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Engine smoking heavily after rebuild... H E L P !!!
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camelotr
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PostPosted: Thu Apr 08, 2010 6:12 pm    Post subject: Engine smoking heavily after rebuild... H E L P !!! Reply with quote

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 mini 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/revving 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, revving willingly. The oil pressure is good (hot, cold, idle, revved).

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:

- changed heads (two reconditioned 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 (0.00236in)
- Bores round, not tapered (within 0.02mms)
- 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
- Below TDC same shinnig areas, honing gone.
- Pistons covered in black carcoal, but the piston crown is clean on some areas (mainly front and rear side

And here I stand after struggling for 7 weeks day-and-night.

Please help me if only possible. What could go wrong with these engines? I am totaly out of ideas…

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af2
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1933 Willys Coupe

PostPosted: Thu Apr 08, 2010 8:05 pm    Post subject: Reply with quote

If you are using Synthetic oil you will never get the rings to seat.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Fri Apr 09, 2010 1:31 am    Post subject: Reply with quote

what brand of oil are you using ? certain brands dont work well with new motors (Castrol). are you sure the intake valve seals and guides are good ? what engine temp is it running ? if its too cold, it will be difficult to seat the rings.
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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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Knarley Darley
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PostPosted: Fri Apr 09, 2010 3:00 am    Post subject: Reply with quote

If your ring gap is only .001, they are butting and causing damage/excessive wear. You mentioned the hone marks already gone at the top of the cylinders after a few hours run time. This is not normal. When the ring end gaps close up all the way we have noted on the dyno that the crank case becomes pressurized and will not hold vacuum even with a vacuum pump, and the engine will consume a lot of oil. Also you need to check the radial depth of the ring land to make sure the ring groove in the piston is .005 or so depending on your bore size deeper than the width of the ring. In other words the ring when compressed all the way into the piston groove is capable of being slightly counter sunk, if not it will have blow by and oil consumption. Good luck, and keep us updated.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Fri Apr 09, 2010 3:12 am    Post subject: Re: Engine smoking heavily after rebuild... H E L P !!! Reply with quote

camelotr wrote:
Ring gaps: 0.25-0.35mms (0.01-0.014in)


look closer Knarley Wink

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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camelotr
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PostPosted: Fri Apr 09, 2010 3:24 am    Post subject: Reply with quote

10sec.et wrote:
what brand of oil are you using ? certain brands dont work well with new motors (Castrol). are you sure the intake valve seals and guides are good ? what engine temp is it running ? if its too cold, it will be difficult to seat the rings.


I have tried a couple until now. All mineral 15w40 and 20w50. Some get burned quicker, some slower, but no real difference it gave.

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Last edited by camelotr on Fri Apr 09, 2010 3:45 am; edited 1 time in total
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camelotr
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PostPosted: Fri Apr 09, 2010 3:27 am    Post subject: Reply with quote

Knarley Darley wrote:
If your ring gap is only .001, they are butting and causing damage/excessive wear. You mentioned the hone marks already gone at the top of the cylinders after a few hours run time. This is not normal. When the ring end gaps close up all the way we have noted on the dyno that the crank case becomes pressurized and will not hold vacuum even with a vacuum pump, and the engine will consume a lot of oil. Also you need to check the radial depth of the ring land to make sure the ring groove in the piston is .005 or so depending on your bore size deeper than the width of the ring. In other words the ring when compressed all the way into the piston groove is capable of being slightly counter sunk, if not it will have blow by and oil consumption. Good luck, and keep us updated.


The rings can counersunk in the grooves (0.1-0.2mms in the worst).

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camelotr
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PostPosted: Fri Apr 09, 2010 3:46 am    Post subject: Reply with quote

Engine temp 90-95 degrees.
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Knarley Darley
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PostPosted: Fri Apr 09, 2010 5:35 am    Post subject: Reply with quote

10sec its been a long month. OOPs on that one, but it still seems like the thing should look perfect with no noticeable wear.
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Paul P
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PostPosted: Fri Apr 09, 2010 10:59 am    Post subject: Reply with quote

Knarley the engine temp is in Centigrade... Laughing
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Paul P
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PostPosted: Fri Apr 09, 2010 11:01 am    Post subject: Reply with quote

Was the engine bored with deck plates? If it wasn't that might explain part of your problem.
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2001 Focus 2.0 Zetec
stock cams, bolt-ons and tune
15.63@87 MPH 1/4mi

1971 - Chevelle 408 SBC N/A
6.59@104.03 MPH 1/8mi
10.40@127.73 MPH 1/4mi
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camelotr
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PostPosted: Fri Apr 09, 2010 5:08 pm    Post subject: Reply with quote

No, it was not. But being honest, none of my engines were ever. Do You think it is necessary with a cast mini block?
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squeeezer
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PostPosted: Fri Apr 09, 2010 5:13 pm    Post subject: Reply with quote

do you have reduced manifold vacuum due to a more agressive camshaft????

is it running rich (gasoline) as well???

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camelotr
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PostPosted: Fri Apr 09, 2010 5:35 pm    Post subject: Reply with quote

In one engine I use a hi lift cam with moderate timing. The other engine i a fastroad. Not that high on lift, but a bit long. Though it is hapy to idle around 1000, soo not too high (with mini-measurings, the first cam is around 260degrees and the orher around 280).
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af2
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1933 Willys Coupe

PostPosted: Fri Apr 09, 2010 7:04 pm    Post subject: Re: Engine smoking heavily after rebuild... H E L P !!! Reply with quote

camelotr wrote:



The oil gets burned (deep brown) after a few hours idling/revving 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.





I wish I would have seen this earlier.

It is sucking oil from somewhere. The lack of hone could be from detonation from oil induced combustion.
Just scratchin my head in Grass Valley.
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