another dumb question - please be patient

[BulldogTom]

OK, so the exahust manifold was cracked. We need to take it off and we finally got it off. When we took apart the intake and exhaust manifold, there is a metal flapper valve between them. Is that the choke?

We got a spare exhaust manifold from Tim but the flapper valve is missing. If the machine shop cannot repair the crack in the exhaust manifold, do we need to weld the flapper into place? Is that the only way?

What is the proper way to reinstall the manifolds?

Thanks for any help you can offer.

Tom

Lodi, CA

[TodFitch]

That flapper is the heat riser. The shaft that it is on extends out though the manifold and is supposed to have a thermostatic spring and counter weight. When the engine is cold it directs heat from the exhaust manifold up into a "hot spot" to help vaporize the fuel. Once the engine warms up the thermostatic spring relaxes and the counter weight moves the flapper to a position where the exhaust does not go into the "hot spot".

Many people feel that this features is not necessary with current fuel and/or how they drive the car. I personally find that the engine warms up faster with it and I can push the choke knob in much sooner (my car does not have an automatic choke).

Heat riser repair kits can be purchased from Then And Now Automotive, also known as the antique parts cellar.

The choke itself is on the top of the carburetor just under the air cleaner. It may be closed by a cable (older cars) or by a rod from a little box that is bolted to the manifold that has a thermostatic spring, a coil and a wire (P15 era). The wire connects to the starting circuit and actuates the coil to close the choke when you start and then the thermostatic spring opens the choke as the engine warms up. (At least I think that is how it works, I don't have a car with one of those so I've never actually had to deal with it. I am sure someone will correct me if I am too far off.)

[Plymouthy Adams]

not the choke, but it will affect the chokes operation as it is intended to quickly heat the maniold for a quicker choke pull off. known as the heat riser, it is a thermostatic operated valve, its purpose is to quickly raise the heat of the manifold for better atomization of the fuel..a cold engine needs a more dense charge of fuel in the mix...as the temp rises, the valve opens..the valve also will open when the engine is revved due to high exhaust flow..you can observe this on a cold engine by watching the movement of the valve balance move when revved..if not on the car or malfunctioning the choke will stay on longer increasing fuel consumption. If it fails closed it can restict gas flow and cause excessive heat..a properly working valve is good to have, but it is better to fault open or not have it at all compared to the other condition

Edited July 26, 2010 by Tim Adams

[Bob_Koch]

David Erb wrote a nice article about the exhaust valve. It's on the DPETCA site:

http://dodgepilothouseclub.org/know/riser/riser.htm

[BulldogTom]

Thanks for the info on the heat riser.

How about the proper way to re-install the manifolds?

Thanks again.

Tom

Lodi, CA

[Merle Coggins]

Bolt the two manifolds together, with the proper gasket in between the two, but leave the bolts slightly loose. Now install the assembly onto the engine. Snug up the manifold nuts and the 4 bolts that hold the two pieces together. This will help ensure it all lines up properly before everything gets it's final torque.

Merle

[48Dodger]

Hey Tom, I found another Exhaust manifold. I'll check the heat riser. We can swap them if it'll work better.

48D

[greg g]

How and where are you going to use your truck. If you live where it is 40+ all year, the heat riser is probably not and issue. If you are only goig to drive your truck in the summer, probably not as well. I have mine welded in the closed position (horizontal allowing exhaust flow a straight exit. Also have welded the pivot pin area to seal up a small leak. Plus I have a thin stainless piece between the two manifolds which completely blocks the exhaust. I usually only drive in the summer but I have had the car out on good days in the 30's. I have not had a significant driveability problem in thise situations. As stated they do aid in complete combustion and keep fuel from going back to droplet form in a cold intake but it is critical only for everyday winter driving. (at least in my opinion)

[BulldogTom]

Hey Tom, I found another Exhaust manifold. I'll check the heat riser. We can swap them if it'll work better.

48D

Too late. The new one is at the machine shop getting milled. But thanks for the offer.

