Opel Manta Turbo Ecotec Build

[Later-A-body]

Interesting idea regarding the S-10 front clip. There is an alternative I was going to bring up later in the build but it seems like a good point to post it. I have been discussing the idea of a C4 Corvette front cradle and suspension set up for the Manta. These are available as new units in various widths, and retain the factory GM suspension pieces. The '84-'87 Corvette's incorporated an 11" front brake rotor as opposed to the '88-'96 cars 12" set up. I think the 11' is plenty for a 2100-2300 pound car, and allows the use of a 15" wheel if that is what I decide on. People have been hanging these C4 set ups on street rods for years so I know they are a good alternative if the original cross-member becomes an issue.I have been in contact with a few different companies that produce these kits. It appears initially that the concept will work, but I need to have more time to do all the measuring.

[cornfedbill]

I thought I would change the color down the road, but have decided the green is going to stay.

I like the green too. It stands out.

[SRD art]

The C4 set up would be a great alternative. That base geometry would be way better than the S10's.

Thanks for the compliments on the 'Vette. I was pretty bummed to let it go, I owned it for 9 years and put over 70,000 miles on it, but I had to make a choice between projects and that would need the most amount of fab work so the G-body stuck around. I've watched for buying another over the years but they're getting so rare and the prices have been more than I see as a good value. Most I see are nice running cars whereas I prefer to pick up a cheaper beater with a decent body to start with. I figure it hurts less to cut up something that isn't nice, lol. I picked up the Monza a little rough and no drive train super cheap and as a wagon fan it fit the bill even better. Funny you mentioned color changes on the 'Vette, here's a copy of the alternative colors I explored, I guess we think alike. :D In the end I'm a big fan of orange so that won out.

One of the things I do with clients is explore different ideas, so if we got together we could do both a green and blue version, and of course play with stripes and wheels, flares or not, body mods, etc. should you want to explore those type things. Just hit me up when you get close to being ready for the rendering and we'll go over the process, I'd love to help out. Till then I'll keep an eye out for more project progress.

[Later-A-body]

Yes Ben, I will definitely keep you in the loop if I can swing the rendering.

[68Formula]

Love the early Mantas. And the drivetrain combo is a brilliant idea. Can't wait to see the finished product. Any ideas on the suspension upgrades?

[Later-A-body]

Looking at the possibility of a Corvette C4 front suspension if the original set up is an issue with the engine oil pan. The rear end has a factory 3-link with a panhard rod, so I would like to keep that in place by fabricating all the brackets and transferring that set up to a stronger rear diff such as a GM 8.5" 10 bolt, a Ford 8.0 or 8.8". I want a rear diff that is not too heavy though.I will narrow whatever rear end that I choose so I can fit a decent rear tire under the back.

[andrewb70]

Mustang guys use Explorer rear ends. One of the sides is shorter than the other, so they shorten the long side to match the short side and grab another short axle. They are 31 spline and would be indestructible in this application. I wouldn't use the Explorer brakes, but get some lightweight Wilwoods instead.

Andrew

[Cassius]

Lovely project! I had a -71 SR for a couple of years, sold it maybe 2 years ago to Poland (I live in Sweden) for ~8000€ https://www1.garaget.org/archive/4/3...47-2618982.jpg

Here in Europe these cars rarely get that much swapped in the front suspension, the original geometry is actually pretty damn good from the start! I even heard of a Porsche 911 that swaped in a Manta A front suspension since he felt it was better suited than the stock one. (An early 911). It's pretty easy to install a coilover instead of the stock spring/damper setup, they do get quite short with limited travel thou if one does not reconstruct the top of the crossmember to allow a longer unit. Lower control arms needs strengthening (boxing them usually is enough). Many install an extra swaybar to stiffen the front end since the original is part of the lower control arm.

The most common brake swap, atleast here in Sweden, is calipers and discs from Opel Rekord E 2.2. They are about 10" and vented, others use Volvo 240 hubs with custom steel bushings for the wheel bearings and the Volvo 4 pot front calipers mated to ~265mm vented discs. It also quite easy to use the Opel Omega 3000 front brakes which come in both 280 and 298mm diameter, the discs needs some machine work to fit while the calipers are bolt on.
For the rear end most use the Volvo 240 rear axle if they are going to push more than 300hp, otherwise the stock one will hold up fine. (The stock one can take 400+ as long as you stay away from hard launches with sticky tires).

