FX Holden Race Car Project

[immortality]

Damn.

Good work.

Maybe add a external drain from the back of the rocker cover down to the sump?

It really came alive at the end of that dyno pull before it blew the catch can.

[vlad01]

Sounds really good. Regarding what Immortality said about draining the rocker cover.

A really counter intuitive thing about the rocker cover and ventilation and oil drainage is, they don't play nice together. An very renown Porsche and VW engine developer (when I had an interest in those things back when I was young ) told me a very valuable thing that I'll never forget, push rod engines and rocker breathers make things worse and that a good breather should be out of the crank case or in a V engine at least the valley if oil drainage is far easier than any blow by countering it.


So it goes like this, if your pushrod engine relies on oil drainage via small passages which they typically do and often these same passages are also for breathing in the OEM design. When a hot or race engine build is considered, then the blow by being vented up from the crank case and out the rocker is more forceful than the gravity draining the oil out of the head passages. So you get a situation when the oil is being essentially aerated back up the drains and the oil continues to accumulate, more so if the engine is turning some decent rpm which pumps more oil up there than normal. So all these things just exacerbate each other.

When you have a closed off rocker and head ventilation, then the pressure difference from the crank case and heads become similar or same. The oil can then assume it's normal draining. Any overflow issue is now going to be about the supply vs the draining, and no longer an air pressure forcing the drainage to back up and in worse cases in the reverse direction.


The best place from the top of my head (no pun) on this engine might be the dizzy hole, you might need to make or install some sort of air/oil separator to stop excessive oil mist venting out being where the crank is before it goes to the catch can, but it should be heaps better than the oil being forced to fill the rocker cover.

You should be able to confirm this but popping off the rocker oil cap after a pull like that and see how much oil has accumulated.

But the whole rocker cover and oil cap need to be air tight.

One of the ideas I have on my next hot engine which will require decent ventilation and a catch can or two plumbed back into the intake duct, I found a nice big spot under the throttle body in the intake valley for a breather than can be drilled and tapped or welded in, and with no balance shaft there should be ample opening for air to flow up and out without affecting drainage too much. I have seen lots of people drill the shit out of the valley all along the cam tunnel for "cam lubrication" and drainage but it often can initiate the block to crack straight down the valley.

[VK_3800]

Nice, you fixed so many things at once that you're dealing with the opposite end of the spectrum now. Changing the oil pump will definitely help, any sustained high rpm is always going to need a good breather system with good baffles and vapour separator.

[immortality]

Sounds really good. Regarding what Immortality said about draining the rocker cover.

A really counter intuitive thing about the rocker cover and ventilation and oil drainage is, they don't play nice together. An very renown Porsche and VW engine developer (when I had an interest in those things back when I was young ) told me a very valuable thing that I'll never forget, push rod engines and rocker breathers make things worse and that a good breather should be out of the crank case or in a V engine at least the valley if oil drainage is far easier than any blow by countering it.


So it goes like this, if your pushrod engine relies on oil drainage via small passages which they typically do and often these same passages are also for breathing in the OEM design. When a hot or race engine build is considered, then the blow by being vented up from the crank case and out the rocker is more forceful than the gravity draining the oil out of the head passages. So you get a situation when the oil is being essentially aerated back up the drains and the oil continues to accumulate, more so if the engine is turning some decent rpm which pumps more oil up there than normal. So all these things just exacerbate each other.

When you have a closed off rocker and head ventilation, then the pressure difference from the crank case and heads become similar or same. The oil can then assume it's normal draining. Any overflow issue is now going to be about the supply vs the draining, and no longer an air pressure forcing the drainage to back up and in worse cases in the reverse direction.


The best place from the top of my head (no pun) on this engine might be the dizzy hole, you might need to make or install some sort of air/oil separator to stop excessive oil mist venting out being where the crank is before it goes to the catch can, but it should be heaps better than the oil being forced to fill the rocker cover.

You should be able to confirm this but popping off the rocker oil cap after a pull like that and see how much oil has accumulated.

But the whole rocker cover and oil cap need to be air tight.

One of the ideas I have on my next hot engine which will require decent ventilation and a catch can or two plumbed back into the intake duct, I found a nice big spot under the throttle body in the intake valley for a breather than can be drilled and tapped or welded in, and with no balance shaft there should be ample opening for air to flow up and out without affecting drainage too much. I have seen lots of people drill the shit out of the valley all along the cam tunnel for "cam lubrication" and drainage but it often can initiate the block to crack straight down the valley.

TK on the old AV8 forum said the same thing, at high rpm you are fighting windage more than anything.

I'll be honest, I can't remember what a Holden 6 head looks like internally for drain back. I also seem to remember when they modified the pickup size going to the pump they also modified the oil pressure bypass and exhausted it externally back to the sump as there is a much greater volume there now too. Damn shame AV8 shut down because all that info was lost.

I noticed a few US forums have shut down too, I had bookmarked a few pages with interesting info over the years but those links are now all broken

[Holden202T]

yeah it was a really slow ramp too which wouldn't have helped things, a normal drag race is not that long hahaha!

This is the oil drain holes from the head, then there is also a pushrod in each of them, so not a big hole, then from the lifter gallery theres a few large holes into the crank case

[immortality]

Wow, yeah that is worse than the 304 heads which are known for filling rocker covers at high rpm.

I've also heard of people putting roll pins into the ends of push rods to reduce oil flow to the top end.

[Holden202T]

yeah i've heard of the same thing .... there are also oil restrictor pushrods available so i'll see if i can get them in the size i need ... one way or the other i'll work something out!

[vlad01]

I've personally seen that happen on 304s, stock too!

There certainly are pushrods with restrictors. I was also under the impression good solid and solid roller lifters for racing applications were already oil metered for less top end oil, no?

[heff0018]

Great job on the sump.

[Holden202T]

Thanks Heff!

There certainly are pushrods with restrictors. I was also under the impression good solid and solid roller lifters for racing applications were already oil metered for less top end oil, no?

I honestly cant remember what lifters are in it, i seem to recall i wanted cool face lifters but they didn't have them in stock and was going to be like 6 months wait so i got edge orifice ? other than that not really sure ....

i had a quick look at crow cams options, they do a restricted on but its 0.100 shorter than what i have now .... so have to see if any other brands do one in the right length