6.5 Girdle

[MaxPF]

My instincts tell me the girdle is plenty adequate.

I had an epiphany when I was working on my build. I dropped the crank in the block and was staring at it when the cause of block failures occured to me.

When the cylinder in any engine fires around TDC the stress put on the crank is not torsional, as many people think (that happens many degrees of rotation later), but rather a bending moment. LAter in the rotation there is a combined torsiona and bending moment. These bending moments flex the crank in the main bearing supports, and tend to push the caps back and forth along the axis of the main bearing bore. This, combined with the spreading force put on the main cap block threads from the bolts and the limited thread engagement of the outer holes, is what I believe initiates cracks in this region.

A sturdy girdle (preferably much heavier than the one DSG sells, but the DSG girdle is far better than no girdle) ties the caps together, and minimizes movement in the axis parallel to the crank bore. In theory this should drastically reduce the stress on the main webs. Since the caps won't move as much the crank's bending moment will also be reduced in magnitude, and this should (again, theoretically) reduce fatigue stress in the crank. Using studs in place of main bolts to get full thread engagement and reduce the spreading force on the bolt holes is also a big help. This is how I am building my 6.2, and I think these steps will pretty much solve the block and crank issues that these motors are known for.

[HammerWerf]

MP:

Any pictures of the Jesel Roller Rockers available to post?

I recall the Grape was experimenting with some Mopar Roller Rockers.

HammerWerf

[More Power]

I just wish I had Andrew's machining skills... .

Jim

[gophergunner]

wow............i want!!!!!!!!!!

[Truckie117]

WOW does that fix the problem with those stupid nylon push pins who's Idea was that anyway? That is awesome machining.
Can I buy those anywhere?

[More Power]

The mods shown here were Andrew Ashwill's original ideas, as they pertain to the 6.5, and the full article was first published here in TDP in 2002. This electronic DS4 equipped 6.5 produced 226 horsepower and 426 lb-ft of torque at the rear wheels - on a chassis dyno. He was also running a Peninsular non-wastegated turbocharger and his own custom-built charge air cooler. Everything was top-drawer....

As I recall, the rockers and related components were off-the-shelf components, but the shaft mounts on the heads needed to be machined to accept them. You'll also note the aluminum spacer that raises the valve cover a small amount to provide a little more cover clearance - for the rocker adjusters. A little tin-smithing could work too, to create blisters in the valve covers for more rocker adjuster clearance... if it could be done in an aesthetic way.

Jim

[Slim shady]

I cant take any more. That man's machine work is spectacular, he is an artist when it comes to machine work.

I hope he will do a girdle for me.