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cptpugwash
18-10-14, 09:49 AM
Never given it any thought before, so have been trying understand how it works via some hunting around the net,but a little confused about a couple of things

Understand the pcv valve removing the blow by gasses from the sump but..
How does the fresh air breather work :beuj:, with some just being a filter open to the atmosphere and some being plumbed into the air filter

Also always thought if there is a little wear in the piston rings and or bores, then a little oil comes out of that fresh air breather, but whats actually happening inside the engine to cause it to do that :beuj: (after some googleing it seems it can happen on new engines too)

Seems pcv valves are rated too :beuj:

Stilltrying ......if you read this, couldn't find your comment on things being wrapped around the breather, but seems some valve covers don't have an oil baffle fitted under the breather holes

Thanks

Rich
20-10-14, 05:20 AM
i took my pcv out and run a pipe from the rocker,via an oil catch can and then back into the air filter .my engine a v6 so the other side is just vented out a pipe with a small breather filter tucked out the way.

fad15
20-10-14, 05:47 AM
Going to run a valley breather in mine. Blocked of the V Cover holes. Just some scotchbright in the breather block and then back to a hidden catch tank. Not a fan of things sticking out of V Covers, looks like an afterthought.

Plumpcars
20-10-14, 06:44 AM
On my W block I just have a valley breather but I possibly want to add a pair of valve cover breathers at some point(Although I like the look of the clean covers). I've never had trouble with pcv valves although i think many misunderstand them. Have used them successfully on many reasonably stout street engines. In very basic terms the valve is drawing by means of a vacuum controlled valve when the engine is under certain conditions. The open to atmosphere breather on the other valve cover is drawing in to replace the air in the crankcase that the valve draws into the intake. At high intake vacuum the pcv is closed and at low vacuum it is open. With an engine in good condition all usually works well. Various things can cause oil to mist around the open air type breathers but it's pretty much down to excessive crankcase pressure or poor baffling under the breathers. On my blown small block I have stubs in each valve cover which are hosed #12 to individual catch tanks. The tanks are then fitted with open to air breathers.

fad15
20-10-14, 06:04 PM
Nothing wrong with a bit of vapour flying around, was brought up with it....:beuj:

cptpugwash
20-10-14, 07:06 PM
Thanks for the replys
Haven't heard of a valley breather before,going to have to do some more googling on that one, like the idea of clean rocker covers too :tup:

So at full/part throttle the pcv valve opens and draws the vapours out and at the same time fresh air is draw in
Like the idea of a breather tank, guessing they work the same way as a pcv valve, cept they catch the vapours instead of recycling them with the intake charge, figuring that must mean a cleaner air/fuel mix

Going to have to look into fitting one of those :)

Image there must be more crankcase pressure with a blown engine

cptpugwash
20-10-14, 07:16 PM
Going to run a valley breather in mine. Blocked of the V Cover holes. Just some scotchbright in the breather block and then back to a hidden catch tank. Not a fan of things sticking out of V Covers, looks like an afterthought.

Be interesting to see how you do that :tup:

fad15
20-10-14, 07:42 PM
S Easy. Hole in the valley plate with a cover over it and enough room to put some 'scotchbright' type material inside. This 'condenses the mist to droplets that fall back, leaving only the highest boiling point vapours to be exhausted. If these then go to another catch tank then the result 'should' be a mere hint of blue smoke. Its basically an early type V cover breather, but in the valley plate, not on each cover. I was always wiping the oil from the chrome Rocker cover on my 1500X Flow, just around that 9.99 chrome brather I got from some speed shop...



Well thats the theory. Seems to work for a lot of guys that dont mind the odd dribble of oil here and there.

