wabbit

Thought i better post this one in the holden section. I'm not sure on the oiling paths for other marques.

After deburring the block, I looked at other ways of getting the oil from the heads to the sump. The next obvious place to look was the heads.

Holden V8s have a history of oil leaks from rocker cover gaskets due to too much oil in the heads when a high volume oil pump is used, so we'll explore why it is so. (apparantly not due to the glass and a half of milk).

The heads have only 4 X 10mm holes to drain oil from the heads back to the sump via the valley. These holes sit almost horizontal when the heads are on the motor, so gravity is not your friend.

and here's a picture







I drilled the holes out to 7/16", which is just over 11mm, because it's what I had. It still leaves over 2mm of metal between the oil return hole and the water galleries.

Now, enlarging a 10mm hole to approx 11mm doeasn't sound like much, but it gives an increase in area of 21%. The 7/16" bit i used gives an increase of 23.4%.
I'd be greatly appreciative if somebody has the flow rates for standard and high volume pumps


And here's a picture of the drilled gallery







A pic of the top of the heads showing the difference. The unmodified head is on the left.





Pic from the bottom with the unmodified head again on the left.




The holes have to be drilled from the bottom of the heads.
VERY CAREFULLY. I put half a dozen layers of thick, silver tape over the hole and drilled through that. Slowly, slowly, wins the race. Even taking your time, it only takes about 2 minutes per hole.

Clean up with a die grinder and chamfer the holes and you're away

All that's need now is a quick shave to clean up any dags and ensure the surface is flat and then it's time to put it all back together.

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Tiny

Wabs: Another good thing to do to match all your hard work on the heads is to sit them on the block and make sure there is no obstruction from the block itself!

I know that my chev needed quite a large ammount taken off an area under the head ( but not on teh deck surface) to un-shroud the oil return holes from the heads!

Good info mate, Thanks for the pics.

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wabbit

good point,Tiny. the holden V8s don't have any trouble normally. i had to grind a bit out of the block to match up with my enlarged holes, though.


i put this in the holden section on purpose because i don't have any other engines to work on.

it would be good if you had some piccies or a spare block to do for the chevs.

i'll do all of them if somebody wants to donate a windsor, cleveland, mopar and chev for me

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folden@308

what about the gasket did ya have to enlarge it or use it as a template

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wabbit

the only gaskets i've got here at the moment are an old pair of Felpros.
they have an oversized hole there, anyway. other brands may need the holes enlarged

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folden@308

any sugestions other than carfully on the gasket

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rorym

I just looked at my VN heads and they are the same..2 holes per head but they are 11mm now..I wonder if you could crib another 1mm?
R

wabbit

you could be pushing the friendship a bit there, Rory. a little core shift and you could bugger a good set of heads.

I did a set of VT heads recently, and they were 10mm, so your VN heads may have been done already.

if you want some more drainback, i'd look at punching a hole through below the flange that the rocker cover sits on and drain through that.
there looks to be enough meat there for that, but you could cut up and old head, if you have one, and see exactly what we're looking at.

i've also seen restrictors in the pushrods that seem to do the job. a few Yanks have tried it and the theory sounds good.
with roller rockers, you really only need enough oil to cool the valve springs

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rorym

I will check the size of the holes again..But pretty sure they were 11mm..My VN heads were a 200k motor, never been apart..wonder if the VN ones are bigger?
R

ProStreet427TT

On my Grp A motor I ran a -10 drain hose from the centre of the manifold (under the plenum) & 1 from the front of each r/cover back to the sump. You would be amazed at just how much oil sits in the valley at revs.
I had a h/v pump & at only 3000rpm constant (on the dyno) it filled the valley & was pumping it out the return I fitted to the manifold... all through the dyno room. I had forgotten to tighten the fittings on the sump & it had vibrated un-done. It took an hour to clean the dyno room up before we could continue.

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