Interesting experience with heat riser

[Dave72dt]

Looking at it, I think it works by having the spring weaken when it gets hot. Then gravity acting on the counterweight and the flow of exhaust against the flapper valve in the manifold move the assembly to the hot position. When it cools off the spring regains its strength and pulls the flapper to the cold position against the force of gravity on the weight.

Bi metallic springs move because of the differing expansion rates to the two metals the springs are made of. Two thin strips of metal joined together as opposed to an alloy of the two metals.

[48ply1stcar]

I have been following this post because I was putting the final touches on my engine.  Thanks Shel_ny for the pictures.  Those pictures are not in my Service Manual.  

The spring steel on my counter-weight was rusted out so I cut a piece out of a spreader used for applying mud on drywall.

 

 

 

[Niel Hoback]

   Joe, not real sure, but I think the weight will only go on the shaft one way because it has a flat side.  I'll go out and look today.

[Joe Flanagan]

I just attached the vacuum gauge to the port on my intake manifold. I disconnected the line to the wipers to do this but I have one of those fuel pumps that assist the wipers and that line is attached to the fuel pump. With it disconnected, I can hear the fuel pump but it doesn't seem to affect the way the engine runs. Can I take the reading like this? Will having the line that goes from the intake manifold to the fuel pump disconnected affect my reading? Do I need to plug that line? As I say, having it disconnected does not seem to affect the way the engine runs. The reading I get is about 19, which, on my gauge, is right on the border between normal and late timing. 

[Dodgeb4ya]

The counter weight is positioned on the shaft by a small metal alignment tab.

Also the stop damper needs to be installed. It sets the weight at the correct cold position so it's not rolled CCW too far.

The spring must be in good conditioned and not over wound. 3/4to 7/8 CCW wind is all that is needed to tension the weight.

Chrysler six shown but similar to the Dodge and Plymouth.

Bob

[Joe Flanagan]

I have a strong suspicion that's where my problem is. But as someone else suggested, I don't think now that my rough idle and hesitation is due to the heat riser. I just checked for a vacuum leak using carburetor cleaner and found none. Did a very thorough search, too. No sign of a leak. Could be my timing is retarded, since the vacuum gauge seemed to indicate that to be the case. Will be checking the timing soon and will report back. 

[Dodgeb4ya]

I don't think your running issue is heat riser related.

[Joe Flanagan]

Yeah, I've pretty much ruled that out, I think. I advanced the timing using a vacuum gauge (I currently don't have a timing light but will be borrowing a neighbor's this weekend). I got it to 20. There is still a lugging or missing going on. It's fairly minor but every time it does it, the vacuum gauge drops to 19. It's very regular. The movement of the needle is very slight but it goes between 19 and 20, concurrent with the miss. Last time I set the timing with a vacuum gauge I was way far advanced when I checked the timing with a timing light. There are old posts about the effects of timing that is too far advanced and I don't want to damage the engine. So I'm going to check and see what 19-20 on the vacuum gauge translates into with the timing light. 

After advancing the timing, the car seems a little better starting off in first, but not great. I played with the idle mixture until I found its optimum spot. No effect on the rough idle, though.

Other things I checked: Looked under the hood with the engine running at night to see if there is any arcing between the spark plug wires. No sparks to be seen anywhere.

I checked the wires at all spark plugs and at the distributor cap. Everything is tight.  

[Lloyd]

Yep, using a vacuum gauge to adjust timing will advance the timing if you try for the highest reading on the vacuum gauge. A regular small downward movement on a vacuum gauge can be a valve. But before you do anything get your timing set properly and then check your idle adjustment again.

[Joe Flanagan]

The other thing I noticed since advancing the timing is that it bucks in second gear. It only happens if I'm cruising in second, let up off the gas, and then step on it again. It's very noticeable. I think I'll be more comfortable setting my timing with the light. 

Regarding the vacuum gauge, the needle moves about a half inch between 19 and 20. The explanation on the second chance garage website on how to interpret a vacuum gauge says that if it moves up and down 3 to 4 inches it could be a burnt or stuck valve. Since mine is moving so little, am I out of the woods? 

[Don Coatney]

Not all vacuum gauges read the same. I once hooked my engine up to a gauge belonging to a friend. The needle bounced all over the place but my engine ran great. Upon returning home I connected my vacuum gauge and the reading was once again steady. I bought my gauge about 50 years ago from JC Whitney.

 

[Lloyd]

You have to consider what may be making the needle move. Look at it from a practical view point. The vacuum you are measuring is created by the pistons on intake stroke and the throttle plates regulating the amount of air flow into the intake manifold. A low or fluctuating needle means you are losing vacuum somewhere between the throttle plates and the pistons. If the needle is dropping on a regular basis then most times it is something mechanical, every time this part is activated you lose vacuum. I would not go by how far the needle drops as in 3-4 inches means this and less than that means that. There are degrees a valve can be burnt or sticking. It may be a little, it may be enough to give you 3-4 inches. Main thing to notice is that it is a regular fluctuation.

Another good test is a compression test, this will tell you a lot about what is going on with your engine and can help pin point the fluctuation you see on your vacuum gauge to a specific cylinder.

[Joe Flanagan]

Well, I failed the dollar bill test. I read about it in an old post here on the forum. I just finished cleaning and gapping the spark plugs and tightened all the manifold nuts and the carb-to-manifold nuts. Some of them were pretty loose. Anyway, I've still got that lugging thing going on and it seems to be noticeably worse. I decided to try the dollar bill test and it gets sucked into the tail pipe every few seconds. So it would seem I have either a stuck or a burnt exhaust valve. 

So, two questions. 1: What should my next step be? 2: Should I start a new thread? This isn't about the heat riser anymore. 

[Don Coatney]

Did you replace the valve guides in your engine? How many miles do you have on your engine? Results of your compression check?

[Joe Flanagan]

Valve guides were new with the rebuild a few years ago. I have about 700 miles on the engine. I have not done a compression test but from what I've been reading, that looks like the first thing I should do. 

[Don Coatney]

Once you get 5,000 break in miles on your engine then report the dollar bill test.

[Joe Flanagan]

Seriously? It could be a case of the engine not being worn in enough? I sure hope that's true.