However, all these parts are common "here" in Europe, stateside I'm guessing they will be quite hard to source.. Corvette parts sound like good alternative. Rear axle wise, the Volvo 240 was fairly common in the states aswell and had a Dana 33 rear axle, they came in two variants "1030" and "1031", the later has a bigger ring gear and is usually considered stronger. Both models have a a lot of options for gearing and limited slip differentials. I believe that the Cherokee used the same differentials as the Volvo axle so spares and parts should be easy enough to find stateside. They are maybe an inch wider than the stock axle so it a pretty good fit. Here in Sweden, the ones doing a lot of dragracing tend to put bigger things in when going past 6-650hp since they need to swap warped driveshafts every now and then when they reach those power levels.

If there is One thing I regret when fixing my car up it was that I didn't enlarge the wheel arches.. They are really small and sit pretty low on the Manta A. I had planned to use Ascona/Manta B arches all around but didn't take the time to do it. Just raising them a bit does a huge impact on how the car looks! Stock it resembles a toy car, with bigger, raised arches it actually starts to look like a sports car. Here's an example:



More on the "rat manta": https://www.opelgt.com/forums/member...-n-slow-2.html

They also look stellar with the ducktail enlarged and more defined. Think BMW E46 CSL rear wing style. Another thing I started to investigate was putting recessed Camaro Gen 2 or Charger -68 tail lights on it, thats something I belive could really lift the rear end of the car.

Another easy thing that really made a difference on my car was the front lip from a VW Golf GT1 Mk1 (not present on the pic above), the larger one that is in two pieces.

[Later-A-body]

Lovely project! I had a -71 SR for a couple of years, sold it maybe 2 years ago to Poland (I live in Sweden) for ~8000€ https://www1.garaget.org/archive/4/3...47-2618982.jpg

Here in Europe these cars rarely get that much swapped in the front suspension, the original geometry is actually pretty damn good from the start! I even heard of a Porsche 911 that swaped in a Manta A front suspension since he felt it was better suited than the stock one. (An early 911). It's pretty easy to install a coilover instead of the stock spring/damper setup, they do get quite short with limited travel thou if one does not reconstruct the top of the crossmember to allow a longer unit. Lower control arms needs strengthening (boxing them usually is enough). Many install an extra swaybar to stiffen the front end since the original is part of the lower control arm.

The most common brake swap, atleast here in Sweden, is calipers and discs from Opel Rekord E 2.2. They are about 10" and vented, others use Volvo 240 hubs with custom steel bushings for the wheel bearings and the Volvo 4 pot front calipers mated to ~265mm vented discs. It also quite easy to use the Opel Omega 3000 front brakes which come in both 280 and 298mm diameter, the discs needs some machine work to fit while the calipers are bolt on.
For the rear end most use the Volvo 240 rear axle if they are going to push more than 300hp, otherwise the stock one will hold up fine. (The stock one can take 400+ as long as you stay away from hard launches with sticky tires).

However, all these parts are common "here" in Europe, stateside I'm guessing they will be quite hard to source.. Corvette parts sound like good alternative. Rear axle wise, the Volvo 240 was fairly common in the states aswell and had a Dana 33 rear axle, they came in two variants "1030" and "1031", the later has a bigger ring gear and is usually considered stronger. Both models have a a lot of options for gearing and limited slip differentials. I believe that the Cherokee used the same differentials as the Volvo axle so spares and parts should be easy enough to find stateside. They are maybe an inch wider than the stock axle so it a pretty good fit. Here in Sweden, the ones doing a lot of dragracing tend to put bigger things in when going past 6-650hp since they need to swap warped driveshafts every now and then when they reach those power levels.

If there is One thing I regret when fixing my car up it was that I didn't enlarge the wheel arches.. They are really small and sit pretty low on the Manta A. I had planned to use Ascona/Manta B arches all around but didn't take the time to do it. Just raising them a bit does a huge impact on how the car looks! Stock it resembles a toy car, with bigger, raised arches it actually starts to look like a sports car. Here's an example:



More on the "rat manta": https://www.opelgt.com/forums/member...-n-slow-2.html

They also look stellar with the ducktail enlarged and more defined. Think BMW E46 CSL rear wing style. Another thing I started to investigate was putting recessed Camaro Gen 2 or Charger -68 tail lights on it, thats something I belive could really lift the rear end of the car.

Another easy thing that really made a difference on my car was the front lip from a VW Golf GT1 Mk1 (not present on the pic above), the larger one that is in two pieces.

Cassius
Thank you for all the information on the Manta. I have seen some threads on people using the Volvo 240 rear axles in these cars as well. I do also agree with you on the wheel openings. It would be nice to open them up a little, but I am not a fan of fender flares. Maybe just a little bit raised would help. I was looking at the idea of '70-'81 Camaro tail lights, but I may be able to get a set of NOS Manta parts so I will see. I do admit I would rather stick with the original suspension and fabricate a coil-over set up. It will depend on cost, modified stock vs C4. The Corvette set up would make the brake equation much easier. I see you modified the front bumper and pulled it in. I do plan to follow that idea on both front and rear bumpers. Thanks again for the tips.

[Cassius]

The front bumper on my car was actually stock, not modified It does look quite flush in that pic thou.

Flares aren't needed, some cars rock them, other don't It was just the best pic I could find ;) The wheel openings on Ascona B and Manta B have a slightly different shape and are a tad bigger. I believe they would fit perfectly! But they will surely be difficult to source in the states. In europe there is replacement parts for the rears, the front you would need to source the whole front fenders.. They have the same type of design as the originals so it's likely only true purists would notice the difference! I'm sure there are other cars that could work as donors for these aswell. I once did a photoshop with those flares.. just can't find it now :/

[JJK]

……...a stronger rear diff such as a GM 8.5" 10 bolt, a Ford 8.0 or 8.8". I want a rear diff that is not too heavy though.I will narrow whatever rear end that I choose so I can fit a decent rear tire under the back.

If you really want to get outside the box, here's a little known donor candidate. A DJ-5 Jeep (that's a 2wd postal Jeep), circa 1970, has a Dana 44 with 3.73 gears and Trac-Lok, and it's 49" flange to flange. That's what a supremely-qualified builder put behind a Honda S2000 engine & 6 speed in a '66 Sunbeam on another forum.

[andrewb70]

If you really want to get outside the box, here's a little known donor candidate. A DJ-5 Jeep (that's a 2wd postal Jeep), circa 1970, has a Dana 44 with 3.73 gears and Trac-Lok, and it's 49" flange to flange. That's what a supremely-qualified builder put behind a Honda S2000 engine & 6 speed in a '66 Sunbeam on another forum.

A Dana 44 would be plenty strong!!!

I just did a search on car-parts.com and there are a total of three rear ends listed. Two of them are in California, at this place:

http://www.jwjeep.com

Their inventory numbers, 7M1382 and 2E0058, one has 48k miles, the other 56k miles, both at $550. The first one shows a 3.73 gear and the other shows 4.89 gear.

Andrew

[langleylad]

Mustang guys use Explorer rear ends. One of the sides is shorter than the other, so they shorten the long side to match the short side and grab another short axle. They are 31 spline and would be indestructible in this application. I wouldn't use the Explorer brakes, but get some lightweight Wilwoods instead.

Andrew

I wasn't able to find a aftermarket performance brake kit that bolts to an Explorer 8.8 . I went with Powerstop brake pieces for my build.

[Later-A-body]

A Dana 44 would be plenty strong!!!

I just did a search on car-parts.com and there are a total of three rear ends listed. Two of them are in California, at this place:

http://www.jwjeep.com

Their inventory numbers, 7M1382 and 2E0058, one has 48k miles, the other 56k miles, both at $550. The first one shows a 3.73 gear and the other shows 4.89 gear.

Andrew

Damn...we were just up there to pick up the Manta. I will look into it. Thanks Andrew. It sounds like a great swap candidate. I wonder though if there is a rear disc brake kit available for that rear diff? If so let me know, As for the gears, I would take the 3.73, but I wasn't planning on that steep of a gear ratio. Since the car will make at least 300 hp, and weighs 2150-2300 pounds, I figured I won't need more than a 3.42 gear. Plus the tire diameter dictates this since they probably will be around 24". I'd like to keep the revs down on the freeway. The trans I have has a .73 OD 5th gear.

[JJK]

Per the aforementioned forum (where the engine/trans were from an S2000): ".....I had the axles reworked at Dutchman's to fit the S2000 rotors. They are 5x4.5" and just happen to be the same pattern as the wheels you may have noticed in some of the previous pics. While at Dutchman's I had new bearings and retainers pressed on."

