Now i know why my air filter, carb throtte, snorkle, heat riser tube plug up with black carbon thus constricting air flow to the truck causing poor starts. Firstly the heat riser valve spring is not functioning and has a small leak on the shaft. The valve is in the closed position all the time, probably causing blowby out the leak and into the air system. My air filters get carboned in a matter of days and my truck starts running poorly. Do you recommend opening the heat riser valve open or closed all the time? The only thing I can do right now is to vent the snorkle away from the exhaust leak, and filter the heat tube to prevent carbon from entering the carb? This is a big pain, but I am not putting on a new exhaust manifold on(500.00), that just does not make financial sense. Any suggestions would be appreciated.


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> Now i know why my air filter, carb throtte, snorkle, heat
>riser tube plug up with black carbon thus constricting air
>flow to the truck causing poor starts. Firstly the heat
>riser valve spring is not functioning and has a small leak
>on the shaft. The valve is in the closed position all the
>time, probably causing blowby out the leak and into the air
>system. My air filters get carboned in a matter of days and
>my truck starts running poorly. Do you recommend opening the
>heat riser valve open or closed all the time? The only thing
>I can do right now is to vent the snorkle away from the
>exhaust leak, and filter the heat tube to prevent carbon
>from entering the carb? This is a big pain, but I am not
>putting on a new exhaust manifold on(500.00), that just does
>not make financial sense. Any suggestions would be
>appreciated.
>
>
>https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=858&.jpg

Couple of suggestions.......

Try PB Blaster a couple of days (Engine COLD) on the joints to the heat riser valve. Spray 2 days occasionally and then on 3rd day spray and start tapping with a hammer on both sides of the joint. You should be able to loosen it up fairly well. once freed up you can either see if it works correctly OR wire it back in the open position.
With the loss of restriction the engine should pick right back up.

Also if the heat riser is a separate unit (sandwiched between manifold and pipe) you should be able to find an adaptor at a muffler shop.
If not you CAN remove the exhaust pipe and grind out the butterfly valve (leave a slight stub on the ends) and leave the shaft.

Hope this helps....

Larry

 

Hi again Larry,
The valve is not ceased, it is worn and is loose on the shaft. Just wondering if having the valve open/closed, really affects cold starts,back pressure, and fuel mixture. Maybe because of the shaft leak and the valve being closed it causes carbon to be pushed out the leak, thus being sucked into my carb? maybe I'm complicating the situation, but I do know for sure that because of exhaust gas being released by the small manifold leak the carb sucks in the exhaust gas and the air cleaner becomes plugged very quickly. what do you think?

 

>Hi again Larry,
> The valve is not ceased, it is worn and is loose on the
>shaft. Just wondering if having the valve open/closed,
>really affects cold starts,back pressure, and fuel mixture.
>Maybe because of the shaft leak and the valve being closed
>it causes carbon to be pushed out the leak, thus being
>sucked into my carb? maybe I'm complicating the situation,
>but I do know for sure that because of exhaust gas being
>released by the small manifold leak the carb sucks in the
>exhaust gas and the air cleaner becomes plugged very
>quickly. what do you think?

Your underlying problem is a rich mixture, which is why you found heat riser valve problem in first place. Both are related in a perverse way.

A closed valve will assist in cold morning warm ups as the exhaust is forced into a crossover casting in the heads and intake manifold. Because of this ALL of the exhaust is being forced to use the other pipe to get out. At this point you have a fair amount of exhaust back pressure and it blows out of the heat riser valve. Once the engine / spring on the valve warms up the valve should open).

With the heat riser valve leaking, your cold / warm RICH mixture (yeah warm RICH.....check your plugs, I'd bet they are carbon fouled, then adjust/overhaul your carb.) is being pushed out in the form of carbon deposits at the valve which I would wager to say is staying shut even tho it is free to rotate. This indicates to me that the spring is worn (to release it relaxes or expands.) and that the spring is hanging up.

open the valve and figure out how to hold it open. Check performance levels at this point. If they go up then your on right track. Replace section with straight pipe or if integral to manifold, grind out and fill shaft holes with JB WELD (Don't worry about it looking good worry about it working. Use as much as you think necessary and double it!:7 ) Reinstall exhaust pipe, overhaul carb/tune-up/etc.

Larry

 

If the whole valve (damper) is removed and a 1/4' bolt is sent threw to take up shaft whole would the exhaust open to the carb cause problems? should a plate be installed?

Dan