[Healeys] Oil pressure in a BJ8

Sat Sep 3 08:06:57 MDT 2016

Just a second you guys.... there is something missing here.
It's a long time since I took "Gear Design 101" but a few things that I do
remember are:

   1. If the number of teeth on a gear is increased without changing the DP
   then the PCD (Pitch Circle Diameter) increases.
   2. 2 mating teeth have to have the same DP (Diametric Pitch).
   3. If the PCD changes then the shaft center-line spacing must change.

 *Sooooo..* Installing a cam with an extra tooth on the oil pump drive gear
MUST require a different oil pump drive spindle or a different block (to
alter the shaft center-line spacing) !!!
B.M.C. knew this because, according to the parts book, prior to C.E.38262 a
different oil pump drive spindle was used.. This spindle and the cam gear
would almost certainly have had a different DP.
*Therefore...* It is quite reasonable that there will be catastrophic
consequences if you change the cam without changing the oil pump drive
spindle, things like rapid gear tooth wear, high friction, excessive end
thrust etc....sound familiar?
*Conversely *... Installing an early spindle (designed for a 13 tooth cam
gear) on a 12 tooth cam gear will result in extremely poor gear engagement
and very rapid wear of the teeth of both gears.
Just sayin'.

Michael S
BN1 #174

On Fri, Sep 2, 2016 at 9:58 PM, Chris Dimmock <austin.healey at gmail.com>
wrote:

> Hi Richard,
> Totally valid concern, but there is one factor missing. The speed your
> camshaft is driving the oil pump.
> I've done a lot of research on oil pumps and cam drives since 1998. I
> published an article - prompted by numerous cam drive/ oil pump gear
> failures at Bathurst in 1998 and 1999, which I'll dig out.
> I run the DW pump - but I use the later cam with 12 teeth driving the oil
> pump.
> I also run the DW hardened steel cam retaining plate and DW Torrington cam
> bearing.
> These are all important points which address your concern.
> The big difference is if you use the earlier camshaft with the 13 teeth
> oil pump gear. All the failures I have seen (3 after Bathurst alone) were
> from the earlier cams with 13 teeth driving the oil pump. It's the 13 teeth
> cam which is the major issue.
> It's about how fast you are driving the oil pump.
> Here's some background for everyone else for completeness.
>
> All 6 cylinder C series camshafts have 2 gear drives on them. The gear
> closest to the back of the camshaft drives the oil pump. The gear closest
> to the middle of the camshaft drives the distributor, and the distributor
> drive gear on the camshaft always has 13 teeth on it….
>
> But there are 2 variants of the oil pump drive gear on the camshaft.
>
> The first is what I'll call the “sedan” camshaft. It was typically used in
> early model, low revving C Series sedans,  6 cyl A90 and A95’s, and also
> 100/6's. I’m not sure whether or not it was used in any 3000’s, or when it
> changed. This camshaft is relatively easy to identify, as the gear closest
> to the back of the camshaft, which drives the oil pump, has 13 teeth on it.
> So it is the same diameter as the distributor drive gear on the camshaft –
> both 13 teeth. Usually, these cams have beautiful lobes and have never been
> reground. Because they came from a low mileage sedan.... That's why racers
> regrind them & use them...
>
> The other camshaft, typically found in later C Series engines and later 6
> cyl Healey's, later Wolseleys  etc. (I'll call Healey cam) has 12 teeth to
> drive the oil pump (and still 13 to drive the distributor). Easily
> identifiable because the two gears on the camshaft are different diameters.
> It effectively drives the oil pump 8% slower than the earlier "sedan" cam
> at the same revs.
>
> So I'm guessing your "souvenirs" all have 12 teeth cam drives. Just like
> all those that blew up with the same symptoms at Bathurst in 1998 and 1999.
> Denis Welch explained to us, face to face, the lack of lubrication to the
> cam/ oil pump gear drive issue, at Bathurst in 1998. He even drew a picture
> of how you can tap into an oil drilling in the block, that you thread a
> piece of brake line into, to squirt oil directly on the camshaft/ oil pump
> gears, to keep them lubricated. But he also said - NEVER run a 12 tooth
> cam/ oil pump drive cam over 5,500 rpm - irrespective which oil pump you
> use - because 5,500 rpm on that cam is driving the oil pump closer to 6,000
>
> If you use a standard Healey crankshaft, (so you aren’t going to
> "regularly" rev it over 6,000 rpm) and fit an upgraded oil pump (e.g. the
> Denis Welch hi volume pump) with a sedan 13 tooth cam - you will have huge
> oil pressure. Because the “sedan” cam is driving the oil pump 8.33% faster
> than the “Healey” cam at the same engine revs.
>
> And if you rev the engine with a ‘sedan’ cam at 6,000 or more for any
> prolonged length of time, the oil pump gear on the cam will strip and
> you'll have no oil pressure at all. Because although the engine is pulling
> 6,000rpm, the oil pump is being worked as if the engine was running at
> 6,500rpm –i.e.  8.3% faster… and if you were pulling say 6,400rpm – the oil
> pump is being driven as if you were pulling over 6,900 rpm.....
>
> The cam gear that drives the oil pump on the C Series engine has very poor
> lubrication (it’s based on the BMC ‘splash and drip’ lubrication theory).
> There is no pressure fed oil to the two meshed gears – the oil pump drive
> gear on the cam, and the oil pump drive spindle gear. So as you rev the
> engine  harder, the “dripped and splashed oil” gets thrown off the gears,
> and they run dry, wearing through the hardening relatively quickly, at
> sustained high RPM. This process is all dramatically increased if you are
> running a “sedan” cam, as the oil pump gear on the cam is driving the oil
> pump spindle gear 8% faster....
> You also mentioned the steel camshaft retaining plate failures. Denis
> Welch also offers a Hardened steel version of this plate, and a Torrington
> bearing - which together solve the second issue of wear in this area.
> The ultimate solution is the DW gun drilled cam, which makes the camshaft
> part of the oil gallery, and lubricates under pressure the cam lobes and
> oil pump drive gear and the distributor drive gear. These didn't become
> available until around 2003.
> We pulled the sump off my engine, and pulled the oil pump, after the
> numerous Bathurst blow ups in other guys engines from this issue. See
> http://www.myaustinhealey.com/mechanical_restoration.html
> So your concern is valid, Richard, but the missing piece of the issue is
> the cam gear teeth. Mine is 12. My concern was alleviated after we pulled
> the pump after 3 years driving and some 20 track days.
> A 13 teeth cam drive would definitely be a concern, in an engine revved
> over 5,500
> If anyone is running the earlier 13 teeth cam with a DW pump & Penrite HPR
> they'll have better oil pressure figures than me at the same rpm. :-)
> Best
> Chris
>
> [image: image1.PNG]
>
> On 2 Sep 2016, at 11:30 AM, richard mayor <boyracer466 at gmail.com> wrote:
>
> Chris,
>
> I hate to be negative about your good oil pressure but I fear you may have
> a problem.  I am assuming that you have the "high pressure" oil pump from
> DW.
>
>
> ......... Many of us racers have used the DW "high pressure" oil pumps and
> discovered that at some point, all of the teeth on the cam and driving
> spindles have been ground off to such an extent that we have lost all oil
> pressure.
>
>
>
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-- 
*If you can't fix it with a hammer, you've got an electrical problem.*
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