Our guess is that the longer transmission you're using resulted in increased working angles that are also probably not equal. The cure may be to simply raise or lower the tail of the trans enough to restore the proper angles, though if you find that the rearend's pinion has to be repositioned to achieve this, you can alter it by placing small wedges designed specifically for this task between the spring pads on the rear axlehousing and the springs. Most drivetrain parts suppliers can provide the wedges. Another way to change driveshaft angle very quickly for evaluation is to raise the height of the transmission tailshaft by installing a shim between the trans mount and the crossmember.
One more thing: There is yet another rule that states that there must be at least some working angle for each U-joint, otherwise the load is constantly placed on the same point on the U-joint's cup and cross-shaft, eventually wearing tiny grooves and prematurely consuming the joint.
Save That BlockI have a '69 Camaro with a non-original engine. The engine was a 0.030-over 327 four-bolt-main engine that I'm in the process of restoring. I had the block decked and punched 0.060-over with torque plates and had the rotating assembly balanced. While measuring the new crank with Plasti-gauge, one of the rear-main bolts stripped before I managed 50 lb-ft of torque (the spec is 74 lb-ft). What is the best repair for this? I have a Heli-coil set for 71/416-14, but I don't know if this is the best fix. Is tapping to the next size (11/42-inch) better, and if so, what do I torque the bolt to? I don't want to scrap the block for this. I also thought that a main-stud kit would help (assuming I did Heli-coil it) but was told that the block must be line-bored after the studs are installed because of the increased clamping force. What is the best option?Steve MelbyHowell, MI
First of all, drilling the hole to a larger size would probably be a mistake for multiple reasons. For starters, redrilling requires precision alignment; you'd need to use a fixture like the ones machine shops use when installing splayed aftermarket caps. In addition to the alignment issues, enlarging a bolt-hole in that particular area sounds like an invitation for cracks in the surrounding main webbing. Besides all that, having two different-size fasteners on opposing sides of the main cap would likely create issues, since the clamping loads would probably not end up equal.
Heli-coils, as you point out, are not only an accepted repair method, but are actually the preferred method of most shops. In many cases, the threads are actually stronger after being repaired. Going with main studs would also be advisable. If one hole stripped out, the others are likely not far behind. Might as well relieve the wear/stress of any more torquing from those areas. Besides, main studs are a simple and cheap means of adding a little extra strength to the bottom-end anyway.
On the line-boring issue, there is some debate. Some shops feel it is unnecessary to resize the mains after changing to studs, while others recommend it (including ARP with regard to its own stud kits). However, the procedure that would be performed if resizing were required would be align-honing, not align boring. Typically, align-honing is used to correct minor resizing issues, while align-boring, which involves a more aggressive cut, is used when the mains need to be completely resized, as when new or different caps are being installed. The bottom line is, after the studs are installed, main-bearing clearance should be checked, and this will require an inside micrometer or dial-bore gauge. Even if there is a discrepancy, align-honing is not a major operation at most machine shops.