Plumpcars
21-10-14, 06:47 AM
On earlier Chevy small blocks as an example you will see a road draft tube coming out at the back of the valley. this was just a baffled long tube that came out and down to the bottom of the car. It used the negative pressure caused by the car travelling along to draw out breather fumes and away under the car. Very basic and before long they moved onto pcv valves as emission thinking started to kick in through the sixties(They had been designed earlier though) My W block had this arrangement along with an oil fill tube at the front of the manifold with a breather in to allow air to enter. That road draft tube can be removed and a pcv fitting connected in its place and run to an intake source. I remember a guy on the HAMB just drilled and tapped an aftermarket Chevy intake to basically put his pcv in the valley. Don't drill into the wrong part though!

jsf55
21-10-14, 08:48 AM
If you want a good read http://www.w8ji.com/pcv_system.htm

cptpugwash
21-10-14, 05:46 PM
Thanks for that link, haven't read it fully yet but looks like someones put a lot of work into that one

roscobbc
21-10-14, 07:29 PM
My 'stroker' 489 cu in was initially built-up with vented press-in rocker caps in the cast 'tall' Brodix valve covers. Unfortunately when I drilled out the covers to fit the vents on one side the hole was directly above an oil jet on one of the rockers, literally squirting oil right up inside the vent and out on the rocker cover - couple this with some crankcase pressure at high revs and things were messy. Ulimate cure was a PCV system and these
http://ecx.images-amazon.com/images/I/51k0ATBiJgL._SX355_.jpg

fad15
21-10-14, 07:59 PM
Can someone clear something up for me, cause that article has got me thinking. As I remember it the only crancase venting on the older engine was a pair of V cover vents, so where did the fresh air come from, cause i dont recall the problems stated with varnishing etc on this type of set up.

Thing is that with 8 separate throttle bodies on my EFI, I have to take a vac pipe from each to run to the vac sensor for the ECU. Dont think i can stab into one of them for the feed from the engine breather without upsetting the vac signal.

Any thoughts?

roscobbc
21-10-14, 08:54 PM
Older engine didn't need 'ventilation' as such - all vapours would naturally vent out of engine - if engine has some 'blow past' then it will exit the engine a bit quicker (and stink the car out!). I am planning on going the same way as you (8 stack efi) - simplest thing will be to tap the inner side of each inlet runner and run small diameter tubing from each runner to a common manifold (small sealed box) somewhere under the runners out of view - can't see any reason why the pcv connection can't run from this manifold too. Vacumn will be equalised to all runners and should be more than enough to cope with pcv duties. You main issue will be drilling and tapping the runners on the inner side of the stacks unless you can do it from the lifter valley side of the manifold.

Plumpcars
22-10-14, 08:04 AM
If you think about the older open vent systems they did have more issues with varnish etc. The fumes exited via the two valve cover breathers but what came in was from crankcase pressure as this was a higher pressure than atmospheric. How many times did we strip higher mileage engines down to discover thick sludge in valleys and heads but also baked varnish on valve springs etc.
On my W block the rear crankcase road tube exit had been modified by a previous owner to run a pcv valve with intake from the oil fill tube breather. I run 3 Rochesters though and even getting a balanced feed to pcv from that is a pain so I've initially gone back to running just n open to atmosphere system. On the mileage the average rod does I doubt the varnish thing would be an issue.

jsf55
22-10-14, 08:30 AM
If your going to run 8 vacuum lines into an ecu you need to think about smoothing the signal, a small filter, as used on motorbikes is ideal, it was recommended on the megajolt site.

roscobbc
22-10-14, 05:03 PM
If your going to run 8 vacuum lines into an ecu you need to think about smoothing the signal, a small filter, as used on motorbikes is ideal, it was recommended on the megajolt site.
I you run ALL 8 lines in to a common plenum or chamber and take the pcv and possibly a vacumn line to the distributor the vacumn signal will be as smooth as it can get. The chamber obviously needs to be sealed but only large enough to house the unions for 8 lines from the runners, one to distributor plus a larger one to the PVC valve. The real question is what size pipes will be sufficient from the intake runners - will brake tube size do the job?

fad15
22-10-14, 05:15 PM
OK.


Thanks for all the feedback its very interesting and sorry about the HiJack:embarrassed:
The Kinsler comes with a tapping on each throttle throat (8 of them), 90 degree fittings and a manifold for all 8 to go to. This is connected via 1 pipe to the vac sensor. I have made another manifold to split the vac signal to the sensor and the modulator on the transmission, using 1 of the 2 on each pair for each thing.

To add an additional 8 more stab in would make it look like spaghetti junction and to put it bluntly 'it aint going to happen'
I am also concerned about the effect of this to the vac signal for the ECU. So I guess I will live with a bit of blue mist and a regular decoke (remember them?) every....... At about 1500 miles a year, lets say 25 years.

