RSR Type Engine mount cross bar
 

Hi,
I'm actually thinking about drilling my standard Engine mount cross bar to give it that outstanding RSR-Look.
Has anyone out there experience in doing that . Need information reg.
How many holes; which diameter each, some reinforcement neccassary, etc.

Are there any risks connected with this (less rigidity and/or dynamic stiffness)

Thank you in advance and I am looking forward to receiving some helpful comments and pictures

HJT911

It will be less rigid. The holes, even if smooth, create stress concentrations. If drilled and not deburred sufficiently, they will cause fatigue cracking.

I think the RSR mounts were originally stamped, which is a cleaner cut than drilling.

I would also want to reinforce the ends where the bolt tubes are mounted, and add a sort of I beam flange on parts of the crossbar to regain the rigidity lost with the drillings.

I have done it by hole saw and then radiusing the entire thickness by grinding and sanding. This extra work was not for beauty, rather to eliminate stress risers.

Clint at Rebel Racing sells them:

Engine

Thank's for the reference.
Had just a look at Clints homepage. Looks like the bar has also one flange only as it is standard and not two as it was for the original RSR Bar.

nice!

Very nice, and considering you can easily sell your un-drilled one if it is ok, it's a rather inexpensive upgrade.

Talk to Alan at Canford Classics in England. He makes very good quality reproductions at a very reasonable price.

The originals were curved on both the top and the bottom for rigidity and then the holes were punched to eliminate weight.

I have an OEM that I can take some pix of if you need one to reference, but as others have already pointed out, you will weaken your bar and RSR bars have curved edges top & bottom which also helps rigidity.
That being said, I may order this one for my SC...

Rennline Stainless Steel Engine Mount Cross Bar - Porsche-Rennline, Inc.

I used two different sizes for the holes.

http://forums.pelicanparts.com/uploa...1318921169.jpg

Those of you that are paying attention will notice that this is the same bar as previously mentioned as being sold by Rebel Racing.

JR

Also sold by our host: Pelican Parts - Product Information: REN-M01S-RS

How much of an issue are the stress issues you guys talk about if the bracket is used on a basically stock motor?

This is an original one from an SCRS. ----- You gotta love ugly welds. ;)

http://forums.pelicanparts.com/uploa...1318941283.jpg

http://forums.pelicanparts.com/uploa...1318941298.jpg

http://forums.pelicanparts.com/uploa...1318941311.jpg

http://forums.pelicanparts.com/uploa...1318941325.jpg

Peter,

Do you happen to know which is the top side, as Porsche installed that in the car?

Thanks,
Jeff

This is the Rennline version that came with my car.

Rennline Stainless Steel Engine Mount Cross Bar

http://www.users.on.net/~quozl/Image...d/IMG_7486.jpg

http://www.rennline.com/images/m01s-rs.jpg

http://www.rennline.com/images/M01-RS-1.jpg

http://www.rennline.com/images/M01-RS-2.jpg

Cheers Al

Jeff

The top is as you see it in the first photo. The side shown in that photo is also the side that faces the rear of the car.
I absolutely love how this thing is made. It's all about function.

Peter,

Thanks for the additional information. It's interesting to see how Porsche made these, and how the aftermarket "copies" are made in a completely different way.

Cheers,
Jeff

You will want the extra rigidity of the I beam flanges on top and bottom.

The main issue is fatigue cracking. Drilling the holes will shorten the lifetime of the part but it is difficult to know by how much since it depends on how the hole is drilled and finished. If it is deburred and beveled nicely then it may not really be an issue, but stamping the hole out is better.