RV8 on carb- breathing arrangements
Discussion
Hi all, I'm wondering if anybody has any idea of the rocker breather arrangements I should be looking at for my '93 pre-serp running an Edelbrock 500cfm carb. I'm looking to change the rocker covers from the current Edelbrock-branded jobbies to some more original Rover-style ones but they differ in their breathing setup.
This is the LH bank as it stands, it has a mushroom-style pushfit oil filler cap with an internal gauze which seems to act as a vent to atmosphere. This started blowing smoke and dropping oil onto the exhaust manifold a few weeks ago after the car was pushed particularly hard round Thruxton, and ever since has continued blowing smoke even at idle (despite no discernible change in oil level or pressure). I was considering replacing or thoroughly cleaning the cap to see if it cured the issue, but I already had my new covers on order so I haven't bothered. The old covers run on adapter plates which are nicely drenched and appear as though they may be warped so I want to get shot of the job lot ASAP.
And this is the RH bank, with a flame trap connected directly to the air filter. This mists oil slightly but not dramatically and seems to function perfectly, I was planning to plumb the flame trap on the Rover covers in the same fashion.
And to the carburettor, you'll see that there are three ports on the front of the carb, one connected in the picture. The LH (as viewed in the picture) port is the vacuum advance port and was connected to the distributor (don't be alarmed, I took the hoses off to get the diameter). Again there's no problem with this one. The centre port is the PCV port, which disappears off into the fibreglass front wing nether and confuses me. The RH port is something else distributor-ey from what I can gather, and has been blanked off. I should note that the car has always run perfectly and until the mushroom cap started blowing oil/smoke was losing very little oil. (New gasket on the way for the carb air filter btw!)
And so to me lovely shiny new (sort of) covers, firstly I'll point out that a spray job and TVR badges are in the works so don't worry about that
though the blue is growing on me... 
The mystery to me is how to plumb this lot in. Firstly, am I correct in thinking that flame trap to air cleaner is a plug-and-play in the same orientation again?
Secondly, the little port that's cast into the other rocker cover- what do I do with this then? I understand that I've lost some breathing capacity through replacing my filler-cap-cum-vent-to-atmosphere mushroom with the standard screw fit cap, so does this mean I should be looking to plumb this to the intake somewhere, or to atmosphere? In which case presumably I'll need a valve of some description betwixt the two?
Beer tokens to anyone who knows what I ought to do with this lot
This is the LH bank as it stands, it has a mushroom-style pushfit oil filler cap with an internal gauze which seems to act as a vent to atmosphere. This started blowing smoke and dropping oil onto the exhaust manifold a few weeks ago after the car was pushed particularly hard round Thruxton, and ever since has continued blowing smoke even at idle (despite no discernible change in oil level or pressure). I was considering replacing or thoroughly cleaning the cap to see if it cured the issue, but I already had my new covers on order so I haven't bothered. The old covers run on adapter plates which are nicely drenched and appear as though they may be warped so I want to get shot of the job lot ASAP.
And this is the RH bank, with a flame trap connected directly to the air filter. This mists oil slightly but not dramatically and seems to function perfectly, I was planning to plumb the flame trap on the Rover covers in the same fashion.
And to the carburettor, you'll see that there are three ports on the front of the carb, one connected in the picture. The LH (as viewed in the picture) port is the vacuum advance port and was connected to the distributor (don't be alarmed, I took the hoses off to get the diameter). Again there's no problem with this one. The centre port is the PCV port, which disappears off into the fibreglass front wing nether and confuses me. The RH port is something else distributor-ey from what I can gather, and has been blanked off. I should note that the car has always run perfectly and until the mushroom cap started blowing oil/smoke was losing very little oil. (New gasket on the way for the carb air filter btw!)
And so to me lovely shiny new (sort of) covers, firstly I'll point out that a spray job and TVR badges are in the works so don't worry about that
though the blue is growing on me... The mystery to me is how to plumb this lot in. Firstly, am I correct in thinking that flame trap to air cleaner is a plug-and-play in the same orientation again?
Secondly, the little port that's cast into the other rocker cover- what do I do with this then? I understand that I've lost some breathing capacity through replacing my filler-cap-cum-vent-to-atmosphere mushroom with the standard screw fit cap, so does this mean I should be looking to plumb this to the intake somewhere, or to atmosphere? In which case presumably I'll need a valve of some description betwixt the two?
Beer tokens to anyone who knows what I ought to do with this lot
Your new covers are designed for a breather system which is connected to engine vacuum. The vent with the wire wool insert is the connection to vacuum. The mushroom vent is to allow a small amount of air into the cover so fumes can move across the engine to the the vacuum connected vent.
