I'm just finishing up a carb rebuild and I noticed this plastic looking deal that is right below where the carb attaches. I think that it is broke and there is supposed to be a line going to it. I was hoping to replace but since I don't know what it's called I'm not sure how to identify it. Thanks for any help you can provide.

 

Here's a better pic now that I took it off. It's definitely broke. Any ideas where I could find a replacement?

 

Looks like a Canadian modification to me.

 

Isnt that where the butterfly valve is supposed to be?

 

It looks like the altitude compensator. Is there a short U shaped formed hose on the side of the carb (connected just above the butterfly valve) with the broken off plastic nub still in the end? If it is, basically it's a by pass that opens at hight altitudes, alowing additional air, helping mainly at idle. You could probably block it off and never notice. For a replacement, I'd try a salvage yard or a place like Apex Auto.

 

I don't have the hoses hooked up right now. Here is a pic of whats inside.

 

PCV valve.

I think Divindriver once it was called something else in the SA. Well, my experience is with older stuff, and it functions as a PCV valve, so that's what it is.

There are ways to fix a broken one. glazedham installed an aftermarkey PCV on his stock fitting. Note it has a short 5/8" nipple like a heater core fitting.

 

Glad i saw this before i posted up the same question
Lol so is it pcv or alt comp

 

on an SA it is the alt comp. if youre not driving over a mountain pass any time soon, it's not needed. GL finding a replacement. i believe these are NLA. i'd putty the hole and not worry about it. block off the nipple. if you drive over a pass, just change out your jets lol

 

Yes, Altitude compensator on the SA. SA Nikkis don't have the big cylindrical Alti Comp on the rear corner; instead, they have this, which is essentially a large-diameter air bypass valve.

They are infamous for breaking when removing the carb, because the hose that connects them is short and rigid, and the plastic gets brittle with age. You have to pull the hose to the left and up as you raise the carb, to preserve them.

Judging from its condition, looks like its been broke for awhile. Part number is 8761-13-770, but I've no idea if they are still available or not.

 

If you still can find fram PCV valves in your area, look for part number FV266. Also get a foot length of 5/8" heater hose. Now clean out the guts of the "alt comp" (feels weird to even type that much when I know it's a PCV valve heheh). Push the hose on the nipple. Figure out how long is a good length by shoving the hex body of the new PCV valve in. It fits snug inside the hose. Maybe use a nylon zip tie for peace of mind or a hose clamp.

The direction of the PCV valve is important but I can't recall which direction it's supposed to go here. One end is threaded with BSP threads (unimportant). The other end is like a 5/16" barbed nipple which is the same as the straight nipple on your oil fill tube. Connect a short length of 5/16" hose and shorten the heater hose until everything fits nicely.

Adjust the mixture screw(s) until it idles well.

 

If it was a PCV valve, it would logically be expected to connect to the crankcase at some point, yes? The "C" being for "crankcase?"

It doesn't.

The SA's equivalent of the PCV valve (Called the Ventilation Valve) is at the rear left of the rats nest. It interconnects the cranckase, tank, and bowl vents to the manifold below the carb.

This dingus we're looking at is a pressure-differential calibrated bypass, not just a one-way valve like a PCV valve. It bypasses air around the throttle plate but only at certain partial pressures. Mainly effects idle mix anyway.

 

Yeah it's been busted since I bought the car last summer. I found a used one on ebay for 27.00 shipped but I am gonna try the fram idea above. $5 shipped off ebay so if anything at least it will seal up that hole. Not exactly sure how important it is. We don't have any mountains here in NoDak. Thanks for the idea.

 

why its 8761-13-770! Mazda calls it a compensator, they have plenty, $43.44 is the list price.

 

Here's a picture of one I replaced awhile back and the formed hose that attaches to the carb. If you find the hose, it will have the broken end still in it. Like I said, you can probably plug both ends off and never notice or you may be able to splice it back together or get a replacement. Its up to you.

 

Wow, they actually still have them? Well, as my plastic tops break off, I'll probably replace them with the proceedure mentioned above. Unless I want a true factory look. Thanks for the part number.