[Later-A-body]

I haven't had too much going on with the Manta lately, but was able to pick up some seats for the car. I decided to go to one of the local Pick-Your-Part yards. I found a 2008 Mazda RX-8 with some really nice seats. This car was on my list of potential donor cars because I like the seats they have. I think I may have ruined somebody's day because both seats were already unbolted as if someone was coming back for them. I literally lifted them out without using a wrench. They are manual seats, fairly lightweight with black / grey leather. I had to measure them to see if they would work, and luckily they fit great. I will need to cut out a small box located on each side of the floor to allow the seats to sit flat. This allows me to keep this project on a budget. I will eventually reupholster them and add some more bolstering, but these are are in real good condition for where I'm at with the car now. Total cost was $103.00.

[andrewb70]

The seats look great!

Andrew

[SRD art]

Congrats on the seats! I also grabbed some Mazda seats for my car, from a '99 MX-3. I've had them in the car for several years and they're very supportive and comfortable. Even having driven the distance from Utah to Georgia twice no complaints on feeling stiff or uncomfortable. I spoke to a custom upholsterer once and he said factory seats tend to be better than aftermarket- they're engineered better, are stronger, longer lasting, and overall feel better than even the major popular seats that a lot of Pro Touring guys use. My son bought after market seats for his car and my opinion mine feel much more comfortable. I'd say you got a good score there.

Good luck with axle hunting!

[Later-A-body]

Congrats on the seats! I also grabbed some Mazda seats for my car, from a '99 MX-3. I've had them in the car for several years and they're very supportive and comfortable. Even having driven the distance from Utah to Georgia twice no complaints on feeling stiff or uncomfortable. I spoke to a custom upholsterer once and he said factory seats tend to be better than aftermarket- they're engineered better, are stronger, longer lasting, and overall feel better than even the major popular seats that a lot of Pro Touring guys use. My son bought after market seats for his car and my opinion mine feel much more comfortable. I'd say you got a good score there.

Good luck with axle hunting!

Very much in agreement. I have tried some aftermarket seats and found them to be uncomfortable or not well constructed unless your spending Recaro money. I have 2011 Honda CRZ seats in my Grand Am, and my fathers '65 GTO has Saab seats, (both from the junkyard and redone).

[Later-A-body]

It has been a few months since I posted on the Manta build, and that is because I have done absolutely nothing since then. It would be great to report that I have been working day and night on this project, but not the case. I have been able to purchase a lot of parts needed in anticipation of the disassembly process. I was able to buy a new windshield, NOS weatherstripping and trim, a complete front and rear suspension parts set up including HD ball joints, tie rods, control arm bushings, etc. After doing more research on the car, I realized these cars have an excellent reputation for having a well designed front and rear suspension, so I will be staying with the factory set up and upgrading components such as custom made front and rear coil springs, or possibly a coil-over set up in the front. One area I have decided not to spend money on is the factory rear differential. I understand these can handle up to 250 HP if built, but not much more. So I am looking at swapping in a Ford 8". And there is a good reason I want an 8" Ford. They are lightweight and can handle much more power than this car will produce. The Ford 9" and 8.8 are way too heavy, at least 50-75 pounds more than the 8", and will add unnecessary weight to the car. Plus it's overkill. I would rather spend the money on the Ford than invest in the Opel diff and possibly have a failure. The 8" can easily handle 450 HP. The Opel will not make more than 325 HP. I also get to pick whatever rear disc brake kit I want. Gears, posi, all easy to get. I will need to swap the rear trailing arms over to the new diff. The Manta has a 3.44 rear gear ratio. I plan to leave the stock rear end in the car for now in order to see what I think of the 3.44's. The car is so light, I feel that I will not need a higher numerical ratio since the 5-speed trans ratios are fairly steep....3.75 1st gear, and the power level vs a 2200 pound car. Probably looking at a 3.25 or 3.40 ring and pinion when swapped. I also want to find rear disc set up that uses a small rotor diameter such as 9.5-10" rotor for the rear. I am planning an 11" rotor set up up front. Wheel size will be 15" so big rotors are not needed and wont fit anyway. I am open to suggestions as always. Hopefully I will have more updates to post soon.