So, I just did some blacktop oil return and coolant routing investigation, and I'm a bit
shocked. Those big drains you can see in the head gasket don't do s*** until the head
is half full! Which leaves the two small ~12mm ones rear and mid-front to do the work.

Furthermore, adding external drains to it is really tricky, difficult but possible at the back
on the intake side, but hard core/impossible at the front on the intake side.

Another thought crossed my mind, too, contrary to every engine I've ever seen, (see next post)
the right place to take your breathers off is smack in the middle of the top of the engine
and up high, which would also require some custom fab etc but would ensure that even
in a nasty flood of overflowing, it'd stay dry.

That could be emulated by taking the breathers off the usual places, routing them
together and upward, and plucking it off the middle of that. This quite possibly would
have saved me on the ute at Hampton Downs.

I guess the equivalent is to take the LHS breather and route it upward and RIGHT and
away, and vice versa for the RHS breather, otherwise it's just a giant funnel out of the
engine and into the guard :-D You heard it all here first. Probably.

I guess the purpose of that central "drain" isn't a drain at all, what in fact is, is the
channel through which blow by can escape through the head and breathers, and for
that it'd work admirably. I'd probably leave that completely alone even though it has
big potential to get a lot of oil out of the head. I wonder what 16v shit is like?

For the 20v, the entire intake side is all ports, and the gaps between the ports align
with the head bolts, and the area below the ports is 100% cooling, which only leaves
these two tiny areas at the front and back, but the back one is ultra tiny due to the
shape of the casting and the cam belt etc. I wonder if the inter port gaps can be
used in some clever fashion - maybe, just maybe.

I think I'll have to get some sort of table setup and take this smoky blacktop apart.



Thinking about this all from a FWD perspective

1. Cruising - no big drama, RPM low, oil level approximately flat, oil able to casually drain out of both left and right side front drains (front and back of engine, exhaust/LH side)
2. Braking - no big drama, regardless of RPM, oil pushed at in excess of 1g toward the drains means excellent oil return, if insufficient, the rather high centre passage will come into play much earlier due to the effective angle of the surface of the oil
3. WOT Acceleration in 1st gear - no big drama, only lasts a second or two, later gears pull very low Gs, much like cruising, but RPM in the 6k to 8k+ range, both oil returns will be working hard with some minimal pooling in the head at the intake side due to mild Gs.
4. Hard Turning Left - no big drama, high effective to-sump pressure driving oil out of head through RHS drain at front of engine, if feed was excessive, and corner was long, loss from breathers could occur, but most corners just aren't.
5. Hard Turning Right - no big drama, exactly the same as left, except LHS drain at the rear of the engine is used.

Summary: Not great while turning, mediocre while accelerating, great while braking, fine while cruising.



The same set of states in an unmodified RWD configuration

1. Cruising - no big drama, RPM low, oil level approximately flat, oil able to casually drain out of both front and rear LHS drains
2. Braking - no big drama, high effective to-sump pressure driving oil out of head through front LHS drain, if feed was excessive, initial speed was high, and RPMs kept high, loss from breathers could occur, but would not be sustained for more than a few seconds at worst.
3. WOT Acceleration in 1st gear - no big drama, only lasts a second or two, later gears pull very low Gs, much like cruising, but RPM in the 6k to 8k+ range, rear LHS oil return will be working hard with some minimal pooling at the rear of the head as supply exceeds expulsion.
4. Hard Turning Left - Terrible, we have a problem! Oil will pool heavily in the RHS of the head where it has NO drains whatsoever. This will take seconds to build up, but once it does, oil will be lost from breathers which are very poorly placed for this scenario, and the head will remain full of oil. This is bad for your bottom end too, as while it's in the head, it ain't in the sump, and your pick up will be sucking air to some degree after the oil volume in the sump has been reduced sufficiently. This is the scenario that drives modification of the head.
5. Hard Turning Right - Exactly like FWD braking, regardless of RPM, oil pushed at in excess of 1g toward the drains means excellent oil return, if insufficient, the rather high centre passage will come into play much earlier due to the effective angle of the surface of the oil

Summary: Disastrous while turning left, great while turning right, mediocre while braking or accelerating, fine when cruising.

