So kind of keeping track of things to come and realized I have no clue what year my Olds 350 is? The 67 has it swapped in where the previous owner explained he thought it was original. He was helpful, as sure it had a power-glide too! Okay, he being wrong all around, I'm at least in the neighborhood.

The engine has factory valve covers with stamped "oldsmobile" letters. The head casting is "6" with corresponding numbers indicating it's a 1970 flavor. The head looks up as pre-smog so that's good. The exhaust manifold has a strange butterfly valve, flapper deal. The rest is bolt-on stuff like Edelbrock manifold/carb, HEI distributor etc., so no clues there.

So, if I were to need parts or accessories, I'm thinking claiming it's a 1970 350 should be close enough? Guessing they didn't make many changes to it for a few years?

The exhaust manifold bugs me. Were they using that type control in 1970? I've seen those used back in the 60's as some sort of thermal control flapper to gag your engine on cold start-up. Could this be the 330 manifold moved over? Yikes!

I have a Frankenstein!!

 

Yup, apparently with a variety of parts. The embossed valve covers were only made in 73-74. The VIN derivative on the block will tell you the year of the block. The heads are 1970 issue. Post the casting number on the manifold.

 

And bimetallic heat riser valves were on every Olds through the late seventies (when they went vacuum-controlled with the early computers), if I'm not mistaken (sorry, I'm not up on late-'70s-and-later cars of any make).

- Eric

 

Much of the info can be found here: http://www.442.com/oldsfaq/ofhed.htm

 

Where might that block VIN live? The 442.com, Heads FAQ mentions pass side of the distributor but no go.

The exhaust manifold numbers would be:

380001 D1 LH (with the thermal valve)

381921 D4 RH

What purpose does that manifold valve serve? Anyone "jam" them or weld them open. Seems to make strange rattles until warm.

 

https://classicoldsmobile.com/forums...s-engines.html

 

— from the Chassis Service Manual

It closes to direct exhaust gasses through the intake manifold crossover, to warm the carburetor.


Sure, all the time. If you don't drive in the frigid cold, they don't really serve any purpose.

- Eric

 

Thanks, I couldn't quite catch on to how it works.

So, any preferred way to tweak them to full open?

I'll check up front for a block ID.

 

The car has two exhaust manifolds, one for each cylinder bank.

If it's a single exhaust car, the driver's side manifold connects to the crossover, which connects to the passenger side manifold, which connects to the exhaust.

If it's a dual exhaust car, each manifold connects to the exhaust.

There is also an intake manifold crossover passage under the carburetor, connected to the center exhaust ports in the heads.

The driver's side exhaust manifold has a heat riser valve at its outlet.

In normal operation, all warmed up, the bimetallic spring on the heat riser valve is relaxed, and the bobweight falls down and keeps he heat riser valve open, which allows the exhaust gasses to pass freely out of the driver's side manifold and out of the system (either through the passenger-side manifold, if a single-exhaust, or straight through the left-side exhaust pipe if a dual exhaust).

When the engine is cold, the bimetallic spring is tight, and causes the heat riser valve to rotate clockwise (as seen from the rear, where the spring is) to its closed position, raising the bobweight against gravity.
With the heat riser valve closed, exhaust gasses can't leave the manifold the normal way, and must instead flow through the intake manifold crossover into the passenger-side manifold, and then out through the passenger-side exhaust. This brings hot exhaust gasses right under the carburetor, warming it and the intake manifold, preventing carburetor icing and fuel condensation, and causing a smoother, faster warmup.

If the engine is pushed hard before it is warm, the excess force of the left-side exhaust gasses pushes against the heat riser butterfly, which is offset, forcing it open against the bimetallic spring, and escaping through the normal path.

As the engine warms up, the bimetallic spring heats up, and the heat riser valve opens, allowing the gasses to exit normally, and reducing the volume of exhaust gasses passing under the carburetor.

As for how to keep it open, I prefer cutting through the shaft, removing the shaft and the butterfly (if still present), tapping out the shaft stubs, and MIG welding the shaft holes.
Simpler ways include disconnecting the spring and wiring the bobweight down.

- Eric

 

Thanks Eric that seems straight forward.

The aftermarket has some replacement manifolds without this feature but Ka-Ching for the pair! These do not cross over as dualed. The intake has been changed to Edelbrock so manifold ports may be long gone. The spring and bob weight are indeed on the drivers side. I don't see any additional plumbing so it's kind of mysterious what is does as is.