964 oil pump in 911 SC

[heathbar]

Hi all,

In the process of having my 3.0SC motor rebuilt as a 3.2SS w/JE pistons and PMO carbs. Had crank cross drilled, cams reground, etc. My builder is suggesting the 964 oil pump as an additional upgrade, but I can't find detailed information about the performance differences between that pump and the stock one (other than "it's bigger"). Are there any concrete data that show improvements with the 964 pump in place of the stock SC? Does this build justify it? Just trying to understand before I do or don't cough up a grand at this critical juncture. The magnesium also makes me a little leery, but the failures seem to be more with the 993 pumps. Thanks!

[Dmitry at Pelican Parts]

Hello - take a look at the link below; there was a discussion about the 964 pump as an upgrade. Hope this helps a bit.

964 oil pump

[heathbar]

Thanks Dmitry. I did see that post, but I didn't see a flow rate comparison between the pumps or any kind of rule of thumb for hp/torque/redline/etc that could be used when selecting an oil pump. Do you know if this information exists?

[KTL]

The 964 pump has a bigger suction/scavenge section and what appears to be the same size pressure sectoin. The longer it is, the more oil it can deliver thru the pump gerotors/gears

This thread is a good read about pumps and oil pressure relief valves and check out the chart in post #59

Ultimate Oil Pressure Relief Valve Thread

Here's another good one 993 oil pump or 4 rib

If you go with the 964 pump, make sure to use the small spring spacer ring to properly shim the relief spring, which ensures the pump doesn't go into bypass mode at a lower than desired pressure. In other words, if you don't use the spacer, the pump doesn't provide as much oil pressure as you want it to. I recall seeing my VDO dash mounted oil pressure gauge showing a little more than 60 psi all the time. Whereas when I was running the SC pump, it was near 80 all the time.

['78 SC]

Heathbar,

I replaced the stock pump with a 964 pump in my 3.0 L 911SC (1982) last year when rebuilding after a major blowup (details here).

My oil pressure was good before, with the stock pump, and good after with the 964 pump. No real difference that I noticed. I did notice, however, that the oil tank level as shown on the gauge comes up faster when the engine returns to idle after running at higher RPM. I attribute that to better scavenging, since emptying oil from the crankcase increases the tank level. I suppose that is a combination of the larger scavenge section, the domed sump and the redesigned pickup all working together to evacuate the crankcase. The original pump had the improved (venturi) pickup to address scavenging issues identified in the early 911 SCs.

I do miss the sump drain plug a bit and the option to reach into the lower section of the crankcase (never know when you might drop something from up top).

['78 SC]

Kevin,

Do you have a part number for the oil pressure relief spring spacer you mentioned? I'm referring to the indicated item in this post Ultimate Oil Pressure Relief Valve Thread

I don't see a part in the Pelican diagram for 964 oil relief.
http://cdn1.pelicanparts.com/catalog/images/Diagrams/93010753101-OEM.jpg

Is this part required for a 964 pump installed in a 3.0 L case?

BTW, excellent treatise by you, John, Walt and Cupcar on the evolution of the oil relief system.

[KTL]

Check out the Porsche classic PET parts diagrams

http://www.porsche.com/all/media/pdf/originalparts/usa/964_USA_KATALOG.pdf

Part 13A is the spacer ring. 964.107.532.00

The screw cap, spring and the spring guide are the same as SC parts. So the 3.6 engine case may have something different about it to require the use of it? But I also recall William knight (KNIGHTRACE) saying that the spacer is needed in the older cases or you'll have lower oil pressure. I find the need for the spacer rather strange because the 930 pump doesn't need it

Also know that you'll need to clearance the webs inside your case for the oil pump to physically fit in its location

[chris_seven]

I think threads of this type raise some interesting questions about oil pressure and flow and it seems that there are not too many clearly established 'bench marks'.

If we start with the scavenge side of the pump as this is the most straightforward part of the discussion.

It seems logical that the better the scavenge the lower the windage losses which becomes increasingly important with revs.

High revving race engines must benefit from better scavenge as this will not only reduces losses but less heat will be transferred to the oil making cooling more straightforward.

In general this must be a 'win, win and I don't see a down side.

The question of increasing flow from the pressure section is much more debatable and needs more discussion.

The real situation is that providing there is sufficient pressure at low speed and idle to allow bearings to separate and centre do we really need more pressure and what is the ideal?

Fluid Bearings really need flow to provide both lubrication and cooling and is we consider that pressure is effectively resistance to flow then does increasing pressure provide any positive benefits?

The flow through an engine will be determined by the width of the oil galleries and the clearances within an engine along with the oil viscosity.

A 'thin' oil which may reduce pressure would tend to increase flow and this may reduce wear.

The change in pump and oil system design over the years is interesting but does raise questions.

The early 2.0 litre engines had a relatively large scavenge section and a small pressure section.

They developed quite good pressure but did by-pass directly back to the crankcase.

If you use the Kremer By-Pass modification then the scavenge will improve and the pressure will still be maintained.

