Lotus Elan

Smoke on big valve engine

PostPost by: jasper2347 » Tue Jan 18, 2022 3:55 pm

Hi all, got a mate with a big valve 130, same as ours. Engine smokes a lot when cold. Is certainly oil not fuel. If you rev it hard when hot it does a little bit, but nothing like when cold. When its warm I would think it is the carb pump jets just making a rich mixture for a second or two and washing the bores. Followed him up the road and there is no sign of smoke, either when pushed hard or on down shifts, so only when stood and cold. Still has plenty of grunt and goes very well. Motor was rebuilt, rebore, pistons, bearings etc around a year ago. Took it back to the builder and they did a comp. test. All plugs out, held on full throttle opening and turned with starter. Readings were all within a pound or two of each other at 185psi. Oil pressure is stable and where it should be. Engine has standard cams and Dellortos. Do these motors have problems with valve guide seals? Any other ideas very welcome. Cheers. :)
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PostPost by: jono » Tue Jan 18, 2022 4:12 pm

There are no valve guide seals on a TC - the guides need to be reamed to size to ensure sufficient oil to lubricate the valves stems but not too much to cause excessive oil burn.
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PostPost by: 512BB » Tue Jan 18, 2022 4:21 pm

Without giving it to much thought and reading your post very quickly, I think the valve guide clearance is to large. You dont say what if anything was done to the head.

When the engine is stopped, oiil is running down the guides into the combustion chambers. Then, when the engine is started from cold, that oil is burnt, causing smoke. Once the oil is burnt off, there is very little smoke, but you might expect to see some on the over run when the engine is hot.

A Big Valve engine should have Sprint cams, not standard.

When I build an engine, I would be very disappointed to see less than 210 lbs pressure on each pot, for many years after a rebuild., when hot. So much so, I cannot turn an engine over with a spanner with the plugs in. I always have to remove them if I am fiddling.

My thoughts, others will have theirs.

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PostPost by: StressCraxx » