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Carb's & Evap Canisters



Well, this has been a real fun week!!!:hb

After not being able to get the '73 started one morning (A really great sunny day), I took the truck and determined to replace the carb that night. After pulling the Edelbrock Perfromer Carb from my '72 Cheyenne, waiting a few days to order in a EGR off-set adaptor, I got it on and then spent the next day driving around trying to get the "NEW" carb tuned in. No luck. Constant backfires through the carb, no good off idle acceleration and basically very rough running in general. I finally figured that the year it had been sitting up (read drying out) had had a negative effect. Back to the Q-Jet. When reinstalling it found that one of the choke linkage arms was too long and would not allow it to close fully. After some bending, got it all back on and working. Bad to running good, but smelling bad. I still have lots of burnt fume smell. My clothes reak after being around it when its running. Sittin, its fine, no leaks, no raw fuel smell. Mainly I end up smelling like a walking Far_, well you get my drift (no pun intended). So, I have to figure the evap canister is not doing its job. Does anyone know how to test that thing? I mean all it is, is a canister of charcoal. I have no clue how to get it to syphon off the burnt fuel properly. HELP:bash
The evap can only filters vapors out of the fuel tank so the car won't smell of raw gas when sitting around a parking lot or closed up in your garage. There is a vacuum duty cycle that will sypon some fumes out of the can while the engine is running to help purge the tank of excess vapors. I know guys that completly remove the vacuum line to the engine (cap it off) and don't have any problems with stinky smells or engine running. The canister will last much longer if it gets purged on a regular basis.

You have a serious carb tuning problem. Refer back to your question about Fuel Injection (sounds better all the time now).

Carbs are tricky as well. You may have the float level too high, and raw fuel is dumping over into the carb at idle and running too rich, or you have the air vents closed too tight, so it is running like the choke is on all the time at idle which results in ultra rich idle.

Looks like you need to slap a vacuum gauge on the intake, and go back to the basics. Tune until you get the max idle vacuum, and look at the throttle blade adjustment. You may have bent the choke arm to full closed all the time.
THanks Chris, I'll keep working on it. I did some vacuume based tuning when I put her back together in January. May need to go back and do some more.

Hey, did you get that email I sent you on the roll bar? Never heard back from your buddy. Would still like to know what it would cost to have one built.

Thanks again.

I replied with his work and home number. He would like to get a call from you as well.

I have that info at home, so if you did not get it, just let me know and I will resend or post here.
Does the carb pad on your intake have the infamous "hot slot" adjacent to the holes for the primaries? This was a bungled design that routed exhaust crossover gases up through a slot to the Q-Jet carb baseplate to improve fuel atomization from a cold start, and required a stainless steel plate between the carb and the pad to protect the carb from the direct blast of the exhaust gases. This plate usually got thrown away when carbs were changed (or stayed there and got burned through anyway), rendering hundreds of thousands of Q-Jets not only unusable, but unrebuildable, and the carb fires that resulted from the lead plugs melting out of the bottom of the carb resulted in the biggest carburetor recall in the history of the industry. If the slot is there and the plate is gone, that heat will destroy any carb eventually; best cure is to drill and tap the holes at the ends of the "hot slot" for allen-head pipe plugs to block the hot exhaust gases - then you can tune the carb instead of putting out the fires.
John, I am trying to picture what you are talking about. I assume (bad idea on my part usually) that you mean the carb base plate and not the intake? My intake is a new Edelbrock Performer. If you are talking about the intake, I will have to look at the old one. I know it did not have a plate. If your talking about the carb base plate, I know it was not solid and had some slots in it. Just cant picture what you are saying (read, my lack of vision). Help me visualize it better.

Take the carb off ( with a full bowl )

Put a CLEAN towel under the carb. Come back in 15 min is if the towel is wet with fuel.

If it is grab a bucket filp the carb over.

There are 2 little freeze plugs on the base of the fuel bowl ( depending on the vintage of your carb) you should be able to see them in a cutaway of the base plate between the two primary throttle plates.

These leak!

Let it dry, rough up the area get some KILLER expoy and seal up that area. Just GLOOP it.

That will take 1 potential problem out of the loop.

Do you also have a VENT in the front top of your carb ( outside the air cleaner area?)

The next thing... is MAYBE your fuel pump is leaking into the block.. pouring gas into the oil sump.... Drive it for a bit and pull the stick

Do you smell gas on the stick? Is the oil diluted?

Thanks Vigman, I check these out. I know that one of the two small plugs had been epoxied. I'll double check it using your method. Thanks for the input.
Did not get your email on the roll bar. Could you either resend, or post the info here? Thanks
Hijinx said:
Did not get your email on the roll bar. Could you either resend, or post the info here? Thanks

All right, when I get home tonight I will post it up.

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