Heat riser exhaust leak - replace with new or ?

[rrunnertexas]

OK, I'm pretty good at removing and replacing the intake/exhaust manifolds on my 1935 PJ 201 since it has been done 4 times in the past few weeks.  Why? Because I'm chasing an exhaust leak and found it this morning.  (All new gaskets are clean and no sign of leaks.) The heat riser shaft bushings have a large clearance and exhaust is escaping through the shaft/bushing.  Shining an LED light and I can clearly see the gap.

 

Has this happened to anyone else?

 

Two thoughts on this....  stick the heat riser valve closed to allow maximum exhaust flow leaving the shaft/butterfly plate in place and plug the shaft leaks with an exhaust rated sealant?  Or, order a new heat riser repair kit and install new bushings and the rest?

 

I'm in Texas, so do I need the heat riser working 100 percent for the first 5 minutes or not worth the effort?

 

 

[sidevalvepete]

Fix it if you can. I think it is always good to keep these old design functions operable if possible. One of the querks of driving these old cars.?

Edited May 15, 2021 by sidevalvepete

[Dodgeb4ya]

A common high mileage wear problem.

In Texas you probably don't need an operational HR.

So.....Installing the kits that are available are a rated grade C- IMO.

The set includes a double set of shaft bushings and shaft,spring and plate.

Grinding and welding required to install.

I have had to ream the bushings in jobs I have done.

The bi-metallic spring wrap is somewhat off also...too loose or too tight...

If your old spring is working properly I'd say use it.

[rrunnertexas]

Yes, the riser and spring are working perfectly as is, except for the leaking exhaust.  High mileage wear problem - and an interesting one to have.

 

The C- grade of the replacement kit does not instill confidence when the new parts are installed.

 

Did you give it that grade to the poor fitment or low quality of the parts?

[Sam Buchanan]

I used a bolt to seal the holes in the manifold when I removed the heat riser on my '48. Different looking manifold but the same idea should work on yours. I haven't missed the heat riser, a blockoff plate is between the manifolds.

 

[Dodgeb4ya]

1 hour ago, rrunnertexas said:

Yes, the riser and spring are working perfectly as is, except for the leaking exhaust.  High mileage wear problem - and an interesting one to have.

 

The C- grade of the replacement kit does not instill confidence when the new parts are installed.

 

Did you give it that grade to the poor fitment or low quality of the parts?

The dis-satisfaction mostly was in the spring not calibrated correctly....I also saw one friends that the spring was completely made wrong...wound backwards!

The bushings can easily be reamed.

There also is in the kit the damper and alignment tab.

But lucky someone is making them!

Edited May 15, 2021 by Dodgeb4ya

[47Jim]

Don’t do whatever I did, just spent half a day reaming the manifold and the bushings, fitting, refitting until it all looked great, loose but not crazy 

then took it to a buddies for him to weld it, the thing got so tight, you could hardly move it with your hand, not knowing anything about welding, I can only speculate that too much heat was applied bending or warping something 

I just cut it out and am back to square one, I’m interested in the solution to your problem 

[keithb7]

On the topic of heat risers. I agree it  may not be of much benefit in the south.  Yet...
 

I learned something interesting. It makes sense to me and I think, is worth sharing.  My .02 to provoke some discussion. 
 

A cold engine is chocked off at the carb intake to create a rich air/fuel mixture. Rich A/F leads to inefficient fuel burn. Leaving behind unburned carbon. It accumulates and builds up. Carbon gathers on the valves, top of piston, piston ring groove behind the top ring, cylinder head etc. Carbon is very abrasive. Like teeny particles of sand grinding away at your engine internals. There will always be some carbon in these engines. Running SAE30? Have a look in your oil pan. Although I’ve not personally studied the sludge build up, I wager there’s plenty of carbon and soot in there. Best to minimize it where possible for over the life of the engine, it builds up. 
 

I’ve seen carbon build up above the top piston ring on the sides of a piston. It can score up cylinder walls pretty good. Then internal engine wear compounds and progresses, pretty quickly. Oil burning escalates, adding more nasty by-products of combustion into your crankcase. 

If enough carbon builds up behind the top piston ring, a piston ring will crack. We know that at the top of a cylinder that’s where the most wear occurs. As the cylinder wears, the cylinder tapers downward, closer to new bore specs at the bottom of the cylinder. The piston rings are sprung. They open outward at the top of the cylinder. More-so as the bore wears. The piston ring gap squeezes closed again as it travels to BDC. As carbon builds up, the ring can’t squeeze inward as it travels down. It jams up against the carbon and the ring cracks. 
 

