15 replies to this topic

[mdj]

Merry Christmas!

 

Finally throwing some time at my UC hatch project after a bit of a layoff. Found this while prepping the tank for EFI.

 

Now, I assume it's not normal for the vapour line to to plugged like that, and I'm going to assume the charcoal canister is cactus as well ..

 

:-)

Attached Files

•  VapourLineWTF (1).jpeg   127.57K   12 downloads

[76lxhatch]

Looks like someone has done it deliberately, but not a good idea

[Shiney005]

I'm guessing that UC has the sealed (non breathable) fuel tank cap, so that little modification would have created a vacuum in the tank. The charcoal cannister should still work fine once plumbed up properly though.  

[mdj]

I'm guessing that UC has the sealed (non breathable) fuel tank cap, so that little modification would have created a vacuum in the tank. The charcoal cannister should still work fine once plumbed up properly though.  

 

Yeah, the cap that was on the car was a bit stuffed so it wasn't sealing correctly. I've put a new lockable sealed cap on. 

 

One thing I've wondered with charcoal canisters, do they block the vacuum pull from the manifold when they're not "purging" ? It strikes me as a kind of crappy thing that air/vapour is getting into the fuel system after the carby/TBI, or is it only during high manifold vacuum when you're cruising so who gives a crap ?

 

Matt

Edited by mdj, 01 January 2025 - 07:22 PM.

[yel327]

Yeah, the cap that was on the car was a bit stuffed so it wasn't sealing correctly. I've put a new lockable sealed cap on. 

 

One thing I've wondered with charcoal canisters, do they block the vacuum pull from the manifold when they're not "purging" ? It strikes me as a kind of crappy thing that air/vapour is getting into the fuel system after the carby/TBI, or is it only during high manifold vacuum when you're cruising so who gives a crap ?

 

Matt

 

Originally they just used the same vacuum signal that a manual distributor uses to suck the fuel vapour into the carby. So it only happens on part throttle, you don't want vacuum advance on a manual at idle and the canister was the same.

[mdj]

Originally they just used the same vacuum signal that a manual distributor uses to suck the fuel vapour into the carby. So it only happens on part throttle, you don't want vacuum advance on a manual at idle and the canister was the same.

 

My car is auto so not using ported vac for the distributor. I'm actually trying to work out the best way to route all this (Holley Sniper 2300) given the engine is from a HJ/LH and the car is UC. Once the Sniper is working I'll fit an ICE distributor and do away with vacuum advance as well but I'm finding the Holley confusing as it has comparatively few ports. I'm thing I'll tee the 'carb' line from the canister into the PCV and run the purge line from ported vacuum. Does that make sense to you, yel ? 

[yel327]

Yes I got yours was an auto, what I meant was the canister uses the manual carb's ported vacuum for the purge signal.

 

I don't think you can tee into the PCV line using a 3-port canister, only on a 4-port (like HJ). With a 3-port canister you need to have a dedicated purge port on the carby. With a Sniper or a Quadrajet you only use one port on the 3-port canister (ignoring the tank connection) as the Quadrajet vents its fuel bowl internally and the Sniper has no fuel bowl. So that means the canister will work whenever it has vacuum pull on it - attaching it to a T in the PCV line means it will always have vacuum pulling on it. However, with a 4-port it has the extra ported vacuum source to turn it on. On the 4-port you have the tank connection in the middle, the rear port with a blank on it and the two ports on the round disc have the ported vacuum signal on the small nipple and the T into the PDV on the larger nipple.

 

If the Sniper has a dedicated purge port then you can use the 3-port canister. I don't think the Sniper does though, see attached:

 

https://documents.ho...m/199r11935.pdf

[mdj]

Yes I got yours was an auto, what I meant was the canister uses the manual carb's ported vacuum for the purge signal.

