When to Align Bore a Type IV case Options

[Kansas 914]

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!

[ME733]

........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.

[Jake Raby]

........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.

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.