k5 Improvements

[K85 Octane]

Boy, there's nothing like bumping a 3 year old thread to ask an unrelated question.

But at least I got to post another picture. Don't hate, Chris

 

[bubba blazer]

I have a 1985 k5 blazer, and I've changed the egr valve, cat converter, tune up, etc, but the nox is high. A mechanic said that because I have headers, and the egr system is a negative back pressure system, it's breathing too good, that's why it won't pass... Has anyone with headers ran into this problem?

Rob -
If you're still looking to lower your NOX try this:
1) retard your timing
2) add a bottle of octane booster and run super unleaded
3 check for vacuum leaks (I had to replace my brake booster)
4) increase your spark (I had a used MSD box with a CA EO# lying around)

Unfortunately, I wasn't able to test individually which of these were the most effective, but my NOX dropped and I eventually passed. I'm running the factory CCC carb and computer and edelbrock intake and shortie/mid length headers on a rebuilt 355 4 bolt block and RV cam. It's running leaner than I like, but getting ok mpg (15-16 highway, 10 avg). Don't feel bad - current CARB requirements are stricter now than when the trucks were new...the state is trying to get rid of our vehicles by making smog harder to pass. If it gets any worse, I may have to consider a LS swap or at least a FI system (the K5 was my dad's so I want to keep it going).

 

[Rob Armstead]

Rob -
If you're still looking to lower your NOX try this:
1) retard your timing
2) add a bottle of octane booster and run super unleaded
3 check for vacuum leaks (I had to replace my brake booster)
4) increase your spark (I had a used MSD box with a CA EO# lying around)

Unfortunately, I wasn't able to test individually which of these were the most effective, but my NOX dropped and I eventually passed. I'm running the factory CCC carb and computer and edelbrock intake and shortie/mid length headers on a rebuilt 355 4 bolt block and RV cam. It's running leaner than I like, but getting ok mpg (15-16 highway, 10 avg). Don't feel bad - current CARB requirements are stricter now than when the trucks were new...the state is trying to get rid of our vehicles by making smog harder to pass. If it gets any worse, I may have to consider a LS swap or at least a FI system (the K5 was my dad's so I want to keep it going).

Thanks for the 411 Bubba!
I'll these tips this week

 

[Rob Armstead]

^try