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Heavy half smog question

Green Monster

Green Monster

1/2 ton status
Joined
Aug 10, 2013
Posts
328
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Location
Thousand Oaks, CA
Hello, I'm new here......just bought a 76 k5. I believe it's the "heavy half" as it has a GVWR of 6200 lbs, 6 in lugs, and no catalytic converters. Since it just passed smog in CA, I'm sure everything is correct. However, I think it has a smog pump. There is a pump mounted on the lower left front of the engine, and the manifolds are plumbed with tubes. I thought the heavy half trucks didn't come with smog pumps. Anyone know? If they didn't, can I remove it? Thanks.
 
Is the smog sticker still on the core support? If so, it would say there.

I'm surprised a 76 would have one, but I think all K5s are considered half tons, no mater what.
 
Oh yeah, and welcome. Seems there are a few new members in the area.

LOL take that thing out tomorrow. I'm going to Azusa Canyon. Test that thing out :D
 
Thanks, K85. Yes, all K5's are half tons, but some have heavy duty suspension that increased the GVWR and reduced the smog requirements. There is no core sticker. Would love to take it out soon, but have to go through it to see what I got!
 
Well, I say you make a few more posts and get some pics up!

I say if you want to take off the smog pump, keep it obviously, and try to pass smog in 2 years. If it's a no go, through it back on lol
 
You're probably right, I can just plug the holes on the manifold. That's the smog pump in the lower left corner, though....right?
 
sounds like a normal 76 blazer. my old 76 was 4x4 manual trans said fed and ca. on the air cleaner.6250 gvwr .it had smog pump air tubes, exhaust heat riser valve,and had the vacum throttle solenoid on the carb.no cat.

heavy half was a 2wd pickup.usually a camper special option.
 
Thanks blaznjon, I ran the VIN and you're right.....just a regular half ton. Glad I don't have cats, though. If I remove the smog crap, will I see much hp improvement?
 
If it's working correct I'd just leave it on. Only robs about 15 hp. If you want to see what it will do just delete the belt and leave it on and hooked up. Put the belt back on when you go for Im test.
 
IIRC, disabling the AIR (air injection reaction) pump will materially change your optimal carb tuning, so if it works, you might just be better off leaving it as is. Otherwise you're gonna have rejet the carb and prolly recurve the dizzy, which seems like a lotta work to un-do in two years.

As mentioned, easy enough to pull the belt from the pump (though IIRC it also runs the alternator so you may want to get an alternator-only belt) ... anyway, run the truck without the pump, and see if runs worse or better.

-- A
 
I doubt it will mater, there isn't an O2 sensor in the exhaust. Now the EGR, that would probably mess with things.
 
just leave it all on there.76 was not a high horse power year and you won`t feel the difference.If thats the motor that came in it ,it has 1.78 intake and 1.5ex valves with the 3/8" thick truck valve stems.the only way you are going to get a noticeable amount of power is to change the heads and and put a cam in it. if you just pull the belt after a while the check valves on the air injection lines will carbon up,smog pump will seize up from sitting and when you go to smog in two years you will buying the check valves at least. put regular ac r45ts plugs in it and gap them to .045 and bump the timing up a few degrees.that year because of the weight specd different plugs with a huge gap like .060 and 2 degrees before tdc.
 
Green Monster said:
Thanks dremu, thinking it may not be worth it, but I may try removing the belt and see what happens.
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Not to mention, for whatever reaosn, once the AIR is disconnected, it seems pretty common for them not to work again when hooked back up. Not sure if there are seals that dry up, if bearing surfaces rust up, or what.

I'd check into the replacement parts for the AIR system before I took anything apart, particularly if you know it has to go back in to be tested in the future.

As I recall, the AIR is relatively quite expensive to replace.
 
Green Monster said:
Hello, I'm new here......just bought a 76 k5. I believe it's the "heavy half" as it has a GVWR of 6200 lbs, 6 in lugs, and no catalytic converters. Since it just passed smog in CA, I'm sure everything is correct. However, I think it has a smog pump. There is a pump mounted on the lower left front of the engine, and the manifolds are plumbed with tubes. I thought the heavy half trucks didn't come with smog pumps. Anyone know? If they didn't, can I remove it? Thanks.
Click to expand...

76 should have a Cat on it, they started in early 75. I believe the only reason for the AIR and smog pump was to give the Cat clean air to help burn off the pollutants.:dunno:
 
Am I wrong in saying the air injection only happens while its warming up? I honestly don't know, but there are vacuum lines and valves associated with the air system, just like the EGR system. I don't think it runs all the time. The pump yes, but it gets diverted to the air cleaner when not going to the manifolds.

The guys bring up a good point, keeping the pump running instead of not. Hadn't thought about that one. It's easy enough to delete, but definitely keep it all.
 
ChrisPerry said:
76 should have a Cat on it, they started in early 75. I believe the only reason for the AIR and smog pump was to give the Cat clean air to help burn off the pollutants.:dunno:
Click to expand...

cats started in 75 on cars or lower gvw trucks. air injection has been around since the late sixty`s.unless some body stole the cat off our factory stock Z28 302 .
 
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