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RAW454 27-05-2019 10:19 PM

Breather Blow-by / BBC Catch Can Ideas?
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Heyaz, so I could probably extend one of these threads, but.. nah:p

BBC Valve Cover Baffle Threads

The reason being, the baffles I used are not stopping my 454 BBC blowing oil out the breather under high revs / pressure. My sitch:

-- 2x billet valve cover breathers: One through PCV into carb air cleaner, other free air

-- GMPP valve covers, machined for breather holes & baffle plates added (to try & fix last time, per above thread)

-- On the dyno or at the track it P!SSES oil out the breather enough to smoke hardcore off the headers (enough for the Calder Fire Crew to chase me down with extinguishers drawn) or leave a pool on the dyno floor (Garry Chev wasn't pleased:rolleyes:)

So... Looking to install a super subtle catch can. Even if only one I hook up for the very rare visit to the track/dyno. Though part of me says, if an issue, leave it in place.

QUESTION: Anybody seen a real subtle catch can setup? On a BBC or other? Ideally keeping this style 'breather' on the valve cover. Or a (safe/legit) temporary solution?

Otherwise I'll get something like this and find a place for it, along with new breathers (would rather not..)

My engine bay FYI:
Attachment 35773
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Attachment 35772

Cheers. Deano.

RAW454 27-05-2019 11:21 PM

Bit of reading on topic. Seems is not uncommon...

69SSBB 27-05-2019 11:25 PM

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My set up might suit what your looking after same valve covers your battery is in boot only thing i had to do was get a matching powder coated black windscreen washer made up as original one wouldnt fit anymore

seanj 27-05-2019 11:29 PM

Whatever you do you’ll need to replace those breathers on the rockers. At full throttle the engine pulls no vacuum, so engine won’t draw excess oil vapours back into the engine.

Either have a better (seperate, media filled) breather and remove your PCV.
Fancy anodised black breather.

Or run a better quality air oil separator that plumbs back into the intake.
High quality air/ oil separator. (Plumbs back into intake). These have replaceable filters.

Frenchy666 28-05-2019 09:01 AM

don't want to be "that guy" but obviously there is more of an issue present for it to have that much blow by... maybe sort that out instead of band-aiding it???

otherwise i recon 69SSBB's setup looks mint :)

RAW454 02-06-2019 09:21 PM

Cheers Coxy.
Looks like a sweet set-up. Wish I'd need it before drilling breather holes & getting baffles welded in:rolleyes: May look at that next time or if swap covers, but probably only after a simple fix to what I've already got to see me through those rare extended-WOT applications.

Thanks Sean.
I think your suggestion is probably the direction I should be looking. There seems to be so many mixed opinions on PCVs, but it seemed to help mine run better years ago when first fitted & run one (& breather on opposite side) ever since. But sounds like you're saying swap the PCV for a 2nd breather/catch can?

Not seen those style of separator per the autobarn link before. Not the prettiest, but I'm sure they're effective.

Yeah, I don't disagree Marc,
But from what Ive read, seems is not an uncommon issue in BBCs. Hence the market for solutions:p Is not litres of oil I'm losing, but makes quite the show when hits the header...

Frenchy666 06-06-2019 12:46 PM

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Originally Posted by RAW454 (Post 204290)

Yeah, I don't disagree Marc,
But from what Ive read, seems is not an uncommon issue in BBCs. Hence the market for solutions:p Is not litres of oil I'm losing, but makes quite the show when hits the header...

didn't want to sound like a douche... ha ha

i haven't experience the blow by yet, but my engine is a stock 502 with few miles on it so i figure i won't for a while. Mine just has a vent back to the intake and the other rocker cover has like a breather/check valve
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RAW454 16-06-2019 09:56 PM

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Starter re-watching some of the older Roadkill episodes (as got MotorTrend subscription & watched near everything else:p) and noticed when the Crusher Camaro had the blown 489 big block, they had zip-tied terry towelling rags around all of the the breathers.

Attachment 35781 . Attachment 35782

But then I looked up more Google pix & they were either not there or had this dealio:

Attachment 35783

In any case, really doesn't seem to be an uncommon thing on BBCs the more I look into it.

I wonder if this towelling is a 'good enough' solution for my very, very rare dragstrip & dyno runs (only time blow-by happens)?

Frank351 18-06-2019 06:23 PM

Check this out Dean :


cluxford 19-06-2019 12:50 AM

My twin catch cans work great, but currently vent to atmosphere. I'm changing that as we speak, LH side one will now use a PCV and route to back of carb

Shan 16-09-2019 04:37 PM

I have been researching this also....

A lot of opinions.

I did do some research, not all catch-cans are made the same. Also be aware "oil seperator" v's "oil catch can" - are kinda different things.

I did some reading on tests for these types of products. Was for a 4x4 site, mainly aimed at Diesel engines, but blow-by is the same issue from what I can tell. The idea is to stop it reaching the engine. They tested the fancy machined alloy units, v's some others made from plastic like Mann and Hummell Provent, also Flashlube catch Can Pro.

The Provent and Flashlube units proved to be noticeably more effective v's the other types tested.

Out of those two - the Catchcan Pro is the smallest. Still yet to find definitive answers on how long the hoses can be in a seperators setup, and what issues there are if it is mounted lower than the manifold intake hose. Would be great to hide the seperator, but I think you need to be mindful of what effect gravity may have on the system and hose length.

Also - with the baffles - how were they designed?

Check this site:

baffle design is important - as they tested. In your case though - sounds more like a PCV airflow issue. Same site sells the rolls royce of PCV adjustable valves. You might want to research that a little more?


RAW454 22-09-2019 09:48 PM


Originally Posted by Shan (Post 204452)
I have been researching this also....
A lot of opinions.

Thanks heaps for sharing Shanan. Interesting about the baffle design results on your link. I'm limited for space with roller rockers and as I say, this is only a factor when under high load on dyno or dragstrip (both very rare) so was looking for an easy bolt-on/off option
(that is not $250-300 like the listed winners). But will certainly take your findings on board :) Cheers.

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