HAC valve question

[dfcruiserguy]

I was replacing all the vacuum lines in the 60 and i was on the last one and while pulling it off i broke the stem right off of the uppermost hose from the HAC Valve, I was wondering how neccesary the HAC valve is seeing as I'm in SC at about sea level, probably under.

P.S. The new vacuum lines look awsome, got em from autozone for in all about 50$ I needed 30 feet of the little stuff and ten of the slightly larger.

 

[Cruisergreg]

HAC doesn't kick in until around 4,000 ft. If your truck hasn't spent much time going back and forth through that height then it's probably been frozen for a while. Just make sure to cap all the ports.

 

[jwest]

You could also try repairing it with a cyanoacrylate (krazy or super glue). Goes by a bunch of different name. It just needs to hold the weight of a vacuum hose.

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[dfcruiserguy]

so the air just flows through it freely at sea level? How does the HAC effect the carb and emissions?

 

[jwest]

The diaphragm in the HAC is sensitive to altitude. At elevation it advances timing and leans out the air/fuel mix.

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[dfcruiserguy]

so my main concern is, do i have to replace it or can i just cover the port up with some putty or something like that and plug up the hose, or does it have to be connected to the HAC

 

[jwest]

Like i said, can you glue the pintle back on the valve?

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[sixty]

plug all the hoses. it will run rich over 4000'. all you have to do is pull one of the plugs to create a vacuum leak to lean out the mixture when you travel over 4000'.

New valve is like $50 from toyota I believe.

 

[jwest]

Pretty sure the new one I just bought was around a hundred. That could've been with shipping.

You'll also lose the advance feature by plugging.

If you insist on bypassing and need to lean the mixture for altitude, there are two HAC circuits (a primary and secondary) you can open on the carb. These are the two outer ports located on the upper air horn facing the front of the motor. The hose in the middle is for the choke breaker.

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[Cruisergreg]

plug all the hoses. it will run rich over 4000'. all you have to do is pull one of the plugs to create a vacuum leak to lean out the mixture when you travel over 4000'.

The HAC's real influence is the additional 6 deg of advance it provides. The enleanment really doesn't do much at RPMs above idle.

 

[dfcruiserguy]

i don't have the pintle, someone threw it away, i'm at or below sealevel and the highsest mountain in SC is only like 40 ft above sealevel, i don't plan on getting to 4000 anytime soon. so is rich good for sealevel or should it be lean. i'm still learning.