My Desmog Keeping HAC Lots of Pics

[mwebfj60]

I mainly did this for my records but thought it might help other high altitude cruisers trying to desmog.

Below is the link to the excellent document Borick and Jim C collaberated to put together. I did mine just a bit differently, kept both BVSV and the choke opener, and a few minor changes.

https://forum.ih8mud.com/attachment.php?attachmentid=517068&d=1304299989


***Update Feb 2017***
After six years, starting at post 101 is a proper desmog IMO.



***Update July 2011***

After seven months of tinkering, these are my final settings that worked the best for me. All connections in the pictures are the same except as noted below.

I have routed the primary advance from the carb to the primary advance on the dizzy and routed the secondary advance directly from the HAC port on the carb to the secondary advance on the dizzy (completely removed the HAC valve and applicable hoses and black/white valve and put a cap on the 3 prong port labeled #16. I ran the carb with the two ports labeled #7 and #9 open for a while and capped for a while and found capped to be a little more powerful).

The large hose coming out of the top of the Driver's side VCV and going to the inlet port below the carb: I found that after the engine came to temp and the violet BVSV allowed vacuum for the VCV to open, I would get stumbling through mid range RPM (I could pull the choke a little and it would correct...too much air sucking in)....I rerouted that line from the top of the VCV to one of the ports on the air cleaner and capped the inlet below the carb. No More Stumbling and the charcoal cannister fumes should still be taken care of through the air cleaner vacuum.

Timing is set right at 5 degrees BTDC. After tinkering with it for the last seven months, it is running absolutely perfect. My altitude here is around 4,000 feet and I took it up to 14,000 a couple of times and it's good to go. No pinging, no hesitations, no backfiring, just nice and smooth from 650 through 2900 rpm.

 

[mwebfj60]

more pics

 

[mwebfj60]

more pics again

***EDIT*** The black and white valve should go the other way, white toward the manifold and black toward the T ***

 

[mwebfj60]

and more pics

 

[nunrush]

Thats a clean looking engine. I'm a noob, could you tell me why you didn't use the Primary Advance off the carb? It went to the dizzy right?

 

[LAMBCRUSHER]

Thats a clean looking engine. I'm a noob, could you tell me why you didn't use the Primary Advance off the carb? It went to the dizzy right?

FWIU, when de smogged, the primary advance and mechanical advance combined make for too much advance, and when combined w/ the smaller advance of the secondary diaphram from the HAC input, it will lead to preignition. Someone please correct me if I am wrong.....

 

[Eporter]

Looks clean! My HAC valve is in questionable condition. I'd like to incorporate the HAC function into my desmogged engine.

SO, how do I created a manual valve? I'd like to just turn a lever on the dash, and manually allow the changes that the HAC does.

Is this possible? I guess a working HAC would be better, but they all seem older, and getting less reliable.

HAC Testing

 

[mwebfj60]

Looks clean! My HAC valve is in questionable condition. I'd like to incorporate the HAC function into my desmogged engine.

SO, how do I created a manual valve? I'd like to just turn a lever on the dash, and manually allow the changes that the HAC does.

Is this possible? I guess a working HAC would be better, but they all seem older, and getting less reliable.

HAC Testing

Just unhooking the HAC lines from the carb and letting the carb vents pull air from atmosphere leans the mixture just like the HAC allows. You could just jump out when you get to altitude and pull the lines open? That's the way I understand it anyways.

 

[LAMBCRUSHER]

You could rig up the ports from the carb to open to atmosphere using a spare VSV, operated by a switch on the dash. But you will still need to advance the timing by about 5-6 degrees. I guess that could be done thru another VSV??? why not? Flip the switch and open three ports to atmosphere, AND open another VSV from the dizzy outer can, and manifold vacuum??? Good question.

 

[FJ40Jim]

Just unhooking the HAC lines from the carb and letting the carb vents pull air from atmosphere leans the mixture just like the HAC allows. You could just jump out when you get to altitude and pull the lines open? That's the way I understand it anyways.

First, lemme say thanks for posting these pics Mweb. Very good reference.

You are correct. The 3 HAC ports would be capped at low altitude and open to atmosphere at high alt.

You could rig up the ports from the carb to open to atmosphere using a spare VSV, operated by a switch on the dash. But you will still need to advance the timing by about 5-6 degrees. I guess that could be done thru another VSV??? why not? Flip the switch and open three ports to atmosphere, AND open another VSV from the dizzy outer can, and manifold vacuum??? Good question.

It's a good idea, BUT...

The 3 HAC fittings on the carb are for 3 separate circuits. If they were all tee'd together, then connected to a VSV, at high altitude, they would work fine. All 3 would pull in extra air through the VSV as they needed it. But when the VSV was closed, the idle fitting would be sucking, and it would pull fuel in through the other 2 fittings. At higher speed, the primary main HAC fitting would suck fuel out of the secondary....

