The Stovebolt Site Forums The Shop Area Engine Shop Heat Riser...?

Hi all.. I have been reading some of the post and of course I'm corn-fused yet again! My truck has a manual choke and the heat rised weight and spring are gone by the PO. As I understand it no heat riser is is needed if you have a manual choke...my truck starts fine and sometimes huffs and puffs through the carburator after sitting for a week or more upon start up...maybe I'm pumping the gas pedal too many times before I hit the floor starter button..it warms up fine and is ready to go in about 3 or 4 minutes...am I missing something good? THANKS, Steve

The heat riser just redirects exhaust through the intake manifold to help warm the air and gas coming into the engine making it vaporize easier.

The choke enrichens the fuel mixture by not letting as much air through the carb.

You probably need both, if your climate permits you can unhook the heat riser.

You need heat to provide vaporization of fuel and to prevent carb from freezing up. Carbs can freeze up on a 100+ degree day. Also needed to improve performance and save gasoline. The only situation where heat is not needed is on the salt flats where the engine is consistently operated with the throttle wide-open.

On the other hand if you are using exhaust heat without the heat riser thermostatic spring fully functional you will have too much vaporization, poor combustion, poor performance, and wasted fuel. In addition your carbs will eventually be destroyed from being way too hot for extended periods of time.

Where we live the climate is very mild...I forgot to maention that the exhaust manifold is of the split welded type giving us dual exhaust....If I need the heat riser what do I do now. I think the hole in the manifold or the stud is broken off but the spring is gone and the counter weight and I would guess the internal flapper is gone?....so what do I need to do if anything? Steve

Mine us rusted open and I've had no problems because of it. Don't worry about it.

Hey Tiny,
THANKS....there seems to be alot of controversey about this problem . Some guys say forget it as the early trucks did not have heat baffles and if you are running a single barrel leakchester like mine the thought of freeze up is almost impossible....yet guys in the colder climates swear that you really need them and I can understand that. It must boil down to what climate you live in and not so much the performance aspect.....maybe? Thanks, Steve

I too have a ex. manifold, stock L6, with the heat spring/butterfly cut out. I live in cold weather, so i figure I will always have heat, I wonder if I should make a spacer between intake and Carb so it doesn't percilate/boil off fuel while in a too hot carb? Anyone?

On my truck there is a heat spacer made from bakalite from the base of carb to top of the manifold. As I said I'm just running a single Rochester carb so heat is not a big deal I would think....more input from the experts would be GREAT...Steve

You exhaust is going to get the intake too hot regardless of how many carbs or what carb model you have. The truck will run with or without but not with optimum performance or fuel economy. As mentioned, your carb can freeze on a 100 degree day. Check Tom Langdon's site and read the tech article about heat and why it is needed.

OK.....what do I do next? Can these be replaced ? THANKS, Steve

Stock exhaust manifolds sell for peanuts here at Stovebolt as well as on eBay. My suggestion is to buy one that works.

THANKS, Mike...seems to be two schools of thought on this issue...our truck according to the previous owner has run this way for over 10 years and some stovebolters say don't worry about it. I think I'll keep it this way until I buy a set of Fentons split exhaust in a year or so...Steve

Think of it this way, It aint gonna hurt anything to make function how it was designed.

Mine has never frozen up because of not having the riser connected. Once, my carb had gunk in its jet and it was freezing half the carb up. Properly adjusted and clean it should be fine.

It only makes a difference on warmup. Its a thermostatic spring not computer regulated! Then again I havent ever been peeking under my hood while driving down the freeway to make sure! Ive had mine disconnected all this past year with no problem or comprimised efficiency.

More of a personal choice on the manifold. Theres nothing wrong with the stock manifold and you can find parts cheap. I dont have an insulator under the carb on mine and it works great.

Mine has a 54 year old engine in it, I dont expect miracle break throughs in performance! I know better.

Good Luck! Jeff

Steve

I'm in a mild climate here too - only 2-3 frosts a year but at times it gets pretty humid.

My 270 has the riser baffle still in place, but stuck in the open position (exhaust gases straight out).The only time I have experienced any icing up has been on warm-up on extra damp or humid days until hot.Otherwise having the riser open is no problem here.

You would be over-heating the manifold in warm weather if your baffle is completely gone though.

Hey Jeff, thanks for the information. The PO of my truck took off everything spring weight so I have been running it this way for sometime. Maybe the mild weather here in CA helps a little. I also have the bakelite spacer between carb and manifold. I think you are also right that once the engine reaches operating temperature freeze up is not too likely. When welding with a MIG set up sometimes we will draw shielding gas for a long period of time and the gauge will freeze up. So I guess it could happen to gasoline but at what flow rate? Gasoline has a very high freeze point even atomized... I don't think its a worry with my Leakchester B. When I change to a Fenton split exahust I guess I will run into other problems. Right now I have split exhaust (dual) they welded another pipe to the manifold. This was done by a lot of guys 1/2 the price of fentons for a dual set up and it sounds nice...THANKS,Steve

Steve, I always have to choke about 1/2in to start my 53 3100.

So I live where we freeze for half the year and bake the other half...... and will need to fix my counter weight and spring......

All the spare exhaust manifolds I have are seized tight...... is there any kits that allows to cut out the old baffle butterfly and counter weight and shaft and re-instal new parts???? I know springs are available but trying to free up those parts even with Oxy torches is not very fruitful.... and once freed up what can you lubricate with to keep them from seizing up again?

Thanks for your help.
Bob C.

Bob - the manual recommends kerosine/diesel - if you've got one off the truck, soak it for a few days, take it out and tap on it awhile, soak some more, peat and repeat

Bill

I just noticed that mine was missing to...I have only had the truck for 3 months now since replacing things that were missing or broken...one more part to order...it seems to run fine but I think I will order that piece.

Hey if you find where to get parts let me know. I have just the pin that holds the spring on..some guys say don't worry about it.. but if I'm going to insatll Fenton split exhaust...someday...I should repair the heat riser...Steve

I just orderd the heat riser or manifold thermo spring what ever you want to call it....Chevy Duty or Classic Parts....15 dollars with 8 dollar shipping..crazy...

Thanks for the information. I wish that's all I had to do. But I did by a complete exhaust and intake manifold with the heat riser working...I guess I can just take off the bottom four bolts from the intake and drop the exhaust pipe a little and slip it on the intake and hook the exhaust back up....seem right? Steve

When I took that part of my motor apart...I sandblasted acourse then painted it....it took alot of pentrating fluid to break the rust off the nuts...so that I could replace the gasket between....

Holcomb...yea, I bet I will need a couple of cans of what we refer to as...Skunk Pee..Steve

My climate does NOT permit...

California weather is crazy right now...not something we are all use to...cold is one thing but it is really cold...so I think I need a heat riser to get my ride going...hopefully this improves things

Its been cold but my truck starts fine and runs real good until the carb. wrecks my day...I'll be working on it this weekend again....hope its just an air leak on the fuel pump intake side of things...Steve :confused: