The Stovebolt Site Forums The Shop Area Engine Shop Exhaust Manifold Heat Rise/damper BUSHING-- UPDATE

Hey guys, all my searches show up "404 error" so I'm relegated to ask the question here.

Sometime ago I remember a thread about the damper that is in the 235/261 manifold that I'm "fixing". I know I can get the new spring, somewhere, but how about those little bushing that I see that fits in the manifold and the shaft of the heat riser goes through. After blasting and cleaning I seen that half of that bushing was worn and gone. I picked out the other half and decided to pick the brains of you guys.
Any secret to putting them in. The one on the heat spring side would/will be easy but how about the one on the side where the weight is? Do I have to cut the weld on the flapper so I can pull the shaft all the way out.

Just need your experience. This is about the last thing keeping me from firing up the 261.
Thank you for any comments or helpful hints.

I working on the same project...mine is stuck & leaking exhaust out the bushing bad, I started to gather parts but now my plan is to remove the damper, cut that rod flush and epoxy that hole to stop the exhaust leak, keepin' it simple over here

I'm interested to hearing your experience tho, so keep us posted!

dont know if this is useful but this is what i did:


my shaft was badly worn and it was leaking

i took a small grinder and cut the welds that secure the flapper to the shaft then tapped out the shaft

i removed it cleaned it and found it had worn out of round and lost some material on its dia.

i took an arch welder and laid some weld over the worn areas of the shaft building up the worn away metal then ground it round smooth and back to shape. checking as i went its good fit back into the manifold hole.

reassembled it all then added a couple of welds to re attach the flapper to the shaft.

cost nothing, took maybe 30 mins

if you want you could run a reamer through the manifold hole first, and grind your welds on a rotary jig to ensure roundness but i found my hole to be round enough and that i could grind by hand well enough round.

what about the bushings tho? What do you have to do with them, I was always suspecting that they were worn out first bcs they are made of soft metal

no bushings in mine, mines a 235 though perhaps they didnt have bushings originally?



can also buy oversize shafts if you dont want to weld/grind your old one

oversize shaft

Mine is a 216, everyone says they do but I have no idea, honestly

Alvin, could you sneak a picture of those "bushings"???
I've never seen a bushing in any Stovebolt exhaust manifold
heat riser bore. All of them that I've run across simply had
a hole drilled thru the casting and that is usually what
ovals out.

As far as repairing it, as Mike has posted, the fix is
normally to cut out the old shaft, ream out the hole to
take an over-sized shaft (available from vendors).
Timing or alignment of the the slot, butterfly, weight is
the difficult part but is critical to the heat riser working
properly.
Denny Graham
Sandwich, IL

I did this with a carb once and the abilities o a machinist neighbor. Remove the shaft and clean it up as appropriate and described above. Go buy some bushings that fit the shaft and drill the manifold to hold the bushings. Should be a cheap and easy fix.

I'm not sure what route I want to go with this...I wanted to rebuilt the thing the proper way, but I've talked to an old time mechanic and another older machinist they talked me out of rebuilding it. Basically what both of them told me was for as much as its worth, just take the dampers out and plug the holes, not going to make much of a difference either way, functioning or not.

What are your thoughts on that?

Well you've been given several proper ways here... or you can go with the lame a$$ route those shade tree guys suggest.
It is your choice after all.

^^^ Those guys are both great mechanics but they worked on these things during the depression so their view on cost/benefit of a repair is alot different

Denny, I'll get a pic this afternoon. As expected it is half worn out on where the bottom of the shaft rode the bushing. It certainly appears original and it had 60 years worth of carbon flakes built up in the intake manifold.

I have it blasted cleaned ect and have decided that I will take the shaft to Ace Hardware with me and see if I can get one that fits good and then I'll drill the manifold out if I need to. I've drove vehicles with the damper removed and they can be a pain until the engine is "up to temp".
I'll keep you guys posted. Do it Once...Do it Right...if you can.

Alvin,

I've heard that too. Not sure if this is right or wrong but here what i was hypothesizing...The purpose of the dampener is to atomize the fuel until the engine reaches "temp" then the heat causes the spring to expand and the dampener opens, but dosen't the choke accomplish the same thing by adjusting the air fuel mixture? If you were to run with the choke adjusted till it warm up then take the choke off wont that compensate for the lack of the dampener, so instead of atomizing the fuel within the manifold by heat, couldn't you just accomplish the atomization by air/fuel ratio.

I don't know, but I'm definitely interested in hearing opinions about your logic there, H4C...

