Hi everyone,

I am just in the middle of getting all the accessories and vaccum line fittings installed on the 455. I am wondering what this part is and what does it do....do I need it? Or can I take it off? I do not remember having one on my previous 455 motor.

 

No, it's not needed. Olds regularly installed extra unneeded parts to reduce profits.

OK, seriously, this is a dashpot. It's designed to slow the closing of the throttle when you release the accelerator suddenly to prevent stalling.

 

As per Joe. It's identified in the CSM which demonstrates the proper setting (employing a feeler gauge), as well. I believe it is part # 412277. I replaced mine a couple years ago.

 

You actually had me thinking...."what the..?"

Thanks for clarifying, I will leave it installed.

 

I thought Joe was unhinged for a second.

 

Okay so I found a diagram of the Dashpot in my Assembly manual. It says (Air Condition only) beside the picture of the Dashpot. My car is does not have A/C, so my question is should I just leave it bolted onto the manifold or remove it? I do not have any rod or bellcrank or required brackets that works with the Dashpot.

 

Are you looking at the correct illustration? The title shown is "cruise control carburetor linkage". Do you have an illustration for w/o cruise control?

 

The dashpot was only used on 68-70 cars with A/C (the cruise control is not the issue). If you delete the dashpot, be sure to reinstall the bolt, as that hole will be a vacuum leak otherwise.

 

Awesome thank you Joe!
I have removed the Dashpot and put the bolt back in.

Slow and steady wins the Races!!

Thank you.

 

Considering that the engines were similar in 71, what was the solution that enabled not using these any more?

 

I’m the least well educated guy in this discussion, but my impression of the purpose of the dashpot was to spike (raise) the idle just a bit when the AC compressor is engaged. To keep the engine idle low when disengaged, and keep the engine from stalling when A/C is engaged.

This compensating device is present on my A/C-equipped ‘66 Starfire. Never was on my ‘66 98 with no a/c.

Chris

 

That particular dashpot isn't actively controlled. It's just a spring-loaded plunger with a diaphragm. It has no idea if the A/C is on or off. All it knows is that when the throttle arm on the carb hits it, the spring compresses, the plunger moves, and the diaphragm slows that process.

 

I believe there was a solenoid on later cars that increased the idle speed when the AC was on. It was in the same location as the dashpot. I guess the dashpot did not totally solve the problem or perhaps a rough idle at too low an RPM was reason enough to replace the dashpot with the solenoid.

 

Those were used for other reasons as well. I think a lot of people overestimate the 50 rpm drop of an AC compressor or so. Sometimes those were anti-dieseling idle stop solenoids, the idea was you adjusted idle to when they were on, and, when ignition was shut off, they'd drop and put you below idle on the throttle, shutting your fuel down, too.

 

Gents, there have been discussions in the past regarding the slow-idle dashpot’s use on the 659 engine A Body cars. Specifically, the 1970 PIM, Engine Assembly, Sec 6 pg 29 & pg 73, specifies its use during the 1970 model year (659 engine: S.M.T ALL & A.M.T with A/C).

Hope this is helpful.