To de-smog or not to de-smog

[ScottH]

Thinking of picking up an 86 GMC Sierra classic that is all stock. Has a 305 with smog pump still hooked up. Would like to get the engine breathing better with an open air cleaner & eventually headers with dual exhaust.

I know its been discussed b4 but what advantages or dis-advantages r there in removing the smog pump & related hardware? Should I just remove the belt or will that cause more problems than its worth? Dont have to worry about inspection as it will be registered as a classic. Also I may be towing a car trailer from time to time so any performance improvement would help.

Any info or suggestions r appreciated.

Thanks
Scott

[Hevy]

If you don't need any of it for inspection I'd remove it.

[broey]

I did it to mine, I saw absolutely zero difference performance wise, but it looked so much better.

[wraprail]

The open air cleaner, while looking cool really just feeds the motor with heated air. Not so good. We use the factory air cleaner base with the "tall" truck lid. I use a Holley so I had to use a 1" spacer under air cleaner base. Plug all the holes not needed and use the factory pipe that goes to the core support. Cut off the baffle for increased air flow. Coat of paint. Now you have a functional cold air intake in the "cheap"
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[Redcap]

Take all that smog crap and toss it directly in the circular file.

[ScottH]

Thanks guys, appreciate the info.

[IdahoMan]

Bump.

I have an 81 Silverado, 305. I wonder if I should remove the smog junk, or if it isn't worth the trouble.

If yes, are there any step-by-step tutorial Thread?

Thanks.

[Dead Parrot]

Check your state's rules first. It will suck if you yank stuff off only to find you need it to pass any inspections you might have. In most states, illegal to pull cats even if you don't have inspections.

Things to keep:
THERMAC - helps engine warm up on those cold mornings. Zero impact once engine hot.
PVC - removes blow by and condensation from crankcase. Since modern carbs are calibrated for PVC, removing can screw things up.
Charcoal canister - provides vent for gas tank and captures evaporated fumes from tank. Near zero impact on performance.

If you have a vacuum advance, try moving it from ported to manifold vacuum. Most folks get a decent low to mid range performance boost.

[Hart_Rod]

I want to pull the smog stuff off of my 87 Jimmy (350 TBI/ 700R4 Trans/ true duals). What can go? What has to stay? Thanks!

Rob

[Hevy]

I would check state laws first then go from there.

[Hart_Rod]

Originally Posted by Hevy

I would check state laws first then go from there.

No issues here.

[Corts60]

Originally Posted by Hart_Rod

I want to pull the smog stuff off of my 87 Jimmy (350 TBI/ 700R4 Trans/ true duals). What can go? What has to stay? Thanks!

Rob

I honestly don’t think you’ll notice a performance gain on the TBI motor. It may just end up making the engine throw codes constantly and keep the light in the dash on. I had a TBI V6 and instead of removing everything, I just got a shorter serpentine belt to leave the smog pump out and left all the equipment there. That way if I needed to, I could just put the bigger belt back on.

[Hart_Rod]

Originally Posted by Corts60

I honestly don’t think you’ll notice a performance gain on the TBI motor. It may just end up making the engine throw codes constantly and keep the light in the dash on. I had a TBI V6 and instead of removing everything, I just got a shorter serpentine belt to leave the smog pump out and left all the equipment there. That way if I needed to, I could just put the bigger belt back on.

Thanks for the info. My smog pump has it's own belt, so I just to it off. I want to remove everything to clean up the engine bay. So far no codes...knock on wood .

[THI]

The AIR Pump is ON/OFF by the computer, the computer receives no information on it so removing the AIR system does not affect anything. EGR removal would require a program change.