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PCV emissions routing with Holley carb


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#1 Cook

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Posted 23 October 2019 - 02:26 PM

Hi all.  I'm trying to work out how I should run my hoses, and I understand that Holley carbs aren't great when it comes to emissions etc.  I have:

 

308 with VN heads

Harrop dual plane intake manifold

Holley avenger carb.

3 outlet charcoal canister (don't know if this is correct).

 

Here's a pic from the carb instructions and I am thinking:

 

1. Instructions say this full vacuum source providing vacuum for the air cleaner.

2. PCV.

3. Power brake

 

What I intended on doing was running the PCV from the rocker cover to #2.

The hose from the other rocker cover to the air filter

 

What I'm stuck with, assuming the above are right, is how/where do I run the 2 charcoal lines to.  I was thinking of capping the carby one and just run the purge to a T piece in the rocker cover line going back to the air filter. 

 

I know a lot of people will say just don't connect them up I would prefer to do so to avoid any grief down the track.  What I don't want though, is to do anything incorrectly which would harm the engine.

 

At present I don't have any trees fitted to the manifold and, if possible would like to avoid that if I can.  Thanks in advance for advice and comments. Cheers Ron

 

 

 

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#2 claysummers

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Posted 23 October 2019 - 06:29 PM

Shouldn't one go to your tank?

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#3 yel327

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Posted 23 October 2019 - 06:47 PM

What month/year? Canisters are different for 1/75 to 5/76 than 6/76 on. Also differ for different carbs. On a 3 port with Quadrajet one port has a bung on it (the front one). Middle goes to tank and the back one goes to the carby purge port, but you may not have that port on the Holley.

With a 4 port (1/75-5/65) the back one is plugged again with Quadrajet, the middle goes to the tank and the 2 ports on the round bit go to:

Front one either goes straight to the ported vacuum port (auto) or into a T piece with the other sides of the T going to the dizzy and the carb ported vacuum port (manual).

Rear one goes to a bigger T as you describe between the PCV and the carby (not the air cleaner though).

To operate the canister you need a ported vacuum port (4 port) or a purge port (3 port). If your car is an auto you already have the dizzy vacuum advance port on the carb but you need a ported vacuum port for the canister, also for the dizzy if car is a manual.

Hope this helps.

#4 Cook

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Posted 23 October 2019 - 08:38 PM

Thanks guys.  Yes one does go to the tank (that's the easy part lol).  The hatch is a 11/76 build so adr27a applies.  The engine block is a QT.  I've tried to compare it to the plumbing on the WB with 253 where the purge goes to the front of the carb (stromberg) which I think is like an overflow catch for the carby.

 

The car is an auto and there is a timed spark vac source on the carby, which I didn't mention before.  So if I understand it right, I need a ported vacuum port. This might sound stupid but can I do this by incorporating a tree into the front of the manifold?  I have three threaded ports there and have just plugged them up at present.  I'll try and throw up some pics tomorrow.  Thanks again.  Cheers Ron



#5 yel327

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Posted 23 October 2019 - 08:56 PM

When I get a chance I’ll post up a parts book photo. I think you will need a 4 port canister though.

The red 4.2 Stromberg for ADR27A has a purge port and the back port on the canister connects to the bowl vent, Quadrajets vent internally hence the bung on that port on the canister.

For the auto you’ll probably want a full vacuum port for the dizzy which pulls some vacuum advance at idle so the converter doesn’t stall the engine when idling in drive. That is the idea anyway for a production car. Therefore if the carb has a ported vacuum port on it, the 4 port earlier canister should connect straight to that port on the carb, so the canister won’t operate until you hit part throttle. The 4th port will simply connect into the PCV line. Images off parts book will show all.

#6 Cook

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Posted 24 October 2019 - 07:11 AM

Thanks Yel. No need to post up the part book.  I've got that and although not quite clear gives me enough info (to be dangerous lol).  

 

Given the Holley doesn't have a vent port then I assume it vents internally, therefore my thinking is that the purge port on the canister isn't required?  

It has a full vac. port for the distributor so that seems to be OK.

So if they are correct, then all I have to deal with is the carby port on the canister (in theory).  Could I run the carby line to a T piece off the rocker cover running back to the air filter?

