Stromberg 97, what's missing?

H

HopRod

Member
Trying to get my new tri-power set up running and pulled the tops off to have a look. Who can see an issue with one of the secondary carbs? This is a Big97 Primary/Secondary setup.
 

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The rear carb is missing some parts. On my tri power setup , it runs on the center carburetor and the end carbs come in just past half throttle. The idle screws are all way in on the end carbs. You must have tight fitting throttle shafts and butterflies that seal on the end carbs.
 

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HopRod said:
Trying to get my new tri-power set up running and pulled the tops off to have a look. Who can see an issue with one of the secondary carbs? This is a Big97 Primary/Secondary setup.
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Hello buddy


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There doesn't appear to be any "J" tubes on the rear carburetor either. What is the brass fitting in front of the accelerator pump hole in the middle carburetor? The 3 carburetors appear to be of the improved idle circuit type.
 
No 'j' tubes in front carb either. Perchance are the end carbs factory setup as secondaries and the idle tubes in #3 omitted by accident.

Seems like a lot of fuel to me.
Charlie ny
 
"There doesn't appear to be any "J" tubes on the rear carburetor either. What is the brass fitting in front of the accelerator pump hole in the middle carburetor? The 3 carburetors appear to be of the improved idle circuit type."
So the internals on the BIG97s are a little different than the original 97.
There are no J tubes on the dedicated secondary carbs by design. The brass fitting in front of the accel pump hole is actually the power valve.

But, the rear carb was in fact missing the idle jets from the factory. They were never installed! Darn thing was running super rich and wouldn't respond to jet changes or mixture screw changes. I have a set of Idle Jets on order, so hopefully that will get them back in business.
 
It appears the power valve is missing too, unless secondary big 97's have the power valves blocked ?

Sal
 
Update:7/27/22
After waiting for the idle jets to arrive and getting Covid, I finally got them installed and tested operation. That did help quite a bit but had to jet down from factory 56 jet to 046 on the primary carb to get the AFR back to a reasonable level.
 
How would you rate the performance of them? Had you ran three "regular" 97's on that specific engine before? I'd love a comparison to be done . . .
 
scicala said:
No accelerator pump. That sure seems odd.

Sal
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Yeah, because depending on the specifics of the engine - it may or may not need the extra "shot" of fuel. I would have left them in - as all one would have to do to "disable" them is not put the little pushrod in.

Same goes for the power-valve in the accel pump well . . . no way to know if the engine needed the fuel or not, so why assume that it doesn't. Though, it is a mechanical power-valve, so without the accelerator pump pushing down on it, it wouldn't do anything anyway.

Heck, one might not need the "squirt", but may need the additional enrichment of the PV under load - so you could just remove the leather from the accelerator pump (kills the accel pump but leaves the PV intact).

Me, I'd run three of the middle carbs - and then tune to the engine.
 
So the new Stromberg BIG97 secondary carbs are purposely designed this way. No power valves or accelerator pumps. You have to run them in a progressive linkage configuration and operate similar in theory to the original OEM tri-power setups of the muscle car era. You run off the primary carb and kick in the secondary's once the engine RPM and velocities are up. So far, I really like them. I haven't had regular 97 on this engine before, but have ad regular ones on another one, but they were set up for methanol.
 
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