Emissions issue

[CRM]

Someone in the past has messed with the smog system. The smog pump is gone. Upon inspection of all the lines, I've come to the conclusion it's messed up. I'm posting a picture of original next to what I have. Any line with an X on it isn't there. I've drawn in lines to show current routing. A couple of lines are plugged. Also found a tee behind the carb that someone had used a screw for a plug. Screw was barely in. I installed a new rubber plug for now. Are there any emission techs here that have any ideas? Should I just pull everything that isn't needed, and what would that be? What would the possible drawbacks be to doing it? Should I just buy a smog pump and put it all back to factory? I'll be putting less than 1,000 miles a year on it. It won't be used off road. More horsepower and better mpg's aren't a concern of mine.

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[newguy11]

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[newguy11]

Above is my hand drawn vacume routing for my sbc 350 after deleting the smog pump and associated valves. ( although I retained the egr ) I hope the above is of some use to you.

I think restoring to factory or deletion the unnecessary equipment are about the same amount of work ( give or take ) it’s up to you.

I deleted the smog equipment because I already had the motor out and wanted to simplify things a tad

 

[newguy11]

This doesn’t look right. This part should be a manifold vacuum T
The pic appears to show a thermal vacuum switch which uses engine coolant temp to turn those vacuum ports on and off.

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[CRM]

Thanks, but that drawing is extremely hard to read. The part you circled is the manifold vacuum source. There is a tee in that circuit.

 

[SirRobyn0]

@CRM I've talked about this in other threads. But here is the basics.

Here's the facts of how the air system works. It pumps air into the exhaust manifold, where it mixes with the exhaust gases, then it goes down the stream into the cat. Having the air mixed in there helps the cat to burn off the bad stuff and also helps the cat reach operating temperature faster. I tried running my truck without the air pump and the amount of exhaust smell was greatly increased. NOx emission will go up as will other emissions, the important thing of note is that NOx is very good at destroying lung tissue. If you happen to have breathing issues then this is very important.

You can run an engine without the cat and without an air pump obviously. Best reduction in emissions comes from having both. Having one or the other functional will help some. In my example above what I noticed was it took about 30 minutes of driving before my exhaust cleaned up with the pump disconnected, and it would sometimes drop out at idle. For me, I'll keep my cat and air pump because I've gotten pretty sensitive to exhaust and the reduce smell is great. If your new truck happens to be an 80's 305 they run such low initial timing that are VERY smelly at idle without the air pump and cat.

You will see no noticeable change in horsepower or gas mileage either way. Yes, there is some drag to the air pump but not enough that you'd be able to notice whether hooked up or not.

My two cents. I'd leave it as is for the moment if possible, once you have the truck on the road if fine with whatever amount of exhaust smell is present or not then pull the rest of the air system off. If your not happy with it then source the missing parts and re install.

Hopefully this helps.

Where you planning to run a cat on the new exhaust system?

 

[SirRobyn0]

Oh and please leave the EGR valve hooked up, and if it's already been disabled get it working, at least within reason. If the manifold passages are plugged up I can understand seeing how it operates without it. Besides reducing emissions it reduces cylinder head temps, which reduces pinging and can help reduce dieseling.

 

[CRM]

Thanks Rob. It doesn't have a cat, and during an extensive search for the factory system and parts, there was no cat listed. It's an '85 with a 350.

 

[SirRobyn0]

Your welcome Casey, but something doesn't seem right about it not having a cat from the factory. My 84 C20, federal emissions came catalytic converter & air pump equipped. C/K10 federal trucks were getting cats by the late 70's. There were rigs that did come factory with an air pump and without catalytic converter, but that was earlier on in the 70's. I wonder if why you are not seeing a cat listed is because the factory pellet type converter is discontinued (and would have been long ago), the expectation if you lived where emissions testing is required is that you'd use a modern day universal type honey comb cat. Light years ahead of the pellet cat BTW. I can't remember this is a Blazer you have is that correct? Let me know and I'll try looking it up tomorrow in my reference material at the shop for you if you want.

 

[fast 99]

If it has a fuel fill nozzle inlet restrictor it likely came with a cat. And yes most light duty trucks had all the period emission equipment.

 

[rpcraft]

Does your state even check emissions on older vehicles? You might check. many states have a provision for vehicles over a certain age being exempt. If that is the case less is best when it comes to emissions equipment. It's often easier to take a lot of it off and remove 40 year old rubber lines to eliminate vaccum leaks and such. Just food for thought.

 

[AuroraGirl]

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[AuroraGirl]

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[CRM]

Thanks again Rob. It is a K2500 truck. We don't have emissions testing over here on the best side of the state, so the cat will not be getting installed. lol.

 

[SirRobyn0]

Does your state even check emissions on older vehicles? You might check. many states have a provision for vehicles over a certain age being exempt. If that is the case less is best when it comes to emissions equipment. It's often easier to take a lot of it off and remove 40 year old rubber lines to eliminate vaccum leaks and such. Just food for thought.

Wa state does not, nor does Pasco so he's good to go there if he chooses not to run it. We all have different opinions on emissions equipment, and I personally would never suggest to someone with a fully intact working system to take it off, but when it's already missing pieces. It's all about his comfort level with whatever comes out of the exhaust (smell ect).