Mark Stielow transmission cross member.

[Tim john---]

Can someone post a clear photo of the transmission cross member under one of Marks Camaro's. I like the way it mounts and offers nice exhaust routing options. There was a picture or two at one point on the forum but I am unsuccessful finding them again. Thank You. Tim john--- PM is fine as well.

[clill]

...........

[Tim john---]

Thank You very much, not the ones I remember but the same idea. I seem to recall a "channel" iron across supporting the transmission verses round tubing on this one. May have been one of his other cars. This helps me get started and I thank you for posting them. Tim john---

[SlowProgress]

I like this style also and plan on doing a version for my car. There are some good photos on the DSE site that show how the doublers are done on the inside.

http://www.detroitspeed.com/Projects/craig-hardee-1969-camaro/data/images1/craighardee1969184.jpg

Also I really like the one the Dutchboys did.

http://i119.photobucket.com/albums/o132/novablue71/2B340D38-58B1-4F9A-B784-B3E5B079FACA_zpsg7rgpzwe.jpg

http://www.lateral-g.net/forums/attachment.php4?attachmentid=54788&stc=1&d=1435562511

[TheJDMan]

The problem I see with that style cross member is that the weight of the transmission is supported by the thin sheet metal floor pan and not the more substantial sub frame rails. While it does provide for more exhaust clearance under the floor, it also is more prone to flexing and possible floor pan sagging. On the other hand a conventional cross member ties all three mount points of the engine/trans assembly into the sub frame creating one complete assembly. It just seems to me that you give up some rigidity by not tying the cross member to the sub frame. Just sayin.

[71RS/SS396]

The problem I see with that style cross member is that the weight of the transmission is supported by the thin sheet metal floor pan and not the more substantial sub frame rails. While it does provide for more exhaust clearance under the floor, it also is more prone to flexing and possible floor pan sagging. On the other hand a conventional cross member ties all three mount points of the engine/trans assembly into the sub frame creating one complete assembly. It just seems to me that you give up some rigidity by not tying the cross member to the sub frame. Just sayin.

Steve, I'm willing to bet it's tied into the rocker panels which will provide plenty of support and strength. DSE did mine in a similar fashion with tubing running the entire width of the car tied into the rockers. It's had 760 hp going through it with no problem.

[jlwdvm]

The Holley/Hooker cross member that is made for LS conversions has ample clearance for 3" pipes. I would say that you could get the pipes to within an inch or so of the floor pan and it bolts to existing holes in the stock sub. Maybe you aren't using a stock sub?

[Stielow]

We reinforce the floor when we do this. Matt at Sled Ally has done this a few times and I have it in Mayhem, Hellfire and Jackass. I have the exhaust 1/2 inch off the floor and have no issue with ground clearance. It also allows you to easily get the cross member in and out.

Mark

[Tim john---]

Great feedback everybody, thanks so much. I am using a stock sub-frame for our Firebird (convertible). Mark, do you have one of your versions readily available for sale ? If so I would surely have interest in purchasing. Our car/application is a 69 Firebird convertible, 2" DSE lowering springs front and rear (leafs), 2004 GTO LS-1(stock), DSE speed kit # 1 front suspension & DSE rear shocks, Ricks SS tank, DSE mini tubbed, Tremec TKO-600 5 speed, stock height DSE body mounts/bushings. If you or Sled Alley has one already sciencied out that I can just install/weld in place I would be very interested. Please advise here on this thread or PM to shake out the details, that would be a great help if you do. Thank You for chiming in. Tim john---

[SlowProgress]

Here is another version from the DSE Craig Hardee 1969 Camaro build.

http://www.detroitspeed.com/Projects/craig-hardee-1969-camaro/data/images1/craighardee1969250.jpg

http://www.detroitspeed.com/Projects/craig-hardee-1969-camaro/data/images1/craighardee1969270.jpg

This is very similar to what I am planning!

Scott

[randy]

very nice but how is the floor being reinforced? That thin plate?

[SlowProgress]

Randy,

What might be confusing is the doubler plates are just something solid to attach the tabs that hold the cross member. Then those plates get connected either directly, or indirectly to the seat pans that weld into the car. The seat pans are really stiff and realistically the body has to be designed for a couple of 300 lb people worst case (just guessing) so they can't bend with a few hundred pounds of load. The seat pans go almost all the way out to the rocker boxes, the main structure of a unibody car. So if the pans could take a couple of heavy passengers they can support the transmission tail housing. The trick is to make all the layers of metal work together, sort of mimicking a standard cross member.
I suppose there is some risk with this idea that the floor could flex too much. But there are a half dozen high horsepower cars out there doing it this way. So I am willing to take the risk to learn something. Worst case add a crossmember later if this doesn't work out as expected.

I guess that's a lot of words to say " seems like a cool idea I am willing to try"

Scott

[randy]

I love the idea. wish i did this to be honest. Eliminates a lot of exhaust clearance issues