modifying oil return holes in head

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ace202

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I'm getting my head (1971 Commando) ready for new guides and I'm looking at the oil return holes in the valve spring pockets.
On the exhaust side the insulating washers cover the edge of the hole and the valve spring seat further shields that area. I'm thinking about grinding the inlet to an oval so that oil can have an unobstructed path to flow.
On the intake oil return is only on the right side. I was going to relieve the interior edges of the spring pockets to provide a path from the left pocket to the right, where the return is located. This should lessen the amount of oil puddled up in this area as well as lowering the level relative to the top of the valve guide.
This type of modification was common during iron head Sportster rebuilds in order to decrease oil traveling down valve guides.
Does anyone have experience with this type of modification on a Commando ?
Is it a non-issue? Solution looking for a problem ? Any possible drawbacks ?
Thanks.
 
My take on this is "Solution looking for a problem"

If you do grind away, keep in mind that there is not a lot of metal between the valve spring pocket and intake tract.

Probably the biggest problem is upon reassembly when too much gasket goo can block off the return passages between the head and barrel and between the barrel and crank case.


I have seen a separate oil drain spigot installed for the intake side where the oil line external to the engine drains down to the timing chest but this is used when porting has encroached on the oil passage in the head casting. Not something to mess with otherwise.
 
Good valve guide seals will prevent any amount of oil swooshing about from getting down the guide/valve gap.
I have watched oil build up in the inlet side, the oil return hole struggles to drain it, seems to be an issue with size and alignment with barrel/gasket.
Some racers drill an extra hole between the valves and use an external pipe.
 
I have not done this but common sense tells me that it should be ok to do.
If I may add, the reduction of crank pressures by the use of various methods should promote head draining in this regard.
God forbid someone should promote a high level of oil in the head as beneficial. :roll:

Dances with Shrapnel said:
Probably the biggest problem is upon reassembly when too much gasket goo can block off the return passages between the head and barrel and between the barrel and crank case.
Click to expand...
Sadly this is all too common. I think using a spray copper coat will eliminate this issue.
 
The reason for the mid manifold external drain in some racers is when bore gets big and/or sleeved enough, in some cylinders it takes out the internal passage, so not an over oiling reason for it.

Exhaust side guides never see suction if the valve seat is intact, its closed for the inhale and exhaust pressure pushes out up guide when open to exhale, so exhaust side oil puddle is a non issue combustion smoke wise.

Intake valve guide does see inhale suction so that's the side with seals, which should seal even if under oil level, which if that high would tend to spill over to exhaust boxes and drain.

God forbid someone should promote a high level of oil in the head as beneficial. :roll:
Click to expand...

My newbie novice often at first recoiled against opinion - I think dry sump rocker boxes is a poor idea, maybe second only to the dry sump dry cam start protection, the valve springs and seat surfaces get most their cooling temper protection from heating the oil splash. If ya don't think our air cooled heads get hot enough springs to benefit with some retaining of what little oil does spatter up there then by all means put it out of mind and giver the gun!

Alan Goldwater measured mid 400's F oil temps in exhaust rocker. i have seen Peel with 425' F at plug rings. Jim Comstock has measured 500' F in deep center of head. Most the heating of oil is not by conduction of heat from combustion but by the shearing friction its saving the metal almost contacting.
With what follows might reconsider which view is most conservative to follow.
This is just me nick picking back at ya, and a non issue for a sanely used street bike, but for those wanting to get away with stuff, every little bit helps.


if a steel valve spring becomes "red hot" it will have also lost its temper, and will take an immediate set when compressed. Valve springs do get hot due to friction and conducted heat from the head and valve. Friction is the primary source of heat in the valve spring, and this friction mostly results from rubbing between the coils of double/triple springs or where a spring dampener is used. It is common practice to use lube oil to cool the valve springs in these instances.

