914 Exhaust Leak, 914 backfires on decel Options

[Nemo914]

Just found this site. Wow. Great info. I have had my 72 914 for 30 yrs. Restored it 10 yrs ago. Still all original--fuel injected. Since then, it has been driven very little (unfortunately). In the last year, I have started getting a popping or backfire on decceleration. It is getting worse and worse. The car drives great and strong other than this annoying habbit. I heard about the exhuast leak possibility and put my had under the car while it was running. I can feel airflow under each heat-exchanger to head connection! Is this normal? I don't understand how ALL could be leaking. I used the copper rings when I connected them 10 yrs ago. Could they be going bad?? I need an expert!!

[Part Pricer]

I will search some other reasons why it might be backfiring before I rip out the exhaust system.

Don't waste your time. The exhaust is the most likely culprit and you know that you already have a problem (broken stud) so start there.

First off, get a can of PB Blaster and soak any and all of the bolts that you will encounter in the exhaust system. Then, start working from the back of the car forward (you really need to do it this way anyway).

Remove the muffler and exhaust from the heat exchangers. This involves six bolts and is pretty easy to do. After you drop these items check them very carefully for rust and holes. Holes even this far back in the system can cause a backfire problem. If you find any problems here, come back and tell us. We can then have a week-long discussion about what muffler you should buy. (IMG:style_emoticons/default/rolleyes.gif) Even if everything is good, you will need to buy two muffler gaskets for reassembly. I would also recommend that you buy new bolts and washers.

Even if you found a problem at the rear, we are not done yet. You mention that these are the original heat exchangers. I would put these at the top of the list of suspects. You live in the Northeast and on the ocean, so I would think that your 32 year-old HEs might have a problem. You are going to have to go in and drop the heat exchangers. There are two things that will make this job a little easier, a torch and a stud puller. Use the torch to apply heat to the bolts that are still there. Use the torch and stud puller to remove the one that is already broken. Drop the HEs and inspect for rust and holes. Replace as necessary. Don't forget that you are going to need new copper gaskets. Those shouldn't be reused. You should also get 8 new exhaust nuts.

If you need to replace them, I would definitely go with stainless steel heat exchangers. I think that you will need to find a good used set for your car.

Now, as far as replacing that broken stud, I'll let other chime in as to what is best.

Assembly is the reverse of disassembly. (IMG:style_emoticons/default/tongue.gif)