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Boxing LM Trailing Arms??
Posted by: Robski ()
Date: January 04, 2021 09:03PM

Hello

Thinking of boxing my trailing arms on my 65 455 Toro conversion. I know they are flexing with the extra weight and torque. The car drives fine but things seem a little floppy on acceleration. Suspension is fully rebuilt with new modified Corvette lowers.

Has anyone done this and do you have any tips? Could this modification result in cracking or failure of the trailing arms?

Also, I was thinking of replacing the rear stock rubber bushings with Polyurethane ones.

Any advice would be appreciated.

Best Regards
Rob

63 Spyder Convert ~stock with a few tricks, 65 Corsa coupe Mid-Engineering 455, 1992 Caddy 6' Stretched Limo, 1972 Triumph Bonneville. My first car was a 64 Monza Coupe at 17 years old in 1985 and I have always owned a Corvair.

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Re: Boxing LM Trailing Arms??
Posted by: MattNall ()
Date: January 04, 2021 09:14PM

I've seen several boxed. go for it. Others Triangulate them, like '68 VW IRS

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
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Re: Boxing LM Trailing Arms??
Posted by: AZ Troy ()
Date: January 04, 2021 10:00PM

AZ Dave has done a lot to his, if he don't chime in, reach out to him. He can be very helpfull & has/had several Torvairs.

Troy G. / Scottsdale Arizona

'65 140 Corsa Coupe
'66 180 Corsa Coupe - Crown Converted in the '60's

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Re: Boxing LM Trailing Arms??
Posted by: Seth Emerson ()
Date: January 05, 2021 12:01AM

How are you anchoring the front tip of your rear arms now? Are you using stock-type rubber bushings. If so, what are you using to stabilize them to the power train? You could change to spherical bearings and eliminate the stabilizers. It is fairly simple.

Seth Emerson

Check my new Performance Corvair Web site [www.perfvair.com]

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Re: Boxing LM Trailing Arms??
Posted by: vairmech ()
Date: January 05, 2021 04:57AM

I box in the trailing arms on the race cars, it's not hard. All you need to do is look at things and not cover up anything you may need to get to.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Boxing LM Trailing Arms??
Posted by: azdave ()
Date: January 05, 2021 05:48AM

Robski Wrote:
-------------------------------------------------------
> Thinking of boxing my trailing arms on my 65 455 Toro conversion.

Here are a few pics from when I was repairing the trailing arm cracks I found on the Toro conversion I purchased out of New Mexico in 2010. I only found these flaws on the right arm but reinforced both sides while I had it apart. They are not "boxed" like others you may have seen before but after 10 years with no issues I think I have fixed my issues. This big block conversion is not a Mid-Engineering setup like you have but the trailing arms could have similar issues I'm sure.

The gap noted between the spring perch and the trailing arm and the related stress crack noted at "D" were my biggest concerns.

Here is a thread where I found other cracks in trailing arms on normal Corvairs.
[corvaircenter.com]

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: Boxing LM Trailing Arms??
Posted by: Robski ()
Date: January 05, 2021 07:03AM

Thanks for all of the fast responses.

Seth. I am running stock rubber front bushings presently. When you say Spherical Bearings are you referring to the Monoball units from Clarks? I was thinking of those but I was wondering if they would lead to extra stresses on the Arm assemblies. I guess if I box and reinforce the Arms that would be lessened. Also, do you mean I can eliminate the stabilizer rods if I use those Bearings?

I have a spare set of "fresh" arms that I will build for the car in case there are some unseen cracks or problems with the ones on the car. This baby was built in the 80s so there are a few miles on it.

It is cold up here in Canada so this is a good winter project before Corvair Season in the spring.

Best Regards
Rob

63 Spyder Convert ~stock with a few tricks, 65 Corsa coupe Mid-Engineering 455, 1992 Caddy 6' Stretched Limo, 1972 Triumph Bonneville. My first car was a 64 Monza Coupe at 17 years old in 1985 and I have always owned a Corvair.

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Re: Boxing LM Trailing Arms??
Posted by: Seth Emerson ()
Date: January 05, 2021 11:09PM

Rob- On a regular late Corvair rear suspension, the front rod that goes over to the Trans mount actually controls the inward or outward motion of the front of the training arm. Chevy made a change in late 65 and dropped the inner pivot point for greater toe-change. The Crown V8 kit added a separate part which also functioned as an adapter between the engine and trans. It provided a mounting point to retain that toe bracket. Many racers (and V8 guys) just eliminate the toe bracket and install that Monoball in the front. The monoball retains the bracket left and right. (But it does remove the designed-in toe gain.) The rubber part in the original bushing was needed to allow the toe bracket to push and pull the front of the trailing arm sideways. The Crown and the Kelmark conversions both retained the driveshaft as the upper link to locate the back of the trailing arm, with the large strut acting as the lower link. I see from your photos that the trailing arm was changed to add another inner front mount in your application. So I cannot say you will be able to eliminate any links. I have seen some metal fatigue in the similar areas on the trailing arms. I sandblasted the arm (protecting the studs) and MIG welded around all the "joints" to stiffen up the whole assembly. Yours looks like it could certainly use that. Is it possible that there is some strange loading while driving that is causing the stress cracks? Does the arm swing through it's travel okay? We also have to consider that these parts are 50+ years old.

