Ok I guess I will back up a bit - what is the difference between line bore and line hone? In any case I have been told that a line hone is always neccessary with a BBB rebuild. I don't get why though. I unerstand the concept of core shift and the journals not lining up but that is something that should have been around when the block was brand new ... if it was good enough for GM and went 150k or so why won't it go another 150k with a rebuild? I know my logic is flawed somehow but I don't know where. Thanks for any help.
Well, boring and honing are two different things. Boring removes way more material than honing. Our 455 blocks are lightweight thin wall castings. Things move around, and cylinders don't wear evenly over the life of an engine. If you care anything about ring seal, the bores must be straight and round, and the main crank bores must be aligned, and perpendicular to the cylinder bores. Everything becomes even more important when spinning that engine way past where it did in the stock engine when new, and making another 100-200 HP.
Any machine work does not "need" to be done until measurement of the existing parts shows that a part or parts are not within specification for the application. The specification(s) may be from the factory for a stock rebuild that will see life as the original parts were designed to do. Different specifications may be necessary if a build is meant to be pushed past it's original design intent, and it's up to the builder to understand the differences based on customer input so that he/she can supply the machinist with new specifications. When I mention "different" specs, I mean they may be necessary not just because someone wants more power, perhaps just more longevity than the factory specs might allow. A good machinist will be able to apply more precision and more accuracy than the factory could during mass production. For anyone not familiar with the difference between precision and accuracy, this pic helps a lot: Devon
That is almost like asking why re-sizing a connecting rod is required in a rebuild.... Same deal with the mains, why not make sure they are within specification so you can have a longer lasting engine. You could re-build and engine with no machine work done just new rings, gaskets and bearings and it would last 100,000 miles most likely.. or 10 miles who knows. Generaly the main caps are cut on the mating faces before boring or honing to make the bore smaller for resizing. On an engine that still has the original caps and not worn badly the only thing needed is honing. If the caps are replaced with aftermarket caps you must align bore before honing due to the additional material left in the new caps. As a general rule align honing is alot faster than boring and usually has a better finish. Align honing may take 30 minutes or so and align boring could take several hours depending on the amount of material to be removed.
If aftermarket caps are pre-machined before installing them,only line honing will be required.(ask me how I know):Brow: Derek
Unless the block half of the mains are out of spec or "ovaled out"... Where can we buy "pre-machined aftermarket" caps for our Buick engines????
"Making sure" means measuring first. If everything checks out, no cutting is necessary. If I walk into a new shop with parts that checked out fine an hour before, and the owner of the new shop says "yep, you will pay me to re-size those" without even putting his reading glasses on, he's fired on the spot. Devon
Sorry Sean,I meant to write can be pre-machined,before installing so all they need is a to be line honed in the block. As far as aftermarket Buick caps,don't think those are available,I usually just make my own. Derek
The GSCA sells billet main caps for the 455, center 3 mains. Just thought I would throw that out there in case anyone wanted to know.
No I don't Derek. I have just noticed them in the GSXtra on their parts page for a number of years now. The phone number for the GSCA is 229-244-0577.
I asked this same question months ago and was told that because of the thin walled design of the BBB and no main skirt, the block will 'settle' over time kinda like how a building settles into its foundation, and that the iron will settle in after many many heat cycles. I was also told that almost every BBB will have some variance because they're all prone to settling. Not sure if the Buick 350 is as affected. I don't think it is (as it is skirted among other reasons that make it a sturdier block), but I could be wrong. I don't suppose it's crucial for stock or very mild builds as long as there's no issues with bearing clearance tolerances and lower RPM use. Measuring to be sure (as Devon suggested) is your sure method of knowing, though since they're all pretty much guaranteed to need something, having it honed or bored will 'make sure' (as Sean suggested) ...though it would be nice to know if all you needed was honing instead of boring, or better yet, nothing at all if the tolerances aren't too far off for your designated application. I was also told that honing removes less material and is not centered, but just trues up any inconsistencies as long as nothing is too far off the mark. Boring will re-center the crankshaft mains if they're too far out of tolerance, and will require the use of different sized bearings and timing gears. That's pretty much it!