It is common practice to fit a 4-Rib pump to these engines along with the By-Pass mod but IMHO they then produce too much pressure and in some cases can cause the safety by-pass to operate.

The 4-rib pump was designed for use with piston squirters and I am not sure what the flow these take but I assume that they will prevent the development of excessive pressure.

It seems clear that Turbo pumps have larger pressure sections to deal with the greater flow rates of the increased squirter volume but using them in engines with small squirters may also increase pressure.

I guess my point is that providing we achieve certain minimum pressures that are stable when the engine is hot do we really gain from increases.

For example using a thick oil to improve pressure may reduce flow and increase wear.

I would generally be happy with an engine that developed 20-25psi at idle and 65 psi at peak revs when hot.

We check all of 'our' engines with a calibrated Stainless Steel mechanical gauge as I tend to have a mistrust of automotive quality pressure transducers - they are just to cheap to be well made.

We have good experience with 964 pumps in SC engines we have used in several Rally engines.

[heathbar]

Thanks everybody for providing all the feedback. My builder told me it's not about the pressure but rather the scavenging and it just didn't sink in. It only took being told about 4 times for me to get it...sad. Especially since the other pictures have pumps with 2 or even 3 scavengers on them! I guess I need to think hard about this, because I don't plan on tracking the car, but I do live in Florida and I want to keep the motor cool (already planning on replacing my crushed oil lines and upgrading the cooler). Still leery of the magnesium, but if it's brand new, it seems unlikely to fail during just the years of "spirited driving" that I plan to do.

[Trackrash]

Originally Posted by chris_seven

I would generally be happy with an engine that developed 20-25psi at idle and 65 psi at peak revs when hot.

I too would be happy with 20 psi at idle.

[DSPTurtle]

I think we need some pics...

['76 911S 3.0]

964 pump with cam line restrictors (in SC engine), no spacer in pressure relief spring:



Idle is about 20psi when warm.

[KTL]

Thanks for sharing that data with the 964 pump and no spring spacer.

Just keep in mind that the cam housing restrictor fittings are the contributor to the raised idle oil pressure. That's exactly what they're intended to do, along with reducing what is believed to be excess oil volume to the cam housing. They also force the piston squirters to activate sooner.
Others argue that a reduction of oil to this critical area of the heads, cams, rockers and valves is not a good thing, since they want as much oil cooling effect as possible here.

[Walt Fricke]

Chris - somehow the VDO oil pressure sender doesn't look cheap to me, but maybe compared to alternate designs it is?

[chris_seven]

I guess a VDO Sender is around $50 here in the UK with URO and others being about $20.

There is no data with these senders in terms of linearity, hysteresis, repeatability etc, etc.

This really means that the degree of uncertainty that these devices produce is difficult to quantify and from a rigorous engineering point of view they could be considered as useless

There will almost certainly be zero errors and also slope errors, they will be influenced by temperature, both ambient and of the oil.

It is also possible that they may be sensitive to the phase of the moon

As a guide I am sure they are OK but as far as 'absolute' measurement is concerned it is impossible to judge. To look at changing pressure on a given engine does have value as long as you don't believe the 'number'.

The instrument which converts the resistance signal to pressure is probably equally difficult to assess so comparing data from one car to another is difficult and this was the point I was trying to make.

The Mechanical gauge we now use has a UKAS Calibration Certificate and it is accurate to 0.5% of indication up to 200degC.

Brass Mechanical gauges as a comparison become unstable above around 60degC.

We paid around $300 for the gauge with its Cal Certificate and an industrial grade Pressure Transducer would be a little less costly but would also need an indicator.

We can now be confident in the pressure generated by a fresh engine and we have eliminated the uncertainty due to relatively poor instrumentation.

[toddu]

Originally Posted by '78 SC

I do miss the sump drain plug a bit and the option to reach into the lower section of the crankcase (never know when you might drop something from up top).

Can an aftermarket sump cover/drain plug be used? (e.g. - Mainely?)

Todd

['78 SC]

The 964 pump pickup and screen fills the crankcase opening and is not removable, unlike the stock 911SC pump screen (both original and improved). This is what blocks access to the crankcase.

An aftermarket sump cover could regain the drain plug (is the Mainley compatible with the 964 pump screen?).

['78 SC]

Here are the 964 and 911SC pumps side by side showing the pickup and longer scavenge section.

[Walt Fricke]

Todd - the convex (on the outside) drain cover can be used - I use it with a GT3 pump on an early case. You can easily enough install a drain plug with a bit of welding, and dimple the screen if needed. Maybe someone makes one with the plug?

[KTL]

Yes the Mainley and the Burnham Performance style of sump covers are domed and allow the fitment of the bigger pumps and/or the pumps with the built in strainer + venturi. Pumps like the 930, 3.2 Carrera, 964/993, 996 twin turbo, GT3 all fit the aftermarket sump plates

Just keep in mind that when you use a larger pump, you have to clearance a few locations in the case where the webs interfere with the larger pump body.