Engine smoking badly after rebuild... HELP PLEASE!...
Discussion
Greetings Ladies and Gentlemen!
I would like to ask Your help.
I have two BMC mini related cars under restoration, a Wolseley Hornet and a Cox GTM. I have rebuilt two pre A+ non „S” 1275 engines for them.
I have done some engine rebuilds in the past few years with success. Not this time though. Each engines are smoking very badly. The smoke is blue, deffiniatly oil burning.
The sympthoms:
The car does not smoke when cold. The oil (mineral 20W50) needs to heat up before smoking starts. If You leave it to idle, a thin blue smoke appears. But if You drive it a bit, the smoke gets a way worse. And if You stop and let it idle again, the smoke is worse then before. If You stop the engine for a while (5 minutes enough), then after restarting it, at first it does not smoke, but after a few minutes, it starts again. The oil gets burned (deep brown) after a few hours idling/reving or 1-200kms ont he road. There is not too much crankcase gas present. When I remove the head, there is oil everywhere (ports, valves, inlet manifold etc). At the first time it was even worse, there were puddles of oil on the pistons. Now the pistons simply look black.
The pressure in the cylinders is good (14-15bars). The car is starting fine, running good, pulling strong, reving willingly. The oil pressure is good (hot, cold, idle, reved).
No oil in water, no water loss, but some marks of water in oil (on the cap only).
The engine specs:
The first engine is a 1275GT, sleeved back to std., bored and honed. New AE pistons, rings, new bearings, CR 9.75, SW5 cam, ported bigvalve head (reconditioned with new steel guides, valves, oil seals.
The second engine is from an Austin 1300. It was bored out to accept Minispares evo 73 pistons. New bearings, CR 11:1, Kent275 cam, ported bigvalve head with 31 rimflow exhaust valves. Head also reconditioned.
What I have done recently to find the problem:
- changed heads (two rconditioned and one old). Also had the heads double checked and tested (vacuum tested the ports)
- changed the oil (20/50 mineral, 15/40 mineral, different brands)
- removed the crankcase vents (clutch side, valve cover) from carb. Checked, they flow free, vented out to a catch tank.
- replaced mechanic fuel pump
- replaced head gasket (Payen, composite)
- replaced piston rings (new to another new)
First engine dismantled (after 4 hours running, plus 200kms road test).
- Piston-bore clearance 0.06mms-0.07mms (0.0025in)
- Bores round, not tappered (within 0.01mms)
- Rings were checked, gaps not lined up, rings facing the right direction, the oil ring started to get shinny on the bottom third.
- Ring gaps: 0.25-0.35mms (0.01-0.014in)
- No bad marks on pistons
- Honing very light, but present. Near TDC shining areas front and rear – honing nearly gone here, only maybe 0.003-0.005mms wear can be measured after a few hours of running
Second engine dismantled (after 500kms)
- Piston ring clearance 0.07-0.08mms (app 3 thou)
- Bores like the other
- Slight scoring to pistons (front/rear)
- Below TDC same shinnig areas, honing gone.
- Pistons top covered in black carcoal, but the piston crown is clean on some areas (mainly front and rear side) Piston skirt/ring area clean
And here I stand after struggling for 7 weeks day-and-night.
Please help me if only possible. What could go wrong with thesse engines? I am totaly out of ideas…
I would like to ask Your help.
I have two BMC mini related cars under restoration, a Wolseley Hornet and a Cox GTM. I have rebuilt two pre A+ non „S” 1275 engines for them.
I have done some engine rebuilds in the past few years with success. Not this time though. Each engines are smoking very badly. The smoke is blue, deffiniatly oil burning.
The sympthoms:
The car does not smoke when cold. The oil (mineral 20W50) needs to heat up before smoking starts. If You leave it to idle, a thin blue smoke appears. But if You drive it a bit, the smoke gets a way worse. And if You stop and let it idle again, the smoke is worse then before. If You stop the engine for a while (5 minutes enough), then after restarting it, at first it does not smoke, but after a few minutes, it starts again. The oil gets burned (deep brown) after a few hours idling/reving or 1-200kms ont he road. There is not too much crankcase gas present. When I remove the head, there is oil everywhere (ports, valves, inlet manifold etc). At the first time it was even worse, there were puddles of oil on the pistons. Now the pistons simply look black.
The pressure in the cylinders is good (14-15bars). The car is starting fine, running good, pulling strong, reving willingly. The oil pressure is good (hot, cold, idle, reved).
No oil in water, no water loss, but some marks of water in oil (on the cap only).
The engine specs:
The first engine is a 1275GT, sleeved back to std., bored and honed. New AE pistons, rings, new bearings, CR 9.75, SW5 cam, ported bigvalve head (reconditioned with new steel guides, valves, oil seals.
The second engine is from an Austin 1300. It was bored out to accept Minispares evo 73 pistons. New bearings, CR 11:1, Kent275 cam, ported bigvalve head with 31 rimflow exhaust valves. Head also reconditioned.