I realised while writing the above that I'm not the first to think about joining the two
side's breathers together and taking off that joint volume. Nissan sort of did it on their
R32/R33/R34 (real) GTRs. Here's a cropped close up of the factory Nissan setup:



Original scaled down: http://stuff.fredcooke.com/NissanSkylin ... maller.jpg
Original large image: http://stuff.fredcooke.com/NissanSkylin ... ineBay.jpg






And these characters at FEAT have improved upon it further with their R32:



Original: http://stuff.fredcooke.com/NissanSkylin ... ineBay.jpg






It could probably be made to look a bit neater with the right sort of central enclosure
and fittings, but the FEAT setup is excellent in terms of keeping the oil out of that hose
even when the head is suffering from major flooding at high RPM with max blow by, etc.

16V 4AGE's suffer from similar difficulties with the crank ventilation. The vent is situated in the top-middle of the intake side cam cover, if you take a looong right hander in an AE86 you're likely to leave a smokescreen. The later smallport 16v's had an added external oil drain, but those only came in FWD cars.
Restrictors for the head oil feed were made by HKS for high RPM 4AGE applications to help combat these problems.

That'll teach me for not mentioning the restrictor head feed situation! If they are entirely
unrestricted in the first place, then yes, that's an important step. If they already have
restriction in place (as the vast majority of engines do) then reducing flow is scary to
me. Here's a shot of the factory restrictor in my Mazda 4 pot, it's 2.5mm ID:








Based on that, I'd say ~2.0mm would be an appropriate size for the blacktop 4AGE to
use, if anything. I see "mototq" recommending that the hole size is a whopping 3mm!
Nevertheless, a restrictor only increases the time to trouble it does not and cannot
solve the actual issue, which is well distributed drainage. And given that in FWD format
these things are happily trackable (I've done it) with zero oil issues through the crappy
little twin ~12mm holes, you've got to wonder just how much restrictor is a good idea.
It's obviously not flowing huge amounts of oil into the head or there'd be a general
issue even in FWD layout usage. EDIT: Another data point for sustained high revs, I once
drove my ex's AE111 home down the motorway at the speed cut of 180kph the whole
way and at no point did it accumulate oil in the head to the point of inhaling it.

I've actually spent a bit of time studying all of my performance engines recently. This
spurt of research was triggered by the issues I had with the ute in the sweeper at
Hampton Downs. But the ute engine actually has the best setup of the lot, aside from
the fact that it only drains down the intake side of the head. It'd have roughly 4x the
drainage compared to the little 4age's 2 small holes (ignoring the high rimmed centre
hole which doesn't count until things are badly out of hand). And it still filled up, but
only on the sweeping right hander, no where else :-)

Volvo redblock: 3 smallish ~15mm holes between the three bores on the uphill side of
the slant engine with head internals cast to create a level playing field.

Nissan RB: 2 very generous odd shaped holes, but both at the rear of the head, one on
each side. Great for straight line abuse, terrible under brakes, and mediocre to bad
while cornering hard for sustained periods.

Ute engine, as discussed, 4 massive drains on the RH/Intake side of the head when RWD

I guess a few photos of the 16v external drain is in order for comparison:









If you can find a better picture, slap it up here! :-)

Next up, cooling systems, though I'll probably hold off publishing that until I have my gearbox-engine interface sorted and can mock things up in the vehicle and see how much space there really is.

Here's the HKS oil pressure up kit with spring, washer, and restrictor plug: https://www.nengun.com/hks/4a-g-parts

And here's the image, cached:







I won't be taking the head off my first engine anyway, so no chance of a restrictor going
in. But if I can safely machine some drains into it while it's still on the block, then I will.