Your existing covers are not vacuum and simply vent into the underside of the air filter.
You mention a PCV pipe going from the carb and then into the wing. This is probably the vac pipe to the brake servo.
So your options are modify your new covers to just breath to the air filter or install the vacuum system used on fuel injected cars.
Steve
Your existing covers are not vacuum and simply vent into the underside of the air filter.
You mention a PCV pipe going from the carb and then into the wing. This is probably the vac pipe to the brake servo.
So your options are modify your new covers to just breath to the air filter or install the vacuum system used on fuel injected cars.
Steve
Steve_D said:
Your new covers are designed for a breather system which is connected to engine vacuum. The vent with the wire wool insert is the connection to vacuum. The mushroom vent is to allow a small amount of air into the cover so fumes can move across the engine to the the vacuum connected vent.
Your existing covers are not vacuum and simply vent into the underside of the air filter.
You mention a PCV pipe going from the carb and then into the wing. This is probably the vac pipe to the brake servo.
So your options are modify your new covers to just breath to the air filter or install the vacuum system used on fuel injected cars.
Steve
Hi Steve, thank you for the response. So if I were to plumb the flame trap (RHS cover in photo) into the air filter as is the current arrangement and then use the small port (LHS in photo) as a vent to atmosphere with some sort of filter would this work?Your existing covers are not vacuum and simply vent into the underside of the air filter.
You mention a PCV pipe going from the carb and then into the wing. This is probably the vac pipe to the brake servo.
So your options are modify your new covers to just breath to the air filter or install the vacuum system used on fuel injected cars.
Steve
Sorry, I'm new to this and trying to work out the logic!
Thank you for clarifying what that PCV pipe is up to, that makes sense to me.
Belle427 said:
On the opposite side of the newer Edelbrock carbs there was also a vacuum port blanked off which could be used if you can find a hose tail to fit it.
As you correctly said the two smaller ports are for distributor vacuum advance, one is full vacuum (lower) and the other ported.
If I can find this vent and be certain of its vacuum-ousness then would that be a sensible connection for the small port on the Rover covers? From my understanding that would have the effect of drawing pressure through the air cleaner into the large flame trap port when required, and pulling pressure from the engine back to the carb under negative pressure?As you correctly said the two smaller ports are for distributor vacuum advance, one is full vacuum (lower) and the other ported.
Again sorry for my lack of understanding, carbs are somewhat alien to me!
I can’t really comment on the Rover v8 but I had one installed on a small block Ford 302.
passenger rocker cover had a breather drawing in fresh air, and the drivers side was piped to carb front large port via a pcv valve.
Worked fine for 10 years with no smoke or oil leaks present, pretty similar to the Rover setup though.
This is the pcv valve that actually slots straight in to your old valve covers but needs a bit of botchery to fit it on the Rover.
passenger rocker cover had a breather drawing in fresh air, and the drivers side was piped to carb front large port via a pcv valve.
Worked fine for 10 years with no smoke or oil leaks present, pretty similar to the Rover setup though.
This is the pcv valve that actually slots straight in to your old valve covers but needs a bit of botchery to fit it on the Rover.
Edited by Belle427 on Wednesday 12th September 07:33
Belle427 said:
I can’t really comment on the Rover v8 but I had one installed on a small block Ford 302.
passenger rocker cover had a breather drawing in fresh air, and the drivers side was piped to carb front large port via a pcv valve.
Worked fine for 10 years with no smoke or oil leaks present, pretty similar to the Rover setup though.
This is the pcv valve that actually slots straight in to your old valve covers but needs a bit of botchery to fit it on the Rover.
This ^ better system than what LR/RR did and your oil will stay cleaner for longer with this style pukka PCV valve, one rocker cover needs to stay vented with an adequate area and the other you can drill fit a bung and fit the PCV into large end 1st then just connect to full manifold vacuum passenger rocker cover had a breather drawing in fresh air, and the drivers side was piped to carb front large port via a pcv valve.
Worked fine for 10 years with no smoke or oil leaks present, pretty similar to the Rover setup though.
This is the pcv valve that actually slots straight in to your old valve covers but needs a bit of botchery to fit it on the Rover.
Edited by Belle427 on Wednesday 12th September 07:33
but central to the carb area, this is a controlled air leak so at idle you make need to wind the pilot/idle mixture screws (there are 2 on each primary choke/barrel) out a fraction to compensate for the small amount of additional air you have entering the manifold or not 
Belle427 said:
It can be botched in as ive tried here.
