cbjroms Posted September 6, 2020 Share Posted September 6, 2020 Did a tune-up yesterday and so decided to do a compression test. Results were 135psi / 120psi / 120 psi / 140psi There is some faint white/grey smoke on harsh acceleration but no water in the oil of oil in the water. Given all cylinders are within 20psi, thinking that everything best left alone for now. Does my thinking make sense? Quote Link to comment Share on other sites More sharing options...
glang Posted September 6, 2020 Share Posted September 6, 2020 You could repeat the test with a little oil poured in the spark holes to see if it changes the results which would indicate some bore/piston ring wear.... Quote Link to comment Share on other sites More sharing options...
Pete Lewis Posted September 6, 2020 Share Posted September 6, 2020 did you do this hot or cold? were throttle held open ?? all plugs out ?? all makes a difference Pete Quote Link to comment Share on other sites More sharing options...
cbjroms Posted September 8, 2020 Author Share Posted September 8, 2020 I have done the test again with the engine cold and the throttle fully open. The table shows PSI for each cyclinder before and after a shot of oil. What does this show? Quote Link to comment Share on other sites More sharing options...
glang Posted September 8, 2020 Share Posted September 8, 2020 well the oil has definitely improved the seal between all pistons and bores but I would say cylinders 2 and 3 have a top end problem as well. This could be their valves not sealing well or a small head gasket leak - possibly between the two? Definitely worth taking the head off to investigate/overhaul.... Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 7, 2020 Author Share Posted November 7, 2020 Decided to take the head off and have a look. Found that the valves on 2 & 3 were not seating properly and a local shop cleaned head, reseated all the valves and checked the head - all for a few beer tokens. Just cleaned the block ready to put the head back on and am wondering how much effort I should be putting into the polishing of the tops of the pistons. This is what they look like after cleaning: Is there any benefit in going further? Quote Link to comment Share on other sites More sharing options...
glang Posted November 7, 2020 Share Posted November 7, 2020 No the pistons will soon be dirty again😁 The important bit is the faces of the block and head as sometimes gasket/carbon remains are stuck on there and almost impossible to see which certainly wont help sealing... All bores look good with no lips or bad scratches I take it? Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 7, 2020 Author Share Posted November 7, 2020 Bores look good and I have cleaned heard and block. I have a Payen head gasket and research suggests that it just needs a thin spead of grease. Quote Link to comment Share on other sites More sharing options...
sparky_spit Posted November 7, 2020 Share Posted November 7, 2020 Don't use grease on a Payen head gasket. These gaskets have a thin membrane layer of some silcone/plastic/slightly-sticky material on both sides which is there to bond the gasket to the head and block faces when torqued up the the correct figure. Putting grease on would negate this and almost certainly cause the gasket to fail. The only place on the gasket where you might feel like putting some sealant is a very tiny amount around the small hole near the rear left-hand-side which is for the oil feed up to the rocker shaft (it's about 1/4" dia and will have a copper edging within the gasket) and can be a common area to leak oil. A thin smear of Hylomar or similar is probably best to use here if you decide to do this. It's worth stating that the head and block faces must be absolutely clean bare metal and free of any old gasket material, oil, or old sealant to allow the gasket to stick properly. Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 7, 2020 Author Share Posted November 7, 2020 Thanks guys, I can see the sticky material - thanks for the warning. Cant see any top or bottom marking on either of the faces. Am I correct in thinking the face with the metal shield between cyclinders should face down (ie it is bottom face?)? Quote Link to comment Share on other sites More sharing options...
sparky_spit Posted November 7, 2020 Share Posted November 7, 2020 Hi Chris - yes the correct way up is as shown in your bottom picture. Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 7, 2020 Author Share Posted November 7, 2020 Thanks for that. I have the head back on and all but the last nut torqued-up. The final nut would not hold any toque and when I tried to undo it, the stud undid instead. When I took the nut off the stud in a vice, it looks like the thread has stripped in the nut. So I am hoping that replacing the nut will do the trick. But I noticed that the end of the stud which was in the block has a slot cut through the thread: Domt want to rsik any damage to the block. Should I replace the stud or just turn it around? Quote Link to comment Share on other sites More sharing options...
glang Posted November 7, 2020 Share Posted November 7, 2020 That is strange and has been purposely cut - I can only think, as a tool to try to clean up damaged/dirty threads in the block or, as a means to allow any liquid in the blind hole to escape as the stud is screwed into place.... I would reuse it (after cleaning the thread) as we're not talking about a highly stressed race engine but Im sure there will many who would insist on replacement. The nuts and their washers however do want to be in good condition and its a bit worrying that one has failed! Quote Link to comment Share on other sites More sharing options...
RobPearce Posted November 7, 2020 Share Posted November 7, 2020 It's normal, actually. Studs to be fitted to blind holes are very often cut like that to relieve pressure as they're fitted. Don't turn it round, the slot is there for a purpose and should always be the end fitted to the block. Quote Link to comment Share on other sites More sharing options...
sparky_spit Posted November 7, 2020 Share Posted November 7, 2020 The slot in the stud is there on purpose and is like that from the factory. Its job is to allow any trapped oil/liquid/air that may be lurking in the threaded holes in the block to escape upwards through the slot. If this is not allowed to escape it can create a very high pressure beneath the stud and cause damage to the block surface. If you want the best nuts with the best chance of attaining and holding the correct torque then the ones from an A Series Mini engine that have a built-in flange are brilliant, and many people (including me) have used and recommended them for quite a while now. Available from Mini-Spares for about a quid each. http://www.minispares.com/product/Classic/Engine/Cylinder_heads/Studs_bolts_nuts/CAM4545.aspx?100409&ReturnUrl=/search/classic/head%20nuts.aspx|Back%20to%20search Looking at them and feeling them, you can tell that they are well engineered and well up to the job. Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 8, 2020 Author Share Posted November 8, 2020 I have ordered a set of those nuts - do you use washers with them or not? Quote Link to comment Share on other sites More sharing options...
glang Posted November 8, 2020 Share Posted November 8, 2020 No, washers are built into the nuts so not necessary Quote Link to comment Share on other sites More sharing options...
cbjroms Posted November 15, 2020 Author Share Posted November 15, 2020 Those nuts are really nice quality - nearly got caught using 9/16 socket rather than 14mm! Having got the head back on, I found that one of the push-rods seemed to long. Had a think and found the screw below in the tappet! Now I thought that I had been really careful about stopping something dropping into the block with the head off. But that screw looks as if it is the same sort of age as the engine and I cant think what it could have fallen-off. It is definitely not something that I had lying around. In fact it looks like this screw butthe parts diagram shows only one required. Just wondering what else on a 13/60 engine this could be missing from? The alternative, I suppose, is that this screw has always been there, sat on top the pushrod ball-end within the tappet. Then when I pulled the pushrod out the screw rolled-off and fell into the bottom of the tappet. Quote Link to comment Share on other sites More sharing options...
sparky_spit Posted November 15, 2020 Share Posted November 15, 2020 Hi Chris - yes your last thought on this is almost certainly correct. The single screw locates the rocker shaft in the correct position on the rearmost pedestal to keep the oil feed holes lined up and should have a shakeproof star washer under its head. However, the screw can come loose over the years and fall out, and it can easily escape down a hole into the open end of a cam follower. The next time the owner takes the rocker cover off and notices the missing screw, a new one is put in its place with no thought to where the old one went. Best bet is to Loctite the screw in place. Quote Link to comment Share on other sites More sharing options...
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