[Bob Dillon]

Guys, question: Does anyone know if Pontiac engines were align bored at the factory? I'm curious as to whether the main caps were fitted and the block then align bored, as we're all familiar with, or whether there was some other method to ensure a straight bed for the crank.
Here's why. Last Spring, when I was assembling my new 455, I accidentally pulled out a dowel pin for #4 main. I replaced it, but then, when I torqued the cap, the crank locked up. I was puzzled. I finally pulled both dowel pins for #4 out with vise-grips, and noticed they were very slightly offset.
I thought I was going to have to have the block align-bored, but then a lightbulb went on. I replaced the main cap and bearing and torqued it down-no lockup. I then used a brass drift to drive the dowel pins thru the top of the cap-it was drilled all the way through-and things were fine after that. The engine has 3K on it and it seems fine.
So, which is it? Caps in a huge box, and use the offset dowels to move the caps to the correct position, or do they align bore? Any old Pontiac factory guys here?

[Bob Dillon]

Guys, question: Does anyone know if Pontiac engines were align bored at the factory? I'm curious as to whether the main caps were fitted and the block then align bored, as we're all familiar with, or whether there was some other method to ensure a straight bed for the crank.
Here's why. Last Spring, when I was assembling my new 455, I accidentally pulled out a dowel pin for #4 main. I replaced it, but then, when I torqued the cap, the crank locked up. I was puzzled. I finally pulled both dowel pins for #4 out with vise-grips, and noticed they were very slightly offset.
I thought I was going to have to have the block align-bored, but then a lightbulb went on. I replaced the main cap and bearing and torqued it down-no lockup. I then used a brass drift to drive the dowel pins thru the top of the cap-it was drilled all the way through-and things were fine after that. The engine has 3K on it and it seems fine.
So, which is it? Caps in a huge box, and use the offset dowels to move the caps to the correct position, or do they align bore? Any old Pontiac factory guys here?

[Pete D]

This is an interesting topic to me as I seem to have a rear main alignment problem. When torqued down the rear main binds. I used machinists blue to see where it made contact. It showed that the binding was caused by the cap being offset because the contact points were on opposite sides on the upper and lower shells. I had changed to studs as opposed to bolts and thought that might be the cause. Did not pan out because I am able to turn the studs in by hand with the cap located on its dowel pins. Is it possible to relocate the dowels? Or am I looking at a line bore?

Silly question I know, but I am always looking for more input.

[Bob Dillon]

Pete, as I said, I merely pulled the dowels out with vise-grips, torqued down the caps (and here I am assuming that the bearing self-centered on the crank; possibly a very wrong assumption) and then drove the dowels in thru the top with a drift punch and soft hammer. The crank then turned freely.
I guess I won't know if this was successful until the next teardown. I'll have my son post it, because I plan to be dead before I remove the engine from this car again. (quit laughing, Gach.) Good luck.

[Roar]

They must have been align bored.

[TININDN]

Bob and Pete - I don't know the answer to your question, but I do know many Pontiac engines upon disassembly show main cap "wobble" on the register pins. Trying to reassemble the engine, without correcting the situation, may pose a risk. What I have done, is have an aluminum disc machined to the dimension of the main cap "hole". Remove the old register pins, and bolt the main cap in place using the disc to center the cap on the block. Simultaneously ream the cap and the block register pin hole oversize. Remove the cap and disc and install the new oversized register pins (hardened stainless steel). Repeat this procedure with each cap. Now you can safely line bore without any misalignment problems when everything is reassembled. I don't know whether this is the "ultimate" solution, but it doesn't make sense to me to spend money on line boring when the caps "wobble" on the register pins. E-mail me for more details - I will send you a copy of an article, with pictures, I wrote on the subject.

[Vascar]

Wow, Bob you have guts. I would've never thought of pounding my mains together. I guess if your car is running trouble free you might never have any problems with it, but it sure would've given me some gray hairs. If all else fails break out the BFH. Hahahaha Bob no offense but you had that coming. You really made my day,but I'm glad you got it running without having to reline bore it. Happy Motoring.