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  #1  
Old 01-13-2010, 09:55 AM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
Posts: 1,282
Heat Riser question

So, I wanted to try and return the rig to as stock a condition as I could (believing that stock would run best and get best mileage etc). I have since decided to try and eliminate some of the maintenance nightmares... So, out goes the AIR system, simplify the vacuum system a touch...and all seems fine.

I had bought a new Heat Riser from BJ's back in May/June (something like that). Anyway, when I went to install it (last weekend), I noticed that as I turned the weight, the flap didn't turn. The weld that held the flap to the weight was very weak and didn't hold up. I ground the weld out and re-welded it myself.

However, I am now concerned about if I welded it in the right position, if the weld may have damaged the spring, or something else. I don't think the Heat Riser is opening correctly. How long should it stay closed? At what temperature should it open? Is there a way to test it?

Maintenance wise, are these things an issue? Do they often fail? Do they require anything (I plan on hitting it with PB at every oil change just to keep rust at bay).

I am almost regretting putting it in. I have the old one (with no flapper) sitting on a shelf...
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  #2  
Old 01-14-2010, 07:55 AM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
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Anyone???

Also, should the weight be toward the inboard side (near the motor/manifold) or toward the outboard side (near the frame)???
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  #3  
Old 01-14-2010, 08:02 AM
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710 Burner 710 Burner is offline
 
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Location: Normal, Oklahoma
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The only thing I can remember is that the weight pulls it open when heat causes the spring to relax.
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Actually, now that I think about it, that could be either awesome or really terrible.


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  #4  
Old 01-14-2010, 08:26 AM
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brad_fsj10 brad_fsj10 is offline
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Join Date: Nov 11, 2002
Location: Pell City, AL 35128
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Heat riser should be installed with the counterweight outboard, between the exhaust pipe and frame. The counterweight should "fall" downward as it is heated, opening the butterfly.

It should begin to open as soon as the spring heats up enough to expand and reduce the pressure on the counterweight. It should be fully open within a minute or two. To test it, lightly clamp the assembly in a vise and run a propane torch over the spring lightly. Don't cook it, but hold it close enough to heat the spring. You should clearly see the spring expand, the counterweight fall, and the butterfly plate open up.

PB Blaster at every oil change is a great regimine for proper operation.
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  #5  
Old 01-15-2010, 01:41 AM
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letank letank is offline
AMC 4 OH! 1
 
Join Date: Jun 03, 2002
Location: San Francisco
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Useless item, sorry. I have been running without it for over 15 years..... and it starts fine even in 25 degres weather.
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  #6  
Old 01-15-2010, 06:43 AM
silvercert silvercert is offline
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mine ticks
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  #7  
Old 01-15-2010, 08:15 AM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
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Quote:
Originally Posted by letank
Useless item, sorry. I have been running without it for over 15 years..... and it starts fine even in 25 degres weather.

Do you still have the stock intake and carburetor? The stock carburetor choke is assisted by a choke stove that receives it's heat from a channel fed by exhaust forced over/through the manifold by the heat riser. I replaced it because I was concerned that without it, the choke would not pull off soon enough...
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  #8  
Old 01-15-2010, 08:42 AM
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710 Burner 710 Burner is offline
 
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I never had an issue with it. I had the spring disconnected because of sticking.
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Quote:
Originally Posted by GrandWag&Prix
Actually, now that I think about it, that could be either awesome or really terrible.


'79 Cherokee Chief "Junaluska"
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  #9  
Old 01-15-2010, 10:10 AM
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billyrb billyrb is offline
BJ's Off-Road
 
Join Date: Aug 15, 2001
Location: Acworth, GA 30101
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TW, you 'can' run without it, it just takes a little longer for the choke to fully open. As mentioned above, the spring heats up and the counterweight slowly pulls the butterfly open. Once the spring cools, it contracts and pulls the counterweight back and the butterfly closes.
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  #10  
Old 01-15-2010, 11:13 AM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
Posts: 1,282
I am glad you chimed in here. I am just curious if you have had other people buy one of your Heat Risers with a bad end weld on them? No bashing going on...I have been extremely pleased with everything I have bought from you guys...but was surprised when I went to put this on...
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  #11  
Old 01-15-2010, 11:52 AM
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billyrb billyrb is offline
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not so far. Doesn't mean it hasn't happened, just means no reports thus far.
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  #12  
Old 01-15-2010, 01:48 PM
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Tatsadasayago Tatsadasayago is offline
Master Mechanic
 
Join Date: May 15, 2009
Location: Sacramento, CA
Posts: 1,035
Where the riser has a great effect is cold starts around 28-34 degrees F with high humidity. Once the engine fires up the incoming air carries moisture which super-cools the carb. Often this will lead to carb icing which causes blubbering or stalls that require a re-start. The heat riser being closed causes the pass side manifold to heat up rather quickly which provides heated air to the air cleaner via the metal flew ducting. This warm air prevents icing and assists the choke after the choke pull-off has opened the carb's choke plate. It's a great drivability feature as well as an emissions benefit because the choke comes off sooner which means a leaner mixture while warming up.

We should keep in mind that everything that was designed into these vehicles is there for a purpose. Sometimes these things didn't work as well or last as long as expected of course!

These Jeeps had to start every time with one or two pumps of the throttle and without any other input from the driver till it was time to move. They also had to pass emissions inspections.
That's a tough job to do, especially 20 or more years later.

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  #13  
Old 01-17-2010, 02:25 PM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
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Ok, well, I think it is not operating correctly. I decided to check it today. Took a small propane torch under the vehicle with me. The weight turns just fine by hand. Heated the heat riser with the torch...and the spring didn't loosen up enough to allow it to turn. I had the weight glowing...and still it didn't loosen up (the weight didn't even budge). So, once it cooled down, I took the spring off (hoping it was just wound too tight). I will see where it cools down to and then heat it again and see how much the spring naturally turns...
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  #14  
Old 01-17-2010, 03:34 PM
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vintagetrks vintagetrks is offline
Bleedin' Gasoline
 
Join Date: May 01, 2009
Location: Paulden Arizona
Posts: 2,027
Got rid of mine. It used to make this clunking noise every few minutes that sounded like a knock. I pulled it no more noise and my rig runs fine without it.
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  #15  
Old 01-18-2010, 02:20 PM
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djongeward djongeward is offline
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Join Date: May 21, 2008
Location: Imperial Valley, CA
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Didn't use mine in my old exhaust setup after the engine build. I didn't add the new one that came with the Thorley's either. I have kept the heat riser and OEM vac control air cleaner for nicer starting. But I live in a desert with rare freezes. Just don't see the point of it unless you want a stock OEM setup because that is what you like. For me it is just one more place to leak or have a problem.
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  #16  
Old 01-25-2010, 12:05 PM
twmattox twmattox is offline
350 Buick
 
Join Date: Feb 24, 2003
Location: Indiana
Posts: 1,282
Well, I unhooked the spring and noted where it was. Applied some heat...and checked to see if it moved. As I understand it, as it warms up, the bi-metalic spring should uncoil (allowing less pressure against the weight allowing the weight to open the restriction plate). However, no matter how much heat I applied, it never un-coiled. Stayed at the exact same place (even when the spring was nearly glowing). I am assuming this means the part does not work correctly...

I can say, that unhooking it and keeping the heat riser "open" made a HUGE difference in power. AND, the choke and thermostatic air cleaner functioned perfectly. Seems like I wasted $70 on this thing!!!
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