I'm preparing to begin my LS1 swap sometime this week and I was wondering if I can eliminate the evap canister. I thought I heard of some people eliminating this, but I always thought that you needed it. If I do need to keep it, how do I go about hooking it up? Do I need to use the wires from the pcm that go to the evap control?. I'm sure I can figure it out once I get started, but I'm trying to minimize down time as much as possible. Thanks.

EDIT: This is on an '86 Z28.

 

Depending on your somg compliance you may remove it with out afecting engine performance. What state are you in?

 

I'm in Florida, no emssions here. I think I have what I'm going to do figured out. I'll leave the evap line from the fuel tank to the charcoal canister hooked up, but that is all. I was told I could get rid of the charcoal canister altogether, but I would have to run a vented gas cap. No matter what I do, I assume I will have to delete the evap functions from the pcm using LS1 Edit. Does this sound alright to any of you guys? What do you guys recommend that I do? Just trying to check myself before I do something stupid. Thanks.

 

If you are going to leave it all in place and NOT run a vented cap, I would go ahead and hook it up and let it be functional. It's only 2 wires and if your 86 uses a canister with a solenoid on top, you can just tie into that and it will work fine. If you 86 uses the earlier style with no solenoid, then just use the solenoid that's on the LS1 intake. We've done both ways and both work fine.

 

Would I be hurting performance at all by simply running a vented cap? There must be some disadvantage to it or most people would do it. I can't look at my 86 right now, but I know the canister has been messed with because one of the hoses that comes off the top has been cut. I don't remember seeing a solenoid near the charcoal canister, but I'll have to check. If I do decide to run the evap stuff, which two functions do I hook up? The evap vent solenoid and what else? Thanks for all the help.

 

There is no performance disadvantage to running a vented cap. I think most people do it that way. Some states require the purge system to avoid fuel vapors being let into the air.
If you decide to use it, you only need the purge solenoid; none of the vent stuff.

If your canister has a built in purge solenoid, use it. If not, use the LS1 purge solenoid to control your canister.

 

Thanks for the assistance. I really appreciate it, as I don't clearly understand what the evap system does, though I have an idea what it is there for. Once again, thanks for the help, what I have to do is more clear now.

 

Evap is used to catch gas vapors. Ever noticed how carb cars have a gas smell? Evap prevents that.

 

John,

Do you still need a fuel tank pressure sensor to do this?

Thanks,

Colin

 

No, you can eliminate the rest of the fuel tank interface stuff. The purge will just work it did in the days before they added all of the rest of the stuff.

 

I dont really understand what you guys are talking about, but I know that it is important for my swap, 68 camaro w/ ls1. I do not have the evaporator canister that the engine came out of. the vented cap you speak of sounds like it is just a vented gas cap? I do not have to deal w/ emissions at all in my camaro and I am planning on using a stock, sumped gas tank. what would you recomend I do.

 

Can you only use the canister from a V8 car?
I want to use one in my '67 ChevyII conversion......

 

Just a plain old vented gas cap should work fine for you!

 

I would think any factory designed purge canister would work ok in this application.

 

I guess what I'm asking is , will the computer / engine not work properly if it is not connected / controlling the canister's operation thru it's electrical connection?

 

It wouldn't work as well if not controlled by the PCM. The PCM knows WHEN to purge the canister and when not to. The PCM also knows that when it commands a purge, the the mixture will richen. If a purge canister is operating by some other means, the PCM will react differently since it won't know a purge is taking place. It will just see the richer mixture and adjust the fuel trims to compensate.

It's easy enough to hook up using either the LS1 purge solenoid mounted on the intake manifold, or any number of other GM canisters that have the solenoid built in to the top of the canister that I would try to do it that way.

 

thanks for the info

 

This may sound like a stupid question but why couldn't you just run the line back to the gas tank using one of the existing return lines (like in my 72 Chevelle) and forget the evap canistor?

 

so lets clerify this: on a stock ls1 setup there is a purge solenoid on the intake manifold and runs back to the solenoid on top of the canister and then to the gas tank. why did gm use a double solenoid setup?

 

I'm assuming John means to mount the canister purge valve on the intake(where the return fuel line is) without using the canister, which requires a remote mounting area.