My 75 Manta small bumper conversion
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Thread: My 75 Manta small bumper conversion

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    Opeler oliper's Avatar
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    My 75 Manta small bumper conversion

    Hello everyone, I wanted to post some pics on my small bumper conversion on my fuel injected 75 Manta. I'll start off with a before/after pic of the rear of the Manta. Please note that I will remove the remaining bits of the big bumper hardware and close the holes. I thought this picture illustrates nicely how the small bumpers were mounted much higher.
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    Member Genemak1's Avatar
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    Ah yes, now that's much better!
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    Opeler opelgtboy70's Avatar
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    What are you using for the rear bumper?

    Karl

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    Opeler oliper's Avatar
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    Quote Originally Posted by opelgtboy70 View Post
    What are you using for the rear bumper?

    Karl
    Bumper came from a 73 Manta (someone painted it black). No mods to bumper hardware were needed. The 73 and earlier Mantas had "dimples" where the bumpers are attached to the quarter panel and fender but I got a good fit by bending the brackets just a little bit. Very straight forward.
    Needed to do some modifications to mount the front bumper, pictures to follow.

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    Front bumper

    If you cut off the tubes for the bumper shocks you will find the early mounting holes.
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    UFOpel Investigator Site Supporter My location Aardvaark (R.I.P.)'s Avatar
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    I like both big, small and no bumpers on them. So nice look.
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    -Mark
    '75 Manta
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    this Opel Manta. I expect big returns.😅
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    Tennessean Site Supporter My location hrcollinsjr's Avatar
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    Quote Originally Posted by opelgtboy70 View Post
    What are you using for the rear bumper?

    Karl
    '73 bumpers had a rubber strip on them, if that is why it looks different to you.

    Harold

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    Resident Curmudgeon My location Opelmel's Avatar
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    Quote Originally Posted by Aardvaark View Post
    I like both big, small and no bumpers on them. So nice look.
    I prefer at least SOME bumpers on them. Never did like the Twiggy look.



    Oh, you were referring to Mantas. Never mind then......

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    Opeler oliper's Avatar
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    Progress!! A couple of more pictures of my small bumper/GT/E conversion
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    Aardvaark (R.I.P.) and Wrathe like this.

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    Can anyone tell me the dimensions of a 72 Manta bumper? Width inside & outside the horns, "thickness", and width of the basic body (front to rear)? Thanks, Doug

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    Member My location Gordy's Avatar
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    Quote Originally Posted by oliper View Post
    Progress!! A couple of more pictures of my small bumper/GT/E conversion
    I wonder if moving the license plate down below the bumper like the early Mantas had would give the tail panel an even cleaner look

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    This photo of my GT with a lowered license may give you another view to help you make up your mind. It will also let you know why I would like the '72 Manta (chrome) bumper dimensions.

    Doug
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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Quote Originally Posted by slracer View Post
    Can anyone tell me the dimensions of a 72 Manta bumper? Width inside & outside the horns, "thickness", and width of the basic body (front to rear)? Thanks, Doug
    Tomorrow when I'm working in my barn again I can measure one up. I can tell you that the Manta body is certainly wider than a GT body, by at least a couple of inches.
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    Thanks, Bob! I've cut the GT FRONT bumper into 6 useable pieces making one fit the rear so to narrow a Manta rear should be child's play (which is good because my wife says I never grew up!).

    Doug

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    Senior Member dallasmanta's Avatar
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    i can see where you would want the skinny bumpers to show off the GTE air dam, and it looks good on your car. Personally having had both types of bumpers and having suffered damage to the skinny ones in parking situations where some one had pushed in the bumpers I will take the big ones any day. Ron

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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Quote Originally Posted by slracer View Post
    Can anyone tell me the dimensions of a 72 Manta bumper? Width inside & outside the horns, "thickness", and width of the basic body (front to rear)? Thanks, Doug
    Doug, I get roughly 58.5" width measures inside the bumper 'returns'. Each return is about 6.5" long or so (inside). Height of the bumper is about 2-7/8", depth is about 1-7/8".

    Keep in mind a Manta tail panel is slightly convex so the bumper is appropriately radiused to match the contour.

    1971-1973 Model 50 Opels (Manta, Ascona, and Ascona wagon) all share the same rear bumper design. The 1973 versions have a rubber strip added therefore have additional holes.
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    Bob, Thanks for the dimensions! Looking at your rafter shot, I'd guess about 1-1/2 to 2 inches max "convexity". The 1-7/8" depth is somewhat surprising, but with the GT more like 3 says I could add a strip to the top surface to make it fit the concave surface of the rear panel and still not be out of proportion. I'll work with these a bit. Is the cross section pretty rectangular with a very slightly convex face? that is what I see on the pics.

    Thanks for taking the time to measure! -- Doug

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    Project 1450 supporter... Site Supporter My location RallyBob's Avatar
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    Quote Originally Posted by slracer View Post
    Is the cross section pretty rectangular with a very slightly convex face? that is what I see on the pics.

    Thanks for taking the time to measure! -- Doug
    It's actually an asymmetrical shape. Top is shorter than the bottom (in cross section), then the face is a small flat, then the bottoms is more angled and therefore longer than the top. I had an old bent bumper somewhere. If I can find it I'll cut it in half to expose the cross section.

    Found a pic of an Ascona rear bumper (same as Manta).
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    Last edited by RallyBob; 12-09-2015 at 06:55 PM. Reason: Added pic
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    '70 GT 'Bonnie', '71 Ascona 4-dr turbo - winter beater, '71 Ascona 4-dr 'Turd' - rallycar, '72 Manta Rallye - hillclimb car, '72 Ascona wagon - 'Red', '72 Manta - caged street car, '73 Manta Luxus, '73 Ascona 2-dr, '74 Ascona 2-dr - Project X, '74 Manta Luxus - factory sunroof, '74 Manta ITB racecar, '75 Manta, '75 Sportwagon, '75 Manta - racecar

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    Quote Originally Posted by RallyBob View Post
    It's actually an asymmetrical shape. Top is shorter than the bottom (in cross section), then the face is a small flat, then the bottoms is more angled and therefore longer than the top. I had an old bent bumper somewhere. If I can find it I'll cut it in half to expose the cross section.

    Found a pic of an Ascona rear bumper (same as Manta).
    OK, It appears to be a GT bumper where the designer could only draw straight lines. Did some comparing to the GT and it is not a bad fit. Body to body at the attach line is 52" so add 1/2 on each side for the gap and 53" inside would work. If the convex isn't too bad, 1 cut either side of centerline should keep the curve and stay "smooth". The 2-7/8 inch height is 1-7/8 on the GT (front) bumper, so an additional +/- 1/2 inch there means nothing as there is nothing it has to fit in that direction. I am going to add about 3/4 inch to the 1-3/4 inch depth (to better fit the concave rear panel) so it will be about 2-1/2 inches depth on the top vs 1-7/8 for the Manta, but the convex mated to the rear panel would probably end up being about 2-3/4 to 3 inches. That may require a "fitting" of the bottom surface to the rear panel also. I have about 10 inches of return to work with, but 6-1/2 doesn't look too bad, but I would need to see the angle of the Manta at the turn as the GT is well off from 90 degrees.

    All in all, I think it would work as a fall back. I should know within a week if I will need to change plans. Is one of those rafter queens of yours available?

    Thanks again for the effort. -- Doug

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    Opeler oliper's Avatar
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    Finally done with the bumper conversion. Here are a few more pictures of my '75 Manta. Removing all the big bumper related hardware and closing the resulting holes were a bit of a challenge for me as I don't really know what I'm doing. But I'm pretty happy with the results.
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