What is needed is a VSV that when off has 3 separated vac fittings, then when on connects all 3 to a common port (atmosphere). Or 3 separate VSV's powered by one switch.

And like you said, one VSV to connect the HAC port on dissy to manifold vacuum at altitude.

 

[LAMBCRUSHER]

First, lemme say thanks for posting these pics Mweb. Very good reference.

You are correct. The 3 HAC ports would be capped at low altitude and open to atmosphere at high alt.



It's a good idea, BUT...

The 3 HAC fittings on the carb are for 3 separate circuits. If they were all tee'd together, then connected to a VSV, at high altitude, they would work fine. All 3 would pull in extra air through the VSV as they needed it. But when the VSV was closed, the idle fitting would be sucking, and it would pull fuel in through the other 2 fittings. At higher speed, the primary main HAC fitting would suck fuel out of the secondary....

What is needed is a VSV that when off has 3 separated vac fittings, then when on connects all 3 to a common port (atmosphere). Or 3 separate VSV's powered by one switch.

And like you said, one VSV to connect the HAC port on dissy to manifold vacuum at altitude.

That makes perfect sense. thank you for clearing that up.

 

[mwebfj60]

Hey Jim, or anyone that knows...why is the passenger side VCV there? Is there a reason you wouldn't want to have the dizzy breathing with the air cleaner when the engine isn't running? Moisture issue? I think mine is toast and I am having a hard time justifying $40 something for a used one. Thanks!

 

[nunrush]

FWIU, when de smogged, the primary advance and mechanical advance combined make for too much advance, and when combined w/ the smaller advance of the secondary diaphram from the HAC input, it will lead to preignition. Someone please correct me if I am wrong.....

Hmmmm I'm gonna have to take a look at my desmog again and redo some things. Thanks for the info!

 

[mwebfj60]

One thought that I bounced around for quite a while was this...what about just routing the primary advance from the carb to the secondary advance on the dizzy and keeping the primary on the dizzy capped. This would keep the vacuum advance at 7 degrees versus 15.

 

[FJ40Jim]

Hey Jim, or anyone that knows...why is the passenger side VCV there? Is there a reason you wouldn't want to have the dizzy breathing with the air cleaner when the engine isn't running? Moisture issue? I think mine is toast and I am having a hard time justifying $40 something for a used one. Thanks!

When the engine is shutdown, the hot manifold boils the gasoline out of the carb bowl. The gas vapor fills the air cleaner and will work it's way down the hose into the dissy. When the engine is restarted the dissy will ignite internally. If the mixture was just right, the flame front could travel up the hose from dissy cap to air cleaner, and blow up the air cleaner. Cool!

I say do it.

Send me an EM, I'll sell a tested good VCV for less than $40.

 

[FJ40Jim]

One thought that I bounced around for quite a while was this...what about just routing the primary advance from the carb to the secondary advance on the dizzy and keeping the primary on the dizzy capped. This would keep the vacuum advance at 7 degrees versus 15.

That works fine and is what is often recommended, especially if the dissy has not been repaired and has the worn governor pin problem (allowing excessive mechanical advance).

For a truck at hi-altitude, I recommend keeping the dissy routing stock: ported vac to primary advance, HAC vac hose to HAC advance. It's less likely that there will be spark knock at hi-altitudes. If spark knock is heard, then retard the base timing a couple degrees.

 

[RAMZ]

Thanks for the pics.

Now where do I start again?

Do you have the JIM C. dizzy and carb?

 

[mwebfj60]

Now where do I start again?

Do you have the JIM C. dizzy and carb?

Glad to help out.

No, I am running the stock dizzy and I rebuilt the carb. It is running really well right now...knock on wood...I am going to pick up a spare dizzy when I find a good donor and send it off to Jim to see the difference. I did get the air pump idler pulley and other little pieces from Jim though. Great to do business with...quick ship...as advertised..and I think we can all agree he knows his sh**.

 

[mwebfj60]

That works fine and is what is often recommended, especially if the dissy has not been repaired and has the worn governor pin problem (allowing excessive mechanical advance).

For a truck at hi-altitude, I recommend keeping the dissy routing stock: ported vac to primary advance, HAC vac hose to HAC advance. It's less likely that there will be spark knock at hi-altitudes. If spark knock is heard, then retard the base timing a couple degrees.

Good stuff Jim, Thanks again!

 

[mwebfj60]

Ok, I rerouted my vacuum to original, ported primary on carb to primary on dizzy, HAC to secondary on dizzy. Got a little knock so I retarded base timing 2 degrees. Then 3 degrees...knock went away. Now the idle is a little rough. Thoughts?