Emissions Reduction on 1964 Plymouth Valiant

I have a buddy with a 1964 Plymouth Valiant with a slant six, the exhaust pipe is paper thin and needs to be replaced. We were wondering if we could use a catalytic converter or if the higher HC and CO levels on the old car would cause it to burn up and or plug.

I wouldn’t, for the reasons you say ('64 probably puts out LOTS of HC and CO), and because the Valiant’s not built to handle the heat a cat gives off. Better to put the time and effort into making sure it’s in tune, including (I think) valve adjustment. How many miles on it?

Just over 80,000. He doesn’t know jack about cars so I’ve been helping him getting it tuned, replaced the cap, rotor, points, etc. set the timing to factor spec of 5 deg adv, rebuilt the carburetor and a few other things. It’s really running great. Supposedly the previous owner rebuilt the head not too long ago (we’re assuming with hardened valves and valve seats) so we’re pretty happy. I was thinking about running the timing more advanced, say 10 deg to see if it would help mpg but haven’t had time to test it out, not sure if it would be worth it or not.

No, sorry, but adding a catalytic converter won’t help anything, and will cause more problems than it solves.

You’d need O2 sensors, and a computer, and fuel injection, etc, etc, etc. Forget it.

Leave the exhaust system as it is. Replace what needs to be replaced, but don’t add a catalytic converter.

A '64 Valiant with a slant six is one of the most reliable vehicles on the planet (I’ve owned several '63 Dodge Darts, same vehicle), but, as good as it is, it will NEVER be a modern vehicle, and you can’t transform it into one unless you, or the owner, are willing to spend HUGE amounts of money.

I suggest you stick with the factory timing and live with the mpg you get. I was never too disappointed with the mpg on my Darts.

If the owner cares that much about mpg he/she should consider a different vehicle.

C’mon, a 64 Valiant is never going to be a Prius. It won’t even equal a modern Camry, or Sebring.

You can’t make this car into something it isn’t.

Here is the best way to time these. Start with the factory specs, then advance 2 degrees at a time until you hear a slight ping when accelerating from about 40 mph in high gear or drive as hard as you can without the automatic downshifting, When you hear ping back off 2 degrees.

“…or if the higher HC and CO levels on the old car would cause it to burn up and or plug.”

Yes, this is what would happen. I don’t know if it would be a couple of weeks or a couple of years but a converter would definitely not last long on an otherwise unmodified pre-smog car.

The best thing you can do is just be extra dilligent about keeping the engine in tune. I’d check the dwell, timing and idle mixture at every oil change and check the plug gap every other. Obviously these old cars are never going to be as clean as newer cars, but if you keep them in tune they shouldn’t be noticably polluting.

It won’t even equal a '74 Valiant in terms of air pollution.

Converters can be used without the addition of fuel injection, O2 sensors, computers, and whatnot. This was done for years before ECC controlled carburetors and FI came along.

I do agree that it’s pretty much a waste of time though and you’re better off keeping it properly tuned up along with advancing the timing a few degrees.

Sounds like you’re on top of things. I had a '72 Duster with the slant 6, bought it used in '74 with 45k miles, sold it to friend in '81 with 130k miles, never had any engine problems, burned no oil. I would recommend you get a dwell/tach if you don’t have one, makes setting the points easier. As for advancing the timing, I’d do it like Oldtimer recommends if you want to, but you won’t see much difference.

Another possibility is that if constantly fiddling with points isn’t your friend’s idea of a good time, a company called pertronix makes a kit that replaces the points with a simple transistorized ignitor. With one of these the dwell and timing won’t wander.

I personally think that having to constantly tune them is the best part about owning an old car, but to each their own.

Ok4450 stole my thoughts and said exactly what I was going to, except I’m not sure I’d advance the timing.

I do want to add that the cat converter operates at very high temperatures and without protection being added your buddy just may look in the rear view mirror and see flames, or perhaps feel his feet getting hot. The ceramic substrate in the honeycomb retains heat, great for causing the “second burn”, but not good without heat protection between it and the floorpan.

As others have stated, it probably wouldn’t last anyway. These old motors put out far more carbon in the exhaust, and that’ll coat the catalyst (the platinum-palladium coating on the honeycomb) and make it useless. It has to remain uncoated to seperate the nitrogen from the oxygen.

Hey, has this got the pushbutton automatic? The row of buttons on the dashboard? I love those. A high school buddy of mine had one back in the '60s and I always thought they were coolest thing. I always thought it was the best arrangement ever.

Cat converter isn’t feasible, but adding PCV is doable if it doesn’t already have it. Would also keep your oil cleaner.

It’s MUCH easier to set up a distributor in these slant 6’s by simply removing it and replacing the points on the work-bench…The BEST ignition conversion would be a factory electronic ignition…This is a long-stroke engine, don’t be pushing the timing up much over 8 degrees. Be sure the vacuum and centrifugal advance built into the distributor are both working properly…Check the static timing with the vacuum removed from the distributor…These engines ran FOREVER…You will find installing a hand choke will solve a lot of cold starting and warm-up problems…

One thought I had is the possibility of raising the thermostat temperature. If my memory serves, those engines typicall ran at about 165F T-stat rating. It might run fine and cleaner with a higher temp. One of the first steps the industry took in reducing emissions was to raise the engines’ T-stat temperatures. That allows them to get to temp faster and run a bit higher. he’d probably have to change the temp sensor and/or gage also, or it might always read in the hot zone.

Original equipment was 180 degrees. 165 was a “summer” thermostat for cars that tended to overheat.

Properly adjusting the idle mixture screw will reduce emissions as much as possible on this car…That and PCV if it’s not equipped that way now…

Yeah, I found that out the hard way, dropped the condenser screw down into the distributor and had to pull it out. I’m glad I did though, had about a tooth and a half on the nylon distributor gear missing. When I rebuilt the carb, I found that the vacuum choke pull off had a bad diaphragm and after looking around for a replacement to no avail, ended up converting it to a manual choke.

IIRC, PCV valves became required equipment on all US-sold cars in '63.
Does anyone else recall for sure?

Yes, I believe it was the last year for the push-button automatic, it’s always funny to see people’s reaction when they see it, especially the “park lever.”

Don’t ruin the Valiant with a catastrophic (catalytic) converter. If you keep the car in tune, the emissions shouldn’t be too high.

I used to time the engine on my 1965 Rambler with a vacuum gauge. The timing marks were off on the engine and the car wouldn’t run well if the timing was set to specifications with a strobe light. However, I would set the idle speed where I thought it should be and hook up the vacuum gauge. As I would advance the timing, the vacuum would increase to a point and then go no higher. I would retard the ignition to the point where moving it back any further would would cause the vacuum to drop. I would tighten the distributor bolt and declare the engine in time.

You are doing the same thing by advancing the timing and road testing unil you are getting too much ping on acceleration and then backing off a couple of degrees.

Old cars were fun to work on. I know of only one way to fix my modern car. When one of those crazy lights iluminates on the instrument panel, it just gets covered with black electrical tape. All I really want to know is that the engine oil pressure is o.k., the engine is not overheating, and the battery isn’t discharging. That is all the cars like the 1964 Valiant told us. We listened to the engine and got the other information we needed.

Caddy, you hit this one right. The vacuum and centrifugal advances should be checked before messing with the initial timing at idle. Considering the age, a little oil on the mechanical weights and springs would probably do more good than upping the initial advance. Need a good vacuum advance too.

Upping the initial timing worked in the 60’s because gas had higher octane then, and of course, the advances were probably working good then. I’d be very careful with todays gas.