Brad

Nah, they don't make any difference who needs a heat riser.
General Motors only puts a factory heat riser system in their
engines because the engineers got bored and had to have
something to do. Keeps the guys on the production lines busy
also, other wise they would be just siting around drinking
coffee.
They should have gone to the school of hard knocks where those
mechanics went, just think of all that money they could be
saving the stock holders.

dg

haha that's clever but...can you still effectively atomize the fuel using other methods, is the question. There are abundance of examples where people have found alternative methods compensating or improved performance of their vehicles by simply adding, subtracting or modifying factory components, for instance look at all the development in the aftermarket performance industries...is that development moot bcs GM didnt produce it from the factory? If GM always gets it right the first time then why are there so many recalls. hahaha

We need a GMC guy to step in here with a picture of their heat riser because them boys at GMC got it right. The GMC heat riser bushing is night and day better than a Chevy heat riser.

Alvin, when you see the GMC version I think that is the way to go and a competent machinist can redo the Chevy version. That's the plan I have for my dual '53-'54 Corvette exhaust pivot. It has a small leak and I think that problem can be solved, I plan on bringing the manifold over to Grigg this summer.

Good Luck, brother.

Denny, as promised here is a pic after I got the heat riser out showing the two bushings. I believe these to be original.

The one on the right was the one that was worn half into.
http://i140.photobucket.com/albums/...xhaust%20Riser%20Damper%20repair%202.jpg

Probably because its the side where the weight is. I had to persuade the other one to come out but still came out intact.

http://i140.photobucket.com/albums/...pe/Exhaust%20Riser%20Damper%20repair.jpg

I got a stick of 5/16" rod and plan to press the old rusted rod out that is pressed into the weight. Then put new bushings in the manifold.

*** Trying to find 5/16 bushings is a joke around my little town. I can drill out the manifold holes to size if need but try finding a brass bushing here with the 5/16 ID! I even looked at the door bushings at the parts house but no luck. I might make me a couple out of a piece of pipe or some kind of tubing. Dang, all I need is two.

*** for those wondering, I took my small dremel tool with a cut off wheel and cut the weld holding the "tongue" to the rod. There was carbon build up UNDER the little rod that dang near welded the two pieces together! Once the welds were cut I took my big ball peen hammer and smacked hard on the end and it fell out. Hey, I thought about using a couple pop rivers to attach the tongue to the rod. I'll probably burn it up using my old stick welder!! The kicker is that the "heat spring" is $17.50 plus shipping. Hmm, maybe I need to just thread it and put an allen head screw in the holes?!

there is a common misconception with aftermarket `improvements`

its not that the after market `designers` are better its just that after market parts suppliers are not restrained by such things as noise, pollution or safety legislation. The oem designers have to find a compromise between all these factors and performance if they are to create a vehicle they are legally allowed to sell.

+1 for what Denny said.


im not sure if criticism of the design as being particularly weak is justified given that most are still working after what 60+ years. Way way beyond the expected product life. The valve only opens twice/start up so really a bushing isnt actually very necessary....at least not for the first 60+ years of use.......

isnt Chevy just a brand name of GMC, dont/didnt the same people largely design for both?


I served my apprenticeship at british leyland and was always being told of the differences in quality, engineer design skill level and reliability between (at that time) Rover, Austins, Triumph, MG, Daimler, Land Rover, Bently (body) , Rolls Royce (body),; etc etc, when the reality was they were mostly designed, fabricated and assembled by the exact same people. im wondering if the same is mostly true of GMC and chevy

First, I stand by what i said... "abundance of examples where people have found alternative methods compensating or improving performance of their vehicles by simply adding, subtracting or modifying factory components" ...this concept is NOT mutually exclusive to the example I used so I'm not sure where you going with that one...

Second, I have not criticize the product or the life expectancy in any shape or form, therein. All I was inquiring about was an alternative way to remedy the problem.

All I was wondering was instead the cost of repairing the heat riser parts and machine work, which may not be adjusted right when you assemble it anyway would another option be to just use the choke. "To start a cold engine the choke is used to enrich the mixture is required. Without the choke, the fuel charge that reaches the cylinders would be too lean to ignite because colder air is denser. Even if the engine did start, until heat transfer occurred, fuel distribution might be impeeded because the gasoline would puddle in the runners of the intake manifold. Another concern is the slow cranking speed of the engine during start and the excessive friction that must be overcome by the starter motor. a choke would be required to enrich the air/fuel mixture, this is kinda what the heat riser does to atomize the fuel and once the intake manifold is hot enough for good fuel vaporization, you can take off the choke as opposed to actually the heat riser doing the job is what i was thinking