I also do wonder with modern synthetic oils if they have the same problems with 'varnish' etc as the old Duckhams 20 50 or Castrol GTX. Somehow doubt it.

jsf55
22-10-14, 05:57 PM
I wouldn't be adding anything to the vacuum sensor circuit for the ecu as it will get spikes from any other operation (pcv valve opening and closing).

I think if you compared a gallon of 25 year old against a current gallon of oil you will find it's changed quite a bit, more detergents and less zdpp which protects it and corrosion and rust inhibitors ... nothing stands still for long !

fad15
22-10-14, 06:44 PM
I wouldn't be adding anything to the vacuum sensor circuit for the ecu as it will get spikes from any other operation (pcv valve opening and closing).

Exactly my thoughts. I did think that the modulator would be a smooth curve so it wouldn't have a negative effect on the vac sensor. I did check with kinsler before I decided to go this way.

Its funny, they go to a lot of trouble for a little advantage. Been reading about the ZF 9 speed auto and one thing they point out is that it reduces emissions by 0.7%. But his could put a vehicle into a lower tax band and help the powers to be to justify a bigger TAX on vehicles that cant meet their 'pie in the sky' goals.

Lets just get rid of a few private jet journeys and we can all enjoy our old cars...

cptpugwash
22-10-14, 08:52 PM
Came across this a little earlier, and sounds like a wrong rated pcv valve can cause lean spots

http://www.nastyz28.com/forum/archive/index.php/t-126001.html

jsf55
22-10-14, 09:23 PM
No doubt, but it can also pull a load out of your engine if it's the wrong rate, also you need to consider how much air is getting in .

roscobbc
26-10-14, 11:09 PM
Fad 15 - an answer to vacumn log install?

http://www.alkydigger.net/prodimages/Walt%20Laner's%20Enderle%20001.jpg

stilltrying
01-11-14, 09:36 PM
Never given it any thought before, so have been trying understand how it works via some hunting around the net,but a little confused about a couple of things

Understand the pcv valve removing the blow by gasses from the sump but..
How does the fresh air breather work :beuj:, with some just being a filter open to the atmosphere and some being plumbed into the air filter

Also always thought if there is a little wear in the piston rings and or bores, then a little oil comes out of that fresh air breather, but whats actually happening inside the engine to cause it to do that :beuj: (after some googleing it seems it can happen on new engines too)

Seems pcv valves are rated too :beuj:

Stilltrying ......if you read this, couldn't find your comment on things being wrapped around the breather, but seems some valve covers don't have an oil baffle fitted under the breather holes

Thanks

Captain, I couldn't find the right episode of roadkill but the hotrod mags collection and delivery of a 32B roadster in the middle of winter had an issue with oil out of breather and that was either a rebuilt engine or a crate motor. Reasonable episode to watch but if not your thing then look at about 7 minutes in. Unfortunately no advice on how to rectify it in that episode so I will continue to try to find the roadkill one.

fad15
02-11-14, 07:44 AM
Its got a vac log in the form of a small log mounted on the valley plate with a pipe to each throttle body. This then feeds the vac sensor and will feed the vac modulator. Its quite a tidy set up.
http://www.torquedup.co.uk/forum/imagehosting/usr_images/1/1/5/115_5455e03cb6edc.jpg



Fad 15 - an answer to vacumn log install?

http://www.alkydigger.net/prodimages/Walt%20Laner's%20Enderle%20001.jpg

roscobbc
02-11-14, 06:25 PM
Thats rather neat Fad15 - SBC or BBC? - Kinsler? did they provide the 'vacumn' manifold? - how do you fide the water lines direct to either side - vs - cast cross over with thermostat housing? - did you use the ones at the rear of the heads too?

fad15
02-11-14, 07:14 PM
SBC. Kinsler provided the fittings, pipe and log with the EFI. Water lines go from each head to twin inlets on the rad. No Xover as yet and no thermo. I figure the small diameter hoses will act like a restriction which seems to be quite popular now in the USA, when thermos are not used. The 2 at the rear are used for temp sensors of the EFI and the temp gauge. May have to put a pipe between them in the future, who knows.

Pic of the engine.


http://www.torquedup.co.uk/forum/imagehosting/usr_images/1/1/5/115_54568268eb6e5.jpg