Johnc Posted September 11, 2022 Report Share Posted September 11, 2022 After a spirited run on the M25 of 15 miles each way to go to a funeral a few weeks ago my Herald started to misfire on the way home, then close to home it was so bad that I thought that I wasn't going to get home. I had thought that it may have been me adjusting the tappets incorrectly and checked them all to no avail. I asked a friend to come and have a look - maybe a fresh pair of eyes would see something I hadn't. He found that the distributor was loose and had probably moved and messed up the timing. We checked the compression and number 3 had no compression. Initial suspicion was a burnt valve, so I took the head off to have a look. I don't know what a burnt valve looks like, but there would appear to be some leakage between cylinders 2 and 3 and the exhaust valve looks dirty to me. I would be grateful for any ideas you all might have. many thanks John IMG_2199.HEIC IMG_2200.HEIC IMG_2210.HEIC IMG_2211.HEIC Link to comment Share on other sites More sharing options...
johny Posted September 11, 2022 Report Share Posted September 11, 2022 sorry cant open those pics... Link to comment Share on other sites More sharing options...
Johnc Posted September 11, 2022 Author Report Share Posted September 11, 2022 Hi Johny I've converted them to jpeg so should be visible now John Link to comment Share on other sites More sharing options...
DanMi Posted September 11, 2022 Report Share Posted September 11, 2022 That exhaust valve seat looks pretty poor, it should be a nice consistent grey, even the inlet is not perfect. It at least wants the valves ground in but probably once in that state the guides are probably worn, I would consider having unleaded seats inserted Link to comment Share on other sites More sharing options...
Johnc Posted September 11, 2022 Author Report Share Posted September 11, 2022 Now that its off I was going to get the whole lot reconditioned, the engine is the only bit of the car that is untouched since I bought the car. The bores look good to me with no scoring and no real signs of wear. My main concern was the the gasket and head show nice clean lines around cylinder 1 and between cylinder 2 and the same around cylinder 4 and between 3 and four, but between 3 and 4 there is a lot of carbon which looks to me as I've its not making a good seal at that point. Cheers John Link to comment Share on other sites More sharing options...
johny Posted September 11, 2022 Report Share Posted September 11, 2022 It would have been interesting to put a little petrol in each combustion chamber to see how quickly it drained past the valves. Anyway as you say now its apart you can check valve guide wear, head flatness, valve spring condition etc and then decide how much you want to spend... Link to comment Share on other sites More sharing options...
Clive Posted September 12, 2022 Report Share Posted September 12, 2022 7 hours ago, Johnc said: Now that its off I was going to get the whole lot reconditioned, the engine is the only bit of the car that is untouched since I bought the car. The bores look good to me with no scoring and no real signs of wear. My main concern was the the gasket and head show nice clean lines around cylinder 1 and between cylinder 2 and the same around cylinder 4 and between 3 and four, but between 3 and 4 there is a lot of carbon which looks to me as I've its not making a good seal at that point. Cheers John I would check the piston rings. Very simple, set the pistons a little below the top of the block, pour on some paraffin, see how long it takes to drain. If there is zero compression, I would expect the paraffin to drain pdq past the rings if they are a problem. You could even hone the bores ane re-ring. if there is no wear evident. Head, a good clean up, get it checked at a machine shop. I see you have a tubulat exhaust manifold, so are craving a little extra power. Heralds run a lowish CR, so a hefty skim may be worth doing, with a better cam. But then you are going down a rabbit hole..... If having valve seats done, get 3 angle cuts. It is pretty cheap, and helpful. Link to comment Share on other sites More sharing options...
johny Posted September 12, 2022 Report Share Posted September 12, 2022 Yes good idea and for future reference when doing a compression test its worth doing a second after putting a cap full of oil in each bore. This is called wet and dry tests and the oil can temporarily improve the piston to bore sealing so if the second reading is substantially higher it indicates a problem with the bore/piston rings.... Link to comment Share on other sites More sharing options...
Johnc Posted September 12, 2022 Author Report Share Posted September 12, 2022 thanks for your thoughts gents - it’s going to a machine shop this week and whilst it is away i will carry out the paraffin test. we did put some oil in to check the compression after the dry test and the result was the same. Ho hum I guess it’s time to start spending some cash again! Link to comment Share on other sites More sharing options...
johny Posted September 12, 2022 Report Share Posted September 12, 2022 Could be worse. I had a Herald many moons ago where the top of one of the pistons separated so the engine still ran but of course one cylinder had no compression! It wasnt till I got the head off and saw three pistons would go up and down while the 4th appeared to just sit there at the top of its stroke☹️ Link to comment Share on other sites More sharing options...
JohnD Posted September 12, 2022 Report Share Posted September 12, 2022 JohnC, The other clue is the appearance of the exhaust valves in 2 and 3, both relatively clean of the excess(you're running rather rich) carbon. This is the effect of water in the chamber. The extra step in compression testing is to add a teaspoonful of engine oil down the sparkplug hole and repeat the test. The oil improves the ring seal, and raises the compression, unless low compression is due to a faulty valve. So you can discriminate between poor ring and valve seal. Now adays, it's not worth doing a valve grind unless you have already had the exhaust seats replaced with steel inserts. In the absence of lead in petrol, the "lead memory" of the element pounded into the cast iron of the seats will last, it seems for ever. BUT, if you grind the valves that memory is ground away as well. A set of steel exhaust valve seats ( not required for the inlets), properly liquid nitrogen frozen fitted to be so tight in the head that they will give you peace of mind forever! John Link to comment Share on other sites More sharing options...
