ptuomov

Mains are 1-5 from the front.

Cylinders from the front are 1-4 on the passenger side and 5-8 on the driver side.

What I call bays are the sections of crankcase separated by mains. Bay 1 in the front is between mains 1 and 2 and the cylinders 1 and 5 pump into bay 1. Bay 4 is between mains 4 and 5 and the cylinders 4 and 8 pump into bay 4.

The big windage / crankcase pressure problem with the cross-plane V8 is equating the pressure between bays 1 and 4 at 45 degrees and 225 degrees of crankshaft angle.

FredR

Andrew,

Seeing your note above and thinking a little, if the stock JK baffle with mesh is fitted I wonder if at some operating point the oil throw is such that in catching the oil, the mesh in effect, because it works so well, effectively blocks up [temporarily] with oil and stops the crankcase from venting up the chimney because of the suspended slug of caught liquid?

Regards

Fred

ptuomov

For a car that retains most of the stock breather system and that only sees relatively short periods of WOT accelerations, the scrubber seems like a good idea. It does stock oil effectively, but reduces gas flow when the scrubber gets saturated.

For car that has a more extensively modified system and/or ProVent, and that will run hard for longer periods of time, then the version of the JK baffle without the scrubber in it is more appropriate.

Horses for the courses.

FredR

Ok- I am with you on the concept. Is this problem a well known/accepted industry concept for this type of crank configuration or is it something you have concluded considering your experience with these motors?

Either way it sounds as though it would be quite difficult to fabricate a solution for such.

Presumably putting the crankcase under significant vacuum [by definition] will reduce the mass of "windage" proportionate to the degree of vacuum which may have an even more significant impact on any crankcase differential pressure.

Rgds

Fred

Alan

Based on how slowly oil fill is on a car with scrubbies in the oil filler vertical stack (now gone) I'd say they can become very restrictive when heavily laden. Likely this then belches slugs of oil when sufficient pressure builds up. Maybe it can work OK for typical light duty use

Better to have a crank baffle that sheds oil based on tight flow direction reversal. John's baffle without scrubbies/mesh will do this - so does Greg Browns version.

If breathing above this is out of an oil filler - I'd think a metal '85/'86 filler could be reasonably modified to have additional similar flow reversal baffles right up the ~vertical section. However for that much fabrication probably better to build a custom solution for the same space with a better top porting arrangement.

Alan

AO

This is the one on the GT. The one I had made for the Euro is essentially the same, except I don't have the pipes coming off the top.





Thanks to Tony for getting this made up for me many years ago!

Alan

Fred if your Provent sees no oil then I think you need to figure out how you are losing oil.

It can't just be that the baffle/scrubbies are too effective - if you are still loosing oil...

I'd double check that cam cover vent 1 way valve, or start thinking about other losses (leakage, valve seals etc). Hard for it to be blowby related if none makes it out the biggest exit hole you have through the Provent... Something is odd here. For any significant volume of oil to make it past the rigs to be lost in combustion - you'd also be seeing major blow-by - so where is it all going?

It's usually pretty clear that the Provent fliter is oiled. You do have a check valve in the Provent drain line or a deep under oil drain tube? - thats a path past the provent filter element.

From my experience crank baffles help, but even full of restrictive scrubbies - they can't clean out all the oil - not even close.

Alan

FredR

Alan,

Valve seals were new and valve stems in generally good condition when we put my S4 motor into the GTS chassis. I remain a bit suspicious of the rings and/or cleanliness of the lands. When in the late S4 the motor used quite a bit of oil but it was consistent and the PO advised of this. After installation in this chassis it seemed to use more oil and then I tried to modify to the GTS breather system- seemingly a bad move. The Pro vent oil out goes to a catch bottle at the moment and that seems to gather more or less nothing. The inside of the pro vent has an oily appearance but the gas out pipe shows no signs of oily residue.

I therefore have to assume the oil is going through the rings and thus the question why? If the JK baffle produces too much pressure drop that may explain ring flutter. Colin's solution may just alleviate the symptoms. I am also thinking of trying the JK bafle with the mesh removed and possibly vent the cam covers into the Pro Vent as well- first- just to see if I can modulate the symptoms. Perhaps I should stick the accelerometer on the car to test performance- it seems to be running OK but I do not have access to a dyno.

Regards

Fred

ROG100

Alan,
As you have a version (of your design) of Colin's vacuum system would you care to share on any improvements you have seen/felt? Less carbon buildup, more power or less oil consumption?
To me all the above are a major issue to GTS owners. On any of my pre 92 cars any of these conditions are not an issue at all.
Thanks,
Roger

ptuomov

The GTS was one big design error, starting from the asinine crankshaft counterweight design.

ROG100

That may be but those of us that own them, love them, and want to try and do everything to make them run as they should.

SteveG

This thread is making me think about that GT engine on ebay. A quick trip to the dump and there will be plenty of room in the basement. I'll just store the GTS engine and as AO said, consider it part of my IRA, could be a good investment, certainly not as risky as stocks.

RKD in OKC

My brain keeps telling me I can buy a LOT of oil for the cost of and engine swap.

SteveG

Absolutely, and that is a viable choice, but like rent, oil will continue to disappear, probably get worse and hinders HP; if I fix this problem, (pick your method), the engine will run cleaner, better and there will be more horses. I never thought I'd advocate putting an earlier motor in this car.

There is something to be said for not fixing what isn't broken, but when did we ever leave these cars alone?

The suggestion to swap, was partly in jest . . .

Alan

Well certainly my system was insired by Colin - for sure - and I'm still interested to see what he & you come up with as a commercial kit offering.

My system is a work in progress so not ready to disclose all the details yet (only in case some turn out to be less than ideal - I have been down many of these 'dead ends' already).

Will share in detail when completed - however I've been running a vac pumped system of various types since approx end April '13 and have put thousands of miles on it. Car has never driven better or consumed less oil, so right out the gate its better. No pre-ignition, better power.

Its basically a GZ pump (like Colin) with a GB crank baffle, Provent attached via adapted filler neck (I have a new filler port direct to sump).

I am in the process of adding a new primary centrifugal AOS in front of the Provent to strip more oil - since the Provent 200 gets over oiled in the current config. This new primary AOS should strip a large percentage of the oil but as its a free flowing design it won't ever get as clean as the Provent filter element can do - so I'm trying to use both. Packaging is extremely challenging as I have virtually no room in the fenders to relocate these (which otherwise might make life easier). This primary AOS allows a larger flow volume around the recirculation loop back to the heads so the Provent only has to deal with the net blowby flow. I do potentially have fresh air flushing into the rear cam cover ports from variable VLVs in the bottom of the air filter box - however these are now set for just a max limit (12") and don't flow anything currently - since the last thing I need is more flow right now.

Ultimately these need to be set up to flush only under low blowby and up to medium total flow conditions - most likely via an additional electrically controlled recirculation flow valve. Control based on RPM and intake vac.

I intend to have a completely sealed closed loop system - this of course demands that the recirculation to the airbox (via the air pump port) be totally clean... not there yet.

Much still to be done - but the new AOS is about ready to go in. It has taken me about 6 months to adapt for it to fit where the air pump filter used to live. Partly because it's complicated, partly that I've been going slow and partly that the fit and plumbing is so tight I've had to make it over and over again.

More results later... I am completely sold on the general direction here - its just down to the details of configuration and installation.

Alan