Exhaust fitting on Backdate 1976

[Philippus]

Hi, I am currently converting a 1976 911 with a 2.7L engine into a backdate.
The rear bumper is made of fiberglass in RSR style.

Unfortunately, the exhaust is in the way; it is a stainless steel exhaust from Cargraphic.
I hadn't even thought that it might be too big.
Do I need to use a different muffler for a backdate bumper, or are there other options?

Pictures attached.

Thanks!


Best regards,
Philipp

[dwelle]

it's quite crooked, it sits proud on the drivers side. if you can solve for that, it should fit fine.

i have a backdated '76 with SSI's and any of the mufflers i've fitted have cleared. i did have to trim the center/license plate bracket ever so slightly to clear the corners of the M&K i currently run. i think a banana would clear fine. it is tight either way...

[Philippus]

Originally Posted by dwelle

it's quite crooked, it sits proud on the drivers side. if you can solve for that, it should fit fine.

i have a backdated '76 with SSI's and any of the mufflers i've fitted have cleared. i did have to trim the center/license plate bracket ever so slightly to clear the corners of the M&K i currently run. i think a banana would clear fine. it is tight either way...

Thank you!

The "banana" is the muffler from the early 911, right?

How much space do you think should be between the muffler and the glass fiber bumper?

Thank you!

[mepstein]

Originally Posted by Philippus

Thank you!

The "banana" is the muffler from the early 911, right?

How much space do you think should be between the muffler and the glass fiber bumper?

Thank you!

As much space as possible. I’ve seen at least two cars melt the glass bumper.

[EC900]

Not too many 2.7’s have that HE configuration, stock for the SC. Someone put that system together as a set to replace the thermal reactors ?

I don’t care for those 930.211.025.00 heat exchangers on a 2.7, although they fit and have been put on that engine from the factory, the crossover and the pre-muffler or cat pipe probably work fine with a stock muffler - but to me, these components seemed to be just too close to the engine adding to heat related problems.

Anyway, fabricating the front pre-muffler (or cat pipe) shorter or FabSpeed and others have a bypass straight pipe but the issue and result may be same since it’s the aftermarket muffler you have. Measurements and flanges will be critical if a custom shop can weld something up.

In all it may be easier just to get a different set of used HE’s for the 2.7 (example:911.211.022.00) but these will require a 2-inlet muffler (stock). So you’ll have to decide is that exhaust muffler necessary for sound or that it’s there, or are you willing to return it to stock configuration.

Your backdate is going to look good, then ponder spending another $4k for a good sounding and proper fitting SSI’s may be your next dilemma.

[RarlyL8]

We've done a lot of these and have mufflers designed for your application.
As previously stated, the muffler you have installed does not sit properly on plane with the bumper. Another problem is the G-body mufflers will not fit the F-body bumper. Best you can do if you wish to keep that muffler is to straighten out the muffler orientation then graft on a custom tailpipe.
If you would like a different muffler what we offer are versions of our single and dual out Sport mufflers designed to fit back dated G-bodies.

[Philippus]

Thank you all!

The problem is that I live in Germany and the car needs to undergo a TÜV inspection, which means it has to be checked by an expert every two years. All exhaust parts must either have a certificate or be original parts.
The current aftermarket exhaust has a certificate, which is why I would like to keep it.

I will try to see if I can align it. If that doesn't work, I will look for another solution.

When I switch to the 911.211.022.00 with a 2-inlet muffler, it will fit with the backdate bumper, right?

[EC900]

It’s your current muffler that is be the problem, maybe it’s for a later SC, maybe oversized, race design…I don’t know, even still it shouldn’t be so crooked, maybe the muffler flange can be cut and fabricated to reduce its length, that’s the fast way to go.
I take it this muffler also fit crooked on your original bumper.
But again as stated by @RarlyL8 the F-bumper on a G-body have issues.

So going the route of complete exhaust change over may not solve a “too close” fitment issue to avoid heat damage to the fiberglass. Btw, you have the thin header flanges so any replacements will have to be such.

I’ll post this Old Pelican ForSale thread on what your system looks like laid out.
Notice the “straight pipe” in place of the pre-muffler (or catalytic converter if yours is U.S. California equipped) and the diameter of the oem stock muffler. Your current muffler seems larger. The straight pipe may not be TUV acceptable, so check on that if you were wanting to replace.

FS: 911 SC Exhaust Heat Exchangers and Muffler

I don’t think there’s anything to adjust other than that aftermarket muffler flange tail section if it was altered before. It’s a flange-to-flange set up, not wiggle room.

You may go out and seek a stock SC muffler - maybe some shop has one laying around that will allow you to try fitting it and then you can check your clearances with the new bumper on before going through on any replacing, cutting, welding, spending time and money experimenting.

[RarlyL8]

The tailpipe location and angle are different on a G-body vs F-body. You will also need to cut/weld a new shorter tailpipe at a different angle. Some of the aftermarket hotdog mufflers are larger than OE which may be part of the fitment issue. What I am seeing in the pictures looks like a 911SC pre-muffler, not a catalytic converter.