The Stovebolt Site Forums The Parking Lot Big Bolts Heat riser and the valves

I recently got my 47 COE fired up and drove it about 8 miles. About half way, it started to die at idle. Somebody suggested heat riser closed, causing the gas to perkalate....which I think is what the winning answer is going to be. I talked to my machanic who was worried about the valves. Said they might have gotten red hot and intake valves CAN get red hot and even snap heads if a heat riser is stuck closed. Question is: is it likely that I have caused valve damage. No heads snapped off since it runs fine, but it has a slight miss. I trust my mechanic, but don't know how well versed he is with old bolts. Any opinions about my valves? I plan to adjust them once my heat riser nightmare is over (hard to get off) but I'm just a little worried about the health of my intake valves. Thanks for the input guys!

Is it likely, could it have happened, I spose it could have. There's only one way to determine that, look at the valves,course thats the operation that doesn't appeal to you, nor would it to me.
Look at it this way, if seeing the valves only meant 4 screws and pulling the valve cover you'd do it to check the valves, right

It's all that work pulling the head that keeps one from taking a look at the valves.
I'd adjust the valves, see how it runs out and if it runs good keep on truckin.
Or you could do a compression test or a cyl.leak down test to access the condition of your motor.

Dan

I don't buy it. Ive seen them run with the heat riser stuck shut & stuck open without any consequences. If it is stuck put some penetrant on it & hammer it back & forth. If you can't get it freed up enough to work at least get it on the open side. The weight is horizontal when it is shut & at about an 45 degree angle when open.

I put a pull closed push open cable like a choke on mine.

If the condition of your valves worries you, run a compression check. A stuck closed heat riser will cause them to be hard to start when they are hot because it will boil gas out of the carb, but damaging the valves sounds a little way out to me. A more likely answer to your engine suddenly not idling is that you have crap in your fuel system or fuel bowl and it moved around. Sometimes you can rev an engine up and put your hand over the carb for a little bit. The extreme vacuum quite often sucks the trash on through. Maybe you should look for a mechanic who has experience in 50-60 year old engines.

I don't agree with the red-hot valves, either. There is too much heat transfer out of the engine for that to happen with your truck. Your rough-idle condition could be related to the heat-riser valve being closed and heating the intake mixture too much for low speed operation. But more likely, it is a fuel mixture matter: idle fuel adjustment, float level, valve adjustment, maybe a vacuum leak. Stuck heat-risers can usually be freed up as described by Wrenchbender, but with your COE, that may be more difficult than with a conventional cab. If the engine idles reasonably well, with or without choke, you don't have a serious valve issue- maybe adjustment is in order.

In your area, unless you run the truck in the mountains during the winter, I don't think you could tell if the heat-riser is working or not after the engine warms up. If it is stuck open, you might get rough idle and stalling during warm-up, or possibly carburetor icing and closed-throttle stalling before the engine reaches normal temperature. Off-idle operation most often is normal even with carburetor ice.

Harvester

Just had to change the title rister to riser, it was driving me knutz

Hi Everybody...wow, thanks for the input. Sorry about the spelling. It is almost off. I couldn't get it un-frozen so off it comes.

Tom(COE)