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425 ci Exhaust Manifold (heat riser) valve frozen


alex bonino

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Was just finishing replacing an aftermarket electric choke with a stock thermostatic choke, and doing the necessary adjustments when i noticed that the heat riser valve wasn't moving. Tried the usual stuff as recommended in the shop manual....tapping the shaft with a hammer, spraying with Liquid Wrench, etc......nothing worked. I'm guessing the valve is stuck in the closed position, which isn't good, so I gotta fix this.

Was interested in if anybody else had run into this, and what they did to free the valve, short of unbolting the exhaust pipe and removing the valve to work on it.

The thermostatic spring doesn't look too healthy either, so I spent some time looking for a replacement heat riser valve or kit ...and there aint none. Will later model Skylark, etc versions fit?

thanks again

Alex

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Trust me, everyone runs into this at one time or another on an old car.

Unbolting the valve piece from the manifold is a good place to start. Then you can play around with it up where you can get at it more easily, without hurting something or yourself.

You can try applying heat. You can try soaking in kerosene.

Or you can just cut the butterfly off and stick it back in. Problem solved! Unless you live in a cold part of the world and you plan to drive the car in winter. Then you want one.

If you can;t get that one loosened up, get a used one that is not frozen and bolt it in.

I don't know what other cars the spring will cross with. I suspect all full size GM vehicles of the era.

I took my butterfly off. It does not get that cold for that long down here in Houston to need it.

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Thanks for the replies, gentlemen!

I kinda figured I'd wind up having to unbolt that mother....you know.....I was just hoping for an easy way out. I'll report back in a few weeks on how it goes.

Based on googling it is indeed a VERY common problem on vintage metal. I've been lucky in the past, i guess - or maybe never even noticed?? (BTW the Chrysler Imperial owners site has a very exhaustive and comprehensive series of articles/threads on the issue.....ranging from one school of thought that says just remove the damn thing, to the other, which maintains the valve is an integral part of the overall cold start/warm up system ie.,carb calibration, choke setting, warm up time, intake manifold temp, etc, etc and that removing the valve messes with that). I'm going to go ahead and either try and fix this one, or find some sort of used replacement.

Is the GM goop still available over the counter at GM or other parts stores??

thanks again.

Alex

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Guest John Chapman

Had the same problem with my '65 Skylark.

Removed the valve and was able to get the butterfly free. Spring is a bit iffy, but with the butterfly valve free seems capable of opening as designed.

For lubricant, I used FelPro zinc anti seize paste. While it's not designed for this use, it seems to be working well four years after the rebuild. I think the zinc content adequately prevents corrosion and acts as a dry lubricant, as the petrolium base in the mix has long since evaporated.

There are more suitable high temp compounds out there, notably nickel grade anti seize which should be stable to above 2500 degrees F. Look for the note that it meets/exceeds MIL-E-907E.

A good industrial supply house will have both.

Cheers,

JMC

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There are so-o-o many penetrants out there that are better than "Liquid Wrench" of which PB Blaster is better & Aerokroil (Kano Labs) is better yet & I've heard reported yet another "good one"--but can't, for the life of me, remember it now.

Soak daily "w/ good stuff", for about a week, & then do your tap & twist thing.

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Guest Riviera66

The correct lubricant is sold by GM... though most dealer parts counters don't know what it is anymore. # is 1052627

Darwin Falk

1966-70 ROA Technical Advisor

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Guest John Chapman

Darwin,

Very useful. Found a list of other GM care products on a Chevy truck site:

1050002 Top Engine Cleaner

1052196 Lubriplate Lubricant

1052271 80w90 Axle Lubricant

1052358 Positraction Additive

1052367 EOS/Assembly Lube

1052627 Heat Valve Lubricant

12345104 Fuel System Trtmt. 20oz

12345347 Hydraulic Clutch Fluid $

12345515 Fuel System Trtmt. 12oz

12345586 Cooling Sys. Fast Flush

12345837 Auto Trans. Conditioner

12345866 Power Stg. Fluid 16oz

12345867 Power Stg. Fluid 32oz

12346290 DexCool Antifreeze

12377916 Synchromesh Trans Fluid

12377967 DOT 3 Brake Fluid

12378508 Auto Trac Fluid

12378470 Dexron III/Mercon ATF

Avialable via GM Parts Direct at: http://www.gmpartsdirect.com/

Cheers,

JMC

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Good luck finding the EOS/Assembly Lube as GM has caved-in to EPA & are no longer producing it. You are limited to finding some current (older) supply that has not yet been cleared from GM dealers' shelves.

Like some mental giant has said before,, "when they're gone-- they're gone" (or something to that effect). Good luck on your "search for EOS".

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