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HiRegards testing the compression as you outlined that would be a blow by test and is normally done with a air line fitted with a small say 0.5mm restrictor , tee for the pressure gauge and an adapter for the spark plug or injector.Now for the downside , the situation was a test on a full size Diesel engine v16 6.5 inch bore 9 inch stroke the Cat guys tried to do that very test , you could hear air leaking ,but the test returned result as good from the Cat manual as I was shift eng for the bank I asked them to repeat the test without the rig on the engine , guess what the gauge read the same , so the test gear was useless.So take care with the readings they can fool you A cylinder comp tester is a gauge ( say 300 psi would be ok for you) with a non return valve between the gauge and cylinder do say five comp strokes and take a reading Great build been following along but I only post if I have something to offerBefore it’s asked we had 6 cat v16 engine for standby power for the computer centre each rated at 1000hp or 750kw continuous rating
.Bit of a random suggestion here.I feel a little embarrassed at suggesting anything to someone who's skill level is far, far beyond my own. OK - The engine the way I see it is basically 2 engines combined. Would it be possible to isolate the 2 halves from each other. (removing parts / blocking inlets etc.) and see if one of the sections can be made to run.? Well sort of run.! as there would be big holes in the combustion strokes (2 not 4) Just an idea to perhaps isolate the issue to which half of the engine needs a tweak.Nick
Hi Achim,Can you put up a video of the valve gear moving when fully assembled? The ones I can see only show the lower (exhaust?) valve being operated. If you can show the piston rod movement as well even better Single cam valve systems are very sensitive to valve clearance. I used to have Triumph Dolomite Sprint with this system
Achim,I have never used an automotive compression tester or leak down tester on a model engine. They are not accurate due to the relatively small engine cylinder volume you are trying measure on a model engine. Model IC engines are relatively low compression by design, and I find if I have reasonable flywheel bounce back when rotating the crankshaft over compression and uniform bounce back between cylinders, that a model engine will run. The factors influencing this simple test are ring to cylinder fit, ring to piston side clearance, and valve and valve guide sealing. The first two factors are easy enough to accomplish with good machine practice and visual inspection. Valve sealing is more troublesome. In my opinion the best test for leaky model engine valves is an inexpensive hand vacuum pump made for bleeding automotive brake systems. If you can pump it down to 25" Hg and it leaks down slowly, the valve should be fine. If it leaks down quickly, it needs lapping. Always put grease or 90W oil on the valve guide to check only the valve seat seal. Cut very narrow valve seats in the valve cage. .010"-.015" wide is good. Jeff