It's obviously simpler if I was going back to original, like I did with my WB so I just had to follow the diagram but not having sufficient ports on the Holley is what i'm grappling with. Cheers Ron



#7 Dr Terry

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Posted 24 October 2019 - 07:42 AM

The Holley won't have a purge port, so it's easier to use the earlier 4-port canister, which has the purge controlled by a vac diaphragm.

 

The vent port on the canister will need a plug (same as a Q-Jet). The small fitting from the diaphragm needs ported vacuum so connect this to the dissy vacuum fitting on the side of the carb. The larger hose from the diaphragm need to be T-pieced to the PCV vac hose.

 

Depending on the size of the cam fitted to the engine you could use the small 'full vacuum' (pictured) for the dissy vacuum advance. This will provide vac advance at idle, the same way the earlier factory cars are plumbed.

 

Dr Terry



#8 Cook

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Posted 24 October 2019 - 08:24 AM

I've found another thread "charcoal canister on 304 into 75 LH". Sorry I can't copy the link but I think it shows some pics of what i think you guys are trying to tell me, thanks to Brad "Hanra".

 

So the lines from left to right:

 

Carb - capped

Tank - to tank

PCV - into PCV line

This one I don't follow

 

Am I getting warmer? Cheers Ron

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#9 yel327

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Posted 24 October 2019 - 08:37 AM

Spot on. Except that is a manual car hence the T piece with the canister and dizzy vacuum into a Ported vacuum port on the carby. Auto version only the canister goes to that port on the carby, the dizzy goes to a full vacuum port on the back of the carby.

This is why there is only one 308 carby once canisters appear. Prior to that time that vacuum port on the front was different for manual and auto hence two different carby numbers.

So hopefully your Holley has both ported and full vacuum sources, ported for the canister and full for the dizzy.

Note that this won’t make you car legal, an auto V8 ADR27A car also has an EGR valve and all sorts of dizzy vacuum controls, plus a thermal switch on one exhaust bank. But having a canister is good as it means you don’t get tank venting smells. I’m actually looking at fitting one to my HK for the same reason.

#10 Cook

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Posted 24 October 2019 - 08:58 AM

Thanks for bearing with me. Got to go out but will be back to hopefully finally sort this out.  Thanks again.  Ron



#11 Cook

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Posted 24 October 2019 - 11:25 AM

Ok lets see if I can get this right, assuming I can find a 4 port canister. Here's the underneath and side pics of my carb.  

 

Canister ports left to right.

 

First port (carb) capped

Second port (tank) to tank

Third port (PCV) to PCV port on carby

Fourth port (?) to full manifold port on carby.  The instructions say this port provides vacuum for proper operation of the air cleaner, pump diverter valve (if fitted), a/c cruise and or temp sensing valve. it also says that if more than one  is require can run a T piece off this.  Is this the correct port to use for that canister port and if so, would I run it via a T piece and continue the line up to the air cleaner?

That leaves the timed spark port on the carby to go to the distributor.

 

If I have all that right then only one other question.  Does it matter which rocker cover houses the PCV valve.  I'm pretty sure on the VN headed motors it came off the passenger side but, if the above is right, I would prefer to run it off the driver's side.

 

I understand what you are saying about still not being legal so I am just hoping that my endeavours will be sufficient to convince the powers to be. Thanks again for your patience.  Cheers Ron

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#12 yel327

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Posted 24 October 2019 - 12:37 PM

No. Timed vacuum port is for the canister, only use this for vacuum advance on manual cars normally. Full vacuum port is for vacuum advance on auto cars. Timed is just a US term for Ported. You don’t want the canister to be operating at idle, hence why you use ported vacuum to operate it.

You want the PCV on the opposite rocker cover to your oil filler, this is why a Torana has the PCV on the front driver’s side as the oil filler is moved to the passenger side front on these. Holdens have the oil filler on driver’s side front hence why the PCV is left rear and breather front right. Torana is arse about (except A/C cars).

PCV suction goes on the opposite corner normally, but you can put it on the same side if need be like an aircon LH-LX V8.

#13 Cook

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Posted 24 October 2019 - 02:13 PM

Strike three. Sorry but I am having some difficulty understanding it all, which isn't hard for me lol.  So I assume the first three ports are correct and only one have a problem with the fourth and distributor advance.  So can I reverse these and run the canister to the timed port and the distributor to the full manifold port? If I can't resolve it this way what can you suggest?

