshaft 4.500 inches of stroke, the rod journal is reduced by at least .250 inch. When stroking the 455 nodular-iron crankshafts to 4.500 stroke with the big-block Chevrolet 2.200 rod journal, they seem to have a problem with flexing at horsepower levels around 700, as I learned in the 2009 Popular Hot Rodding [PHR] Engine Masters Challenge. After two crankshafts wiped out the number-2 and number-4 main bearing on the dyno, it was pretty clear that the crank just wasn’t going to handle it. I know for sure there is a problem with flex at the 700-hp level, but I have several successful builds at 600 hp.

Magnafluxing