 

I don't think you can tee into the PCV line using a 3-port canister, only on a 4-port (like HJ). With a 3-port canister you need to have a dedicated purge port on the carby. With a Sniper or a Quadrajet you only use one port on the 3-port canister (ignoring the tank connection) as the Quadrajet vents its fuel bowl internally and the Sniper has no fuel bowl. So that means the canister will work whenever it has vacuum pull on it - attaching it to a T in the PCV line means it will always have vacuum pulling on it. However, with a 4-port it has the extra ported vacuum source to turn it on. On the 4-port you have the tank connection in the middle, the rear port with a blank on it and the two ports on the round disc have the ported vacuum signal on the small nipple and the T into the PDV on the larger nipple.

 

I see, so the canister port marked "carb" is actually the fuel bowl vent for the carb so I can block that, and connect purge to ported vacuum on the Sniper since I don't need ported vacuum for other uses.

 

But I guess the dedicated purge port on carbs is to prevent fuel vapour collecting in other ported vacuum areas, like distributors which could get interesting. Sounds like the right way is to switch to the 4 port so the purge control is retained. 

[yel327]

That is what I think is required. I plan to use a VN canister in my HK as it has a Sniper too. The VN canister looks like it has the same ports as a HJ one.

[mdj]

That is what I think is required. I plan to use a VN canister in my HK as it has a Sniper too. The VN canister looks like it has the same ports as a HJ one.

 

I looked at a VL one, which looks like a HJ V8 one with one port deleted, but the bottom vent port has a right-angle on it that would complicate mounting in the usual LH/X/UC spot

[yel327]

I looked at a VL one, which looks like a HJ V8 one with one port deleted, but the bottom vent port has a right-angle on it that would complicate mounting in the usual LH/X/UC spot

HK don’t have a spot, hence why I wanted one as small as possible, plus I can use the VN bracket. Vapour line will be where a LH side fuel line runs so it’ll have to be left side somewhere. You are best with a HJ one I think.

[mdj]

HK don’t have a spot, hence why I wanted one as small as possible, plus I can use the VN bracket. Vapour line will be where a LH side fuel line runs so it’ll have to be left side somewhere. You are best with a HJ one I think.

 

 Yeah, I'll do that for now. I've toyed with the idea of using a modern compact one because the originals are bulky and that location they use would be useful for my pipeline projects (power steering/air conditioning) and some of the modern ones would easily fit up under the guards. The challenge is then needing switched vacuum and I haven't been able to find a seperate vacuum operated vacuum valve, so that would need to be done electrically like modern cars. 

Now that I've thunk this through more, I'm starting to wonder of if the "plug" in the photo I posted is really supposed to be there. It has a small hole it it, so it would have the effect of allowing some vapour to pass, but not liquid fuel in the case the car was inverted. Am finding it hard to find detailed technical information on the UC fuel system, or even the ADR27A LX/HX/HZ/VB one for that matter.

[yel327]

Most of the modern ones seem to be switched via the ECU or use a dedicated purge port like the ADR27A ones. That's why the VN one looks good to me. There will be another from a 1975-1976 car that will work.

 

I'm pretty sure the Gregory's books cover the evaporative emissions pretty well.

 

Here is the VP/VN/VQ/VG/VR one. If you buy one get it with the spring bracket, neat little bracket you can attach anywhere and the spring holds the canister in place. This one came off a VP SS I cut up for the donor conversion, I cut all the engine bay brackets out ofr the cruise control, airbox, fuse box etc and got the entire engine, box etc out of it. As you can see they are pretty small, the ports are labelled:

 

TANK.

PCV

The top one is ported vacuum.

 

 VP canister 1.JPG   222.16K   3 downloads

 VP canister 2.JPG   183.49K   3 downloads

 

 

[warrenm]

The "plug" is a restrictor which is factory, it's to stop fuel going into the line, but allows vapour to go to the canister.  

[Shiney005]

It just goes to show, you can never stop learning about these old girls.

[mdj]

The "plug" is a restrictor which is factory, it's to stop fuel going into the line, but allows vapour to go to the canister.  

 

Ah, thank you! This is what I had deduced it must be for but it is great to hear someone else say it. I only have an LH workshop manual + Max Ellery's and the LH manual only documents the original vent to atmosphere tank. I've left it in!