"Red hot" steel implies a temperature of 1000 to 1200 degF. Most valve spring steel alloys lose temper strength above about * 475 degF *. So the notion that steel valve springs can endure even very brief periods of operation at "red hot" temperature is sheer fantasy. As for the presence of carbonized oil deposits on valve springs subjected to severe duty, that is entirely conceivable. Engine oil can produce these type of deposits at temperatures below the temper limit for alloy steel springs.
Click to expand...
http://www.eng-tips.com/viewthread.cfm?qid=334017


OH yeah I went around and around for anti-detonation features in Peel so investigated using more oil through exhuast spindles and open up lifter drains, then I came upon Harley Davison research on both extra flow onto valves and extra flow inside passages, to quickly give up on that idea as only thing it did way over heat the oil and nil cooling of heat to matter.

modifying oil return holes in head
 
Ya right there Steve, If i had to choose between 3 oz or 3 pints of oil flowing through the head per minute ....well let me think :roll:
 
hobot said:
The reason for the mid manifold external drain in some racers is when bore gets big and/or sleeved enough, in some cylinders it takes out the internal passage, so not an over oiling reason for it.
Click to expand...


Steve Maney supplies his big bore barrels with oil drains (except the 1,007 cc which is an 83 mm bore).

The external drain is an old practice which predates the "big bores". The reason for the external drain is as I stated above where there is not a lot of material between the port wall and the drain gallery in the cylinder head. I have several heads with the oil drain blocked off (partially filled with epoxy) as porting encroached on the drain gallery in the head. This is a practice that is even found on some stock bore 750 cc race Nortons.

@ace202 - I want to re emphasize that there is not a lot of metal between the intake port walls and the spring pockets where you asked about "relieving the interior edges of the spring pockets". You could daylight through to the port and any metal removal in the area will increase the likelyhood of port to valve spring pocket cracks radiating from the guide in the future.


Opening up the drain hole site a little bit probably will not hurt anything so worth a go at it if you see a problem there but don't over do it. Honestly, when the cylinder head and oil get warmed up the oil drains rather well from there. As mentioned above, the copper coat gasket compound is a good safeguard against getting too much compound in place and blocking the passages.
 
IIRC water carries like 6 times more heat away than oil so its
not very efficient cooling for balk of engine heat, but can help
an otherwise air cooled engine in some places. For some sense to oil cooling, Japan research showed in took minimum of .6 liter per min per out size piston to lower crown temp 100' F. BFD unless already right on the edge of pre-ignition.

I'm a confused yet [shush it] on which principles to apply to Norton head oil logic and function. Its age old to current practice to polish case walls and head and block oil drain paths to speed the oil drain, which is contrary to letting some accumulate. Best i can glean is its an oil protective practice to avoid oil picking up too much heat over the friction induced kind, but nothing that helps engine per say.

Some super hot rods spray extra oil at the valve springs. Do any Nortons have spring heating issues and if so could the meager head oil help at all?

Norton flipped the spindles to stifle oil when going from 3 to 6 start oil pump speed. Peel will have lightened factory lifters which includes some meat off the drain bevels, would some extra exhaust rocker oil and drain down help any when the boost is held a while to get those pesky bee line wonders out my way to the next corner.
 
" any metal removal in the area will increase the likelyhood of port to valve spring pocket cracks radiating from the guide in the future."

I guess that's a good enough reason to leave the intake side alone. That and the fact that the intake has seals and ,i would think, run cooler than the exhaust side.
I will rework the holes on the exhaust drains, just a little bit. I'm thinking the cooling effect of any pooled oil is minimal but the chance of 'burning' the oil increases the longer it sits over the exhaust port. I remember some of that Harley oil research, used to work at a dealership.
Thanks for the input.
The idea of running an external line so as to not preheat the oil to the timing compartment has got me thinking, but just thinking, that's another topic for another project on a future rebuild.
 
I'll post pix of my Dreer/Baisley 880 head, it uses an external drain...
 
I can't speak for norton motors but exhaust valve seals are common/useful on most engines. The Venturi effect of gasses rushing from the comb chamber through the exh port creates a venturi-generated vacuum at the valve guide/stem which can draw oil past the unsealed guides. Many engines that did not originally spec an exh guide seal later included them. Ducati actually sent me a set of exh valve seals for my first Duck, a '92 900 ss. They stated they had "upgraded the spec" but they just sent me some seals; they did not offer to install them; I had to do that myself. :)

We installed positive type exh valve seals on all engine builds beginning in the late 70s.
 
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