Cylinder head

[Alan]

But, Bob, Austin were using Ricardo designed heads at least seven years earlier than the late Ruby. The Ulster and the Nippy heads are both Ricardo designs. You are right about the harshness on 2 bearing engines, but I think the whole 3brg/ HC head thing was to maintain performance in the face of ever increasing weight. As an automobile designer that sounds very familiar.

[Zetomagneto]

I fitted a HC head to my Ruby - this head is reputed to be the best all-round in the development of the ideal head, but you could get a similar increase in compression ratio on a later LC head by "wedging" this (5-degree angle). I have had this done on one and it will be fitted on my Swallow saloon engine shortly.

I can't honestly say that changing from a LC to HC was really that noticeable, ok, the changeover was part of an engine re-build and I didn't drive the car for several months whilst this was all in progress so I may have forgotten what it was like before.

However, the one modification that did make a really noticeable difference (to me) was the fitting of flatter tappet blocks - the valves open & close quicker, which mean they are open longer, giving a better charge and evacuation, that really helped performance, the engine has a purposeful grunt (so it seems to me!), the engine is noisy under load (always was), but once cruising speed is reached, the engine is quieter as less revs seem to be required at any given speed. Going up hills is not the trepidation it once was!

Fitting the tappet blocks requires the tappet guides to be cut down (in the tappet chamber) as after grinding they end-up being slightly shorter than before and there is insufficient space to adjust the tappet gap before fouling the guides. Simple enough to cut down (Austin helpfully provided a guide line to cut...!), but it will be necessary to whip the block off to do this, a methodical approach to removing, cutting and re-fitting each individual guide meant I was doing each one in 20 minutes, so the whole operation, could be done in a day, but two is better, particularly, if you are using a silicone gasket for the joint between the crankcase & block to allow this to settle over night before giving the nuts the final tighten.

Hi Garry, quicker and more accurate to take the block to your local friendly machine shop and get them to mill them off in situ, downsides it cost money whereas your Method is free.

[Rogerfrench]

Surely the advantage of the 37 head over earlier heads, Ulster, Nippy , etc., excluded, lies in improved breathing as much as compression ratio?
Downside is the poor plug position, where it runs relatively cool and oils up in a worn engine. Why Austin didn't stick with the Nippy head is a bit of a mystery.

[Charles Levien]

I have fitted late Ruby high comp cylinder heads to several 'unknown' Austin 7 engines and in most cases the results were far from satisfactory, ie rough running, loss of power.   The reason has always been that the 14mm plugs of the late head oil up, causing the engine to run on three cylinders.
The late head is very prone to plug oiling, so unless you have an engine with good bores and piston rings, I would stick with the early head.   These are much more kind on an old unrebuilt engine and an engine running on four cylinders will always be better than one running on three.   Also kinder to the crankshaft if the engine is an unknown quantity.
If you have a nice rebuilt engine fit a later high comp head or a Ricardo aluminium head.    Best bet is to get your engine running sweetly on its low comp head and assess its overall condition.

Seems a pity not to use the later head on the grounds that it oils the plugs — I would look at fitting a Powerspark electronic ignition to your DK4A and enjoy the nice fat sparks!

Charles

[Reckless Rat]

With the 37 head I have changed to NGK B5HS plugs. - the BP5HS plugs have a longer nose and are more susceptible to oiling than the B5HS.

[Charles P]

I've never had a problem with the 37 head. My blown car runs a 37 head (with a lowered CR) and doesn't oil plugs despite having two stroke in the fuel. That said I do have a nice fat spark created by a properly rebuilt ML magneto - the higher you rev, the bigger the spark.(which tends to be the other way round with new fangled coil systems)

[Steve Jones]

I've never had a problem with the 37 head. My blown car runs a 37 head (with a lowered CR) and doesn't oil plugs despite having two stroke in the fuel. That said I do have a nice fat spark created by a properly rebuilt ML magneto - the higher you rev, the bigger the spark.(which tends to be the other way round with new fangled coil systems)

I've only ever had one engine that oiled it's plugs with a 37 head. It was built years ago and had a slightly slack re-bore from the start. It did do a zillion miles much of it in competition. Malcolm borrowed it when he was building his Ulster and I fitted a L/C head before he took it away. It still burnt oil but it didn't oil its plugs. We always referred to it as 'Old Smokey'. It's still on the floor in my garage - I might even re-build it one day.

I imagine Charles' engine is bored properly and doesn't burn much oil if any at all. His re-built magneto will probably overcome most things! Whilst I don't criticise anyone who uses electronic ignition, those that know me will understand it when I say I'd rather poke my eye out than use such a thing myself!

