engine rebuild question

Hi,
I am rebuilding and upgrading my 2.4. I hope someone could help me with a question. In Bruce Andersons book he shows a picture of an engine case that has had the main bearing webs "boat-tailed" or had the sharp edges rounded off. It states this will increase hp by 10hp in a 2.0 due to increased air flow under the pistons as they travel. I would like to do this to my 2.4 but I am not sure just how much to take off and exactly how it is done. It is not covered in detail in the book. Do any of you know how this is done, or where I can find instructions? Is it worth the bother in a 2.4?
Thanks for any help,
mike

There are probably a couple of ways to do it, but I'm sure a hand-held die grinder will work just fine. And, any gain of 10 hp without the purchase of expensive parts or precision machine work SHOULD BE APPEALING!

Another of Bruce's recommended internal case modification is also worthwhile, though not giving any free hp, and that is the bypass mod for the oil passage ... and note that new relief valve pistons are needed afterwards.

And, don't forget the cooling tin mod, either!

------------------
Warren Hall
1973 911S Targa

Yes, I have an oil pump from a 76 and will do the engine case and tin mods as in the book.
Thanks for your help.
Mike

I had my mains boat tailed at ollies for cheap, I still had to finnish them off with some emery cloth. To tell you the truth the Magnesium is realy pretty soft. If you took a piece of fairly coarse grit emery cloth about the width of the main and basicaly went over it like you were shinning a shoe you could get it down in pretty good order and you wouldn't risk taking too much off. You just want to smooth things to let the air flow easier.
You will be tasting metal for the next week though if you did do it this way.

IF I ever get my 2.4 case back from
Competition Engineering, I intend to do
the boat tailing mod myself. Competition
wanted $200 for the job which was reasonable
but with all the other expenses I have
going with this 5R case I decided to
defer to myself.

So let me get this straight,
as I asked the same question a month ago with no response.
Using coarse emery cloth, I can smooth down
the main bearing webs by hand without a lot
of effort due to the soft mag metal? Page 178 in Bruce's book gives a pretty good
image of the result. I intend to give it
a try too.

Bill
2.4S someday...

[This message has been edited by zotman72 (edited 03-22-2001).]

Yes, I finished off the machine shop job with the fine emery cloth, it worked fine with some effort. I figure get the bulk of the meat down with the coarse then switch to a fine to really polish the webs up ta the end. Cut a strip about the width of the web lay the cloth over the web and pull down back and forth like shinning a shoe.
You will eat dust even with a mask on, dust does get very where in the local vacinity. If you have a shop vac you may want to set this up to try to suck the dust as you work. Get all your other critical parts out of the area.

Thanks guys,
All I need to do now is,,,,,,,,, get out in the garage!