Mg case inspection, removing headstuds w/case savers
 

I picked up most of a 2.5 engine project from another Pelican recently. I am going to try to rebuild this engine myself using the forum and Wayne's book.

Long-story-short on the motor is that it was originally a '71T engine that was rebuilt 20+yrs ago as a 2.5 w/E cams, stock crank, stock ports, & carbs. Everything was done right, all of the machine work on the case was done by one of the reputable Porsche machine shops that we all know, etc.. The motor served well for many years up until a missed shift at the track recently. On my bench right now I have a Mg case with all of the mods and machine work, a few broken rocker arms, some bent valves and a possible bent crank. Thats all I know so far.

I want to make it live again. The first thing I think I need to do is have the case inspected. It already has case savers and Dilavar studs from the first rebuild. Should I remove these studs, or should I pay the machine shop do it? I have successfully removed Dilavar headstuds from an SC case before, but Im thinking this has to be a little different since it's a Mg and already has case savers installed.

TIA

If the inserts were installed correctly the studs should come out easy and leave the insert behind, lot better than an old mag case without them.

If the case already has case savers, you should be good to go. If it was done with Timeserts, I'd recommend replacing them as they can eventually fail. The Dilivar studs should be thrown away and replaced with your favorite choice of steel head studs (there are alternatives, I chose Supertec for my engine). Then, have all the specs carefully checked and machined as needed.

It's nice to know that you've gotten such good service from the engine already, and hope that it will continue to serve you well.

I'm in the process of rebuilding my engine. I have a sample of 1 so I'm not pretending to be an expert. But, I do have a Mg case and have been reading everything I can get my hands on, especially Wayne's and Bruce's books. I also just got my case back from a noted left coast machine shop with mods specifically suited to today's 42 year old mag cases. So, with that caveat...

Time Serts are used specifically in these Mg cases because the external threads are more coarse and "bite" into more case material. This makes them more suitable for use in Magnesium than than their Helicoil counterparts. If you have Helicoil inserts, those are more likely to pull than Time Serts.

Do you have iron or aluminum (Nicasil or Alusil) cylinders? It's my understanding from what I've read that the Divalar studs have thermal expansion rate closer to Mg and Al. According to Bruce Anderson's Engine Rebuilding Course, Divalar studs should be used if you have a Mg case and Nicasil or Alusil cylinders thus "virtually eliminating crankcase problems." It's not a matter of stud strength but rather what the studs will do to the case. The newer, post 1984 with black epoxy coating Divalar studs are preferred for use to the older shiny silver studs that tended to break from corrosion. Then again as Jack points out, looking at the price of Divalars brings a host of aftermarket stuff into play. The point is, do some homework, you mileage will literally vary here.

I suggest you remove the Dilivar studs and replace them with OEM steel studs. Steel studs never break. Dilivar stud eventually will fail.

You may find that the time-certs will come out of the case with the studs. I just did a mag case engine with certs and about 8 or 10 of the time certs came out with the studs. I removed the time certs from the studs by heating them with a MAP gas torch until the glue burned off and then unscrewed them from the stud.

^^^I'm glad to hear!^^^ I was actually going to ask about this soon here. I already have my new OEM steel studs but Mr. Anderson's support of using Divalar studs in his rebuilding course pamphlet boardered on emphatic and had me second guessing my decision.

2.5 case
 

Sherman, glad you got home safe and have jumped right on it. Hopefully, everything is checking out to your satisfaction. As for your questions. I never had any issues with the case savers, d-studs etc. But as you may remember I used nikasil not alusil. So if you are going to use the nickies, which I would recommend my choice 35 years ago was for d-studs. Still would be my choice. I always like the similar expansion rates. If you look at the mounting surface of the cylinder at the case and at the heads do you see any indication of leakage? I don't recall any time that the bolts or studs ever got loose. If you put in the cheapy steel cylinders (please don.t) you might consider steel studs. I would leave d-studs alone unless you see corrosion or bends or other problems. best Henry

Thanks again, Henry! Everything looks real good so far. I haven't been able to get anyone at Competition Engineering on the phone yet, but I'll keep trying them. Im going to go ahead and pull the studs just to make it easier pack and ship the case out for any prep work in may need.

I talked with LN Engineering earlier and it sounds like they can do 92mm or 93mm P&Cs that will fit the case. So, it may wind up being a 2.6 or 2.7 short stroke when it goes back together. If that wont work I'll do the 2.5 with 9.5:1 JEs an E cam, stock ports, and carbs. I cant wait to get into this project. I've wanted to build a motor like this since about 2005. This is going to be a fun project!

On the studs...

Im starting to check prices on parts and tools so I can budget for the overall build. The 993 head studs are $47 each. Wow. Steel studs are about $275 for a set. I don't even see Dilavar studs for sale.

The Supertec Performance studs are a real bargain, IMO. Im buying those regardless of what I build. Henry Schmidt at Supertec gives a lot to this forum. I'd rather just buy his parts and never worry about head studs again.