Steve

[Bill Sheehan]

I've never had a problem with the 37 head. My blown car runs a 37 head (with a lowered CR) and doesn't oil plugs despite having two stroke in the fuel. That said I do have a nice fat spark created by a properly rebuilt ML magneto - the higher you rev, the bigger the spark.(which tends to be the other way round with new fangled coil systems)

I've only ever had one engine that oiled it's plugs with a 37 head. It was built years ago and had a slightly slack re-bore from the start. It did do a zillion miles much of it in competition. Malcolm borrowed it when he was building his Ulster and I fitted a L/C head before he took it away. It still burnt oil but it didn't oil its plugs. We always referred to it as 'Old Smokey'. It's still on the floor in my garage - I might even re-build it one day.

I imagine Charles' engine is bored properly and doesn't burn much oil if any at all. His re-built magneto will probably overcome most things! Whilst I don't criticise anyone who uses electronic ignition, those that know me will understand it when I say I'd rather poke my eye out than use such a thing myself!

Steve

In all these years I haven't heard of plug-oiling problems with the '37 head until now, but would suggest it's subject to the condition of the rest of the goodies.  I was convinced of the difference from an early head back in the mid-Seventies when visiting Barry Risely in a Hobart suburb during a two-week tour of the Island..  As there aren't many places where you can accurately check your oil in Tassie (!), I was not surprised to find the top of his house was level with the street.  He entered his block via the next street below.  He doubted I could get up onto the rear parking level in my '25 Chummy and he was correct - I got half way, not helped by the ruts and waterways on the steep surface.  His '29 Chummy was in good condition and he told me he also could not get up the rise until he fitted a '37 head (& nothing else).  He sailed up with ease every time.  As one who always believes in what actually happens rather than rely on theory alone, I was convinced of the value of the later head, and I know many who still are.  Even a small increase in Neddies surely must be helpful?   Cheers,  Bill

[Michael D]

Fouling plugs can have various causes; not only oil in the. combustion chamber . Way into the sixties fouling plugs were a phenomenon one could face with temperamental Italian cars driven at loo low revs, leading to bad combustion and carbon deposits on the plugs.. So a not too rich mixture and decent spark would be things to. go for. Sometimes people even fitted / changed. to different plugs; 'hotter' or 'colder' depending on driving style.

As with regard to HC heads: David Dye supplies (new) Ricardo heads and John Barlowe the Whatmough Hewitt heads of his own 'Brand';... Both are of pre war design which would keep you out of scrutineering trouble in VSCC circles. I've got one of each...but need to get the Rosengart running properly on its LC head first...In view of Bil's contribution above methinks I'l go for either of the HC heads and keep a spark plug socket in the boot in case the plugs do foul up; if that is one of the authentic properties of a car with a HC head so be it.

[John Cornforth]

I run a 2 bearing engine with a Phoenix crank, and changed from a LC head to a '37 HC head some years ago.  Plug fouling only happened once, during a freezing cold Easter week on Guernsey when the poor thing never got properly warm.  A change to NGK plugs effected a cure.  If your ignition system is weak, a slightly oiled or carbon fouled plug will begin to stop sparking and you enter a vicious circle of increased misfiring and worse fouling.  I suspect its more to do with the smaller size of 14 mm plugs and the reduced gap between insulator nose and body, rather than the positioning in the head. So the message is, keep the ignition system in A1 shape, and keep the engine hot by driving technique or in cold weather by slackening the fanbelt or muffling the radiator.

One factor which doesn't ever seem to get a mention is that the later head has a "squish" design. The flat part of the area above the piston has a clearance at TDC of maybe only 20 thou, which induces useful turbulence in the compressing mixture as it is forced sideways at the last part of the upward stroke.  In theory at least this is one factor which should reduce the need for ignition advance.

The HC head definitely gave a harsher feel, presumably because of the greater mean and peak cylinder pressure.  The latter is increased further if too much advance is used, and I suspect that the extra noise and more "spiky" peak pressure isn't in fact accompanied by much useful increase in mean pressure, i.e. torque.  Above about 2500 RPM as torque falls due to restricted breathing (untuned engines) and the general engine noise rises, the harshness is less apparent.  For a lightweight special where the revs rise relatively quickly through the gears harshness is probably less of an issue than say in a heavier saloon that may spend more time around the 2000 RPM mark.

For my engine, apart from an increase in mid-range torque due to higher CR, I also found the 37 head improved power above about 3000 RPM presumably due to better breathing.  A sensible maximum change-up point from 3rd to 4th gear was increased from about 3000 RPM (27 mph) to 4000 RPM (35 mph).  This drops the revs back to 2400 RPM in 4th, which on all but steep hills allows one to carry on up in 4th rather than being stuck in 3rd.  For me, improved hill-climbing ability is probably the biggest plus point of the later head.