My Desmog Thread (5 Viewers)

[jawjatek]

Well, truck fired right up, smoked a bit from all the PB and Gunk cleaners, and started leaking coolant like a sieve! Guess I'm a better mechanic than I am a plumber. Had to re-do the thermo housing, tap and re-seat the BVSV plug with joint compound this time, and break out my new hose kit from SOR. Now the leaks are plugged and the truck is ready for a test run up 20 miles to a buddies shop with all the tune-up tools, timing light, etc, and we are gonna tune it. I test drove it around the block to heat it up and check for leaks, and she is running much smoother and seems peppier. Can't believe I got all the vacuum plumbing done right the first time, thanks to all the good info on this thread and in the FSM. The engine looks much cleaner without all that crap! I'm stoked.

 

[WHG423]

Doing my desmog now. Everything is going well so far. I am needing my carb and dizzy dine by Jim C. if possible. I have sent three e-mails lately with no reply. I know you are busy Jim, but if you are out there, contact me please. I got the plug kit and pulley from you a couple of months ago. Good stuff!

 

[ayerswc]

alternative to a stock VCV?

Does anyone know if it is possible to use a generic check valve or two in place of the stock VCV? Mine was removed at some point in the past, the part is discontinued, and I am having a tough time sourcing a used one.

Not sure how (directionally) the vacuum is flowing through the stock one.

 

[FJ60Cam]

I don't remember what hoses *should* be connected there, but I just had a tee in the hose coming from the air cleaner. From the tee, one hose went to the distributor (with a check valve to prevent gas fumes from migrating back to dizzy cap) and another hose with no check valve going to the hot air flapper on the air cleaner.

I ran it without the check valve for a long time (not knowing that it was needed), and had the occasional dizzy "pop" at startup. I managed to crack a dizzy cap, though it still ran fine. I just happened to notice it while replacing it.

 

[2fj60]

My desmog is complete except removal of cat. I also rebuild carb and put new intakexhaust gasket not running bvsv and didn't recurve the dizzy just had to retard the timing bout 5 degrees. The truck runs great more throttle response! I love ih8mud!

 

[FJ60Cam]

Congrats!

My $.02 - leave the cat in. Losing it doesn't free up any power, just more noise and exhaust smell. BTDT, and I ended up putting one back in.

Post some pics!

 

[2fj60]

Here are some pics...

 

[2fj60]

Here are some pics...

 

[BreckenridgeCruiser]

So my question is this. I have a bad VCV valve (passenger side) and while looking for a replacement I was wondering if I could just go straight from the dizzy breather to the vacuum intake on top of the air cleaner on the passenger side. Why the need for a valve to open the dizzy to vacuum when the truck starts, but not have it open to air when sitting?

Also... Per the earlier posts (943/944), where are the gas fumes coming from? How do they get into the dizzy to cause the pop?

Any help or explanation would be helpful.

Thanks!

 

[BreckenridgeCruiser]

Okay... Just answered my own question with a search for VCV. JimC states that the fumes come from boiled gas from the carb filling the air cleaner and the VCV keeps them from going into the dizzy and then being ignited by the spark.

So if a VCV fails, I thought it fails closed... If so, then how are gas fumes getting into my dizzy to make the pop?

 

[klinetime574]

Got some questions that I think can get answered here. I referred to the photos posted by @Trapper50cal to aid my desmog process. The questions are to clarify some sort of hidden details.

Charcoal Canister - The lines on the top marked "to tank" and "to purge," should they be swapped if the truck has been desmogged?

Secondary Advance Port on distributor - Trapper appears to have had that line running to the port where the "gas filter" used to be on the intake manifold. It seems like that would supply constant vacuum to the advancer, and would make it sorta pointless. Unless it only activates under a certain vacuum range. So did I read the pictures wrong?

VCV under air cleaner - The ports parallel to each other that are 3mm and 6mm. Are those lines T'd together and then run to the distributor cap?

 

[Joe_E]

Got some questions that I think can get answered here. I referred to the photos posted by @Trapper50cal to aid my desmog process. The questions are to clarify some sort of hidden details.

Charcoal Canister - The lines on the top marked "to tank" and "to purge," should they be swapped if the truck has been desmogged?

Secondary Advance Port on distributor - Trapper appears to have had that line running to the port where the "gas filter" used to be on the intake manifold. It seems like that would supply constant vacuum to the advancer, and would make it sorta pointless. Unless it only activates under a certain vacuum range. So did I read the pictures wrong?

VCV under air cleaner - The ports parallel to each other that are 3mm and 6mm. Are those lines T'd together and then run to the distributor cap?

-My charcoal cannister is hooked up the normal way.

-Dizzy hose goes into back of oem carb. If Weber powered, i forget what i did last time.

-Correct on VCV valve

 

[klinetime574]

Thanks for the reply @Joe_E

I've got the "whoosh" when I undo the gas cap. Swapping the lines should fix that, but will there be a downside?

I got the primary vacuum advance correct. Into the carb same as you have it. I'm wondering about the second hose barb on the distributor. Yours is capped.

 

[taro]

If I'm remembering correctly, I believe the second port on the distributor is for the hac. Did you keep it? I had to toss mine because it was broken. I'm at sea level in Florida though.

 

[FJ40Jim]

Kline, the fuel tank purge system needs a source of ported vac through a BVSV to correctly suck on the tank occasionally. A hatchet desmog & weber swap eliminates that functionality. To prevent the whoosh (and longterm fuel tank weld failure), swap the hoses on top of the canister. That will allow the tank to breathe easier.

 

[Borick]

Does the line swap apply with the OEM carb also? I get the whoosh. Stock carb.

 

[klinetime574]

Kline, the fuel tank purge system needs a source of ported vac through a BVSV to correctly suck on the tank occasionally. A hatchet desmog & weber swap eliminates that functionality. To prevent the whoosh (and longterm fuel tank weld failure), swap the hoses on top of the canister. That will allow the tank to breathe easier.

@FJ40Jim thanks for the response. I forgot to fix my signature. I'm back with the Aisan carb now. VCV's and Violet BVSV in place.

So do the lines need to be swapped if running a stock carb desmog set up?

My engine at the moment:

 

[FJ40Jim]

If everything is hooked up correctly (it sounds like it is) and the tank is still getting a lot of pressure/vacuum, then it is time to try swapping the hoses on the canister.

FWIW, the AC idle up system is all there, it just needs connected from manifold vac fitting to VSV, and VSV to idle up can on carb.

 

[klinetime574]

If everything is hooked up correctly (it sounds like it is) and the tank is still getting a lot of pressure/vacuum, then it is time to try swapping the hoses on the canister.

FWIW, the AC idle up system is all there, it just needs connected from manifold vac fitting to VSV, and VSV to idle up can on carb.

@FJ40Jim Thank you for another reply. I'll swap the hoses.

The AC idle up isn't hooked up because my AC doesn't work yet and I couldn't remember which hose went to which port on the VSV. I'll get that fixed soon.

While I've got you reading, where should the secondary distributor advance port connect to? I believe Trapper50cal had his connected to the intake manifold. But would that not provide constant vacuum on the advancer?

 

[FJ40Jim]

One of the advancer fittings should go to ported vac on the carb base.
The other is not used. Cap it or dump to atmosphere.

Trapper might have connected his to manifold vac for constant hi-altitude advance.