I have a -62 Valiant project that is lacking the exhaust alltogether. I've noticed that many people here recommend enlarging the exhaust size, but they are usually talking about more or less "built" engines. How about a pretty much stock slant (170 or 225)?

I'm quite happy with the way my -65 Valiant sounds (stock engine, stock exhaust), so I'm not looking for changes for the sake of sound (the moped boys here take care of the sound department for all of us), but if there is something to be gained in milage or power, I might be interested. I believe the company that makes the exhausts (for slants among others) here in Finland makes the pipes in the size you like.

Any ideas or experience? Also, does it need to be the same size all the way or should the tail pipe be smaller diameter? And the muffler? I have always just bought the stock size for my -65, so this is unfamiliar territory for me.

For a single exhaust run 2 1/4 inch (57.15mm) pipe to the muffler and 2 inch (50.8 mm) pipe after the muffler. It will increase flow which will increase economy and power.

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Casually looking for a Clifford hyperpak intake for cheap.

Answering a bit your question about performance, I used to have a '98 3.3 flex fuel Grand Caravan. Being EFI and with sensors everywhere it is a different beast from our slant sixes but I had the silencer exchanged for a "flow master" type and the pipe from there onwards expanded by 1/4 inch.
To me the most noticeable improvements were related to acceleration and highway mileage. I found that the motor would rev faster allowing me to pass others with less effort. I'm guessing it has to do with exhaust leaving the system faster, thus relieving pressure to the pistons at the exhaust cycle. Mileage improved by 2-4 miles. Maybe has to do with less exhaust having chance to enter throttle body through the egr valve?

It should roughly translate to our sl6...

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'71 Dodge Dart, old Chrysler Corp.
My slant 6 will never, ever, be unrepairable

Thanks for the input. So far "bigger is better". Any conflicting opinions? Reminder: this is a stock engine. The stock pipe I have on my -65 would seem to be 1 3/4" (it's measured on the outside, right?) all the way.

How about sound? I'd prefer keeping it down, it's fine as it is. Will increasing the pipe size automatically increase sound (if the muffler doesn't change except for the in- and outholes)?

You will get a slight increase in sound with a 2.25" exhaust, but if you have a good muffler, it should not be much. I also recommend 2.25" single exhaust, from the manifold all the way out the back.

Happy Slanting!

Lou

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Home of Slant6-powered fun machines since 1988

When Chrysler made the "Super Six" package available for the slant six, 2 1/4 inch pipe was the stock exhaust size with that package. Using a good muffler will keep your engine quiet.

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Casually looking for a Clifford hyperpak intake for cheap.

Another vote for a bigger, thanks Dart270.

Does anyone have experience with a 62-65 Valiant and an enlarged front pipe? Even the stock pipe is a pretty tight fit in my car. Is there enough room in the engine bay, so that it doesn't start hitting any part of steering/suspension/clutch linkage? I just heard from the company that makes the exhaust and they expressed the same concern.

FWIW, my SuperSix has 2-1/4" all the way, with a stock-style Maremount muffler, and it droned quite badly. I installed a tail pipe resonator that slightly reduced the drone, but did not eliminate it.

Seat of the pants performance with the otherwise essentially stock engine was small, but noticeable, and there was no measurable difference in gas mileage.

The "Super Six" exhaust also had a resonator after the muffler.

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Casually looking for a Clifford hyperpak intake for cheap.

Should easily be able to fit a 2 1/4" pipe through there. I have 3 header tubes going through that same real estate.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Yes, my convertible is a '64. I bought one of the pre-made pipes and it hit the torsion bar when starting and accelerating. I put a 1/4" dent in the pipe and that eliminated most of the contact, but I'm going to take it in this winter and have it slightly rerouted.

Mine is an automatic, so I can't speak to manual models.

Yes you can go too big! 2 1/4" is more than enough for a stock slant. The biggest restriction is in the manifold itself!

I have 2 1/4" on mine from the manifold to the muffler and 2" from the muffler to the bumper. Cheap "turbo" muffler and it breathes great! Has a real nice mellow tone to it and almost no interior resonance.

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"if it aint broke, fix it till it is"
78 Plymouth Volare Super Six wagon
89 Volkswagen Golf GTI 16v
92 Chevrolet K1500 5.7
98 Ford Escort ZX2 zetech

Thanks everybody. It helps a lot to hear experiences and opinions.

It would seem 2" is the biggest the company will make for -62 (or-65). It's not a big increase in diameter (12,5%), but perhaps it might make a good start.

Is it better to have the same size all the way, or smaller size at the rear? They said the stock was (according to their knowledge) 45mm froont and 38mm rear, but that they usually make it 45 all the way, when making stock. I noticed some of you had same size all the way while others not. Having same size might be more convenient perhaps, but is there a benefit to having smaller diameter rear pipe?

BTW, According to them, the whole thing from end-to-end is same between -62 and -65. This surprises me a little. My books say the front pipe is the same, but the muffler and rear pipe have different numbers and with the changes between 62-63, I'd expect there to be some difference somewhere...

The pipe diameter can decrease after the muffler because the exhaust gasses have cooled by that point in the system and do not take up the same volume. Have a reduction in pipe size after the muffler makes the exhaust quieter.

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Casually looking for a Clifford hyperpak intake for cheap.

Thanks Reed, that sounds very good. I've been a bit afraid of increasing pipe size, as it seems to increase sound too. A silent car is more in my style.