Line Bore, yes or no?
 

My friend , rebuilding a 2.2T engine, got a call from the machine shop today. "Suggesting" meassuring and possible a line bore. What are the chances, this is nessary and what things need to be done after a line bore is done? The machine shop talked about other things like, mag cases "squish" in a bit which makes the heads not fit right (cams get closer to the crank) and the chains are loose. And in turn, more machine work is needed. Also, shuffle pins.
We're thinking, just a line bore should sufice.
Thoughts?
Thanks

An align bore is needed on most mag cases. You renew the bearings and torque up the case bolts/nuts and the crank binds. The cylinder bases should be surfaced on the same plane as the crank centerline. Case savers so the studs don't pull on assembly or later on, etc.

If he's going to line bore it, you'd better ask some questions. If he takes it back to zero, you'll use stock type bearings (assuming crank is still standard). If he's gonna bore the holes to a bigger diameter, tell him to price and obtain the correct bearings FIRST. And as John mentioned, the spigot heights will need to be corrected, along with case savers/big serts for the head studs.

If it's a mag case, it almost certainly needs the bores corrected, otherwise the crank won't spin freely when you reassemble it.

Yes, after John's post, he's moving forward on getting the crank bore specked out. I started pricing bearings but, like you said, not sure the size yet. Odd that +.025 bearings are twice the price of standard. Hum? It does make sense, that if you aline bore the cases, the bore maybe slightly different per each cylinder. Something I never thought of before. Everything I knew of machine work, that the shop talked about, made sense to me but the things I wasn't familer with now makes sense from your responses and great info.
Thanks for the replies, very much appriciated.
Bob

The other way to straighten the case is shaving the center flanges then rebore the mains back to standard. Expensive but standard bearings are least expensive.
Then you have to figure what is a value on a 2.2 motor that shouldn’t be exceeded.
Bruce

Couple things:
- Mag cases do pretty much always need work, so no shocker.
- Depending on how the case distorted, it is sometimes possible to bore back to standard without any other work. It would be lucky if this is the case, but worth asking. Boring oversized leaves you buying expensive, hard to find bearings.
- If the bores have worn/distorted larger, there is an option to surface plane both halves of the case and then line bore back to standard. A lot of work.
- not sure I get the bit about the heads being closer and chains being loose. It’s common to account for this with thicker cyl base gaskets or spacers if needed. Or even different idler sprockets.
- There are only a few shops who are qualified to do this work. Hopefully you’re using one of them.

When I rebuilt my 2.2 in 2015 the bill from Ollie's was $2,400. Nothing special about the case, but if it's at a machine shop, the while-you're-in-there's are significant. Line bored, decked the spigots, case savers, etc etc. Price of admission with mag cases.

If you do line bore to oversize, ask the shop to leave the #8 bore alone. It is less affected by reciprocating forces and carries less load, and usually the bearing itself is fine despite lots of use. An oversize OD #8 is (or at least was) very expensive.

Actually the #8 bearing bore is extremely important. The front of the crank does the most movement, hence the reason for the full circle bearing.

Its often never measured with the thinking its Ok. And, the bearing is fitted to align the case half's when measuring the #1-7 bores, and the #8 is never measured. Tell tale issues going on typically show up on the inter shaft shells.

OK, didn't realize I had more responses. Lots of info to sort through.
I didn't think of thicker cyl gaskets to compinsate for the cases being machined. And, I would think, the chain tenssioners would make up for loose chains.
The shop he's going to is Soren up in Santa Rosa, CA. Seems to have a good rep with lots of 356 and VW parts in there. My friends been pretty sick lately and hasn't got the cases into the shop yet. He was going to stop by my house, pick up his new valves and deliever today but he's at the Dr.
I'll pass on all the info and let him decide what to do. I'll tell him to bring the #8 bearing with him when dropping off the cases.
I think it was Bruce Anderson that once said; "Mag cases are made out of sand".
Thanks for all the info and responses.

I’ve had 2 mag cases redone by Ollie’s and they’ve done a really good job since they’ve been doing this for years. My point is, if there is any question about the capabilities of the shop your planning to do the machine work, save yourself some potential headache and just send it to a known professional / expert shop.

Stretch

Ollie's is where we send our Mg cases, have done so for years with good results. Have no reason to search for another machine shop to do them. Will be sending another one in a couple of weeks.

Cheers

If the mating surfaces of the case halves get 'clipped', and then the main tunnels are line bored back to std, how do they also correct the ims bore? It doesn't go all the way through like the mains?

Also, does it present an issue with distributor pinion engagement, or is the amount removed small enough to be compensated for with gear lash?

Just a side note: If you remove material from the case halves, how do you get the correct gear engagement/ backlash for the distributor? The answer is, you can't.

Mike,

Never had an issue with the distributor.

Cheers

I know of two engines that had problems with distributor fitment after case halves were machined, but did it to my next case again anyway since I plan to run crankfire.
Henry, does that mean you prefer 1st over line bore over the case half treatment?

I'm with Henry on this one.

We do line bore work, but only resize the main housing bore to the next larger size. Have seen a lot of the "other" work and never in all we have seen have any of the housing bores straight to the original alignment. Not sure why, but from pictures of how some do it, there is no control over "bar sag".