wantng to pcv valves to 1275 ,45 weber carb ,have done this in the past but created too many problems, it cut HP quite dramaticlywhile connected,and ,regained when disconnected,wondering if 2 valves[1 each port] might be the answer,anyone with experience?any advice please

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16v, twin cam, 'a'series, cooper S replica,3x dcoe webers,Around 200 HP and heaps of torque

I run a small balance tube between the 2 ports. I have a Toyota PCV in one side and the brake servo in the other. It works fine, haven't seen any power loss. And it idles much better than with the PCV on one port only. Carby is a 45DHLA Dellorto (similar to a DCOE).
The other pipe coming from the left is water heating, as I had a carb icing problem @ 110KMH when cruising.



Here's another I did recently, with a 40mm Dellorto:

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have just gone through this with my car. I didn't notice any change in HP with the PCV valves hooked up however with running only one PCV valve in a fully sealed system I was still getting a buildup of crankcase pressure which would blow oil out my dipstick at around 6500rpm. I only have the rocker cover to vent my crankcase.
I have since made some changes and have a filter in the top of the charcoal canister to vent any excess pressure if needed. Running with 2 PCV valves will also help with setting the idle mixture screws correctly.


The PCV valves I used were from the local wreckers. For 10 bucks I got a mixture of valves and hoses to try different ways of plumbing in the valves. Dozens of different cars had these right angle ones which plug into their rocker covers.

2 valves was what i was thinking for better balance and more flow,balance tube sounds good but thats what i thought might have caused problems with performance,[in 1967] so maybe 2 running to separate posi,s on motor,got a pair of plug in type valves but not happy with bore of tube on them ,limits capacity too much i reckon, maybe toyota valve has bigger bore.wondering if bmc mushroom type valve has same function as pcv valve,seems to be a more complex unit,plus need a bank loan to buy a pair,motor has around 100 bhp according to dyno bloke,and rev limiter will be set 6500 rpm,reckon might get a fair amount of blowby at that,so bigger capacity could be needed.all advice will be considered,thanks for posts

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16v, twin cam, 'a'series, cooper S replica,3x dcoe webers,Around 200 HP and heaps of torque

Mine works fine at 8000 rpm, with a single PCV valve.
If you have lots of blowby, rebuild the motor or run hoses to a catch tank, don't rely on PCV valve(s) to act as a Hoover.
[edit] we tried doing this on Laingy's 1377 stroker, it didn't work. It turned out to have a broken ring.
Another rebore & new pistons/rings fixed it.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yep, Mine is probably due for a rebuild but it is still hauling ass so I don't need to throw 8K at it for no real benefit.
My empty charcoal canister is acting like a catch can and in the past 2 months there has been no buildup of oil in the canister.

motor is ok [1500 k,s].on race motors i,ve seen huge vents about 25mm dia and 2 of em,was told by a reputable engine builder if you want to pull high revs they are the way to go ,and vent them into a catch tank,hoover was mentioned isn,t that what the bmc valve does, keeps a slight vacum in sump at all times,reducing oil leeks etc.also what type is the single valve?

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16v, twin cam, 'a'series, cooper S replica,3x dcoe webers,Around 200 HP and heaps of torque

Yes it does but it flows no more than a Toyota or other brand does. It holds a vacuum only if there is little blowby.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.