truth Posted April 6, 2016 Share Posted April 6, 2016 checking if anyone has knowledge about how compression release handle works heres my thinking the lobes on #2 and 3 and 6 and 7 have 2 heights as the pictures show so when the lever is pulled out the lobes hold valves open longer to aid in hand cranking once started the handle goes to in position and allows all lobes to be the same? i was starting to think the wear was on the cam but i think its made this way in order for compression realease to work or am i completely missing it? pictures show typical 2 height lobe on cam [013 and also the yoke that slides the whole cam] 030 and 031 pics shows the distance the cam moves when operating the handle [32 and 33 show same distance thanks for any help im a green horn working on a fiat tipo 55[american built] sure would appreciate anyone w knowledge on this chiming in Link to comment Share on other sites More sharing options...
Dandy Dave Posted April 6, 2016 Share Posted April 6, 2016 What is this on? Decompression releases have been around for many years. Since the first internal combustion engines were built. You photos are rather blurry, but I have seen similar systems on different applications. Old Caterpillar diesels for instance. Dandy Dave! Link to comment Share on other sites More sharing options...
truth Posted April 6, 2016 Author Share Posted April 6, 2016 this is an american fiat tipo 55 9 litre 1916 17 or 18 Link to comment Share on other sites More sharing options...
Mark Shaw Posted April 6, 2016 Share Posted April 6, 2016 Early compression releases were just valves at the bottom of the cylinders that could be opened to vent the combustion chamber. This is important to do before starting horizontally opposed two cylinder engines with old style oilers. Excess oil continues to flow after the engine stops and can accumulate in the cylinders & cause hydraulic pressures that can crack the cylinder. Compression releases allow the excess oil to drain while priming the cylinders with the fuel/air mix. Cranking with ignition off and compression releases open solves this problem and primes the cylinders to fire when the ignition is turned on. Link to comment Share on other sites More sharing options...
truth Posted April 7, 2016 Author Share Posted April 7, 2016 i probably wasnt as clear as i could on how this car is set up there is a compression release handle on front of this car [pic] when lever is pulled out the whole camshaft moves in the block and thus the rollers on the lifters are in line w the higher spot on the lobe once it starts the lever is pushed in and all the rollers are now riding the same height on the front side of the lobe i just assumed this was in practice during this era? maybe fiat is the only car that had this type compression release for starting?im wondering if any other cars have this Link to comment Share on other sites More sharing options...
DonMicheletti Posted April 7, 2016 Share Posted April 7, 2016 Compression releases were very common on the larger old engines, Packard, etc. A 1920 American La France pumper I worked on had one Link to comment Share on other sites More sharing options...
mike6024 Posted June 26, 2016 Share Posted June 26, 2016 Raised cams integral with the regular cams, and the camshaft (slides) endwise... without moving the timing gear. So you're correct in understanding how it works. Explained at the bottom of page 1174 here - http://books.google.com/books?id=8swqAAAAMAAJ&pg=PA1174&lpg=PA1174&dq=fiat+model+55&source=bl&ots=T3VrcyjLpE&sig=JPUZFxCpHS2GRM2o8C8_CAGMfdQ&hl=en&sa=X&ved=0ahUKEwihyoSg9MTNAhWIKGMKHfsHCKwQ6AEIKTAA#v=onepage&q=fiat model 55&f=false Link to comment Share on other sites More sharing options...
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