Engine: Line Boring

[JoeHall]

If I understood corectly in a recent thread, line boring may result in the crank & cam gears being too close together. I understand the principle, but has anyone who has line bored a Stude V8 experienced this problem? I recently turned a 289 block into a machine shop for the usual stuff in a rebuild, and also asked them to check & line bore if needed.

Again, has anyone EVER had a problem with line boring a Stude V8?

Thanks,
Joe

[DEEPNHOCK]

Your question really is generic.
Understanding 'how' a machine shop 'align bores' the crankshaft journal bore is the block is the key.
A machine shop will mill a small amount off of the flat surface of the main cap(s).
That makes the 'hole' egg shaped, instead of perfectly round.
A good machinist will then run the boring bar back through the journals to open them back up to the stock dimension.
Technically the boring bar will only remove material from the main cap(s) and not touch the block half of the journal.
But, there usually is a little bit of tool deflection, or the operator lets the bar just make contact,
so the journal will look the same, and he is assuring himself it is round.
That's the point where a machine shop not familiar with gear drives can get into trouble.
A little slop in a timing chain is one thing... A bind in a gear drive is another.

Just make sure to let your machine shop guy know that this is a gear driven cam, and he should 'stay off of the block'.
He should be able to set his equipment for a lighter cut, for less deflection.
He should understand, and if he doesn't, you'd best take your work elsewhere...
HTIH
Jeff

If I understood corectly in a recent thread, line boring may result in the crank & cam gears being too close together. I understand the principle, but has anyone who has line bored a Stude V8 experienced this problem? I recently turned a 289 block into a machine shop for the usual stuff in a rebuild, and also asked them to check & line bore if needed.

Again, has anyone EVER had a problem with line boring a Stude V8?

Thanks,
Joe

[DEEPNHOCK]

Joe,
Your machine shop should check your crank for straightness, and correct that (if needed).
Then they should lay the crank in the block and torque the mains....
Then they should rotate the crankshaft.
"If" there is a bind, and the 'straight' crankshaft is binding, then the block should be align bored.
Telling your machine shop to 'just do it' if it is needed is going to mean that, of course, it will be needed....
(read that.....extra $$$$)
A true quality, and honest, machine shop will only do what is needed.

<snip>
I recently turned a 289 block into a machine shop for the usual stuff in a rebuild, and also asked them to check & line bore if needed.
<snip>

[Dan Timberlake]

The roundness and size of the main bores >can< exist more or less independent of the main bearings' centerline alignment. All are very important. 0.003 inch is a big bad deal on the bores' roundness or size. A gradual CL bow of 0.003 inch along the length of the block is no sweat. As mentioned, if a straight crank turns free with correct clearances then the alignment is probably good enough. I still worry about (and measure) bearing bores.
One step in checking main bores is using a precision straight edge in the main bores with the main caps off. If more than a few thousandths of misalignment is found there, some amount of block material will have to be removed.
I can imagine a case where block distortion might make line boring necessary even though the individual bores were in decent shape re:roundness and taper.
Or, the opposite >could< be true.

Line honing is a legitimate method. Like precision cylinder honing, It sort of references all the now-ovalized (after cap cutting) bores, so must move the crank and cam centerlines a little closer as bores are restored to good size and profile.

Some machines can bore (the only way to finish main or cam bearing inserts) OR hone.

http://www.sunnen.com/graphics/assets/documents/6d9f3918ddf7.pdf

[Mike Van Veghten]

When properly done, the boring bar should only remove about 2 to 4 ten-thousands (.0002"/.0004") of block material where the oil hole is, with a graduated scale more as cut moves more toward the parting line.
On my block .0003" was removed from that area.

Mike

[PackardV8]

Jeff said:

Technically the boring bar will only remove material from the main cap(s) and not touch the block half of the journal.

Mike said:

the boring bar should only remove about 2 to 4 ten-thousands (.0002"/.0004") of block material where the oil hole is, with a graduated scale more as cut moves more toward the parting line. On my block .0003" was removed from that area.