A little more context:

User 'piimae' modified his 16v head for drainage from the rear right hand side, not quite how I'd like mine,
but good enough in a sustained LH cornering situation with mild to wild acceleration. Here are his pics:












He also made some comments about his usage:



If the 1-1.5mm max is correct, that totally explains the lack of block-head restrictor. I can't go and
measure right now (because I got the wife to lock me out of the workshop, lol) but I think the Mazda
cam journal and lifter bore feed holes are around 3mm or so. Which would explain why the Mazda has
it. I'm guessing the RB heads have decent sized holes into their cams/lifters, too. Solid lifter RB26 has
only one feed to the head, instead of two in other RB engines, presumably just for the cam journals,
relying on splash/flood/spray/splatter/fling to lube the solid lifters.

I had a poke around for photos, and the feeds at the front end of the cams look bigger than 1/1.5mm
to me, but perhaps he meant out of the cams into the other journals.

A few things from this Tomei RB product link: http://www.rawbrokerage.com/tomei-oil-g ... rb26-rb30/

They claim stock RBs have two 2.0mm holes and reduce that to two 1.5mm holes. roughly 1.77sq mm
each, 3.53sq mm combined. 4.91sq mm for the Mazda factory restrictor. 6.28sq mm for the stock RB
restrictors IF their information is correct. Now given the RB head is feeding the same bore size, same
valves, 1.5x as many, 6.28sq mm compares favourably to 4.91sq mm in the Mazda. Yes, it'll push more
oil into the head, but it also needs to. How do we compare a smaller 4age in terms of required flow
path? Not sure, hence my guess of 2.0 which would yield exactly PI sq mm, 3.14. If the Tomei kit
doesn't hurt an RB then I'd confidently say that, aside from the VVT pulley, a 2.0mm restrictor
couldn't hurt a 4AGE either. Here's their picture illustrating one of the issues:

Some photos I took yesterday to go with this write up:

Small left front stock drain: https://twitter.com/FredCookeNZ/status/ ... 2295248896
Small left rear stock drain: https://twitter.com/FredCookeNZ/status/ ... 9534497792
Central left non-drain over exposed: https://twitter.com/FredCookeNZ/status/ ... 7540695040
Central left non-drain under focused: https://twitter.com/FredCookeNZ/status/ ... 6525603841
Where you can't put an oil drain on the right front: https://twitter.com/FredCookeNZ/status/ ... 5042397184
Difficult place where you could put an oil drain on the front right: https://twitter.com/FredCookeNZ/status/ ... 2969063424
Right rear oil drain location, left of 'O': https://twitter.com/FredCookeNZ/status/ ... 0282833921

Inlined, read tweets for better descriptions:

So, first hand, tonight, I saw this RB25DET engine's left front factory side-drain:

https://twitter.com/FredCookeNZ/status/ ... 2569020416









Apparently there are more than what I thought, small holes, all the way down one side, that can be enlarged somewhat. Hopefully I'll see these first hand sometime soon :-) cough, Rob, cough. Links welcome. Ignore the topic, it's good background info to compare with.

Quote from an SAU thread:

"ever since i blocked off my oil line and restricter the other I have had major lifter noise when the car is driven slowly and cruising to work. As soon as i start hitting boost or idle in traffic for a while (engine gets warmer) the lifters stop making noise."

Not too surprising, TBH. There is no way I'd have done that with HLAs still in there. I'd be scared for the camshafts, too, as the HLAs should pump up and work so they must literally be starved of oil to make any noise at all. Ugh.

Here's a couple of pics, first raw, then with my markings. The two big ones on the right are definitely oil drains. The top one on the left I'm unsure about EDIT: Pretty sure this is coolant, not oil. The lower 5 have to be what Rob was describing earlier. They're on the down hill side of the slightly slanted engine. Please confirm/deny what you know :-D

RB wise, I came across the below photo from this thread: http://www.sau.com.au/forums/topic/4523 ... rs/?page=1

Some interesting stuff being done in that thread. Not sure about all of it, but worth investigating anyway.