I bought a sport quiet muffler and it has 4 inlets but my heat exchangers have 2 outlets with a different bolt pattern. Are my heat exchangers non-standard or did I buy the wrong muffler?
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Looks like you have factory '75-76 heat exchangers which has different outlets.

You can either find a muffler to fit the later style exhaust or upgrade to SS heat exchangers in the earlier variety.

Your heat exchangers are of the 75-76 model whereas your muffler is an earlier one. I cannot establish from the muffler flange if this is a 2.0 or a 1.7 muffler.

Is this muffler from Ben @mb911 ? I am sure he will chime in.

So, in order to use this muffler, you will need the right heat exchangers (70-73 for 1.7 or 73-74 for 2.0). The good news is that the earlier ones will bolt on to your engine.

Good luck, I am sure others will give more input!

It is one of Ben’s mufflers but I bought it used. I’m pretty sure it was for a 1.7 or 1.8 because I knew there was a difference between 1.7/1.8 and 2.0. I didn’t realize I would need new heat exchangers because my car is a 1975. Thanks for the explanation

Its also not just the heat exchangers that are different but all the heat ducting underneath too FYI

The good news

If you back date the heat exchangers your car will have more power
The 75 style are restrictive

Your muffler choises will be limited but WAY cheaper than backdating the heat exchangers and ALL that goes with that. Plus you get to skip the joys of exhaust stud nuts. If things go sideways, it's a major headache. The bolt hole spacing in the flanges differs 1.7/1.8 vs 2.0 early style heat exchangers. The hanger too. There are 3 versions, HE specific.

THAT ^^^

May run a little cooler too

I just looked at new SSI heat exchangers and found that they’re over $1,900! Yikes!

that is xee!
glad i bought some 30 years ago when relatively they seemed affordable.
even in 94 i found ads in old mags at $190 a side. that would be about $400 a side in todays money if straight inflation.

maybe you can rustle up a second hand set. they are durable so it should be possible to find some in good condition.

i could be wrong but i think its very difficult to buy any kind of final muffler set up for the cat cars of 75 on. all i have seen are the standard vw mufflers (repro like dansk or old stock if you are lucky) or the muffler you have. all have twin outlets. my problem was a headache here in aus as you can't get a 914 specific muffler at all, got to ship in at great cost. but you can adapt a kombi muffler. but again thats got twin outlets.

Here is what a set of 1.7/1.8 OE HE look like...IF you make the drive to Raleigh I can set a price too good to pass up.