After i ran out of time playing roof AC redesign today i changed gears and started tackling the stumble/almost stall on initial throttle application.

First order of business was to replace as many bad vacuum lines as i could see....2 more to go...the ones to/from the vacuum control solenoid. {i'm not sure who pissed of that Olds 403 emission engineer but he should try changing the 2 vacuum lines behind the power steering pump filler neck}. Next was to look/test all the vacuum actuators....you guessed it the throttle lever actuator or throttle pusher as the parts manual calls it....seized solid.

So the question for today.... does anyone know the part number for a new one? [ps: i'm not really a jamb the BB in the vacuum hose kinda guy but i will if this little gem of an actuator turns into the most collectible piece of GMC history]

Sir, you do know that throttle pusher is only active with the engine running and gear shifter in Drive?





6cuda6 wrote on Sun, 03 May 2020 19:07

After i ran out of time playing roof AC redesign today i changed gears and started tackling the stumble/almost stall on initial throttle application.

First order of business was to replace as many bad vacuum lines as i could see....2 more to go...the ones to/from the vacuum control solenoid. {i'm not sure who pissed of that Olds 403 emission engineer but he should try changing the 2 vacuum lines behind the power steering pump filler neck}. Next was to look/test all the vacuum actuators....you guessed it the throttle lever actuator or throttle pusher as the parts manual calls it....seized solid.

So the question for today.... does anyone know the part number for a new one? [ps: i'm not really a jamb the BB in the vacuum hose kinda guy but i will if this little gem of an actuator turns into the most collectible piece of GMC history]

Try being a tech working in the trade, trying to make sense of all that
stuff like spark retard where there once was advance, and vacuum there when
the engine was pulling hard and there should not have been any, and hoses
galore, and the beat goes on, the beat goes on.
Jim Hupy
Salem, Oregon

On Sun, May 3, 2020, 4:38 PM Matt Colie via Gmclist
wrote:

> I can (unfortunately) tell you how it ended up like that..
>
> After some poor dyno jock finished doing a map of spark and fuel loops,
> somebody looked at the data and said "we can't have this - fix it." That
> meant push off the performance part of the map into a better emissions
> part of the map. That was a what ever it took effort. You would not
> believe
> some of the cheap tricks that were tried. The one I always admired was
> holding the advance curve back in the lower gears so the extra heat would
> get
> the catalyst lit. Another good one used to be keeping the engine near
> stoch (stoichiometric - ideal) but making alternate between rich and lean to
> keep the cat hot.
>
> Great times they were - NOT
>
> Matt - the refugee from dynoland
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
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I can (unfortunately) tell you how it ended up like that..

After some poor dyno jock finished doing a map of spark and fuel loops, somebody looked at the data and said "we can't have this - fix it." That meant push off the performance part of the map into a better emissions part of the map. That was a what ever it took effort. You would not believe some of the cheap tricks that were tried. The one I always admired was holding the advance curve back in the lower gears so the extra heat would get the catalyst lit. Another good one used to be keeping the engine near stoch (stoichiometric - ideal) but making alternate between rich and lean to keep the cat hot.

Great times they were - NOT

Matt - the refugee from dynoland

I think the best ever was Cadillac's 1986 4-6-8 engine.... one of the few cars i never wanted to work on and didnt care what they wanted to pay us...i know a few techs that would have liked to hang the engineers that designed that thing.....lol.

Matt Colie wrote on Sun, 03 May 2020 19:38

I can (unfortunately) tell you how it ended up like that..

After some poor dyno jock finished doing a map of spark and fuel loops, somebody looked at the data and said "we can't have this - fix it." That meant push off the performance part of the map into a better emissions part of the map. That was a what ever it took effort. You would not believe some of the cheap tricks that were tried. The one I always admired was holding the advance curve back in the lower gears so the extra heat would get the catalyst lit. Another good one used to be keeping the engine near stoch (stoichiometric - ideal) but making alternate between rich and lean to keep the cat hot.

Great times they were - NOT

Matt - the refugee from dynoland

Sir, I thought the 4,6,8 engine was started in 1981 with the trunk less Seville? Anyway as a side note.. the last 403 I worked on with a flat spot off idle ended up being a bad carb gasket under the top plate. I took it off to inspect and replace accelerator pump. It was at the GMCMI rally in Tallahassee. Jim Bounds had a used carb he gave me for parts and I salvaged the pump and gasket. Most people remove that idle pusher and the vacuum valve on the front of the pass head and the solenoid on the front of the drivers head, but being OCD ( old, cranky, dyslexics ) I put it back on.



6cuda6 wrote on Sun, 03 May 2020 20:30

I think the best ever was Cadillac's 1986 4-6-8 engine.... one of the few cars i never wanted to work on and didnt care what they wanted to pay us...i know a few techs that would have liked to hang the engineers that designed that thing.....lol.

Matt Colie wrote on Sun, 03 May 2020 19:38

I can (unfortunately) tell you how it ended up like that..

After some poor dyno jock finished doing a map of spark and fuel loops, somebody looked at the data and said "we can't have this - fix it." That meant push off the performance part of the map into a better emissions part of the map. That was a what ever it took effort. You would not believe some of the cheap tricks that were tried. The one I always admired was holding the advance curve back in the lower gears so the extra heat would get the catalyst lit. Another good one used to be keeping the engine near stoch (stoichiometric - ideal) but making alternate between rich and lean to keep the cat hot.

Great times they were - NOT

Matt - the refugee from dynoland

So I have a SOB, 1977 on a Dodge chassis with a heavy duty Dodge 440
I've had the top end of the motor apart. The only emissions stuff I see is
Crankcase (valve cover) breather is into the air cleaner. I HAVEN't found a
PCV valve. The coach was built by Champion. An y idea why it doesn't have
Emmissions stuff? Perhaps it was classed as a truck ??

Does any one have data regarding emissions requirements for 1977 by GVW?
I'm trying to understand why my SOB has so little emissions stuff compared to
what I think I'm reading people have on their GMCMH. I know in the now
discontinued smog testing in Ontario my MH was NOT required to be
tested. I doubt that Dodge could have guessed that the completed coach
would end up in Canada