Percolation and Heat Riser

[1949 Wraith]

My 41 C28 has had issues with difficult hot starts due to flooding from percolation. The car starts hot fine if you open the hood.  I lowered the float bowl level, installed a fuel pump heat shield and made and installed a heat shield for under the fuel bowl\filter combo. I have a non functioning mechanical fuel pump and an electric pump that I turn off about 10 seconds before I shut the engine down. Even doing this I would get seeping at the base of the carb. I have tracked the problem to the heat riser.

The heat riser is not restricted and moves about 70 degrees freely, but it is still in the open position when the car is at full running temp. I installed a new heat riser spring and wound it 1 turn counter clock wise to the stop. This seems to restrict the movement of the heat riser even more and still is open when hot. I am going t try a half turn pre-load on the spring.

Before the upgrade to this site I was reading tech articles that were stickies. I read one on the proper function of the heat riser and would like to re read it, but I can not locate them, I checked in the downloads and did searches, but the filtering still gives me pages and I have not found the article.

Please send me a link to the heat riser tech article.

Thanks Nick

 

 

[P15-D24]

1 hour ago, 1949 Goat said:

Please send me a link to the heat riser tech article.

Because for the format change I have to redo all the tech articles so they work with the new software. Earliest publishing will be late next week. 
I will see if I can pull a pdf version from my backups and email you a copy. Please PM your email address. 

[pflaming]

I do not have a heat riser on my 218. It was broken so I left it that way. Heat risers are really for cold weather starting, the hand choke does the same thing and I can adjust the choke manually to my weather needs. This is an unstudied opinion, thus not a recommendation.

[1949 Wraith]

4 hours ago, P15-D24 said:

Because for the format change I have to redo all the tech articles so they work with the new software. Earliest publishing will be late next week. 
I will see if I can pull a pdf version from my backups and email you a copy. Please PM your email address. 

Thanks, that explains it. Thought I was going senile and that I was going to have to get the grand kids to search for me.

[1949 Wraith]

I was able to get to the tech article using a google search and linking a heat riser picture.

[greg g]

Fully clockwise should be the hot position, this puts the flap horizontal and places the least restriction on outgoing exhaust gasses.  If you can rotate your riser to the full clockwise position and secure it there (mechanics wire) you should be fit to go down to temps around freezing.  If you are planning on fall and winter driving, cut the wire and let it do its thing.  For those fall days when you need the heater, I have tie wrapped the heater return hose to the intake so it transfers heat to the manifold, as my flap is welded horizontal and there is a stainless steel piece between the manifolds assuring that exhaust gasses are not entering the the intake heat chamber.

[Don Coatney]

With my modified dual intake and exhaust setup the heat riser plate is welded in the open position allowing exhaust heat to always heat the intake manifold but allowing a true complete separation of the exhaust. But as Greg mentioned I do not have a carburetor mounted in the original position and the original position is blocked off with a stainless plate, so the exhaust heat to the intake manifold makes no difference.

[_shel_ny]

If you put a new spring on, it may have been one of the defect springs that was wound/manufactured backwards

[1949 Wraith]

7 hours ago, shel_ny said:

If you put a new spring on, it may have been one of the defect springs that was wound/manufactured backwards

I found the tech article on proper set up, Spring seems fine and was  wound aprox , 340 degrees counter clock wise. Weight on top at noon position closed, at open 3 o'clock position. There is tension on spring holding flap in closed position when cold. Hopefully when the manifold heats up the spring, it should expand twisting the flap to the open position. Will be testing her out today.

It will be wired open if this does not work.

[1949 Wraith]

Still not staying open on hot shut down. Wired open for now.

[1952B3b23]

Something else that might help with the percolation is installing a phenolic spacer under the base of the carb. It will help insulate the carb from all the manifold heat. I just installed mine, it's 5/8" thick. I called Tom Langdon and ordered from him:

http://www.langdonsstovebolt.com/

-Chris

[1949 Wraith]

1 hour ago, 1952B3b23 said:

Something else that might help with the percolation is installing a phenolic spacer under the base of the carb. It will help insulate the carb from all the manifold heat. I just installed mine, it's 5/8" thick. I called Tom Langdon and ordered from him:

http://www.langdonsstovebolt.com/

-Chris

Those spacers are used on the 235 Chev straight 6 manifolds. I should probably check to see if they are the same size, as I have a spare manifold with one on

[1952B3b23]

44 minutes ago, 1949 Goat said:

Those spacers are used on the 235 Chev straight 6 manifolds. I should probably check to see if they are the same size, as I have a spare manifold with one on

I just installed one on my '53 Plymouth 218 ci flathead, stock intake manifold. I'm still running the original Carter Ball and Ball carb as well. It fit right on without a problem. You will need to file a little bit of material off the spacer in order to allow the vacuum hole in the base of the carb to pick up manifold vacuum. Also, longer mounting studs will need to be installed in the intake manifold. I went to ACE hardware and bought 2" long automotive studs, 3/8-16 x 3/8-24 thread pitch. They where about $2.50/ea.

-Chris

[1949 Wraith]

I think I have solved my problem. Today the car would not start after a hot ride and a short shut down. Would not start after a half hour with the hood open, which it usually would. I pulled the plugs near the carb to see how wet they were, to my surprise they were dry and clean. When the car had started in the past after a hot episode it would run rough like flooding.

Since the plug was out I checked for spark and there was none. Waited another 15 minutes and the car started right up.

Got the car home, pulled the new 6 volt coil in the 3100 Chevy that is under restoration, installed in the Chrysler and she fires right up even when hot. I am quite sure the coil was being effected by the heat and was on it's last legs, time will tell with the new coil.

Carb rebuilt kit is in the mail hopefully that will solve my gas weeping at the base.

Thanks for the suggestions.

 

Edited September 7, 2016 by 1949 Goat
additional info

[1952B3b23]

I was having some hot start issues as well. At first I thought it might of been excessive heating of the fuel that was the problem. Turned out my points where bad. For some reason I still had spark at all plugs when hot. It must have been to weak though. Just some food for thought if you start having trouble again. 

-Chris