 

The PCV works for me as I have VN rocker covers which have the filler cap on the passenger side so the PCV would be on the opposite cover.  I think I have had a win YEY.  I understand why a lot of people restore back to original and given my very limited knowledge what I most probably should have done but hey, anything that tests the grey matter is good as long as there is light at the end of the tunnel (and not another train coming!).  Cheers Ron



#14 Dr Terry

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Posted 24 October 2019 - 02:22 PM

 So I assume the first three ports are correct and only one have a problem with the fourth and distributor advance.  So can I reverse these and run the canister to the timed port and the distributor to the full manifold port? If I can't resolve it this way what can you suggest?

 Cheers Ron

Spot on, that's why I mentioned your camshaft. If it's a nice smooth factory style high torque cam then the full vac to the distributor should work well.

 

If the engine is not happy at idle, copy the above set-up where both the dissy & canister diaphragm are T-pieced to the timed port & the full vac port gets plugged off.

 

Dr Terry



#15 Cook

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Posted 24 October 2019 - 02:39 PM

Thanks Dr Terry.  I'm hoping the cam is relatively smooth (but my view of smooth and the engine builder's may be two different things). I opted to go a bit milder for driveability.  It's a Lunati 10810703.  I can post up the specs if you like.  Cheers Ron



#16 Chips

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Posted 24 October 2019 - 03:50 PM

wow. That took a lot of reading and re reading to try understand.
 
Now I think my setup is wrong. From the lots of guessing and reading the past few months that got me to where I am at moment.
3 port canister, manual trans. I think that's the first time I've seen/noticed/taken that in.
 
A few hoses should be so simple but yet it's so hard.
 
and the car runs.
 
but it's ok. I'll get there.


#17 Dr Terry

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Posted 24 October 2019 - 04:02 PM

To keep it simple, you can only use the 3-port canister if your carby has a dedicated 'purge' port. Most aftermarket carbies do not.

 

As explained above, you can use the 4-port canister with earlier-style carbies, which is basically what the factory did.

 

Dr Terry



#18 arrimar

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Posted 24 October 2019 - 05:12 PM

This thread is a great reference.

Which reminds me of a friend that was too busy with work so he got a reco'd 202 put in by a professional.

The gearbox came away from the engine on the way home and the carbon from the canister got sucked into the inlet manifold.

#19 Cook

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Posted 24 October 2019 - 05:21 PM

Yes thanks again Yel and Dr T.  It just highlights again the importance of the knowledge base on this forum.  I had read heaps of info from google both now and when I was doing the WB and there is so many variances and, I must say, people on other sites making comments when they are really only guessing.  I'm also pleased if by my inexperience this has/can help someone in the future.  I've sourced a 4 port canister so a bit of fun over the weekend to get it sorted. Cheers Ron



#20 yel327

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Posted 24 October 2019 - 05:55 PM

I was hoping to find a small one, like a VN size but I haven’t checked out what the Holley Sniper has on it yet to operate one.

#21 Cook

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Posted 24 October 2019 - 07:41 PM

I'm not too fussed what i get as long as it fits in the cylinder that it sits in mounted in the guard. Cheers Ron



#22 yel327

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Posted 24 October 2019 - 07:44 PM

VN is half the size.

#23 koalasprint

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Posted 30 October 2019 - 01:01 PM

Hi Ron,

              I have the same carby and canister. I ended up using a T-piece to plumb the canister into the PCV hose. But I blocked the hose internally near the canister because the canister would flow too much air at idle. So in effect my canister does nothing except look the part. Please let us know if you find a 4 port replacement canister. I'd rather have it working than not.

 

Cheers, Steve.



#24 Dr Terry

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Posted 31 October 2019 - 10:51 AM

Hi Ron,

              I have the same carby and canister. I ended up using a T-piece to plumb the canister into the PCV hose. But I blocked the hose internally near the canister because the canister would flow too much air at idle. So in effect my canister does nothing except look the part. Please let us know if you find a 4 port replacement canister. I'd rather have it working than not.

 

Cheers, Steve.

This is exactly what happens if you try to fit a 3-port canister to a carby which does not have a dedicated purge port.

 

The diaphragm on the 4-port type is what cuts off the flow at idle.

 

Dr Terry 



#25 Cook

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Posted 01 November 2019 - 10:40 AM

Hi Steve.  Yes I sourced one from Chris at Dinkum Autos - Moorabbin.  Now all tucked away in it's place.  Cheers Ron

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