What I have done recently to find the problem:
- changed heads (two rconditioned and one old). Also had the heads double checked and tested (vacuum tested the ports)
- changed the oil (20/50 mineral, 15/40 mineral, different brands)
- removed the crankcase vents (clutch side, valve cover) from carb. Checked, they flow free, vented out to a catch tank.
- replaced mechanic fuel pump
- replaced head gasket (Payen, composite)
- replaced piston rings (new to another new)
First engine dismantled (after 4 hours running, plus 200kms road test).
- Piston-bore clearance 0.06mms-0.07mms (0.0025in)
- Bores round, not tappered (within 0.01mms)
- Rings were checked, gaps not lined up, rings facing the right direction, the oil ring started to get shinny on the bottom third.
- Ring gaps: 0.25-0.35mms (0.01-0.014in)
- No bad marks on pistons
- Honing very light, but present. Near TDC shining areas front and rear – honing nearly gone here, only maybe 0.003-0.005mms wear can be measured after a few hours of running
Second engine dismantled (after 500kms)
- Piston ring clearance 0.07-0.08mms (app 3 thou)
- Bores like the other
- Slight scoring to pistons (front/rear)
- Below TDC same shinnig areas, honing gone.
- Pistons top covered in black carcoal, but the piston crown is clean on some areas (mainly front and rear side) Piston skirt/ring area clean
And here I stand after struggling for 7 weeks day-and-night.
Please help me if only possible. What could go wrong with thesse engines? I am totaly out of ideas…
stevieturbo said:
Valve guides, or what have you done with the breather system ?
I have had the cylinder heads reconditioned with new valve guides, valves, seals. I had them tested (vacuumed the ports) and two different testers told me they are ok. I also have tried an old head on the engine, and it still smoked.
The breathers were disconnected from the carb at the first time and vented out to the air. But I have tried repluging them o create vacuum, but no use.
I am realy gratefull to everybody, especialy Pumaracing for giving me of Your time.
Just today I have collected a small company of specialist (engine builders, race car mechanists, car restorers) and we have concluded just about the same as You told me earlier.
You helped me to make my decision to get my sleeved engine redone. It I succeed with this, I will get another engine and have it bored to 73mm to take the EVO's.
Realy thanks alot! I will report on the engine when I get it back and fitt it.
Pumaracing: the running in article is brilliant. I have added to my favorites.
BMC forever.
Just today I have collected a small company of specialist (engine builders, race car mechanists, car restorers) and we have concluded just about the same as You told me earlier.
You helped me to make my decision to get my sleeved engine redone. It I succeed with this, I will get another engine and have it bored to 73mm to take the EVO's.
Realy thanks alot! I will report on the engine when I get it back and fitt it.
Pumaracing: the running in article is brilliant. I have added to my favorites.
BMC forever.
Edited by camelotr on Friday 9th April 20:14
Edited by camelotr on Friday 9th April 20:34
You may be all right. Although I have succesfully ran in quite a couple of engines in the past. Plus the two engines were treated quite differently.
The first was stated up, ran at 2500 for 20 minutes for the cam, them lowered the revs and set the carb and the ignition.
Then stopped for a night. Next day I have stated the engine. This time I noticed the smoke (although it may have been present last time as well, just I was busy with other things). After this I did not wanted to go out without finding the souce of the smoke. I have revved the engine a bit and ran it on higher revs (3000+) for a while. Removed the head, made a dozen tests/changes (replacing head, gaskest, mechanic fuel pump, oil, etc). After no success, I have done some road tests (on the first couple of runs. I have treated this engine gently. 200kms - no use.
The second engine was run on high idle (2500) for a longer period, maybe 30 minutes. Then taken out and given load on the engine. I have treated this engine harder. 500kms - no use.
Although I have not checked the mixture with WBO, but I am pretty sure it was not "out of scale". The engine ran without hesitation - realy well.
I dont know. But after reciving the engine back, I will try to be more precise.
The first was stated up, ran at 2500 for 20 minutes for the cam, them lowered the revs and set the carb and the ignition.
Then stopped for a night. Next day I have stated the engine. This time I noticed the smoke (although it may have been present last time as well, just I was busy with other things). After this I did not wanted to go out without finding the souce of the smoke. I have revved the engine a bit and ran it on higher revs (3000+) for a while. Removed the head, made a dozen tests/changes (replacing head, gaskest, mechanic fuel pump, oil, etc). After no success, I have done some road tests (on the first couple of runs. I have treated this engine gently. 200kms - no use.
The second engine was run on high idle (2500) for a longer period, maybe 30 minutes. Then taken out and given load on the engine. I have treated this engine harder. 500kms - no use.
Although I have not checked the mixture with WBO, but I am pretty sure it was not "out of scale". The engine ran without hesitation - realy well.
I dont know. But after reciving the engine back, I will try to be more precise.