It wont work 
the opening on the rocker cover with the mushroom is not big enough to allow the free flow of clean air to evacuate the fumes through the PCV unit what you have there is crankcase pressure city when driven hard 
if in fact that is what your using Sardonicus said:
This ^ better system than what LR/RR did and your oil will stay cleaner for longer with this style pukka PCV valve, one rocker cover needs to stay vented with an adequate area and the other you can drill fit a bung and fit the PCV into large end 1st then just connect to full manifold vacuum
I'd definitely agree with the above, whats described by Simon here is basically my setup, and it works absolutely perfectly even on full spank; there are no acrid crankcase smells, the engine idles nicer and the setup gives initial throttle application engine response/drivability benefits too.The standard Range Rover setup on our cars is actually a combination of excessively aggressive vacuum governed by the orifice size of a brass insert, and critically venturi vacuum at the throttle body. To say it's crude is a massive understatement, critically the aggressive vacuum generated inside the plenum is not only directly connected to the crankcase, it's also connected via an open hose directly to atmosphere at the throttle body! The fact that none of the hose work is properly regulated by any form of valving is crude at best, and can in my experience after extensive experimentation lead to idle stability and drivability issues.
It seems clear from it's design that the source, flow, and volume of air/gasses is constantly shifting, on full throttle the air in the plenum is more or less at atmospheric pressure so clearly there's little or no vacuum, the engine will likely be working hard too so there's both a considerable increase in crankcase pressure/gas volume and no real vacuum to properly draw it into the plenum, this is a challenge that must be overcome. While the rise in crankcase gasses themselves will ensure they naturally pass up the standard un-valved setup because (in theory and engine gasket dependent) it's the least point of resistance, unfortunately it's just not enough to manage the huge volume of blow-by that builds in the crankcase at full chat, of course there's a certain amount of fogging into the plenum that goes on but quite clearly you need more than that!
This is where the carefully placed drilling on the throttle body steps in, essentially it's positioning creates a condition known as venturi vacuum which is sufficient to help manage all those crank case gasses at full throttle, the gasses that lower plenum port is no longer drawing into the engine because the plenum is now at atmospheric pressure. As the speed of air increases over this drilling which to be clear is on the atmosphere side of the throttle butterfly, a vacuum is created (venturi vacuum) which is used to draw the excess vapors past the throttle butterfly and into the engine to compensate for lack of vacuum engine side of the throttle butterfly at wide open throttle .
I've described this system as crude which is it, but in fairness it does work acceptably, well if you're measuring acceptable as it's ability to manage crankcase gasses. However there are some downsides to running what is effectively an open pipe from the crankcase directly into the plenum engine side of the throttle butterfly, worse still there are further down sides to running what is effectively a second open pipe from the mostly high vacuum plenum engine side of the throttle butterfly directly to atmosphere at that venturi vacuum port on the throttle body.
Venturi vacuum is all well and good but if the depression inside the plenum is greater than that produced by venturi vacuum, which it will be 90% of the time, then what you've got yourself with that hose that goes to the throttle butterfly is a very effective vacuum leak.... which even with the benefit of a stand alone ECU can introduce tuning challenges you'd be way better off without.
Thanks for taking the time to contribute chaps, it's really appreciated.
The flame trap casing which fits these covers is the same diameter as the port on my air cleaner, so I'm quite happy to use this as the 'intake' breather, if my logic is right then this won't require any valve or restriction as such? I should note that the flame trap has no internal gauze as it stands, literally just a casing.
Assuming I'm to fit the standard filler cap through the other threaded hole on the covers, then that leaves only the small diameter port to do anything with (before getting to altering the covers). Would I be correct in saying that this is going to be too restrictive to use as an 'outlet' breather, even to the carb vacuum port (if I have one)?
And presumably the ideal setup would be to have a PCV valve on the outlet breather, this is true both for venting to the carb and for venting to atmosphere?
Which means that my options are to bore a larger hole in place of the small outlet, and fit either a valved/mushroom breather to atmosphere or a line to the vacuum port with a PCV valve en route?
Hopefully I'm not completely failing to understand this!
The flame trap casing which fits these covers is the same diameter as the port on my air cleaner, so I'm quite happy to use this as the 'intake' breather, if my logic is right then this won't require any valve or restriction as such? I should note that the flame trap has no internal gauze as it stands, literally just a casing.
Assuming I'm to fit the standard filler cap through the other threaded hole on the covers, then that leaves only the small diameter port to do anything with (before getting to altering the covers). Would I be correct in saying that this is going to be too restrictive to use as an 'outlet' breather, even to the carb vacuum port (if I have one)?
