Burning oil while running in?

[abri]

I got the freshly rebuilt 1275 S motor going last night and have since driven it some 60 odd kilometers. I noticed on the first run that it was smoking but since it was at night I couldn't quite make out the colour or how much. I followed some advice to put load on it to help the rings bed in, for example driving up hills in a high gear. I've just come back from the last run of about 40km (last night was about 20km). It smokes when under load and at higher rpm...especially when the two are combined. Oil pressure is good, about 80 at running speed (say 60mph) and about 45-50 at idle. Temperature is on or slightly below normal. The difference in oil level between the start and end of this last 40km run is about 10mm on the dipstick.

Given these treatments, figures and the result, is this normal for a motor that's being run in? Or how justified am I in shitting myself, which I am currently doing.

[irlmin]

I assume all the usual stuff like valve guides / seals are correct and unworn / replaced , rings gaped and positioned correctly on the pistons pre assembly , machining to correct tolerances . what oil are you using ? I have seen people use modern synthetic oils on rebuilt engines and it will never 'run-in' if this is the case . If oil is 20/50 mineral I would continue to your run-in procedures for another few hundred km before you worry .
G

[abri]

Head was redone and guides checked about a month before I pulled the motor for a rebuild. Seals are a month old. Ring gaps and positioning correct. The bores were not machined, just honed and measured to decide on the rings.

I'm using Engen Premium SAE 40 oil.

[carbon]

That oil consumption does sound too high. In my limited experience a rebuilt engine doesn't use a lot more oil during running in.

Did you have this engine running before rebuild, and was it using oil at this point? As well as bore/ring and valve guides you can also get high oil consumption if the piston rings have too much (vertical) clearance in the piston grooves.

Other check to make is that the crankcase breather is working OK, in case you are getting pressure in the crankcase which would increase oil consumption.

[Spider]

Sorry to say, but sounds like it's glazing to me.

It's not sucking oil from a crank case breather is it? Temporarily disconnect the breathers and block up the Carb / Manifold side and see what it does.

Got a Brake Booster? That's not cactus is it? Temporarily disconnect the Vacuum Line and plug the Manifold side of that up, see how it goes.

Usually if it smokes at first start up and doesn't settle within the first few minutes, it's started glazing, for which the only cure is to hone the block again and fit new rings.

See what the other guys suggest though.

[swifty]

After having experienced glazed bores many years ago it the one thing I dread about rebuilding engines . It's just so much work to strip it all down again .... On initial start up now I run the engine with cheap oil and run at 2500 rpm for 20 to 30 minutes . Then let it cool down overnight . I personally wouldn't run it up a hill in 4 th gear , isn't that labouring the engine rather than loading the engine ? . I tend to use a hard bit of acceleration and drive around the streets ( no motorways ) . ... Ken

[abri]

@ Carbon, the motor was burning oil before the rebuild, that's why it was rebuilt. The symptoms were exactly the same, blowing out smoke only when at higher rpm and going at cruising speed (above 50mph). We made sure the rings were the correct thickness for the ring lands.

@ Spider, I'll disconnect the PCV and booster on the next run and see if that helps. There was no smoke at start up apart from the little bit when it burnt off the small squirt of oil I put down the plug holes before cranking it to get the pressure up. It does not smoke at all at idle or driving slowly, say up to 50mph. The cylinders were not rebored, just honed with a bottle brush honing tool (not sure what the correct term is).

@ Swifty, yes, I'm dreading the thought of having to pull it all apart again.

[carbon]

Abri,

I've had blocks rehoned a couple of times and fitted new rings with good results, but I have always had the honing carried out by good machine shop. This gives a consistent 45 degree cross-hatch on the bores. I would be very wary about using 'bottle brush' as these may bust the glaze on the bores but I don't think the finish is nearly as good as proper hone.

Sounds like you have done all of the checks on the pistons. Other additional check you could try once you get head off is to use one of the old rings, and to position this at top/middle/bottom of the cylinder and measure any difference in ring gap. Difference / 3 = amount of bore wear or difference on bore.

Your oil pressure sounds OK, if the 45/50 idling when engine is hot after a decent long fast run then it's very good. I've had high oil consumption in the past when the big end clearances were getting slack, I think this allows more oil to be thrown onto the bores and gets to point where rings can't keep it all back.

[cheleker]

abri, "running up hills in high gear" to put a load on the engine is just the opposite of what one should do! Here's a good article for you: http://www.minimania.com/ENGINE-_Runnin ... dure_guide

[wantafaster1]

I would suggest a load is perfectly acceptable, but making it labour or struggle isn't. I drove my car after less than 15 minutes running to help bed the cam in, after approximately 4 miles on the road I gave it a run up a good hill about 4000 revs in top. My compression is perfect, the only time I see any smoke is a puff on start up because I don't have stem seal on the exhaust valves.
After 200 miles I changed the oil from the basic Miller 20/50 to Valvoline, and in the 800 miles since I have put in under a litre. That includes 2 days at Blyton and some "testing".

I know a fellow well who does historic formula Ford engines, they are loaded up on the water brake flat out as soon as they are up to temperature. I used to run in my racing Honda at 10,000 revs, or 4/5ths of maximum. My best one for compression was done the same as the mini, I rode it as soon as soon as it was hot after the initial start up.

[cheleker]

wanta, I interpreted "a load" running up hill in 4th as making the engine struggle as if it should be in 3rd or even 2nd. Also called "lugging", so we agree on that point.

[Spider]

wanta, I interpreted "a load" running up hill in 4th as making the engine struggle as if it should be in 3rd or even 2nd. Also called "lugging", so we agree on that point.

An Engine Reconditioning Book I have, that was published by ACL (who did manufacture piston rings) says (if I recall correct);-

"When up to temperature, in top gear, accelerate 3 or 4 times from (and they quote a speed which I think is) 50kph to 80 kph"

That's it (as far as their recommendations go).

The speeds I use for this is 2000 to 3000 RPMs, which is around the road speeds ACL quote.

[abri]

So far I've driven the car just over 100 miles and even though the smoking is less, it is still smoking. I've been doing the accelerating numerous times and put load on the engine to get the compression to expand the rings into the bore face. I'm going to drive it some more to see if it improves but my hope is waning that it will come right.

[surf-blue-850]

Maybe try some 'running in oil'?

[foxy52]

wanta, I interpreted "a load" running up hill in 4th as making the engine struggle as if it should be in 3rd or even 2nd. Also called "lugging", so we agree on that point.

...The term used to be called "hunting"..never let yr engine hunt for a gear as it cant ??!! correct gear selection while running in is crucial as is gear selection and not over revving....i always used older 10/40 semi synth oil and after 500 miles or so change to 10/40 mobil semi synth...but wadda I know..?? 4 other super mighty and mighty engines along with mine and some are built for the likes of the Kirkpatricks et al.. my engine builder par excellence will only use a high grade 10/40 semi synth..even old Slark senior said he had never seen a better built head ?!!...eh Paco ???!!....u can keep any type of 20/50 its sludge by comparison and using it caused probs for me many many years ago on a freshly rebuilt engine !!!...just my six penneth !! foxy52

[Austin Costin]

Just a thought, if the engine seems to be "the same" as it was before the rebuild it would be worth a quick look at the carb needles and plugs just in case you are over fueling and washing the bore.

[Spider]

Just a thought, if the engine seems to be "the same" as it was before the rebuild it would be worth a quick look at the carb needles and plugs just in case you are over fueling and washing the bore.

I would tend to think the exhaust colour would be black and not white if that was the case. These days with unleaded fuels, the plugs would probably foul pretty quick too.