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Can anyone tell me (a) how much you can mill a 2.0 sohc head before you lose adjustment on timing belt (it has an oil pressure type adjuster) and (b) what kind of compression will that be making? Or is there a magic # to shot for, to build a certain compression? thanks in advance.
Budman
 

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Couple things to think about. One is the clearance of the edge of the valves to the deck of the head. You don't want to shave the head enough to reduce that clearance or cut into the valve seat itself, using a straight edge against the head and using feeler gauge you can make that determination. Second,there are adjustable sprockets so the cam timing can be corrected in this instance. Then there are other ways to increase the compression through camshaft timing itself by adjusting the camshaft opening of the valves and closing of the valves, a DOHC helps with this, but a different camshaft profile of the SOHC can be done. If the engine is out of the car so the block can be decked, based on the clearance of the piston at TDC to the deck block is another option to raise the compression, along with pistons which are made to raise the compression. How much you can raise it, best to use any online computer compression computer to determine how much you will have to remove in order to get it where you want. If you could get into the PCM and adjust the timing levels within, on 87 octane, you should then be able to get her up to 12:1 by reducing the advance curve without an issue, I've gone higher than that on 87 octane, but not on a computer controlled car. Timing is half the key, it has to be slowed down, the other is removing any sharp edges inside the combustion chamber to alleviate any hot spots that could develop with higher compression ratios and the heat created.
 
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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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The Neon (PL) service manual says no shaving or planing of the head, but that is for stock applications. I have resurfaced them lightly with a Roloc disc (non-directional pattern) when replacing head gaskets.
The pistons are notched for valve clearance, so there may not be much room for machining. These are an interference engine.
Supposedly the 1995 cam was the hotter grind. It discusses this and other things in the books.
The biggest improvement for my '96 was converting to stick-shift. It gave some real 'snap' and brought the car alive off the line. I also installed the Mopar Performance PCM (stick-shift only). Premium fuel is suggested.
If you are looking for tricks to massage the 2.0L SOHC, there are plenty of ideas in the now out-of-print Mopar Performance and CarTech Neon books:

 
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