Manta Mirage build

[john chesnut]

Today I finished a project that i had in my workshop. I moved the car that I had been working on into my garage, did a quick clean and then put the Manta into the shop. I removed the body to get a good look at the frame and suspension.

The person that I bought the car from was installing C5 Corvette rear suspension. He used a kit from a company called DOBBERTIN. You can see the aluminum piece that bolts to the frame. Then the C5 cradle bolts to the Dobbertin piece. He had test fit a SBC engine bolted it to a Boxter S 6 speed transaxle. (Adapter from Kennedy) I can see where he had cut out part of the frame and the aluminum cradle to make it all work. I plan to keep the C5 suspension and use the Boxter transaxle. I have an LS engine ready to go. I'll probably use it.

In the front he was in the process of fitting a tubular suspension which I believe is based on Mustang 2 geometry. I plan to remove this and install C4 Corvette suspension. I have the parts and jigs for it.

I found that the frame had been cut completely in half. It looks to me like it was shortened. I've read that the Manta had a 96 inch wheelbase. My car has a 94 inch wheelbase.

The frame is very heavy. I'm trying to decide whether to use it and finish it as necessary. Or, build a new one from scratch. One thought is to build a frame with a longer wheelbase. I'm thinking like 6 inches longer. This of course, requires fiberglass work. I would make the extension to the middle of the cockpit. Then I would be extending the side pods, internal tub, and doors, side windows.

I need to decide if I'm going to keep things simple and build the car with the existing frame and not touch the body. Or, if I'm going to build a new frame and modify the body. I never seem to take the easy approach.

[S1965C]

Rick Dobbertin is a hot rod legend. I would be comfortable installing anything that he has fabbed. This will be a fun project to follow. I tend to stick to the KISS principle (Keep It Simple, Stupid!)...I’d leave the body alone and focus on what’s underneath.

[1795]

John,

That is one substantial frame. I suppose one consideration would be how much time do you want to spend on this project. Either way that you decide to go, it will be an interesting build to follow. Helps to have something fun to follow during these cold winter months.

Jim

[HUBBELL RACING]

Cool car. Definitely lengthen cockpit that will make it safer for your feet & legs. I wanted to buy a real McLaren 1970s Can Am car until I saw that your feet are in front of axle with only fiberglass & aluminum To “protect” your feet. Then my Coach & cre Chief told me the car would likely kill me.

[Anthony]

Originally Posted by HUBBELL RACING

I wanted to buy a real McLaren 1970s Can Am car until I saw that your feet are in front of axle with only fiberglass & aluminum To “protect” your feet. Then my Coach & cre Chief told me the car would likely kill me.

Well, you could always just look at it ! Maybe start it up now and then !

[john chesnut]

I had a gentleman contact me about getting a frame and body for my Cheetah inspired car. I have the body but need to build the frame. This will mean that It will be a week or so before I can get really started on the Manta. That being said I looked at it a little more today.

I think that the frame was cut and the front re clipped, not shortened as I fist thought. The original Manta used VW bug front suspension. Towards the end of the run they switched to Mustang front suspension. I think they clipped the frame to accommodate that change.

The front suspension cradle can easily be moved forward or backward. I unbolted the upper control arm and cradle. There is room to move it forward by 5 inches. I slid the cradle forward by 5 inches. I also cut the front off of the cockpit tub. I can see where making this change will greatly increase leg and foot room and make the car much more comfortable for me. I think that I will make this change.

I found that the upper control arm spacing as mounted is 27 inches. This is the same width as the C4 UCA spacing. However, the Vettes lower control arm spacing is several inches wider. The result would be more room to move the clutch MC to the left, closer to the frame rail. This would be an advantage. The other advantage of using the Vette suspension is that wheel spacers would not be needed. This will greatly improve the front suspension geometry. I'm pretty sure that I will go with the Vette suspension. I can build a nice cradle for it.

Foot protection is something that will be improved with extending the wheelbase. There is a clip that will bolt to the front of the frame to which the radiator will mount to. I'll incorporate an internal bumper to provide more foot protection. The reality though is: Get in an accident in this car and more than likely serious bodily harm or death will occur. At ride height the top of the side pod height is only 15 inches.

