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700/900 Series General Forum for the Volvo 740, 760, 780, 940, 960 & S/V90 cars |
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head gasket life?Views : 1918 Replies : 54Users Viewing This Thread : |
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Jan 22nd, 2022, 14:04 | #51 | |
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V70 D5 SE Geartronic 215bhp Saville Grey 2012MY 940 LPT Manual 1996 740 SE 1990 |
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Jan 22nd, 2022, 14:06 | #52 |
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This goes on a bit but it's talking about tight squish
https://forums.tbforums.com/showthread.php?t=124192
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V70 D5 SE Geartronic 215bhp Saville Grey 2012MY 940 LPT Manual 1996 740 SE 1990 |
Jan 22nd, 2022, 14:19 | #53 |
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There's obviously a way round that Mark as many new petrols turbos are running 18psi and 10:1 compression or similar. Yes, you read that right and yes, i queried it when i first heard it. I've still not got to the full facts about it so there's scope that it's incorrect but i daresay someone knows. It flies in the face of everything that has previously been known though.
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Jan 23rd, 2022, 14:07 | #54 |
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On our redblock engines tight squish means having the the outer circumference of the piston come to within 1mm of the cylinder head at TDC.
The idea is that the mixture of air and fuel is squeezed out of those areas at high velocity to increase the efficiency of the combustion process. There is a lot of info about this on line. You would need to measure (very accurately obviously) the height of your pistons in the block compared to the deck of the block. In other words how much they stick up above the block or how far down in the bore they are. Then using the compressed thickness of a head gasket one can work out how much needs to be skimmed off the block. (Skimming the head has no effect on this calculation.) Alternatively, using a head gasket with a lower/higher compressed thickness would also acheive the same goal. As far as I know the only gaskets that are offered in varying thicknesses are Cometic multi layer steel gaskets and ironically they recommend having the head and deck skimmed to provide a suitably flat surface. Although I think it true to say that most cylinder heads now need some work to be re-used. The thread quoted from tbforums includes a post from stealthfti (post #8) - the late, much respected Tom Fritz and includes much of the info you need to know. He was a proponent of tight squish and often posted regarding it. Tim |
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Jan 23rd, 2022, 15:17 | #55 | |
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