21-11-2018, 02:46 PM
(This post was last modified: 21-11-2018, 02:47 PM by Steve Jones.)
(21-11-2018, 02:19 PM)Malcolm Parker Wrote: 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