lo-fi Posted May 23, 2018 Share Posted May 23, 2018 Very sorry to hear that! The sad truth is, it's probably a bit of everything. Oil control rings can wear faster than compression rings, so a compression test doesn't tell the full story. Did you measure the valve guide clearance? If they're out of spec, the seals won't seal well either. At the age these old things are now, getting hold of something that isn't in need of major work is a challenge. If the bores aren't worn enough to warrant oversize pistons, something shy of a grand ought to see it back to being a fresh, reliable, not so smokey engine, which isn't so much more than what another man ask for "a good lump" and is actually a pile of scrap. You might get a bit more lucky with the 2.5, but it's always a gamble these days. I have three 2.6's in the garage to prove the point Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 23, 2018 Share Posted May 23, 2018 How long did you run it? It could just be oil in the exhaust, takes a long while to burn that off - I know, my audio has been doing it 100K How bad is the smoke? Unless terrible, I would simply drive it, it may well get better. Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 23, 2018 Author Share Posted May 23, 2018 1 hour ago, lo-fi said: Very sorry to hear that! The sad truth is, it's probably a bit of everything. Oil control rings can wear faster than compression rings, so a compression test doesn't tell the full story. Did you measure the valve guide clearance? If they're out of spec, the seals won't seal well either. At the age these old things are now, getting hold of something that isn't in need of major work is a challenge. If the bores aren't worn enough to warrant oversize pistons, something shy of a grand ought to see it back to being a fresh, reliable, not so smokey engine, which isn't so much more than what another man ask for "a good lump" and is actually a pile of scrap. You might get a bit more lucky with the 2.5, but it's always a gamble these days. I have three 2.6's in the garage to prove the point I didn't measure the valve guide clearance but with a thin smear of oil on the valves there was no detectable sideways movement as far as I could tell, without any oil on them there was a little sideways movement. Cant do a grand it just isn't possible, but I take your point with an unknown "good lump". Argghhh 21 minutes ago, Bowie69 said: How long did you run it? It could just be oil in the exhaust, takes a long while to burn that off - I know, my audio has been doing it 100K How bad is the smoke? Unless terrible, I would simply drive it, it may well get better. A bit more info, on first start up it smoked bad so I left it running for a good hour and then drove it for 10 -15 mins, the oil seemed to clear after driving so I thought all was good, took it for an MOT today and it smoked straight away again on start up so left it to get up to temperature and then drove it another 15mins, this time it wasn't running very happy at all (plugs fouled maybe??), anyway had to get to the MOT which was pre booked and it smoked the MOT station out, much to their amusement but not mine. Not really sure how to get a definitive answer as to what to do? Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 23, 2018 Author Share Posted May 23, 2018 (edited) If I were to do valve guides, head skim, unleaded seats, new valves, that would be the top end all good. But as my block isn't 100% flat I really should get that skimmed as well, but then I could have a stuck oil control ring? So as rings are not much to buy I could re ring it. If I were to re ring it how do I go about determining if the bores are at an acceptable wear limit for new rings to work. I.e how much bigger can the bore be than the piston? At what point does it need a re bore and oversize pistons? Thanks for your continued help. Edited May 23, 2018 by sixtwoeight Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 24, 2018 Author Share Posted May 24, 2018 Removed the plugs and no.1 is the worst being very black. Looking back at my compression test results no.1 was the highest reading. 1 = 185 2 = 160 3 = 170 4 = 160 To my mind that is odd, I would have thought if there was a problem with the rings on no. 1 then the reading would be the lowest - although if there is a problem with the oil scraper ring on that cylinder then could compression still be Ok but allowing oil to be on combustion chamber. Need to ascertain whether to completely recon head or look into rings. Quote Link to comment Share on other sites More sharing options...
Snagger Posted May 24, 2018 Share Posted May 24, 2018 It's likely that oil is getting into no.1 and helping the rings seal better. You can't check bore condition by play on the piston. You need to remove the pistons and use a bore gauge to check their dimensions at many points, differing vertically and rotationally to check for taper and ovalising. You can check the pistons' condition while they're out, and if good and the block only needs honing rather than a rebore, you can fit the new rings. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted May 24, 2018 Share Posted May 24, 2018 There's no need to remove the pistons for a quick check actually, but yes, a dial bore gauge is the way to check them for ovality and wear - 3 points down the bore and measure across the bore 90 degrees apart will give you a good estimate of the wear, from just 6 figures. The figures are likely in the workshop manual, which I don't have to hand. I think on a Rover V8 the absolute limit is 6 thou or similar. That amount of smoke is odd though, unless there are broken rings I can't see that it is your problem, I would more suspect an oil gallery leaking into the combustion chamber, or as originally thought, seriously worn guides. Are you in a position you remove a valve spring with the head on? If so, take it off and give the valve stem a really good wiggle, any more than a tiny amount and guides definitely need doing. Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 28, 2018 Author Share Posted May 28, 2018 Right, took the head off and looked into the inlet and exhaust ports and don't think there is any oil leaking down the valves. So, took the sump off and removed the pistons and found that 3 out of the 4, has the oil control rings stuck. Quote Link to comment Share on other sites More sharing options...