Adding 5 inches to the wheelbase will require lengthening the body. I'll do that in the middle of the doors/side pods. This also will require new side windows. I think the car will look better with the added 5 inches.

I have a fuel tank that fits into the side pod space. It's 10 by 10 by 43 inches long. It hold 18 gallons. With the LS engine that will give good range. I'll turn the other side pod space into luggage space. By lengthening the side pod by 5 inches I'll have 10 by 10 by 48 of space.

I have some other ideas to finish off (hopefully improve) the frame. My thought at this time is to use the existing frame and make mods to it.

Having fun

[Buzz]

Bummer that the build thread is delayed, but nice to see you're getting orders for the Wildcat. As I mentioned in the other thread, I almost bought a running Manta back in the late 80's, but I backed out due to what was clearly shoddy work by the owner/builder. He'd taken lots of cheap shortcuts and though the car looked great from 15 feet away, close inspection revealed a lot of crude details and poor workmanship. Your build will be a completely different story and I'm looking forward to watching it progress.

[john chesnut]

I couldn't resist seeing what lengthening the body might look like. So, today I did that mock up.

A few observations:
1---The rear cradle can be moved a little rearward. I'm thinking 1 to 1.5 inches. This will more closely center the rear tire and provide a little more room between the front of the engine and bulkhead. This would put the final wheelbase at 100 inches.
2---For the mock up I simply moved the front body clip forward by 5nches. I moved the lower doors and the gull wing uppers forward as well. I filled in the rear of those pieces to the rear of the body with duct tape.
3---The face of the dash will have to be cut and moved rearward by 5inches.
4---The side pods will have to be cut in the middle and lengthened.

I like the look. Lengthening will make the cockpit much more comfortable for me. I think that I will make this change. And, install C4 vette front suspension.

[1795]

John,

Looks nice. The extra length looks fine. That red duct tape blends in nicely. I think you are good to go, why waste time with all that fiberglass There was a television show back in the 80's with two guys from Canada that fixed all sorts of things, including their van with duct tape. Can't recall the name of it, maybe the Mackenzie Brothers?

Jim

[Morris]

John

Have you done a Torsional test on the frame....???

[john chesnut]

I like duct tape Jim!

Morris, I'm pretty sure that the frame will twist like a pretzel! I don't have a good way to tie it down to do a test. The body, to me, looks like a fast race car. The reality is that the kit wasn't built with high performance suspension or frame.

I bought this kit because I've always liked the look of the car. I have to decide whether to keep the build simple or build it for high performance. The fact that it's going to have Corvette suspension and LS power I'm pretty sure that I'll end up building a new frame. I think between building a lighter but stiffer frame and using an LS engine that I can get the final weight into the 1800lb range. I'm not building a race car. But if I can build it with performance to more closely match the looks I would be happy.

[PDUB]

The length looks fine, John. I was kinda wondering about the idea, but it looks great!

[HUBBELL RACING]

Originally Posted by john chesnut

I couldn't resist seeing what lengthening the body might look like. So, today I did that mock up.

A few observations:
1---The rear cradle can be moved a little rearward. I'm thinking 1 to 1.5 inches. This will more closely center the rear tire and provide a little more room between the front of the engine and bulkhead. This would put the final wheelbase at 100 inches.
2---For the mock up I simply moved the front body clip forward by 5nches. I moved the lower doors and the gull wing uppers forward as well. I filled in the rear of those pieces to the rear of the body with duct tape.
3---The face of the dash will have to be cut and moved rearward by 5inches.
4---The side pods will have to be cut in the middle and lengthened.

I like the look. Lengthening will make the cockpit much more comfortable for me. I think that I will make this change. And, install C4 vette front suspension.

Looks fantastic. It deserves real race car suspension not crap. A roll bar would make it stiffer & safer

[t walgamuth]

Originally Posted by 1795

John,

Looks nice. The extra length looks fine. That red duct tape blends in nicely. I think you are good to go, why waste time with all that fiberglass There was a television show back in the 80's with two guys from Canada that fixed all sorts of things, including their van with duct tape. Can't recall the name of it, maybe the Mackenzie Brothers?