Tom

Lodi, CA

[BulldogTom]

How and where are you going to use your truck. If you live where it is 40+ all year, the heat riser is probably not and issue. If you are only goig to drive your truck in the summer, probably not as well. I have mine welded in the closed position (horizontal allowing exhaust flow a straight exit. Also have welded the pivot pin area to seal up a small leak. Plus I have a thin stainless piece between the two manifolds which completely blocks the exhaust. I usually only drive in the summer but I have had the car out on good days in the 30's. I have not had a significant driveability problem in thise situations. As stated they do aid in complete combustion and keep fuel from going back to droplet form in a cold intake but it is critical only for everyday winter driving. (at least in my opinion)

It is going to be a daily driver for my son (if we get it done before he goes to college!). We live in Lodi, so the temp below 40 is rare, but it happens. With the Valley Fog it may be an issue, but I will make sure he warms it up real good before leaving for school.

Thanks for the info.

Tom

Lodi, CA

[Harvey Tank]

when I installed my exhaust and intake manifolds I left the four bolts lose, and mounted the manifolds to the block with out the gaskets inplace. bolted it up tight. metal to metal. then tightened the four bolts. my thoughts are with out the gasgets you have the two machined sufaces well mated to geather. the gaskets thicknes could vary. then I removed the manifold, and installed the gaskets. its a little more work but I feel well worth it.

[Aaron]

This area in the square is leaking like exhaust like crazy. I need to redo my exhaust pretty soon, but should I fix this first? What's it going to take to fix it? Do I need to take the entire manifold off?

[greg g]

There is a gasket between the intake and exhaust manifolds. there is no practical way to replace it without pulling then seperating the manifolds, probably breaking at least three of the four bolts holding the manifolds together.

[JBNeal]

This is another area of performance improvement I'm going to attempt on the '48. When I first removed the manifold, there was no valve or shaft for that matter to divert exhaust into the intake manifold chamber...besides, that chamber was chock full of carbon. Since I had no shop manual when I first got the engine running, I put a couple of small bolts in the holes where the diverter valve shaft would be to block them off. As I recall, the motor ran decent for the first year that I drove it. As it's summer time 9 months out of the year here in TX, I never noticed a problem in cooler weather. Below freezing weather is usually accompanied with nasty winds, rain and/or ice in these parts, so I never drove this classic in any foul weather.

I have since installed the diverter valve to see if the engine would run any better. When it's in the 40s, it seems to run a little better, but the rest of the year it seems to want to stall out. So I uncorked the spring and let the counterweight hold the diverter so the exhaust would flow straight out, and that helped out.

I reckon I'm gonna try to remove this diverter valve and block off that chamber from exhaust gases with a metal plate of some kind. I kinda wished I had left that old carbon in place as it filled all of those voids rather nicely. It probably allowed for some insulation from the heat and kept the charged air density higher in warmer weather. I reckon I could fill those voids with melted lead from some old wheel weights or takes some scrap steel and a blow torch to fill the volume with slag.

[Aaron]

There is a gasket between the intake and exhaust manifolds. there is no practical way to replace it without pulling then seperating the manifolds, probably breaking at least three of the four bolts holding the manifolds together.

What is everyone using for gasket between the intake and exhaust and between the manifold and the engine block?

Can you just buy stuff to cut and fit?

[Young Ed]

I suspect most of us are just buying a manifold gasket set. They are pretty cheap. Still gotta meet up with you one day next time we head out to aberdeen. Sadly so far the next time sounds like christmas

[TodFitch]

What is everyone using for gasket between the intake and exhaust and between the manifold and the engine block?

Can you just buy stuff to cut and fit?

Parts book shows one gasket for 1933-59 and you can buy a manifold gasket kit that is just the manifold to block set or one that also contains the gasket for between the intake and exhaust.

In practice, my 1933 seems to use a different gasket than is in the kit and I found I could buy high temperature gasket material from my local auto supply and have made my own for that one.

[BulldogTom]

My gasket kit included that one. Fit perfectly. Got the whole kit from Napa.

Tom

Lodi, CA

[ggdad1951]

going back to the heat riser aspect of this thread...I've been soaking my frozen one for about 2 months now with a shot of penetrating oil every other day, still frozen solid....

[Merle Coggins]

going back to the heat riser aspect of this thread...I've been soaking my frozen one for about 2 months now with a shot of penetrating oil every other day, still frozen solid....

I had the same problem. I finally took a torch and heated the casting just above the pin on each side. It freed right up and has been free ever since.