Manta Montage Suspension Swap

[dave]

I finally have the Manta up on the frame bench to start the suspension swap. Powertrain plans are LS3>G86-20. Rear suspension sourced is C5 and front suspension plans are for C4.
The rear structure will be removed and a new rear clip built to accommodate the C5 parts. I am considering building a new structure to accommodate the C5 and eliminating the cradle once I find good measurements for the upper control arm mounting points. I have looked at the Performance Trends Suspension Analyzer but the measurements they give in some cases differ from actual component part measurements so I'm not done hunting for good info re mounting the parts especially the upper control arm points. I like the look of the Activepower GT40 method of hanging rear c5.
And I know already the rear will be the easiest part to install ...C4 in the front replacing the mustang 11 will really be challenging but I really like this kind of work.

 

[dave]

Bonus was the Manta was built flat and square...no twisted sister here.

 

[Lenny D]

Sweet. I just dropped a bunch of SolidWorks C4 component models on the Vettemod.com site. They were modeled from caliper measurements so please verify. Is there a cad model download section on this site?

I’m very slowly working on a c7 rear suspension design. By my measurements most c7 parts differ a bit from c5/6 parts. Wish I had SEMA access to real GM models. Sigh.

To me, it looks like the GTM has a lot of antisquat. Active power not nearly as much. By the way, somewhere someone posted the GTM pivot points. It may have been on the factory 5 forum.

 

[dave]

Thanks for the insights...I will check out the sites you've referred/contributed to.

 

[Jack Dunn]

Dave, have you considered using the rear suspension you already have? If you were planning to use matching C5 suspension front and rear, I could understand changing the rear suspension, but you aren't. While I realize that the montage V8 rear suspension uses 1980s FWD front uprights, the components and design of the rear suspension look solid, and it is not fundamentally different than the C5 rear you propose. And while the C5 suspension pieces you want to use are strong, they aren't extremely light. Building a whole new rear suspension is a lot of work and money, and what you already have looks pretty serviceable (if only to get it running!). Just my opinion.

 

[Terry Oxandale]

It may be inconsequential for your vision, but remember the C5 uprights will take some larger diameter wheels if fitted around the uprights. This was one of the many, but lower ranking reasons, I chose to use/fabricate uprights that allowed a somewhat reasonable tire sidewall for the era these cars where produced in.

 

[dave]

Thx for the input and wise words fellas. Yep I considered many things before I dived into this chassis reconstruction. The manta suspension just looks weak in many areas and has to go.

 

[Jack Dunn]

There is much to recommend using modern Corvette suspension for your project, and I respect your decision. In my case, I find that getting a project up and running in a reasonable time keeps my enthusiasm up to finish the project. Everyone has their own priorities.

 

[dave]

Sweet. I just dropped a bunch of SolidWorks C4 component models on the Vettemod.com site. They were modeled from caliper measurements so please verify. Is there a cad model download section on this site?

I’m very slowly working on a c7 rear suspension design. By my measurements most c7 parts differ a bit from c5/6 parts. Wish I had SEMA access to real GM models. Sigh.

To me, it looks like the GTM has a lot of antisquat. Active power not nearly as much. By the way, somewhere someone posted the GTM pivot points. It may have been on the factory 5 forum.

The GTM seems to me to stick pretty close to stock C5C6 suspension points (upper control arm pivots pretty much level, lower control arm pivots a little over 2" higher on the front over the rear) while the Active power setup also has the upper arm points level and the lower arm pivots with the front pivot only a little higher than the rear.

 

[dave]

Sweet. I just dropped a bunch of SolidWorks C4 component models on the Vettemod.com site. They were modeled from caliper measurements so please verify. Is there a cad model download section on this site?

I’m very slowly working on a c7 rear suspension design. By my measurements most c7 parts differ a bit from c5/6 parts. Wish I had SEMA access to real GM models. Sigh.

To me, it looks like the GTM has a lot of antisquat. Active power not nearly as much. By the way, somewhere someone posted the GTM pivot points. It may have been on the factory 5 forum.

The GTM appears to have a pretty close rear suspension layout to stock C5/C6-upper arm pivots level /lower arm pivots @2" higher front than back. Active power upper seems pretty much level upper /lower only a bit higher in the front than rear pivot.

 

[Neil]

I would not be in a hurry to replace the Mustang II front suspension; it has good geometry and there are quite a few options for fitting larger brake rotors on those hubs. The a-arms can be replaced with tubular arms to reduce weight- there are places like Speedway Motors that offer those replacements.

When I restored the Mirage that Manta Cars built as their factory demonstrator, I beefed up the factory Mustang II a-arms and had them zinc plated with a yellow-gold passivation.

 

[Lenny D]

It would be great to hear from someone who has driven a GTM and active power back to back on a track.

C5+ spindles allow for zero scrub. And one can fit longer a arms in a tight envelope.

 

[dave]

I would not be in a hurry to replace the Mustang II front suspension; it has good geometry and there are quite a few options for fitting larger brake rotors on those hubs. The a-arms can be replaced with tubular arms to reduce weight- there are places like Speedway Motors that offer those replacements.

When I restored the Mirage that Manta Cars built as their factory demonstrator, I beefed up the factory Mustang II a-arms and had them zinc plated with a yellow-gold passivation.

Good advice as always, Neil. I'm doing the back end first as it was quite sketchy with the locked out citation spindles, citation brakes and pinch bolt secured ball joint. Not worth bothering adapting halfshafts or brakes to.