Jim

Red Green,.... after fixing a broken wheel on his mini van with duct tape "This fix is only temporary.....unless it works!

[john chesnut]

I have a disease. It's the "what if" disease. I can't leave well enough alone.
I've been looking into transaxle choices. The Boxter S 6 speed is the one that I've seen recommended. It's suppose to be strong enough and uses cable shifting. From what I've read it shifts very well. It looks like a good used one is $2-3000.00. Then you need an adapter to hook it up to the LS, fly wheel and clutch assembly. From Kennedy adapters these parts are about $2400. Then you need to have axles custom made to go from the Porsche transaxle to the C5 hubs. The problem is that the trans gear ratios are not great for the LS. People recommend skipping gears when shifting. And, at 75mph the RPMS are 2900 and change.

There are other options of course. All pretty expensive. I'm not rich. I have always had to build on a budget. And, sell something to build another car.

I've built a few cars with C5 parts. In one I shortened the torque tube by 23 inches. I've also looked at eliminating the torque tube and bolting the engine directly to the transmission. The transmissions in the C5 (both manual and auto) bolt directly to the Diff.
In my shop I have a C5 auto trans, diff, and the bell housing to bolt it directly to the engine. Using all of these parts greatly simplifies getting all components that were designed for each other. The diff is limited slip and the trans has the correct gears for the LS. The problem is that this combo is long. This is because the transmission would be in front of the diff. In the Porsche and other transaxles the transmission is behind the diff.

I decided to mock up the car using all of the Corvette parts. Since I had a couple more rolls of red duct tape I was good to go. The result is a 107 inch wheelbase. This is the same as the C8 vette. If I were to go this route I definitely have to build a new frame. The fiberglass work wouldn't be that much as it would be a 13 inch insert to fit behind the bulkhead and rear clip.

I haven't decided what way to go. I'll print off the pictures and pin them to the wall. I'll stare at them for a few days. Of course I could just build a similar car from scratch. Having fun.
Pictures with 107wheelbase (tires are sticking out because I didn't move the suspension to the correct wheelbase)

[1795]

John,

Recognition is the first step towards curing your disease . It is hard trying to fight an urge that you have. I find myself sometimes having to fight a desire to do something that really is not required.

I can't offer any opinions on what you should do. Just take your time, think ten steps ahead and consider possible problems that may arise half-way or towards the end of the build. It's tough, especially when we do not have unlimited resources. Good luck.

Jim

[C5GTO]

Have you looked into the Audi transaxles that a lot of GT40 builders have used? I don't know the specifics myself but have heard they're available at a reasonable cost and if the gear ratios work in a GT40 then they should also work for your car.

My opinion on the latest stretch is that it's too much. I think you'd be better off finding a more traditional transaxle and not doing the extra stretch.

[Buzz]

From a purely aesthetic point of view, I have to agree that the previous stretch mock-up looked a lot better. This one looks really long in the midsection. As always, it's a blast following your builds and the different options/solutions that you explore.

[t walgamuth]

I like the stretch just fine. It will also make the car easier to drive, possibly. I'd want at least 55% of the weight on the rear...possibly as much as 60%. I'd put in the lightest parts I could find too.

[john chesnut]

Thank you for your input. I've decided that the stretch is too much.

I think that I've figured out a solution for a pedal assembly that will allow me to have the leg room that I need with out lengthening the cockpit.

I think that I'm going to keep the wheel base stock and bite the bullet and spend what it takes to get a transaxle that has gear ratios to match the out put of the LS engine. This will allow me to use the body as is.

One thing that I'm pretty sure that I'm going to do is build a new frame. Something more in line with what the Ultima has. (not a copy of course) Why go to all of the trouble of using good suspension and not have a frame to match.

Joel, Your GTO build was one that I followed. And, your Miura build is awesome. You have great vision, talent, and PATIENCE!

Here are a couple of pictures of the Ultima frame.