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Pulling smog on 1986 305 V8

kennyw

kennyw

@squarebody.chop.shop on IG
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I have a 1986 C10 with a 305. Looks like the HEI has been changed to non-ESC. Air pump and related excess smog likely is contributing to vacuum leaks resulting in a poor highway performance so I want to reduce to essentials only. Looks like I can leave this carb but should I leave this electrical connection?

20210401_124145.jpg
 
That is the mixture control solenoid. If leave it and remove other components the computer will have a hissey fit. Should be upset with the early HEI. Me I wold swap the qjet for a non CCC carb. and do away with the rest. A nice 4g or 4gc electric choke.
 
The feds are trying to make manufacture of egr block plates and the like illegal.
 
Wes Harden said:
That is the mixture control solenoid. If leave it and remove other components the computer will have a hissey fit. Should be upset with the early HEI. Me I wold swap the qjet for a non CCC carb. and do away with the rest. A nice 4g or 4gc electric choke.
Click to expand...
That may be why I cannot get this thing over 55 then if this is CCC, but I thought that was a 4 pin plug. Either way, I have a spare carb to try.
 
Can't get it over 55 may be a backed up cat, a flat cam, stretched timing chain. Not necsesarily in that order.
Disconnect and plug everything at the carb except power booster and pcv. Check for vacuum leaks, fix those. Then get a vacuum gauge on manifold vacuum.
This will show mechanical condition of engine. Unplug the mc solenoid, if it'll stay running.
 
Wes Harden said:
The feds are trying to make manufacture of egr block plates and the like illegal.
Click to expand...
It won't be long till guys with shops & equipment to manufacture things will be outlaws. The non producers have gained a majority over the producers at this point.
 
That's not CCC, there is no TPS that I see.

IIRC that's some sort of temperature based enrichment solenoid.

Don't think it's a hindrance but the non-CCC Q-jets with other electrical components are pretty rare, so it's certainly not one I'm an expert on in regards to inner workings.

Trucks were the only vehicles (at least US spec) that got the hybrid Q-jets, all the cars were CCC, and so were most of the trucks, so finding someone at this stage that knows that design well is gonna be tough probably.
 
Back in the day lots of guys just got a HEI with vacuum advance and a pre-1980 Q-jet that had no mixture control solenoid and ditched the factory EST spark HEI and the electric carb,blocked off the EGR valve and removed the air pump ,plugged all the ports in the exhaust manifolds for the "flute pipes"...
All that gained maybe 20 hp and made passing emission tests difficult or impossible ("visual" had to look factory)...

The poor performance could be related to tall highway gearing and the 305 not being the best torque monster GM ever had...even an empty C-10 weighs over 4000 lbs and square bodies have lots of wind resistance..
I've seen a few TH-350's with a defective stator that made the truck a dog on acceleration and limited the top speed to about 70 mph...
 
I don't 'see" the tps either but IDK of any other system it could be.
 
dyeager535 said:
That's not CCC, there is no TPS that I see.

IIRC that's some sort of temperature based enrichment solenoid.
Click to expand...
That is what I was finding with my searches on here, but I'm not sure if it is OK to unplug it and run without it hooked up or if i should trouble shoot it and get it working.

Alternately, I have a normal qjet i can rebuild and toss on a well.
 
Not sure if my signature shows up, but all the Q-jets variants used are covered in the parts and service manual as I recall. I'm sure those would better spell out its purpose.

I'm thinking it would work without it, failure mode one would think would be to "normal" operation.

Personally I think if I was gonna try and set a qjet up, I'd stick with the later styles. Electric choke, lots of adjustment. I don't think they really have much disadvantage vs the older designs, except the older styles seemed to have a lot more effort put into tuning them (in terms of aftermarket books and articles). Never really had a problem with the later design.
 
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PDF page 9 here http://www.mediafire.com/download/m...Series_Service_Manual_1984_Revision_Pages.pdf

It's a dual capacity pump.

"DUAL CAPACITY PUMP- (M4MED ONLY)
M4MED carburetors include a float bowl-
mounted dual capacity pump valve assembly and a dual capacity pump solenoid assembly. When the engine is cold, more fuel is necessary to insure a smooth transition from idle to part throttle. When the engine is warm, less fuel is needed. The dual
capacity pump solenoid is activated by a coolant temperature sensor. When coolant temperature is approximately 170° F. (77° C.), the pump solenoid is energized, opening the dual capacity pump valve, reducing the capacity of the pump by about one-half."

Guess disconnected would be bad when the engine is warm.
 
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