Rerouting '79 exhaust

[kmoses]

After trying for two weeks to get my '79 exhaust system rerouted using a very early 4-2 exhaust manifold (4151276 used on '67 to '71), it now fits! The biggest problem was locating a down pipe that would clear everything and allow the rest of the exhaust system to tuck in properly. It fits so well I may even be able to avoid melting my emergency brake cable.

[argonaut]

That looks great! Nice work! It looks a lot higher and tighter than the stock exhaust with catalytic converter that I just replaced on my 81.

How do you like that nice quiet whisper of the stock exhaust!?

[klweimer]

Really nice work.

[kmoses]

I will let you know how it sounds when I get it running. I am just hooking everything back up, routing control and electrical cables, fuel hoses ect.. I've had the car stripped for rebuild/refurbish/repair for almost year and I hope to have it on the road by the third week in May which will be one full year since this project started.

[argonaut]

Which down pipe did you end up using?

[kmoses]

I ended up buying a used factory 1800cc down pipe purchased from Midwest-Bayless (the factory down pipe is stainles steel with .109" thick tube). Because I used an early spider 4-2 exhaust manifold and not one from a 1800cc engine, (the early 4-2 was all I could find) there were problems with clearance (tie rod, rear transmission mount bracket, pinch weld at bottom of transmission tunnel). I ended up cutting the welds that hold the down pipes to the flange, making a new flange from 1/2" steel, bolting the flange and pipes back in the correct position, tack welding them and then welding the tubes inside the flange after removing the down pipe assembly. It only took a small movement inside the flange (about .070") to make everything fit perfectly. Other than that, it was a direct bolt on!

[argonaut]

Okay, that makes sense. I know the 1.6l and 1.8l engines had a shorter deck height and thus a shorter 4-bolt downpipe. To my knowledge 78-79 used a longer 4-bolt downpipe, but they were routed over the the side of the car to accommodate the catalytic converter, rather than down the center of the car. Then the 80+ cars used the longer 6-bolt manifold, instead of a longer downpipe to accommodate the taller deck height.

So 2.0L with a short 4-bolt manifold would need a custom lengthened or tweaked downpipe (like you did) to run down the center. This is what I would like to do with my 75, that is why i was curious.

[kmoses]

The rest of the exhaust is the AR performance center pipe and rear muffler that has a 2" OD from the down pipe back (EX7-423-Z and EX8-427-Z). I also added and additional clamp at the back of the transmission to the rear of the down pipe like the early cars have.

[scampbel98]

Nice work. Do you know the Midwest part number?
Are you saying you cut off a 6 bolt flange and used a 4 bolt?

[kmoses]

The down pipe I used from Midwest-Bayless is [SKU: 4310530-U8] 2-1 Downpipe 1.6L-1.8L Fiat 124 Spider it was a OE used unit. The top flange is a 4-bolt and the bottom connection is a slip fit to the center section. I was also able to make the same modification to a '73-'74 downpipe from AR [SKU: EX5-474 ] and get it to bolt up to the early 4-2 exhaust manifold and clear everything as shown in the following photos.






I added a two bolt flange to the center section to allow removal of the downpipe without removal of the center section or rear muffler.

[Nanonevol]

Confused. This is a different car?

[kmoses]

Same car I've been working on for almost a year, why do you ask?

[scampbel98]

Ahh, so you went down the middle. I've got a 4-2-1 setup, but it's a 4-bot and not 6-bolt. The factory one was a 4:1 Federal with 4-bolt flange for the catalytic converter (gotta keep it for TN). The downpipe I have now turns hard to the side of the car, hits the cross member and the steering arm thingy.

I had to massage the downpipe a bit with a hammer to clear the steering. I'll shoot pics in a bit.

[Nanonevol]

Just that you mentioned 2 downpipes, one from Bayless one from A/R...

[kmoses]

Yea, I ordered a complete exhaust from AR and the down pipe did not fit well. I then ordered a used OE down pipe from Midwest-Bayless that fit better but was still hitting in places. I then modified the OE down pipe so every thing cleared and fit. I then applied the same modifications to the AR down pipe to see if it would fit, like the OE and it did. The AR was going to be my spare but I sold it with an extra 4-2 manifold as a "kit" to a member who wanted to route their 2L exhaust down the car center and have the down pipe clear properly.