timpress Posted March 29, 2022 Report Share Posted March 29, 2022 (edited) Hi All, I recently had my later TR6 block bored and decked for an engine rebuild I am doing and during the rebuild process I now find that the pistons protrude slightly above the block deck by about .45mm i.e. they stick out. Based on the fact that a compressed head gasket is around .9mm, I wont have much tolerance between the pistons and the head. I am waiting for the machine shop to call me back but as I wanted to carry on with the build tonight, I wondered if any one knew whether this clearance would suffice when engine is warm or should I be looking for a little thicker head gasket (non recessed), getting the piston crowns machined very slightly or any alternate thoughts? I will truly know if I have a problem when it is rebuilt and running but would like to get ahead of this. Also just in case, does anyone have any TR6 blocks for sale? Late type with reinforcement bar. Thanks Tim Edited March 29, 2022 by timpress Quote Link to post Share on other sites
Andy Moltu Posted March 30, 2022 Report Share Posted March 30, 2022 How much did they take off the block? You could get the pistons turned down so they don't protrude. Quote Link to post Share on other sites
JochemsTR Posted March 31, 2022 Report Share Posted March 31, 2022 I have 0.2mm protrusion (intentionally) with 0.8mm compressed gasket. So 0.6mm clearance. Anything else, I consider too much. I would look for a thicker gasket, or have the pistons maschined. A thicker gasket is obviously easier and cheaper. Jochem Quote Link to post Share on other sites
sheldricka Posted March 31, 2022 Report Share Posted March 31, 2022 To get around this same problem I used a cooper head gasket from Burton Power, they used to do these in two thicknesses. I found out I had the same issue after I replaced the head gasket and then had the piston hitting the base of the head! Quote Link to post Share on other sites
timpress Posted March 31, 2022 Author Report Share Posted March 31, 2022 Thanks for all the responses. I am going to have my piston crowns machined slightly to reduce the protrusion. Quote Link to post Share on other sites
Jim F Posted April 6, 2022 Report Share Posted April 6, 2022 As you pull together you plan to assemble the engine its worth knowing what the cylinder head combustion chamber volumes are. That will influence piston clearance, compression ratio etc. There are a few work sheets/spreadsheets around to help pull all the calculations together. Quote Link to post Share on other sites
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