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Join Date: Oct 2012
Posts: 26
type IV case machining specs

I hate to ask this , but how do porche people determine if a type IV case is still usable or needs to be machined? If you find enough high spots is it okay if you get a measurement that is low, or you don't continue with the evaluation if you find one low spot?
Thank you for your expertise!
Old 03-08-2018, 04:07 PM
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Join Date: Jun 2002
Posts: 467
Type 4 cases

Interesting you ask that, ive looked into this myself. I just read that type 4 cases dont need machining because they are considered bulletproof. I once took a type 4 case to a machine shop to check for line boring and after line boring they ruined it. Over bored it to the point no bearings would fit. Iíve rebuilt type 4 engine cases with designation EC,
GA,GC and I donít check them anymore.
Old 03-13-2018, 09:04 AM
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Thank you for sharing your knowledge! I think this thread hit 100 views with no response so you either have to think it's a moron question or is offensive in some way.

I have a EA case that is beat in every way except the lifter bores, thrust saddle and everything. I tried for few years to source a good case to no avail. I had heard that type IV's did not warp but was very skeptical after my own experience. I figured that no one actually measured one up and just assumed everything was okay.

I guess if ever pay good money for one I'll have to buy it from a builder and have them supply the bearings for it as well. I live in NYS and there is basically NO used ACVW or 914 parts available.
Old 03-13-2018, 06:39 PM
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The conventional wisdom used to be that Type IV cases don't need machining. That was ~20 years ago, when they were much newer than they are now, and it was in contrast to the Type I cases which are align-bored pretty much as a matter of course. In more recent years, it has become more common for Type IVs to need some machining.

I don't know the specs, though. A good machine shop with 914 experience should know them, but I'm not one of those.

I do know that some cases do need align-bore, but the oversized bearings are not that easy to find. All of them should at least be checked. The surface that the cylinders seat on should be checked for flatness, as I have heard of cases where the center between the two cylinders is starting to collapse toward the inside of the case!

There are likely other things to check, like if there is any damage from over-tightening the oil sump retaining nut, and if the edges of the case are actually flat, and more that I don't know about. Like I said, a good shop with 914 experience would be more likely to know the specifics.

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Old 03-14-2018, 07:53 AM
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