2088 replies to this topic

[neglectedtorana]

Hi Heath,

 

My engineer told me to reinforce the trailing arm mounts during my build by adding some flat bar inside and bolting through it.

This is how it looked. I don't know why there is 2 of the first pic.

 

Hope you get everything sorted before the Optima and maybe even get some time to relax.

 

Cheers, Tom

 

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[Heath]

Pretty smart engineer! I still don't think that bracing work would have quite saved me from this problem but it would have helped. Mine has been stitch welded and has a brace from the lower arm mount to the upper arm mount, so its position on the floor is a lot more secure than standard. BUT I haven't made the integrity of the mount any better, and that has become the weakest link. I am told Group C A9X's when they were new had issues with the integrity of those mounts also. They are fairly long and also flimsy.

 

You would take a bit of a weight hit but you may have to consider fitting an engine oil accumulator in there somewhere?

Yep, the plan was to make the sump as good as I could and give it a proper test before adding any band-aids like an Accusump. So that's back on the table now of course.

 

The Porsche starting to look "more fun" now Heath? 

lol, I just kicked it back into life after about 6 months on the weekend. Gotta fix a few things and take it to LuftWasser this coming weekend. I get to put my mind at ease with the luxury of racing a dry sump! Haha

 

Hi Heath,
Regarding the oil surge issue/ track day surge issue.
I had a look back through your engine pics, but couldnt find any that showed rocker cover drains? ( maybe I missed them).
I have had the same issue on track days with a fully tricked up track sump. As the experts say, a trick sump only works if the oil is actually in there, and not all pumped up into the top of the engine.
We added drains ( 6 cyl ) and all good.
Apologies if this is all old news to you.

Thanks mate, I believe that was absolutely a huge concern of the car when I raced it with the old sump, but with the new sump I actually did add a drain-back on each side. The only reason you can't see it in the rocker covers, is that I tapped it below the covers, in the oil bath of the cylinder heads themselves.

https://www.gmh-tora...atch/?p=1101531

[RallyRed]

Thanks mate, I believe that was absolutely a huge concern of the car when I raced it with the old sump, but with the new sump I actually did add a drain-back on each side. The only reason you can't see it in the rocker covers, is that I tapped it below the covers, in the oil bath of the cylinder heads themselves.

https://www.gmh-tora...atch/?p=1101531

All good.

[AbsynthHatch]

I heard suspension bind involving the top arms on a torana can be rather bad, which by the looks you proved.

Is there an option to go a Panhard rof & add in a very soft bush in the top arms to avoid binding?

[Peter UC]

There's no binding as Heath converted the top arms to a wishbone, this would just be from the lateral load placed on the mounts.

[SHEEL]

I wonder if there is more load because of the wishbone setup...

 

I've got no idea with engineering things, especially suspension geometry / load etc... just throwing the idea out there

[Bigfella237]

There's no binding as Heath converted the top arms to a wishbone, this would just be from the lateral load placed on the mounts.

Unless the axis of both pivot points (IE the mounting bolts) on the upper mounts are parallel, which they aren't on a Torana, then there MUST be bind through the arc of travel.

 

I'd think that this bind would be exacerbated with a solid "wishbone" setup because each side doesn't move independently like the two-arm factory setup.

 

Looking at the result, you can see how the pivot points have tried to 'straighten' themselves...

 

 

 

[Heath]

I have a fair idea of how it pivots as I can just bolt my wishbone into the car without the diff and take it through its range of travel, which of course I have done.

 

It isn't a perfect system with infinite articulation (and it would be better with rose joints, not that I would want the NVH sacrifice of having undampened mechanical connections at both ends), but within the tiny range of travel that my rear suspension actually sees, I don't think the angular misalignment is problematic. And the angle of the ends mean that the the force vectoring has a fair bit of load acting nicely in shear through each bush and 1/2" bolt (double shear) which I think is somewhat desirable. 

 

Keep in mind the car has done 20,000km with this geometry in the rear end and it goes on the hoist very regularly as it's a shitbox that always needs work, so I am looking at things often. I believe this damage is very recent... like at Wilby Raceway on sticky rubber the other week recent.

 

Adding a panhard bar to this setup would corrupt the roll centre... you'd have two features fighting each other. At that point I would put a top link in the car that's straight down between the rear seat bases.

[Peter UC]

Just to add to what Heath said, I also moved the arm through it's range of motion and, although there is a twist through the bush, there didn't seem to be any loads that would have caused the arm to bend the mounts other than lateral loads.

[claysummers]

Parallel arms will still bind with differentiated suspension travel between left and right.


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[Shiney005]

Hi Heath,

 

My engineer told me to reinforce the trailing arm mounts during my build by adding some flat bar inside and bolting through it.

It didn't take long to figure out that 10 inch wide slicks were going to find the weak point.  This is from October 1974.

 

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[76lxhatch]

It didn't take long to figure out that 10 inch wide slicks were going to find the weak point.  This is from October 1974.

 

Screenshot 2024-04-10 113740.png

Unless replaced with significantly more bolts than rivets I don't see the advantage in terms of strength. Making certain suspension parts "bolt-on" for racing purposes could be another matter of course?

 

edit: oh unless they have very large washers I suppose

Edited by 76lxhatch, 10 April 2024 - 02:39 PM.

[Hatchback13]

Always interesting reading with you Heath. Cheers

[Rockoz]

One thing I noticed when playing with Griceys old hatch was that there were links between the roll cage and the upper suspension mounts.

The area was 'upgraded'.

A mate had a UC years ago with a 308 in it.

He had lots of trouble with the floorpan cracking around the upper mounts.

It was suggested that he reinforce the area, and I showed him what was done to the race shell.

But he wouldnt part with the extra bucks.

Eventually it ripped apart that badly that he scrapped the car.

 

Cheers

 

Rob