Oiling and Oil Pumps
The stock Holden system is simple and relatively trouble free on a stock or mild engine, but could use some help with high rpms and high hp. The Holden, like nearly all engines, has a bit of a problem supplying an appropriate amount of oil over a wide range of speeds. Increases in the crank speed do lead to a slight increase in oil requirements due to the increased throw-off, but its nowhere near the increase in oil flow provided by the pump as revs increase. The net result is less-than-ideal flow and pressure at low speeds but too much at high speeds. Depending on the oil viscosity and the bearing clearances it will take anywhere from 20 to 30 litres per minute to oil the little six. The standard size oil pump can supply this and so should be sufficient for nearly any high performance engine, and the only application I can think of where a high volume pump might be useful is an engine that runs at unusually low speeds and high loads; a turbo engine perhaps. It's surprising how much power is absorbed by an oil pump, and if you've ever primed a Chev with a power drill and dummy distributor you'll have experienced it first hand. Whenever there is an excess capacity the unused oil blows over the relief valve, and the energy that goes into this work is converted into heat. In other words it makes the oil hotter, and this is another reason to avoid the high volume pumps.
It's worth remembering these motors are pretty long in the tooth so you'd want to check out any used pump carefully before using it again. Check the clearance between the tips of the gear teeth and the pump body and reject any pump with more than a few thou clearance. Also check the end clearance and keep it down to about 2 thou. Backlash between the gears isn't really critical but check for badly worn or scored gears, or worn shafts and bushings. If there is any doubt about a used pumps condition it's best to replace it.
Higher speeds and looser bearing clearances - both of which are typical for a high performance engine - will require higher volumes of oil. The standard pump will handle this, but the stock suction too small to ensure an adequate supply. The standard suction line is made from 1/2" steel tube, with an I.D. of about 7/16". If you want to retain the factory suction arrangement (and it's perfectly fine with a factory style sump) it pays to enlarge it a little. There's no need to go overboard, flow capacity is proportional to the square of the tube diameter so even a small increase in tube size will help substantially. A 5/8" tube will work, but remember to also open up the fitting and the drilling in the block that leads to the pump. The stock pickup can be reused with the bigger tube; it may pay to slightly flare the end that is attached to the pickup to ease the entry into the tube, like a little bellmouth. Don't forget to reattach the support brace to prevent the tube from cracking. Your local hydraulics supplier should be able to provide the tubing and fittings.
The other way to upgrade the suction line is to use an external line, and this is the approach commonly used with so-called competition sumps. The original suction line is plugged and a hole drilled in the appropriate spot towards the front of the pump cover plate. A threaded adaptor is silver soldered to the plate and a hose run from this to the sump. Using this method means you can make the suction line as big as you like, but 5/8" to 3/4" I.D. should be plenty for any application. Again, you need to maintain this dimension all the way from the pickup to the pump port. There is really no need to use those gay looking anodised fittings and stainless braided hose - the appropriate stuff from your local hydraulic hose shop is at least as good. It's important to reface the cover plate after attaching the adaptor to address any minor distortion that may have occurred.
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| Typical 3/4" external suction line. |
A short passage, about 7/16" diameter and a few inches long runs from the oil pump and intersects the main oil gallery just behind the no. 4 main. The main gallery is about 9/16" in diameter and runs the full length of the block. From the main gallery to the mains are 1/4" drillings to oil the main bearings. Mains 1,3,5 and 7 have additional 11/64" holes leading from the mains back to the cam bearings. No. 1 main also has an additional hole that leads to the cam gear nozzle. Opening up the passages to 1,3,5 and 7 is good insurance against the cam bearings bleeding too much oil from these bearings.
The main oil gallery intersects the lifter bores, so check that none of these bores are worn otherwise you'll be bleeding off oil before it gets to the crank. Years ago some builders ran external lines to the end bearings but if you don't run excessively thick oil or excessive bearing clearance, drill the passages to the odd numbered mains and you have sufficient pressure this is unnecessary. I can't stress enough the importance of keeping the viscosity down and also of not loading the engine until the oil has warmed up. I've seen several cranks/bearings that have been burnt simply because the too-thick oil that was used didn't flow quickly enough. On the other hand I've also seen other engines where the oil has been thinned dramatically (through fuel dilution) where the bearings have survived nicely.