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Re: Boxing LM Trailing Arms??
Posted by: vairmech ()
Date: January 06, 2021 04:20AM

One other thing I do is I also make a plate to go inside the trailing arm where the bearing mounts. I use 3/16" plate and cut the appropriate shape from my cardboard template. I fit the steel plate in after removing the studs. Once I get the plate to sit in tight I clamp it in place and weld it in. Once done I finish the opening for the axle housing matching the original and then drill new stud holes and install the studs. You will notice that everything is a LOT firmer when putting the studs in.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Boxing LM Trailing Arms??
Posted by: azdave ()
Date: January 06, 2021 05:52AM

Seth Emerson Wrote:
-------------------------------------------------------
> I see from your photos that the trailing arm was changed to add another inner front mount in your application...

Seth,

Those photos are from my Toronado conversion as purchased 12 years ago. I showed them as examples of where he might see trailing arm failures if you have an engine with tons of torque and fat tires. Since Rob has the Mid-Engineering kit he would not have those extra inner arms added to the trailing arms but he might see the same spot welds and metal fatigue issues I had.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: Boxing LM Trailing Arms??
Posted by: Robski ()
Date: January 06, 2021 05:59AM

Hello

Thanks for the information. The arms pictured above are not mine. I had mine blasted when I rebuilt the arms and I did not see any obvious cracks or issues at the time. I will get my extra ones blasted and do a major inspection before I do any work to them.

The monoball units seem to be what I need. I will get the arms reinforced in the areas suggested including the bearing mount plate. With the big heavy lump in
the back I need as much strength as I can get.

Are there any reinforcements required for the front of the arms around the Bushings?

Cheers
Rob

63 Spyder Convert ~stock with a few tricks, 65 Corsa coupe Mid-Engineering 455, 1992 Caddy 6' Stretched Limo, 1972 Triumph Bonneville. My first car was a 64 Monza Coupe at 17 years old in 1985 and I have always owned a Corvair.

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Re: Boxing LM Trailing Arms??
Posted by: joelsplace ()
Date: January 06, 2021 08:38AM

"Chevy made a change in late 65 and dropped the inner pivot point for greater toe-change."
My feeble memory can't seem to find this info. Does anyone have pictures? Was the change actually an improvement?

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Boxing LM Trailing Arms??
Posted by: jjohnsonjo ()
Date: January 06, 2021 01:29PM

Joel, there was a change, I tried to buy some used original from Clarks a long time ago, but the sent me the 2nd gen twice, so I gave up. They changed this because it was causing some tweetyness (is that a real word?) on crowned roads at certain speeds. I have it somewhere, but who knows. It was a primitive attempt at active steering.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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Re: Boxing LM Trailing Arms??
Posted by: Seth Emerson ()
Date: January 06, 2021 02:15PM

Rob - I didn't add any reinforcement at the front of the trailing arm. That said, the new outer shell for the spherical bearing has a shoulder. To install it, you press it in so it seats and matches the original bushing shell, in left-right position. Then you tack weld the shell in place - three or four places. The actual bearing can be replaced without removing the outer shell in the future. When you are done you will still need to do the "on-the-ground" toe setting.

Seth Emerson

Check my new Performance Corvair Web site [www.perfvair.com]

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Re: Boxing LM Trailing Arms??
Posted by: thewolfe ()
Date: January 06, 2021 02:47PM

Another option is to replace that bushing with a johnny joint spherical bushing. A little more work to install but will be less jarring on the street and probably last longer.

Nate Wolfe
Portland OR
65 Corsa 180

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Re: Boxing LM Trailing Arms??
Posted by: RexJohnson ()
Date: January 06, 2021 06:34PM

I believe that the front rod inner attaching point change that Seth is talking about happened very early in the production year. I have looked at quite a few Corvairs and parts over the years and the only 1st design brackets that I have seen came on a August of '64 LOS built Corsa conv. body # 19. It might have been a Sept build but I think it was August.

RJ tools
Salem,Oregon

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Re: Boxing LM Trailing Arms??
Posted by: Robski ()
Date: January 06, 2021 09:03PM

Daaaang

I think I will go with the Johnny Joints. They would solve a lot of problems.

Elegant solution.

Thanks Everyone!

Rob

63 Spyder Convert ~stock with a few tricks, 65 Corsa coupe Mid-Engineering 455, 1992 Caddy 6' Stretched Limo, 1972 Triumph Bonneville. My first car was a 64 Monza Coupe at 17 years old in 1985 and I have always owned a Corvair.

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Re: Boxing LM Trailing Arms??
Posted by: Spectre ()
Date: January 07, 2021 04:37AM

I need to look at my 65. Built in 3rd week of Nov '64.

David Clamp


1965 Corsa convertible - 140 4spd/3.55/AM-FM

2013 Mustang GT convertible - 5.0, 6spd auto, Procharger i-1

2003 Miata SE - 6spd manual (wife's toy)

"Victory is mine!" - SG

Norman, OK

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Re: Boxing LM Trailing Arms??
Posted by: RobertC ()
Date: January 07, 2021 11:25PM

I always thought that the front strut rods on a LM rear suspension was to limit / stop toe-in changes ("torqueing" the bushing).

Yeah, I know - rubber bushings.

But, the average (majority of) US car buyers really would not like a "solid" suspension.

YMMV

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Re: Boxing LM Trailing Arms??
Posted by: JimBrandberg ()
Date: January 11, 2021 05:19AM

What about the notion that when you firm up the trailing arm front swivel is when you can start seeing cracks further back since the trailing arm doesn't just go up and down but follows the drive shaft arc.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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