To Girdle or Not????

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As some of you may know, I'm in the process of modifying an all aluminum 3.0L inline six BMW diesel. Yes, it is a new and unknown world; hence the question.

The block is cast aluminum unlike the billet cummins block available from Schieds. When Dan priced out my aluminum cummins build, I did not see a quote for a girdle on the mains.

The BMW block is deep skirted as is the cummins.

Should I go ahead and get a girdle made for the little girl and if so, who in this country would be willing and able to provide said girdle???


BMWBlock_zps4d459770.jpg
 
My guess is the factory rods $hit themselves long before you'll need a girdle.
 
How much power are you looking to get out of it? I might go the Mazda route of a lower static compression and compound boost and the bottom end will likely be fine. How many mm are the main bolts?
Have any more photo's of the mains? The bolts and caps look stout from the side view.
 
Any machine shop could do it. They just need measurements.

I think finding the correct fasteners would be more difficult that getting the girdle made.
 
I don't see a reason not to add a little extra security to the aluminum block. If you're going through the trouble to have rods made why wouldn't you through a girdle in there too?
 
Joesixpack said:
How much power are you looking to get out of it? I might go the Mazda route of a lower static compression and compound boost and the bottom end will likely be fine. How many mm are the main bolts?
Have any more photo's of the mains? The bolts and caps look stout from the side view.
Click to expand...

The power goal is 700HP. I going to try to turn this thing to 7000rpms. Of course if necessary, we may have to give 'er a little sniff of nitrous to obtain the power goal.

Will (Big Blue24) cut one set of pistons down to 13.7:1. He is cutting the second set of pistons down to 12.5:1.

The main bolts are 10MM and threaded all the way to the head of the bolt????

I have delayed looking for aftermarket fasteners because of the girdle question. I would prefer not to run one as I am very weight conscious. However, I think even say a 1/4" or 3/16" girdle would have to help sure up the aluminum block.

More pics as requested:

BMWMainCapBolt_zps140e5fbb.jpg


BMWMain3_zps06fe42c5.jpg


BMWMain2_zpsca2d8203.jpg


BMWMain_zps9ebc74a9.jpg
 
Any girdle that is of the "help" mentality is simply a crank catcher.

If it's gonna flex, it's not going to do it's job. I'd say minimum 1/2" or don't waste your time.
 
Like I figured reasonably stout main bolt for the base power. I'm thinking it makes it with just studs. No machine shop is going to touch that for less than a stack to tie in the mains.
 
OK then. Thanks for the reply's. I purchased two of the engines. I'd like for the first engine to make it through a season, but, who knows.

Any machine shop could do it. They just need measurements.
Click to expand...

I would have to argue with ya a little on that statement. I would prefer a shop that has done them with success.

I don't see a reason not to add a little extra security to the aluminum block. If you're going through the trouble to have rods made why wouldn't you through a girdle in there too?
Click to expand...

No machine shop is going to touch that for less than a stack to tie in the mains.
Click to expand...

True, true, very true.

Any girdle that is of the "help" mentality is simply a crank catcher.
Click to expand...

LOL, C'mon now...

I also need to add that the rods and pistons will be lighter. I'm thinking about having the crank lightened as well. I have a feeling the cylinder walls will fail before anything else.

Again, thanks for the replies.
 
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