And presumably the ideal setup would be to have a PCV valve on the outlet breather, this is true both for venting to the carb and for venting to atmosphere?
Which means that my options are to bore a larger hole in place of the small outlet, and fit either a valved/mushroom breather to atmosphere or a line to the vacuum port with a PCV valve en route?
Hopefully I'm not completely failing to understand this!
Coming back to this one, covers are fitted now and looking good, i decided to KISS and fit a vent to atmosphere on the near side and intake via flame trap on the offside.. But spot the problem here.
The 19mm hose to fit the top of the flame trap turned out to be rad hose and very rigid.. So much so that it kinks and collapses en route to the underside of the air cleaner. And I'm also still blowing smoke like buggery from the vent on the near side rocker. Whether these two are linked I don't know, but before assuming that piston rings are AWOL I'd like to sort the breathing setup which means finding a way to connect air cleaner to rocker on the offside (I'm hoping we're not smoky enough for rings to be gone, but won't know for certain til it's breathing properly). I could fit a 19mm elbow and silicone hose, but I don't have the clearance from the top of the flame trap to the bonnet. Soooo... What can I do here? Can a pushfitting of the same bore as the flame trap threads seal properly? Will a breather filter act as an effective 'intake' and I can bypass using the air cleaner full stop? Is ANYONE selling super flexible 19mm hoses cos I can't bloody find any!!!
The 19mm hose to fit the top of the flame trap turned out to be rad hose and very rigid.. So much so that it kinks and collapses en route to the underside of the air cleaner. And I'm also still blowing smoke like buggery from the vent on the near side rocker. Whether these two are linked I don't know, but before assuming that piston rings are AWOL I'd like to sort the breathing setup which means finding a way to connect air cleaner to rocker on the offside (I'm hoping we're not smoky enough for rings to be gone, but won't know for certain til it's breathing properly). I could fit a 19mm elbow and silicone hose, but I don't have the clearance from the top of the flame trap to the bonnet. Soooo... What can I do here? Can a pushfitting of the same bore as the flame trap threads seal properly? Will a breather filter act as an effective 'intake' and I can bypass using the air cleaner full stop? Is ANYONE selling super flexible 19mm hoses cos I can't bloody find any!!!
You could use an original efi hose which has the short elbow, then cobble something together with joiners etc.
https://www.island-4x4.co.uk/breather-hose-britpar...
https://www.island-4x4.co.uk/breather-hose-britpar...
Belle427 said:
You could use an original efi hose which has the short elbow, then cobble something together with joiners etc.
https://www.island-4x4.co.uk/breather-hose-britpar...
I was looking at those but I think RV8 Landies use a different style flame trap with a different diameter. I've found a local supplier of silicone hoses so I'm hacking some of those apart tonight to see if I can get away with some tight radius bends without kinking.https://www.island-4x4.co.uk/breather-hose-britpar...
You could use this and shorten to suit?
https://rimmerbros.com/Item--i-ERC9116A
Lots of options at Rimmers:
https://rimmerbros.com/ItemList--Rover-SD1-Fuel-Sy...
https://rimmerbros.com/Item--i-ERC9116A
Lots of options at Rimmers:
https://rimmerbros.com/ItemList--Rover-SD1-Fuel-Sy...
N7GTX said:
You could use this and shorten to suit?
https://rimmerbros.com/Item--i-ERC9116A
Lots of options at Rimmers:
https://rimmerbros.com/ItemList--Rover-SD1-Fuel-Sy...
Hi Iain, I spent some time talking to Rimmer Bros today and whilst they were of course very helpful they didn’t have an ID figure for those hoses, I could have chased further or simply ordered some but whilst pondering my options I stumbled across some Samco silicone ones from Merlin Motorsport at Castle Combe (excuse the poorly lit photo)-https://rimmerbros.com/Item--i-ERC9116A
Lots of options at Rimmers:
https://rimmerbros.com/ItemList--Rover-SD1-Fuel-Sy...
- and these are bloody brilliant. So much more flexible and resistant to kinking than the silicone hoses I’d tried before, Neil Garner recommended them and whilst I wasn’t convinced because ‘silicone is silicone right?’ they’re chalk and cheese. I couldnt possibly have routed the old hoses from flame trap to air cleaner without them folding up, but these should work a treat. Although I haven’t cut and fitted them yet because I’m going to order in some BRG ones, the blue ones are always in stock so can be returned no problem hence using them to offer up and test fit
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