Basically all you need to do for the bearings to survive is this:
1, Use a pump suction line of at least 5/8" and open up the passage to the pump
2, Use a die grinder to blend the passages between the pump and block
3, Drill the passage from the pump to the main gallery from 7/16" to 1/2"
4, Drill the passages from the main gallery to the odd numbered mains from 1/4" to 9/32"
5, Shim the relief valve to approx. 65psi.
Naturally all the oilways in the block and crank will have to be thoroughly cleaned, and if you avoid excessively loose bearing clearances you should have no trouble maintaining enough oil pressure. Two to three thou should be enough to ensure a reasonable flow across the bearings, but not so loose as to drop the pressure too much at lower speeds. Most lifters have a 3/32" oil feed hole; if there is too much flow to the top end the hole can be filled with low melting point silver solder and redrilled. This method should be more reliable than the old "pipe cleaners in the pushrods method".
Of course all this work will be for nothing if the oil pump pickup becomes uncovered, even if only for a second. The primary objective of any oiling system will always be to provide a constant, uninterupted flow of oil. Do whatever is necessary to build or buy an oil pan that will suit the intended use of the car. Under full load the bearings can be burnt in a painfully short time without oil - picking up a momentary bubble of air may damage the engine in a time period too short for the oil pressure gauge to react. This is one thing you absolutely must get right.
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| Oilways leading into and out of the pump have been shaped and blended to reduce pressure drop.(photo courtesy Jeff O'Rourke) |
Choose your oil carefully and be aware that nearly all modern petrol engine oils will be unsuitable for a high-output Holden straight six. Unfortunately you can't find out much about an oil just by reading the container - even the SAE viscosity numbers cover such a wide range to be almost useless. An example of this is an oil marketed as say SAE30 that is at the high end of the 30 range. This oil may actually be more viscous than another oil at the low end of the 40 range that's marketed as an SAE40. It pays to check the makers Technical Data Sheets where you will find accurate specs on the viscosity at various temperatures as well as other info. While we're on the subject, viscosities really have little relation to an oils lubrication abilities so there is no point in running a thick oil, the increased drag just robs power. If you can't maintain adequate pressure with a 15w-40 oil you have problems. Years ago monograde oils had a significantly higher load capacity than multigrades but today there is very little difference so definitely go for the multigrade. It's crucial that you be gentle with the engine until it is thoroughly warm - keep the revs and the loading down until then. A 15w-40 will circulate from cold and give sufficient protection when hot. Leave the SAE 50s and 60s to the Harley guys.
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| Oil manufacturers rarely state whether the product contains zinc on their label. This one from Pennzoil is an exception. |
For those running a flat tappet cam - and this will be nearly everyone - look for an oil that contains zinc dithiophosphate (ZnDTP). Almost none of the modern petrol engine oils and only some modern diesel oils have it, the reason being modern roller cammed engines don't need it and also because it tends to foul catalytic convertors and oxygen sensors. You mightn't find the ZnDTP level mentioned in the tech data sheets but it will probably be in the Material Safety Data Sheets. More than likely you will end up using an oil designed primarily for diesel engines (eg. Rimula Super) and these generally work very well. Just don't put it in a very high mileage engine that hasn't previously been using diesel oil. The high detergent levels will quickly loosen up the accumulated crud in the engine with unpleasant results. For competition use there are quite a few racing oils (eg. Valvoline) that have high zinc levels, and these are even better than the diesel oils in high rpm applications. The reason for this is that the high detergent levels in the diesel oil tends to partly counteract the zinc compounds - the zinc is trying to attach itself to the load bearing surfaces while the detergent is trying to remove it. For any reasonable valve spring pressure the diesel oil will be fine but for high rpm, heavily sprung engines a dedicated high-zinc racing oil will be safer.
What about synthetics? It's possible to pick up a few horsepower by using synthetic oil but there are a couple of things to watch out for. Firstly, make sure you use a mineral oil to break in the cam and bed the rings, and be 100% certain that the rings are fully bedded in before switching to synthetic. Also make sure the bearing clearances are suitable for the thinner synthetic oil - if the engine has been set up with "old-school" clearances for thick mineral oils you may find that the oil pressure drops excessively. If you limit bearing clearances to .002" - .0025" you should be ok.
As for filtration, the stock setup is fine. Just be aware that many replacement filters are of exceptionally poor quality, and this includes the "performance" brands. A good choice is the Baldwin B9; a Fleetguard LF3538 would also be acceptable. Also be aware that many remote filter adaptors are quite restrictive so check them carefully before use.