The Stovebolt Site Forums The Shop Area Engine Shop Heat Riser on Fenton Intake 56 235

I put the Fenton dual carb intake on and used the original exhaust manifold. It bolted up perfectly. The heat riser moves under spring tension and the weight will flip up when you raise the rpms. Someone mentioned that the exhaust will corrode the aluminum manifold. If the weight flips up when you raise the rpms the exhaust is directed down the exhaust pipe right? Will the new Fenton be OK?
Thanks Sharon

the heat riser shouldn't be related to rpms (?) down is the normal operating position, it should only go up with the spring tension when cold.

Just went out to check, the engine is cold, the weight is down and you can lift it under spring tension. Am I correct in saying the flap inside on a cold motor will direct exhaust up to the intake? As you raise the rpms you can see the weight lift up. This seems correct too, because you want to direct exhaust down the pipe. The weight lifts more easily by hand when the engine is warmed up. Is this correct?
Sharon

Just got home from work. Looked at heat riser and the weight is all the way up on its own. I guess the spring is doing it's job, right?
Sharon

There is something not right, RPM's have nothing to do with this, only temperature, you should be able to remove the spring completely and the weight will just sit there in the down position. The flapper in the normal operating position (weight down) directs the exhaust down as you say, with weight UP, (engine cold) the flapper just makes the exhaust go up and over, forcing a more intimate contact with the bottom of the intake. Since I have an exhaust just sitting in the garage, I should post some pictures on the tech tips on where the stuff is oriented under which conditions, as this comes up all the time. Only thing is I need to have my wife help me with the postings....except for a brief period, I haven't had a spring on mine ever, in 30 years, and noticed no consequences at all, and it has been in some really cold situations. I didn't even know what it was for or what it did until about 2 years ago when it was running roughly (never did figure out what happened, it just started running well again) That is when I studied it a bit. Got a new spring, but there was a chunk of the old one stuck in the flapper shaft, and I only tried it for a while and it made no difference that I could tell, just frustrated me. But to answer your question, I am pretty sure it shouldn't be doing anything in relation to RPM's. We will have to wait for Dave for a more definitive answer. I do know if it opens up after it is warm it will make the engine run really, really bad.

Yeah I'd like to know about this also. My heatriser will move when you gun the engine also. Maybe the bi-metal springs get weak after so many years? John

When you "goose" the throttle, you are creating and putting out more exhaust. This extra exhaust is being applied to the flap and overcoming the little temp sensitive spring--just be glad it is free and working--it can be a pain if the flap sticks in the shut position-restricted exhaust flow and cooked carb- (vapor lock) conditions can be had. If stuck in the open position you only need to run the choke a little longer as it will be a little "cold-natured" 'till it gets warmed up.

In the fifties, when the old chevys were in their heyday--those flaps were usually removed when somebody had their manifolds "split" for duals (this is in Texas) and nobody cried about it. As it wasn't missed, and you always had the good sounding free flowing exhaust.

Just curious -- how old are you guys- that is, what generation are you guys from-- I'm from the flathead V8 and split manifold six hot rod era (oh yeah, and the twin valve cover V8 stuff too)

I was born after these trucks were made.... LOL I always just liked the look of them myself. Always like the inline six cylinder engines. May split my exhaust manifold, but leave the heatriser in one side....
John

I would like to see some pics because I am still confused. On my cold engine-not running, the weight is down. You can lift it under spring tension. With a hot engine-not running, the weight is lifted up I guess by the spring. Maybe mine is backwards. I'd like to some pics so I won't have to take the intake off and look inside.
Thanks Sharon

not a fenton intake but you will get the idea

...click...

...click...

I just ran across your video in a search. It answers all my questions. A picture is worth a thousand words. DADS50
Thank You
Sharon

"GOOD JOB" Dads50.

thanks
It can be a bit difficult to describe the operation..
open/close...heat on/heat off...
spring expands/spring contracts.

the visuals help me

If your heat riser is not functioning properly, your crankcase will become contaminated with unburned gas (unless you live where the outside air temperature is 180 degrees). This will lead to premature bearing failure. The heat riser directs instant heat to the underside of the cold intake manifold, warming it up to keep the air/fuel mixture atomized. Without this warming of the intake, the fuel will fall out of suspension and pool up on the bottom of the cool intake runners, then get sucked into the cylinders. Since liquid gas isn't combustible, it leaks past the rings into the crankcase.

52Carl. DADS50 video explained everything. Mine is working properly.
Sharon

Hold on there, I have to disagree that yours is right. I may have a freak exhaust manifold that is backwards from everyone else. But the one I have been referencing is actually from a 53 216.(if that makes a difference) But the weight down would be the engine hot, and the weight lifted up (by the spring) would position the flapper in the intake heating configuration. The way the flapper is designed WOULD make it flutter with RPM's if you have it backwards. It isn't a balanced flapper, the greater part of it is oriented so as to force the weight down to the warm engine position as exhaust pressure/velocity increases. (giving you the flutter you described) I will try to get some photos posted today. So unless someone took mine apart at some point in the past, and put it together sideways, hot is down, and cold is up.

sounds right
...dennys pic...

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0605.htm

if you have duals and on a cold morning you notice LESS "white smoke" coming out of the heat riser side tail pipe, then you know that the flap is at least at that time in the closed position and doing its job.