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Breather Question..


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#16 Spider

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Posted 23 January 2018 - 07:57 AM

Do not vent to air, usually the cause of oil leaks and a dirty oily engine compartment - as suggested you need to pull a small amount of the crankcase gases into one of the carbs.

 

Yes. There's no need on a road car to vent to air and as Rorf has said, Oil Leaks and a generally Oily engine can be expected.

 

I doubt it's legal to vent straight to air, maybe on the earlier cars, but doubtful on later ones.



#17 myminipickup

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Posted 23 January 2018 - 08:33 AM

There's other PVC Valves available if that's the way you want to go, but as Graham has touched on, they aren't brilliant, OK, but not brilliant.

 

Have you got your carbs yet?

 

Do these have a CCV Port on them? This is a 1/4" - 5/16" dia tube that comes out of the carb bodies between the butterfly and the piston at around 450 angle.

 

If so, almost as Dusky has suggested, only I'd plug the breather on the timing cover or swap it for one without.

 

i dont think they have a ccv port? HS2 carbs I think



#18 Spider

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Posted 23 January 2018 - 09:11 AM

 

There's other PVC Valves available if that's the way you want to go, but as Graham has touched on, they aren't brilliant, OK, but not brilliant.

 

Have you got your carbs yet?

 

Do these have a CCV Port on them? This is a 1/4" - 5/16" dia tube that comes out of the carb bodies between the butterfly and the piston at around 450 angle.

 

If so, almost as Dusky has suggested, only I'd plug the breather on the timing cover or swap it for one without.

 

i dont think they have a ccv port? HS2 carbs I think

 

 

CCVs were fitted to HS2, 4, 6 (not all) and HIF's.



#19 myminipickup

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Posted 23 January 2018 - 11:14 AM

 

 

There's other PVC Valves available if that's the way you want to go, but as Graham has touched on, they aren't brilliant, OK, but not brilliant.

 

Have you got your carbs yet?

 

Do these have a CCV Port on them? This is a 1/4" - 5/16" dia tube that comes out of the carb bodies between the butterfly and the piston at around 450 angle.

 

If so, almost as Dusky has suggested, only I'd plug the breather on the timing cover or swap it for one without.

 

i dont think they have a ccv port? HS2 carbs I think

 

 

CCVs were fitted to HS2, 4, 6 (not all) and HIF's.

 

 

I'll take a look.. But i've not seen it.



#20 jabos7

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Posted 30 January 2018 - 01:37 AM

I've run into a similar problem, going from an HS2 to an HS4.  Bought one of a pair, but had to get the one that matched my HS2 linkage

set-up.  Just so happens this carb didn't get the CCV port, instead its mate did.  So now I"m trying to figure out how to drill

out that position on the carb body and get a port/pipe in there.

It looks daunting due to angle and trying to prevent a vacuum leak.  -I might be stuck venting to air via a catchcan?

 

Suggestions welcome!



#21 Spider

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Posted 30 January 2018 - 04:30 AM

  So now I"m trying to figure out how to drill out that position on the carb body and get a port/pipe in there.

It looks daunting due to angle and trying to prevent a vacuum leak.  -I might be stuck venting to air via a catchcan?

 

Suggestions welcome!

 

I've done a few and I wouldn't be to concerned about fitting one, though, you will want a drill press to keep it all square while drilling.

 

There's a number of ways to mount the carb to drill it, one way is to drill a piece of 6 mm x 50 mm flat steel such that you can bolt the carb up to it - either end of the carb is fine for this. Then camp that piece of steel (which the carb bolted up to it) in a drill press vice, eye off that landing where the CCV Port is fitted and get it as level as you can, it's not super critical, just the best you can. Drill a small pilot (say 1/8") and then open this out to 5/16". Be sure it's a good, well sharpened drill bit so it does drill on centre, it the sharpening is off, it will drill over size. Normal Jobbing Drill bits are in fact a few thou under their started size, so your hole should end up 2 - 3 though under 5/16".

 

You can buy short lengths of brass tubing from hobby stores in various diameters, grab yourself some 5/16" Brass tube, cut off a short length usually about 1-1/4" long is enough, use a tube cutter for this. Then press the tube in to the Carb with some loctite (for insurance) - job done.



#22 cal844

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Posted 30 January 2018 - 04:58 PM

One of my 1275 engines and my 998 (all A+) are vented to air, the other has the charcoal canister lines(I've removed the Canister and plugged the lines)

Edited by cal844, 30 January 2018 - 04:58 PM.


#23 Dusky

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Posted 30 January 2018 - 05:13 PM

There really is no good reason to vent to the air on a road car. I'll eat my shoes if someone can give me 1 good reason.



#24 Spider

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Posted 30 January 2018 - 05:17 PM

There really is no good reason to vent to the air on a road car. I'll eat my shoes if someone can give me 1 good reason.

 

I agree, but I'm trying to think of a reason, even a rubbish one, only so we can see you eat your shoes !!!



#25 johnR

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Posted 30 January 2018 - 05:46 PM

interesting question for me as well - the 1275 I'm building has the two oil separator/breathers and I've also got some sort of valve on my inlet manifold (on the right) as well as the servo vacuum port.

Should I remove the valve and vent into the carbs after joining then separating the hoses to balance the flow?XUJQb36.jpg



#26 gazza82

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Posted 30 January 2018 - 11:05 PM

Using the connection to the inlet creates a slight vacuum in the crankcase which can actually reduce oil leaks on a a-series.

#27 Spider

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Posted 31 January 2018 - 04:43 AM

interesting question for me as well - the 1275 I'm building has the two oil separator/breathers and I've also got some sort of valve on my inlet manifold (on the right) as well as the servo vacuum port.

Should I remove the valve and vent into the carbs after joining then separating the hoses to balance the flow?XUJQb36.jpg

 

Your Carbs have the CCV Ports and your Inlet Manifold looks like it has either a PCV or it could also be a non-return valve, as used with some Brake Servos, fitted to it.

 

To me, for Crankcase ventilation the CCV wins out over a PCV. If you think about why these systems are here and how each works, you'll see why.

 

Your engine will (or should !!) have the highest blow-by under wide open throttle and that's where any crankcase ventilation needs to work (or flow) the most.

 

OK, so what happens to Manifold Vacuum under wide open throttle?

 

And how much Air is flowing through the Inlet system under Wide Open Throttle and also Cruise (& Idle) conditions?

 

The CCV Port(s) don't work on Vacuum like the Manifold and PCV does, they work on flow rate, ie, the more air flowing through the Carb(s), the more they 'draw'.






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