Johnc Posted September 16, 2022 Author Report Share Posted September 16, 2022 I’m taking my head in today to have it reconditioned. As far as i know it is completely standard, i’m running a single HIF44 carb on a log manifold with an extractor exhaust manifold and standard cam. Will it be of benefit to have the head skimmed to increase the compression ratio? John Link to comment Share on other sites More sharing options...
chrishawley Posted September 16, 2022 Report Share Posted September 16, 2022 Possibly many opinions in this respect: But, for myself, if the engine is just doing general roadgoing duty, I'd skim only the miniumum required to correct any defects - whatever the engineer determines that to be. My reasoning behind that is an analysis from the early 1970s which indicated that whatever performance mods were made to the small triumph engine it was generally only in the upper rev range that significant power gains could be demonstrated. Assuming that a Herald is not generally driven hard, staying close to standard may be preferable. Link to comment Share on other sites More sharing options...
Johnc Posted September 16, 2022 Author Report Share Posted September 16, 2022 Thanks Chris - i will see what needs to be done. Link to comment Share on other sites More sharing options...
Johnc Posted October 1, 2022 Author Report Share Posted October 1, 2022 Afternoon all My head is back with new valves,springs,guides and seats. Prior to refitting i have cleaned all the old crud off the engine and noticed that the pistons have been marked with a punch, does this mean that it has been rebuilt in the past or would this have been standard from the factory. Also there is no marking for a top side of the new Payen head gasket - it would appear that it could be used either way - is this the case. thanks in advance John Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 1, 2022 Report Share Posted October 1, 2022 the triangle is a mark to identify which way round you fit the pistons its quite normal payens dont tend have a way up fit it dry , add a smear of sealer around the rocker oil feed hole use HD nuts and good qualit washers or get integral nut and washer fro minispares th4 old washers are very likely to be deformed by nut pressure this often causes the gasket to fail due to loss of clamping Pete Link to comment Share on other sites More sharing options...
johny Posted October 1, 2022 Report Share Posted October 1, 2022 I guess you mean the centre punch marks just above the triangle which as Pete says is standard. So yes I think the engine must have been apart and someone wanted to remember where each piston went and put a number of punches to match the cylinder number👍 Link to comment Share on other sites More sharing options...
Johnc Posted October 1, 2022 Author Report Share Posted October 1, 2022 Thanks Johny and Pete - I have new nuts from mini spares. Hopefully it will all be back together tomorrow and we can see if all the work will have been worthwhile. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 2, 2022 Report Share Posted October 2, 2022 worth a retorque after a few hundred miles and re check tappet gaps afterwards pete Link to comment Share on other sites More sharing options...
Johnc Posted October 12, 2022 Author Report Share Posted October 12, 2022 Good morning All So I fitted the rebuilt head, reassembled everything, including a new starter motor. With hi expectations of a now perfect engine I started it up and and adjusted the timing to its correct position. It was running quite roughly ( to the extent that the bonnet would rock about). I checked everything again including the HT leads ( plugs are all new). Still rough. checked the compression and I’m getting 130psi on all cylinders except number 3 which is down at 50psi. This was the same with some oil in the bore. I’m now thinking that this was the issue all along - assuming that this is caused by the rings failing to seal can I take the piston out from underneath with the block in situ and just change the rings or does this mean that the whole short engine will need to be rebuilt? thanks in advance for your advice. john Link to comment Share on other sites More sharing options...
Clive Posted October 12, 2022 Report Share Posted October 12, 2022 Just now, Johnc said: Good morning All So I fitted the rebuilt head, reassembled everything, including a new starter motor. With hi expectations of a now perfect engine I started it up and and adjusted the timing to its correct position. It was running quite roughly ( to the extent that the bonnet would rock about). I checked everything again including the HT leads ( plugs are all new). Still rough. checked the compression and I’m getting 130psi on all cylinders except number 3 which is down at 50psi. This was the same with some oil in the bore. I’m now thinking that this was the issue all along - assuming that this is caused by the rings failing to seal can I take the piston out from underneath with the block in situ and just change the rings or does this mean that the whole short engine will need to be rebuilt? thanks in advance for your advice. john Nope, you cannot drop teh piston out from the bottom as the crank will be in the way. And I am not at all sure even with teh crank out it is possible, and if you would get the piston back in (ring compressor needs a flat block to work) Now, no difference with the oil added? That should improve things considerbly if the rings are the issue. So it sounds like a valve problem to me. A leakdown test may be worth doing (I did a ghetto version with my compressor at 40 psi, made a plug adaptor. You listen for where the air is escaping) Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 12, 2022 Report Share Posted October 12, 2022 to remove a piston its has to be head off sump off and raise the piston out from above to be as low as 50psi also suggests to me its more than rings you should get that with no rings have you checked the cam is lifting the rockers fully ??/ Pete Link to comment Share on other sites More sharing options...
Johnc Posted October 12, 2022 Author Report Share Posted October 12, 2022 Thanks Pete and Clive - I will do a little more investigation tomorrow. When it’s running there are a lot of fumes in the rocker cover, would this change your joint diagnosis? john Link to comment Share on other sites More sharing options...
johny Posted October 12, 2022 Report Share Posted October 12, 2022 That certainly sounds like rings but I take it you saw no damage to the bore when the head was off (a broken ring might score the bore)? How much oil did you put in for the wet compression test as you can be quite generous as it will drain away past the rings before next starting the engine... Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 12, 2022 Report Share Posted October 12, 2022 rocker chest fumes are generally down to blow by and a ring problem so you may be on the right track did they fit new valve guids on the head rework ?? as worn they can contribute to fumes Pete Link to comment Share on other sites More sharing options...
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