Edited by camelotr on Saturday 10th April 07:52
Thanks again. This is a real "Engine academy". I though I know something, but deffiniatly not.
I thinks my engines were done not 100%. I will try to press the machinist do a better work next time. He has the right equipment, and knowledge. I think he was not keen enough on his employee.
The articles are perfect.
Can You advice me more? I think if I would like to come out of this problem, I should at least try to leanr as much as possible.
I thinks my engines were done not 100%. I will try to press the machinist do a better work next time. He has the right equipment, and knowledge. I think he was not keen enough on his employee.
The articles are perfect.
Can You advice me more? I think if I would like to come out of this problem, I should at least try to leanr as much as possible.
That would be the nicest thing. Although as far as I know, Pumaracing wont accept any orders now.
Call me a foul, but I still thrust my machinist. He is an honest and enthusiastic man, soo I give him another chance. Although we will double check everything...
Call me a foul, but I still thrust my machinist. He is an honest and enthusiastic man, soo I give him another chance. Although we will double check everything...
Edited by camelotr on Monday 12th April 07:20
I had a damn good turner a couple of years ago. He was realy good. Not just accurate, nice things he did, but he even had BRAIN to think a bit and try figuring out the best solution. He even managed once to do an SU needle to 0.003mms accuracy...)
After a while things went on wll, bussiness developed, and he employed two coworkers.
And end of the story. The quality droped to the bottom of the sea.
Things done without soul and some insight, are just converting the material to trash.
After a while things went on wll, bussiness developed, and he employed two coworkers.
And end of the story. The quality droped to the bottom of the sea.
Things done without soul and some insight, are just converting the material to trash.
Pumaracing said:
camelotr said:
Call me foul, but I still "thrust" my machinist.
Now you see there's your problem. Never mix business and pleasure 
Edited by Pumaracing on Monday 12th April 07:26
Revenge of grammar.
If we succed with the resleeving, I will be left with the other block which has been overbored- thus useless. Atl est with theese pistons. We have here in my country a pretty good piston manufacturer, who is able to do custom pistons at an affordable price.
This gives me an option to have a custon set made for the existing size.
I think it would be good to have some piston pin offset this time. What amount would You advice? Any other modifications that would make any good?
This gives me an option to have a custon set made for the existing size.
I think it would be good to have some piston pin offset this time. What amount would You advice? Any other modifications that would make any good?
I do not want to go for 73.5 - if only posible. This is a restored car, and not quite nice to leave its engine without the option of a final rebore. This is the final option.
I have built 3 engines with the pistons of this manufacture without problems. Although 2 were 998 engines and only one 1275. Even this was a stock engine with 63 hps.
This time I wanted to give EVERITHING for my engines, and did not counted the costs, only used the best possible.
The piston maker would use the original pistons for basic design, only add some modifications as I order.
I dont want to reinvent the wheel, just if this would be my next step, why nor get the pistons better with some offset.
How much would it be? 1mm, 1.5mms?
I have built 3 engines with the pistons of this manufacture without problems. Although 2 were 998 engines and only one 1275. Even this was a stock engine with 63 hps.
This time I wanted to give EVERITHING for my engines, and did not counted the costs, only used the best possible.
The piston maker would use the original pistons for basic design, only add some modifications as I order.
I dont want to reinvent the wheel, just if this would be my next step, why nor get the pistons better with some offset.
How much would it be? 1mm, 1.5mms?
Pumaracing said:
I do recall a test Dave Vizard did many years ago (...) I'll ask him if he remembers next time we speak.
Realy NICE... erm... great... or even more!...Soo You know Him personaly. Humm. A Legend for me. His books tought me nearly everithing I khow of engines.
He must be in a nice age though.
Soo...
I have sent my sleeved engine back to the machinist to have a second go. This time he bored it to give 0.03-0.04mms piston-bore gap, and a better honing finish (I asked him to let min. 0.05mms for the boring).
Engine assembled, started in situ for 10 minutes around 2500. Then hit the road.
Voila: the engine smoked. Although the some was only half of that was last time. But still present. At least the plugs kept dry. I was not happy, but had a full tank, soo why not? Let's mini a bit. After 500kms, things changed a bit. The smoke is barely visible on idle and the end of the exhaust started to clean up. But if You rev it, it still puffs blue smoke.
Better, better, but still not good enough...
I have sent my sleeved engine back to the machinist to have a second go. This time he bored it to give 0.03-0.04mms piston-bore gap, and a better honing finish (I asked him to let min. 0.05mms for the boring).
Engine assembled, started in situ for 10 minutes around 2500. Then hit the road.
Voila: the engine smoked. Although the some was only half of that was last time. But still present. At least the plugs kept dry. I was not happy, but had a full tank, soo why not? Let's mini a bit. After 500kms, things changed a bit. The smoke is barely visible on idle and the end of the exhaust started to clean up. But if You rev it, it still puffs blue smoke.
Better, better, but still not good enough...
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