Discussion
After a few problems with my car with over heating and not being able to get it tuned. It turns out that the head has been skimmed a few too many times. When tested I was told compression may be as high at 12 to 1.
To fix this there is some head work that can be done (David Vizard) that will help flow but also reduce compression. The question is how low do I need to get it back to for 98ron and how much needs material removing for a 1725cc engine?
(e.g will the plan work)
To fix this there is some head work that can be done (David Vizard) that will help flow but also reduce compression. The question is how low do I need to get it back to for 98ron and how much needs material removing for a 1725cc engine?
(e.g will the plan work)
E-bmw, there are quite a few factors to that including cam timing, fuel injection, and even spark plug type. Being a 1960 engine its longer stroke than the newer stuff. So I know I can make lots of changes to make it work it's not a race car so just want to keep the orginal head, but happy to mod that to make it work.
What is managing your engine? Carb & Points of something more modern. 12:1 is no problem on modern EMS, but you are unlikely to be able to get the spark range wide enough on with mech control (ie dizzy with bob weights and a vac capsule)
Also, whats the Cam spec? 12:1 only matters if you fill the cylinders with air well...........
Also, whats the Cam spec? 12:1 only matters if you fill the cylinders with air well...........
This is a fairly ludicrous, not to say stupid, question. You don't even tell us which type of engine although we might surmise from the 1725cc it's a Humber or Alpine Rootes type engine. It's vanishingly unlikely to really be at 12:1 CR regardless of how much the head has been skimmed and in truth you clearly have no real idea yourself but you seem to think we can calculate exactly what needs to be done to fix it when the entire scenario is just your guesswork to start with. Does the idiocy of this not strike you at all? I suppose not or you wouldn't have asked the question.
Maybe another leg with an Austin Taxi? 2178 diesel which could be, with fake media a 1728 
Once you have properly measured the compression ratio and have the actual ratio there are a number of options.
I would consider a thicker head gasket as an easy option.
You will have already calculated the volume the gasket adds to the calculations and from that you will understand how the thickness and the diameter to the fire ring affect the compression ratio.
Because your engine is a push rod engine you may get to the end of rocker adjustment, however if the head (or block) has been skimmed in the past you will probably be restoring the adjustment available to the normal range
I would consider a thicker head gasket as an easy option.
You will have already calculated the volume the gasket adds to the calculations and from that you will understand how the thickness and the diameter to the fire ring affect the compression ratio.
Because your engine is a push rod engine you may get to the end of rocker adjustment, however if the head (or block) has been skimmed in the past you will probably be restoring the adjustment available to the normal range
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