lo-fi Posted May 28, 2018 Share Posted May 28, 2018 Ah, that'll to it. A good find Compression test doesn't always tell the full story. A good rule of thumb for bores is literally a finger nail. The rings never travel to the top of the bore, so you're left with a step when the bores wear. If you can catch a finger nail on it, it's going to need a visit to the machine shop. In an ideal world, of course. Are you planning to put them back in once unstuck or a light hone and fresh rings? Glad you've got to the bottom of it, should run quite sweetly once you've got it back together again. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted May 28, 2018 Share Posted May 28, 2018 Can you still get Cords? The top rings had a step in them to avoid the wear ridge. Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 28, 2018 Author Share Posted May 28, 2018 The plan is ( I think) to hone the bores and fit a new set of rings plus big end bearings. There is a ridge at the top of the cylinders and I expect a machinist would say re bore - and he may well be correct, but as the car will only do minimal mileage I will take the risk with a hone and new rings and hope for the best. If it doesn't work then il be having to spend a lot more money on it so in that case I would have wasted the cost of the rings and some of my time, so well worth the risk I think. Obviously if I had some spare cash I would bite the bullet and spend £1500 on the engine. Quote Link to comment Share on other sites More sharing options...
lo-fi Posted May 28, 2018 Share Posted May 28, 2018 Sounds like a reasonable plan. Big end bearings are a great call, they're bound to be a bit worn. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted May 28, 2018 Share Posted May 28, 2018 11 minutes ago, sixtwoeight said: The plan is ( I think) to hone the bores and fit a new set of rings plus big end bearings. There is a ridge at the top of the cylinders and I expect a machinist would say re bore - and he may well be correct, but as the car will only do minimal mileage I will take the risk with a hone and new rings and hope for the best. If it doesn't work then il be having to spend a lot more money on it so in that case I would have wasted the cost of the rings and some of my time, so well worth the risk I think. Obviously if I had some spare cash I would bite the bullet and spend £1500 on the engine. I'd get rid of the ridge, if the top rings hit it you'll cause damage before you get out of the drive. As I said, you may be able to get stepped rings, otherwise you may be able to scrape the ridge away. Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 28, 2018 Author Share Posted May 28, 2018 8 minutes ago, lo-fi said: Sounds like a reasonable plan. Big end bearings are a great call, they're bound to be a bit worn. Glad you agree, fingers crossed and all that! 1 minute ago, rtbarton said: I'd get rid of the ridge, if the top rings hit it you'll cause damage before you get out of the drive. As I said, you may be able to get stepped rings, otherwise you may be able to scrape the ridge away. Ah ok, I see what you are saying. Cords - is that term I should be searching for? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted May 28, 2018 Share Posted May 28, 2018 Have a good Google ("Cords Rings"), they're a bit like Marmite, people love them or hate them! Google ("ridge dodgers" "Piston rings") there might be some good info there. Personally I'd go for standard rings and a good scrape. I once had an engine where there were two wear ridges about 12/ inch apart, when I took the pistons out the top rings had been omitted so they wouldn't hit the ridge. Quote Link to comment Share on other sites More sharing options...
sixtwoeight Posted May 28, 2018 Author Share Posted May 28, 2018 3 minutes ago, rtbarton said: Have a good Google ("Cords Rings"), they're a bit like Marmite, people love them or hate them! Google ("ridge dodgers" "Piston rings") there might be some good info there. Personally I'd go for standard rings and a good scrape. I once had an engine where there were two wear ridges about 12/ inch apart, when I took the pistons out the top rings had been omitted so they wouldn't hit the ridge. Thanks for the advice.. and I thought I was doing things the wrong way! Quote Link to comment Share on other sites More sharing options...
Gazzar Posted May 28, 2018 Share Posted May 28, 2018 How would you scrape the ridge? Just curious? Quote Link to comment Share on other sites More sharing options...
rtbarton Posted May 28, 2018 Share Posted May 28, 2018 You can get scrapers for the job, Google "Hand Scrapers", "Engineers Scrapers" &c Quote Link to comment Share on other sites More sharing options...
rtbarton Posted June 9, 2018 Share Posted June 9, 2018 On 13/05/2018 at 9:07 PM, rtbarton said: OK if there's enough meat for a self-tapper to grip. Another one I removed I made a tool similar to this: Drill a hole in plug, slide the slot into the hole and pivot on the heel. I've found the actual tool I made for the job: Quote Link to comment Share on other sites More sharing options...
lo-fi Posted August 5, 2018 Share Posted August 5, 2018 Just out of curiosity, how are you getting on with it? Quote Link to comment Share on other sites More sharing options...
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