1. Very few OEM blocks require line boring. That procedure is usually for when different or 4-bolt main caps are installed or the very rare block when there is major main saddle misalignment. Mike's and Jeff's statement is good as far as it goes. However, the dimensions given are meaningless. Enough material must be removed to correct whatever misalignment is found in the block saddles. In most blocks, it might only be .0003" or if there is a problem, it might be necessary to cut .003" from the block. There is no fixed dimension of how much will be removed. The answer is "just enough to correct any misalignment."
2. Align honing is the preferred means of correcting small misalignment. Very little material is removed via line honing.
3. Whenever a Stude block is line bored or line honed, the cam-to-crank gear tooth clearance must be verified. If the teeth are within a few thou of bottoming, the gear ODs must be reduced by machining. Remember, the R/truck aluminum gear expands more than the fiber gear, so needs more radial clearance.

jack vines

[Tom Bredehoft]

...the gear ODs must be reduced by machining...

The Diameter only, or how about the point of contact on the gear flanks? Seems to me this is the critical point.

Or...is the fit of the teeth so sloppy that the OD is liable to hit the root of the driving teeth first?

[studegary]

Thank you, Jeff. When I first saw the heading, I thought; He probably means align bore.

[DEEPNHOCK]

No sweat Gary...
It is a good question that Joe is asking.
I tried to keep my reply as generic as possible, as it can get confusing as to what the process is, and what it really means.
(and it is real easy to get past my limited knowledge base)
Mike is right that the final step should be a 'hone' process just like you final hone a cylinder to the final dimension after boring.

I believe the crux of Joe's question is:
(a) Whether his shop is qualified to do this job properly on a Stude engine,
and (b) is it really needed on a basic rebuild.

If this is a 'freshen up' of a decent running engine, then all of these items might not be mandatory.
Mandatory is the operative word.
Sure, a complete blueprinting of every component can be done every time, and the end result should be perfection.
That is what racer's and high performance people strive for.
But, for the hobby owner of a studebaker, a total blueprint rebuild might be fanatical overkill.
And a machine shop will almost always judge the customers needs by his requests, his wallet, and/or his inability to say no.
But that's hard to say if you don't have that knowledge, or ability.
I took apart a 289 a couple months ago that I could turn the crank with one finger.
Just for fun I pulled the center three main caps, removed the bearings, and put a dial indicator on the crank.
It was perfect.
Tom C. and I did the same thing on his blown up 330 cid Stude engine..
The crank was bent, and had runout of .015"....
This is the kind of thing a machine shop should look for.

Perhaps a rebuilding checklist sticky could be put together for people to take with when they take an engine in for work.
Just a thought...
Jeff

Thank you, Jeff. When I first saw the heading, I thought; He probably means align bore.

[JoeHall]

Thanks for the explanations. I mentioned the gears versus chain to the machinist today. He did not forsee a problem, and assured he would get back to me before the surgury if the block appeared to need major alignment.
I recall reading an article years ago that said paying for line boring, most of the time, is a waste of money. I have never asked a machinist about it before, and this is probably the 5th or 6th Stude V8 I have rebuilt. But I knew at least some of the history of those engines. This engine is an overhauled shortblock from 20+ years ago that sat too long, so thought it may a good idea to check it.
Thanks again.

[64Avanti]

When the crank gets a little closser to the crank it is usually the flank of the tooth that interferes not the the tip of one gear interfering with the root of the other gear.

[SilverHawkDan]

47 years of Studebaker and all other brands expereince here. I have seen very few Stude blocks that needed align boring. High nickel blocks that are really thick. Only ones that were very overheated it can affect the line bore. The only other occasion is when you add 4 bolt mains like in Jeff's picture. I personally have never had to align bore a Stude. Verify the crank is straight and install it in the block. Light oil on the bearings. Add the main caps. Turn it over. If it's a "usual" Stude it will turn with one finger and a small combo wrench. The Studebaker block is so strong and hard that machine shops don't like working on them. Kills their tools. I remember boring a 259 block and having to sharpen the cutter after every cylinder. If you doubt it try honing the block sometime. It takes twice as long per cylinder to clean up the cylinder as a brand X block. Just my observations.
Dan

[R2Andrea]

"High nickel blocks that are really thick" SilverHawkDan, you might want to refer to the following thread http://forum.studebakerdriversclub.c...ly-Better-quot Especially posts # 8 and #18.

[DEEPNHOCK]

And read #20, too....
The controvery continues about cast iron

Really thick is an accurate statement, except at the the thin places
Jeff

"High nickel blocks that are really thick" SilverHawkDan, you might want to refer to the following thread http://forum.studebakerdriversclub.c...ly-Better-quot Especially posts # 8 and #18.

[Chucks Stude]

Hey Jeff, whats going in that block? Inquiring minds want to know.