Here is my take.
1) A cold engine runs better with a warm intake. Fuel won't puddle up on the bottom of a warm intake runner.
2) A warm engine performs better with a cold intake. Do not remove the flapper.
3) A heat riser stuck in the warmed-up-engine position will not warm up the intake at start up, and cause the fuel to fall out of suspension and puddle up on the bottom of the intake runner. This liquid fuel will not burn and will end up leaking past the rings and end up in the crankcase, diluting the oil resulting in excessive engine wear.
4) A heat riser stuck in the cold-engine position will cause excessive heat at the intake, resulting in poor performance once the engine warms up (see #2) above).
5) You live in Michigan (a great place to be from BTW). You need a fully functional heat riser. Sure, you can get by with one stuck in the warmed up position (many people do), but your engine will suffer premature wear.
Carl

um...im not denying this.
what i said was that this is not because these people are necessarily better engineers than the oe mnf are, but because in many cases that the oem is restricted in what he can and cant do for legal reasons (such as pollution control) Designs are often about compromises, it can be easier to make performance improvements if you take away/dont have the legal requirement to compromise.



that wasnt directed at your comment, sorry if you felt it was there was other people replying in the thread



i dont think the choke is serving the same purpose as the riser. its about vaporising the fuel not fuel/air ratio




can you get by without a heat riser, yes
will your performance suffer a little, yes


slap some weld on it grind it round and shove it back in - job done, cost zero, good for another 60 years

i think people obsess a bit about these valves, even if it leaks a bit what do you think will happen?

Thank you!! Great info, Carl!

The manifold on my truck currently is frozen in the cold position and I do notice lack of performance when it warms up and at higher RPM's

I also have a manifold that is gutted (it was given to me that way) ...i might try to rebuilt this one bcs its already off the truck, I've seen the springs for sale but I have not seen the over-sized rods, anywhere

post number 4 in this thread

Missed that post...thanks Drmike!

On second though I might go the exxtra mile and fix it the right way, the reason I was gunna epoxy putty it too was bcs it has a super loud exhaust leak there and I wanted a quieter ride so I thought a sure way was to plug the hole, when you fixed your have you noticed any exhaust leaks?

it still leaks a tad as evident by some sooting but the small sound is certainly not an issue and hard to notice unless i go looking for it.

i suspect they have always leaked from new a bit i dont think its an issue unless they are very badly worn

that very well maybe true, but on the other hand i do have a 40 coupe that doesn't have that problem but then again it was a low mile survivor so a lot of the components I've never touched and you can tell it wasen't used hard, while who ever owned my truck beat on it hard everyday

Boy, never dreamed this thread would go where its gone

...no use going into a lot of detail right now but insteadk of paying that high price for an "oversized rod" drop by the hardware store, or Lowes where I got mine, and for less than $4 bucks you can get a 3ft stick of 5/16, which is what mine is, and make your own. Press the old one out, put the new one in and cut a slot for the spring with a dremel cut off wheel or some other. There is also enough room in the flapper to go a little oversize on the rod and still work nicely in flapper.

.....you can drill the manifold to what size you need. But check close for bushings. Either way.....its a nice satisfying project regardless of which, or what, you do to yours. I'll keep mine original....or as Cletis would say "restored to original".

Got my exhaust manifold fixed and figure I'd return and report.
** I decided not to replace the stem/rod. Smoothed it up good.

1. used a dremel tool with cut off wheel, to cut the spot weld, on the "tongue" inside the manifold so I could pull the shaft out. I cut right beside the tongue edge.

2. Yes it has bushings... bought two 3/8" O.D. brass FLANGE bushings at Ace Hardware with 1/4" I.D. Then I drilled the I.D. out to 5/16" which is what the stem measured.

3. The 3/8" bushings fit snug in the manifold but was to long so I inserted the bushing from the inside and using my cut off tool I cut it smooth with the outside, then took it out and inserted it the right way. Before I inserted it I mixed up some high temp JB Weld I had on hand and rolled the bushings in it, stuck them in place, and let set overnight. The JB Weld set up nice and hard and should stop any tiny exhaust leak that may have been there.

4. Then I inserted the stem through the "tongue" and manifold.

5. Put the tongue in place and tacked it with the wire welder.

6. Installed the spring I got from JimCarter. The only place I found it. Sad part is it cost $17.50 before discount.

Wish I could have found a steel flange bushing but I think I'll be alright. The stem/tongue move freely and smooth.

I'm done.....hope tis may help or answer some questions for someone along the same path someday.