Adding HAC on a desmogged 2F (1 Viewer)

[HemiAlex]

I’ve got a completely desmogged truck now with a jimc distributor and a city racer carb.

I’ve got the red HAC pod and nothing else. Where should i start to add the HAC back to my truck? Can i have the hac be switch or manual valve operated when I reach elevation?

I’m driving into CO in September and I’d like it to be all in order.

 

[4Cruisers]

There's a thread here on MUD re: manual HAC, just ran across it a day or two ago.

 

[OSS]

I might be wrong (wouldn't be the first time) but I'm not sure the carb sold by City Racer has the necessary air ports for a HAC system. See the emissions FSM under HAC. It shows where the vacuum hoses connect to the stock carb. If you don't have those ports in that carb, then it no worky.

At altitude the standard fuel mixture will be richer because there's less oxygen and the spark will be too retarded because it won't burn as fast. The HAC system meters in extra air to the carb when the valve kicks on. Essentially a metered vacuum leak.

So if that carb doesn't have the HAC ports, you can still advance the distributor spark via the outer vacuum advancer diaphragm via a direct vac hose to the gas filter fitting on the manifold. That will definitely help. Connect it when you get near 4000 ft.
Also use regular gas. Lowest octane at altitude.

Conceivably extra air could be added to the A/F mixture simply by pulling a vacuum hose somewhere and noting how well the engine ran, but that's pretty sketchy, and potentially could be detrimental if the A/F mixture leaned out too much.

I do know that when the HAC system isn't functioning correctly above 4000 ft, the engine doesn't run as well. It still runs, but you can tell something isn't quite right.

 

[NeverGiveUpYota]

^^^ that one there makes a very valid point.

 

[HemiAlex]

He always does!

I’ve honeslty thought of just using a quarter turn inline valve to pop the hood, and turn enable the HAC to avoid wiring.

I can very easily do that and once I’m at altitude I won’t need to mess with it for a while.

Thoughts?

 

[OSS]

Yeah you can see in the drawing for the HAC system that air gets injected at three locations, so there wouldn't be a way of just yanking a vacuum hose and getting the same effect. But older carbureted engine (like my old '78 Toyota pickup I used to have) didn't have any HAC system at all. I used to drive it up to the local ski resort (8000 ft elevation) and it ran well enough but of course gutless (though traction was another story).

 

[FJ40Jim]

Can't add HAC to the non-US carb, doesn't have HAC ports.

 

[HemiAlex]

Can't add HAC to the non-US carb, doesn't have HAC ports.

Is there any work around to isolate it from the carb to add it?

 

[OSS]

If you look at the drawing you can see that extra air is metered in at three spots in the stock carb when the HAC system kicks in. There's no way to duplicate that in a carb that doesn't have those ports.

 

[4Cruisers]

I set the base timing on my '76 FJ40 with FJ60 electronic ignition at 10* BTDC because I live at 7,240 feet. The '76 carburetor has the vacuum advance port, I just had to hook it up to the distributor (inner, not HAC, vacuum port). Vehicle did great, with a little loss of power, on Engineer, Black Bear, and Imogene Passes in the San Juans. Imogene is over 13,000 feet.

 

[cwwfj60]

I think your better off just bringing a timing light. Add a few degrees once your in CO and ramble on....it's going to be slow either way

Unless of course you were planning on spending a significant amount of time at altitude...then a re-jet would be in order.

 

[HemiAlex]

I set the base timing on my '76 FJ40 with FJ60 electronic ignition at 10* BTDC because I live at 7,240 feet. The '76 carburetor has the vacuum advance port, I just had to hook it up to the distributor (inner, not HAC, vacuum port). Vehicle did great, with a little loss of power, on Engineer, Black Bear, and Imogene Passes in the San Juans. Imogene is over 13,000 feet.

That’s exactly what I run now. This is good to hear.

 

[4Cruisers]

That’s exactly what I run now. This is good to hear.

I forgot to mention that I re-jetted the '76's carburetor when I rebuilt it. I know I wrote down the jet sizes but can't find the info now. Besides, the FJ60 is jetted differently.

 

[IS2SPICY4U]

I just finished desmoging my 2F last week. I kept the HAC. Although port A on the HAC is broken (has been since I bought the 60) so is not connected. Am at low altitude and the most I'd go be around 5,500 ft. Mainly going over the pass to go to Bend for the weekend. I did open the HAC and gave it a good clean, there was nothing but dust in what remained and resembled its air filter in the bottom housing. Am planning on putting a new 'filter', nothing but one of those round make up removal cotton pads from the wife. LOL. Anybody know where can I find a HAC?

