recommendations - engine mount crossmember

[SpyderMike]

I tried to do what I thought was a simple job today...replace motor mounts. They are original (1985) and the bolts wouldn't budge. I was surprised how the cross member flexed. I tried to several ways to counter the torque, but couldn't. Found tears in the cross member near the bolt receptacles. Now I need a new cross member...hopefully something stronger with unthreaded receptacles so I can go with bolt and nut. Any recommendations?

Thanks,
Mike

[yelcab1]

That does happen. Replace it. Or have it welded.

[wildcat077]

Rennline is having their 15% off X-Mas sale,they have a nice reinforced stainless engine crossmember,i installed one in my car after welding the OEM one for the second time ...

Cheers
Phil

[BER]

Mike,

I had similar issues on my '84 Carrera's engine mount crossbar. Bolts would not turn and the crossbar was developing "flex" cracks at the ends.

I ended up replacing the crossbar with the Rennline RSR style crossbar. The crossbar ends where the bolts go are heavily reinforced so there should be no flexing in the future.

I am very pleased with the Rennline crossbar.

Bruce

[sc_rufctr]

This one (Original from an SC RS)

[Ferrino]

Has anyone modified the stock crossmember by welding in some gussets to strengthen it?

[Nate2046]

Originally Posted by SpyderMike

I tried to do what I thought was a simple job today...replace motor mounts. They are original (1985) and the bolts wouldn't budge. I was surprised how the cross member flexed. I tried to several ways to counter the torque, but couldn't. Found tears in the cross member near the bolt receptacles. Now I need a new cross member...hopefully something stronger with unthreaded receptacles so I can go with bolt and nut. Any recommendations?

Thanks,
Mike

One of the first jobs I tackled on my 911. I tried soaking in PB, heating with a torch, etc. Finally said F it, ordered the Rennline piece and bent the original bar. I realize its a bit pricy but didn't see any other way.

[sc_rufctr]

Originally Posted by Ferrino

Has anyone modified the stock crossmember by welding in some gussets to strengthen it?

I haven't but you could copy this. (same one as posted above)

[chris_seven]

The SCRS Crossbar is just a little extreme as it did come from a car that was used aggressively on the European Rally Championship.

The more common RSR Crossbar just uses a second flange to increase the stiffness and these work quite well but can still yield.

Adding a couple of gussets on the corners works quite well.



If you also make the Crossbar from a stronger material it will improve its reliability.

We made a small batch of RSR Style Crossbars using a material with the trade name of DOMEX 700MC. (They sold out quite quickly)

This material has been developed by SSAB for military vehicle applications.

It has a yield strength that is around 4 Times greater than a typical CR4 Deep Drawing Quality steel.

The yield strength is about 120000 psi but it retains the same level of ductility and weldability as more conventional mild steels.

It also retains its impact properties to very low temperatures.

For the relatively small quantities used in the engine crossbar the price premium is insignificant but the performance enhancement should be very good and prevent both deformation and subsequent failure.

[BER]

Our host sells the Rennline RSR Style Engine Crossmember Bar. It is reinforced stainless steel and is offered in painted black or brushed stainless.

I opted for the black bar since since that was a closer match to my OEM crossmember bar that I removed. I also used anti-seize on the new mounting bolts, so they should come out a bit easier next time.

Bruce

[bamboo sc]

Gussets is what they are called. I made mine. But a good shop that welds, and fabricates can do it.

[gtc]

Does anyone sell a gusset kit for these? I can weld them on, but I don't have the tools to cut or form them.

[JohnJL]

Originally Posted by gtc

Does anyone sell a gusset kit for these? I can weld them on, but I don't have the tools to cut or form them.

If you have a handheld jigsaw with a metal blade you can cut them out. Use cardboard to make a template then trace it out on some scrap metal.

[T77911S]

heat the ends.

[SpyderMike]

Ordered the black Rennline unit on sale...Thank you very much!

Here is a view of the tears in the original one:

[BER]

Boy, those cracks looks familiar.

With the Rennline Crossbar you should not have that issue any more.

Enjoy, Bruce

[88911coupe]

Anti seize when you put the next one in as well.

[OsoMoore]

Before attempting to loosen, be sure you raise the engine from beneath until you see all the weight come off the mounts. The rubber will expand out between the big metal washers.

Mine were stiff, but removed without any cracks once the weight was off. I used a long breaker bar, and I applied the pressure in such an angle that I wouldn't bend the crossmember.

[Nate2046]

Originally Posted by OsoMoore

Before attempting to loosen, be sure you raise the engine from beneath until you see all the weight come off the mounts. The rubber will expand out between the big metal washers.

Mine were stiff, but removed without any cracks once the weight was off. I used a long breaker bar, and I applied the pressure in such an angle that I wouldn't bend the crossmember.

You were lucky. If they're seized up you're going to bend the bar period. Its a weak design.

[ThomO]

Restoration Design sells a RSR replica mount that looks interesting