Cylinder head

[Tiger]

My Ruby a non runner came with a low compression head.
I have read a few posts regarding improvements by fitting a high compression head.
Any comments

[Derek Sheldon]

Absolutely if you can find one

[JonE]

Why not get it running and see how the bottom end feels first? It wasn't until I it was properly explained that the extra power has to come from somewhere - more stress on the components and higher engine pressure, that I decided to stick with a later incarnation of the LC heads on my engine (which is unproven). I have inferred that a LC will be sweeter and more gentle... I'm not quite sure if that is a linear progression declining as the CR gets higher?

[Chris KC]

Probably the quickest and easiest way to gain a bit of oomph. Jon is right in saying that noise and strain on the engine will also increase. It's worth checking someone hasn't skimmed any head before you use it - for touring use the standard CR is enough, in my humble opinion.

[Malcolm Parker]

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.

[Steve Jones]

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.

I agree 100% with Malcolm. Get the car running on a LC head first. Make sure that it runs properly and well before looking to even try any 'improvements'. The spark plug issue with the HC head is that the plugs sit immediately above the edge of the bore. Any oil passing up the bore therefore can do little else other than hit the plugs head on. 

Steve

[Tiger]

Great advice yet again.
Will stick with the LC head.
Regards
Tim

[Chris KC]

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.

A pre-requisite for any kind of performance tuning is an engine in decent running order!

[GK5268]

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.

[Bob Culver]

For a modest patent fee Austin could have adopted the later Ricardo pattern head years earlier but chose to wait for the 3 bearing engine. Two bearing engines are distinctly more harsh with the later head, esp when cr raised further. (But distinctly more lively) The firing stress on crank is vaguely proportional to c.r. if you read any elementary text on metal fatigue any increase of stress near the fatigue limit has a grossly disproportionate shortening effect on life measured in cycles (miles). (ie in tests 10% increase might reduce life to 1/10!)
In their day the 2 brg engines were not esp noted fro crank failure. The rash of failures corresponds largely with the Bill Williams special building craze, more spirited driving by mostly young  men in the 1960s,70s, and accumulating mileage.
It is no fluke that those claiming huge mileage with original cranks have not altered.
(The Phoenix cranks are nitrided which process considerably improves fatigue resistance)
Several have reported gains by wedging the post 33 head as small.
The term large radius followers is preferable to ”flattened”. I could detect little difference with that mod alone. The exh valve size and duration is reasonable so doubtful if altering those makes difference at normal revs .The degree of lowering of the follower can be quite small.