I haven't gone up that way yet to test if there is any difference on the engine but am sure I will sometime before the winter. Even though one of the ports is not connected, does the HAC really makes a difference?

Desmog is so fresh that I still have the new vacuum routing in place to test drive it for a few more days. This weekend I'll be adjusting timing and valves. Running it on stock carb and distributor and so far it runs great.

 

[Willard]

This is an interesting concept.

Manual HAC

 

[OSS]

does the HAC really makes a difference?

Yes.

Its definitely noticeable to me at 4000' elevation - and up, but old carbureted engines in the 70's didn't have an altitude compensation system like this, so if all you're doing is climbing a 5000' summit and descending, it's not a huge deal. You'll just have less power above 4000'. If you lived above 4000', it would be worth it to get the system working.

 

[gregnash]

Can second what @OSS said. I live at 4600ish feet and regularly travel to the family cabin which is just over 6k' with having to climb summits that top over 7k'. This does make a difference as the power going below 4k' feels almost the same as above. Kinda like when you know that your secondary is working properly on the carb because you feel that extra little kick. Not a huge difference but something that is noticeable.

 

[IS2SPICY4U]

Yes.

Its definitely noticeable to me at 4000' elevation - and up, but old carbureted engines in the 70's didn't have an altitude compensation system like this, so if all you're doing is climbing a 5000' summit and descending, it's not a huge deal. You'll just have less power above 4000'. If you lived above 4000', it would be worth it to get the system working.

Thank you for the prompt reply. This confirms that the HAC hasn't really been working prob since day 1 then. I did drive over the summit a couple of summers ago and I crawled at 35MPH in second gear all the way up. Down in the valley is back to normal. Noticeable, but I can live with it. Of course at the time I thought it was the infamous exhaust leak/hesitation issues on the 2F.

 

[boerboel313]

I just finished desmoging my 2F last week. I kept the HAC. Although port A on the HAC is broken (has been since I bought the 60) so is not connected. Am at low altitude and the most I'd go be around 5,500 ft. Mainly going over the pass to go to Bend for the weekend. I did open the HAC and gave it a good clean, there was nothing but dust in what remained and resembled its air filter in the bottom housing. Am planning on putting a new 'filter', nothing but one of those round make up removal cotton pads from the wife. LOL. Anybody know where can I find a HAC?

I haven't gone up that way yet to test if there is any difference on the engine but am sure I will sometime before the winter. Even though one of the ports is not connected, does the HAC really makes a difference?

Desmog is so fresh that I still have the new vacuum routing in place to test drive it for a few more days. This weekend I'll be adjusting timing and valves. Running it on stock carb and distributor and so far it runs great.

Can I see a picture of the HAC? Nevermind. Just saw the diagram.im looking at going back to OME carb and dizzy

 

[HemiAlex]

So after stressing about this, I never got the HAC on the truck.

I drove from sea level to 12,800 feet with my 305,000 desmogged 2F. 2,700 mile round trip.

We drove all the way to right before Raton NM before noticed the engine start to change in little subtle ways. First thing I noticed was that the idle dropped lower.

So we stopped and pulled the timing light out, bumped the timing up to just outside the timing window. I assume that’s about 14* initial. I reset the idle and left the fuel screw alone.

That was all I did for the remainder of my trip. It ran for 15 hours over two days without an issue up to aspen. To be safe I ran 93 the whole time and i never heard or felt detonation.

I then spend 5 days driving to and from trails with about 5-9 hours of 4Low climbing up and down mountains.

It never overheated, poured black smoke like i was told it would or even hesitated. I overfilled it about a quart on oil one morning so it smoked a little, but that was it.

It ran back to Texas doing 80mph without issue. When I got back to the altitude that the idle had dropped at, I reset the idle and let the timing alone. Kept running good fuel and now I’m at sea level back home and it’s still not detonating. I usually run 93 anyway because it’s cheap from Costco at 2.80/gal.

It got 15.5 mpg driving there and back on the less hilly parts and did great.

In the future when i get a jimc carb, I’ll add the HAC back. But for now this cityracer Fuji carb and a bunch of timing did everything I needed.