Atomized fuel form droplets too as the A/F mixture rides through the cool intake manifold.  Entering into the cylinders, again not burning efficiently. More carbon. The heat riser valve heats the carb base and intake manifold up much quicker. Enabling cleaner efficient fuel burn as soon as possible.  
 

It gets pretty darn warm down there under the hood of a car in Texas.  Sun and hot ambient temps certainly help. I suspect that the heat diverter valve system still gets things hotter yet. Sooner. Aiding in reduced carbon build up. Its worth having a functional Heat Diverter valve I think.  I’d rather be running a cleaner engine and crankcase. I’d rather be rebuilding an engine at 60,000 miles versus 40,000 miles, for example. 
 

Edited May 15, 2021 by keithb7

[rrunnertexas]

47Jim,

 

Ahhhh, after all that time, money, effort, etc.  - that is very frustrating.  So, lesson learned, when repairing this riser, perhaps make one or two small welds to secure and get out before warping happens.

 

Dodgeb4ya - if I do the replacement route, sounds like reaming is needed.  Forgive my ignorance, by chance do you have a picture of the reamer you used and the size?

 

Keith - I'm so on the fence, replace or JB weld it in place?  Hummm....

[keithb7]

@rrunnertexas

 

Truth be known I don’t know a darn thing about welding either. I did buy a 220V buzz box tho. I am learning. 
 

When I took my engine apart I found the exhaust heat valve floating around inside the exhaust manifold. I welded it back onto the shaft, like your buddy did with yours. Mine went back together fine. It seems to work fine too, when I bench tested it. I don’t have my engine back yet. The machine shop continues to tell me what they think I want to hear.  Like come back in a week.  3x times now.

 

When my engine is back together I’m confident it’ll work. No bent shaft or issues from welding at all. And I’m incredibly talented at making slag! Lol. 

Edited May 15, 2021 by keithb7

[rrunnertexas]

I'll think some more tonight.....

 

A new riser kit is about 100 dollars delivered.  Certainly a joy to install and get working correctly before carefully punching out the original bushings without cracking the cast iron manifold.  Plus fitting the new bushings and hoping the clearance is correct for operation.

 

A tube of JB weld and some careful "staking" of the shaft and bushings to keep the valve free flowing (closed) are 15 minutes of time.

 

Coin toss?  

 

 

[Sam Buchanan]

1 hour ago, rrunnertexas said:

 

 

A tube of JB weld and some careful "staking" of the shaft and bushings to keep the valve free flowing (closed) are 15 minutes of time.

 

Coin toss?  

 

 

 

No brainer.

[47Jim]

What did you decide? Kinda funny, I was watching one of those old Chrysler master tech films on YouTube and it mentioned why you don't want the riser stuck one way or the other.

I was able to fix mine up, cut and ground the welded shaft from the plate, made a new shaft from a 5/16 stainless bolt, some grinding, drilling, tapping for screws, toughest part was trying to make that long thin cut on the end of the bolt for the spring and weight, my hacksaw line wasn't pretty but it worked. I used three screws when securing the plate to the shaft, put a little cut at the end of the screws and spread them a bit the capture, it all works perfect, tested spring action with a propane torch, now hopefully I won't have your exhaust leak at the bushings, we'll see.

Edited May 21, 2021 by 47Jim

[rrunnertexas]

47Jim,

 

I decided to use JB weld to cover the areas where the exhaust was leaking out of the shaft/bushings.   I took the car out for a ride yesterday afternoon and had it up to 55 mph.  Felt pretty good and exhaust noise was gone!   

 

Picture attached of the JB weld (Extreme heat) type used for the repair.

 

Will see how long this will last.

[harmony]

I live in the warmest winter weather area in Canada.  So I get to use my car a couple times a week during the winter time.  When the temps are about around 5C. (42F) and it's sunny, I'm out there. ( no salt on the roads) .  Due to a recent episode with installing a new HR spring incorrectly, I decided to go back to not having a spring.  I have no issues at all even at those fairly chilly temps with the engine running poorly.  I usually warm up the engine a minute or two anyways before taking off.  With fluid drive I don't have the option of feathering the clutch when it's cold or pulling out the manual choke to compensate for the relatively cool engine.  Even on start up my Sisson choke does its job well.  After that brief warm up period the fluid drive holds the car at a full stop and the engine runs smooth while in gear with a foot on the brake. 

Perhaps I may be doing some injustice to the inside of my engine as Keith mentioned, but as far as performance goes, I don't miss that heat riser spring at all.