When does one decide a case has to be align bored? I have a GC case that I am getting ready to take to the shop to check for register collapse but have no idea what the criteria might be to consider align boring.

Thanks in advance!

One of the first is can you get bearings. It may be better to find a case that won't need an alaign bore.

I have a new set of STD x STD main bearings. Never thought about align boring until recently. There are not a lot of cases in Wichita....

if you have a new set of bearings, do not align bore your case unless it really needs it.

Zach

Hi Zach,

I agree - but how does one know when it needs it?

Put the case together, torque the fasteners, measure the roundness of the bearing seats. If you don't have the tools or skills to do that, take it to a machine shop that can. As others have said, good luck finding bearings to fit, so if it is required find the bearings BEFORE you have it bored.

Thanks John,

I will let the shop asseses this when they check for register collapse. Now to find a shop that can do that in Kansas.........

Any machine shop should have a straight edge, and that is all you need to check for register collapse.

Its fixing the collapse that is a little harder. But I bet anyone with a mill would be able to do it.

Zach

Thanks Zach,

I am going to talk to the guys at Kansas Dune Buggy and VW Specialties tomorrow and see if they know what they are doing.

........A crankcase that NEEDS align-boring is a crankcase that is worn out, and has seen plenty of use /or abuse. Many of the other register points are probably toast also....check the cam bore, check the case/crank end play area,.check the cylinder register area , and finding bearings can be a problem....Just get a good replacement case and save yourself a lot of grief.....clean and assemble the crankcase...(only)...with ALL the fasterners torqued to factory specs., then take it to a competant (vw) machine shop for an inspection. Then you will know.

Getting the spigots machined properly requires that the mill head is trammelled (squared) to the mill table extremely accurately.

One of my mills is dedicated to head flycutting and case decking. I keep the head trammelled to .0003"- .0005" over 32". That works out to .0000375"- .0000625" over 4.0".

I also have a heavy steel fixture that stays mounted to the mill table that is decked to the specific trammell. I torque the case halfs to this fixture (and clamp heads to it for flycutting) through the 6 main case bolt bores to simulate actual assembly.

Aside from not having the fixture most shop with a mill don't go to the trouble to trammell to such exacting specification. A typical shop will trammell to .0005-.001" over 4-6". That is not accurate enough for spigots.

Ask a lot of question of the shop you consider for this proceedure. It is not forgiving!

Len,

Thanks for the great information. There is only one place to go for quality work like yours and that is your shop! I hope those that want it done right know that. Unfortunately this is a budget build for the neighborhood kids (and some of the Dad's) to learn from and I am the bank... But I am a lot better informed to talk to the shops here in town.

Rimco in Southern California does a great job with type-IV cases. http://www.rimcovw.com

I usually just mail them down there have the case align-bored, shuffle pinned, drilled and tapped, and have them send it back with bearings to match the case.

Since a correct and good case is crucial to ALL builds (budget or racer) I am sending mine off to Len at Hoffman Automotive (HAM Inc). No one could do a better job than they could - and I am a newbie at Type 4 engine builds.

Mechanically I can put it together - afterall I have watched Jake's Type 4 video like a thousand times - but if you start with junk you will end up with junk!

I have verified that the case is a virgin (never align bored) and I have a new set of Mahle STD x STD main bearings. Thanks to all for your help on this.

Details on build issues as they arrive!

Cheers!

Decking a case requires a fixture to hold the case. Any decent machine shop that has made this fixture should have also matched this fixture to their mill by milling the fixture bearing surface in place on that mill. Once matched you are good unless the mill is badly worn.

Assuming the mill is set up well, which real machine shops will do, a properly made fixture will do the job right.

This is a basic machine shop service and assuming you are using a real machine shop it shouldn't something to be overly concerned about. Yes it is important, but it is not a tricky procedure.

Now, Align boring is something to be cautious about.

Mayor,
This isn't a 356 engine. Very little of the things you have stated here apply directly to the Type 4 engine.

Align bore is necessary when the case no longer meets the sizing requirements of the NEW BEARINGS that you will be using. The bearing OD and ID of most new bearings are not compliant with the factory oversizes of yesterday. Due to this cases must be cut to properly fit the bearing that will be used. One of the biggest mistakes one can make now is to use the factory specs in case sizing, because the bearings are no longer consistently sized.

That said, most STANDARD OD bearings are also no longer the same dimension that they were, so this means that some cases that needed to be align bored in the past can use a certain bearing that consistently measures .001 larger on the OD and NOT need to be align bored to arrive at the proper bearing crush.

Alignbore sizes are chosen with bearing crush as a primary function. Unless the shop cutting the case for align bore has the new bearings that will be used, it will be impossible for them to align bore the crankcase correctly to arrive at the target bearing crush. Any shop that is willing to attempt this process without requiring the new bearings should be avoided at all costs. These places haven't had the required experience to understand that nothing remains the same after 35-40 years of engine application and they'll be doing you no favors.

When we align bore cases we don't accept every one that comes through the door and the work isn't cheap because of the effort required and the pain that was endured to learn the correct way of doing this with the components available in the 21st Century.

Align bore can literally "Make or break" the entire engine project. Done improperly the engine can run 30 seconds and seize with a gut wrenching squeal that screams you just wasted your time and money. Been there.

What is the rough amount of crush we are looking for? 1 or 2 thou?

Is this as simple as measuring the case ID and the new bearing OD?

Ideally the crushed bearing/crank clearance wants to be around 2 thou as far as I know (running clearance)

And I agree 100%, do not align bore a case unless it is absolutely necessary. Most of us are not taking our T4's to the track, just want a bit more kick.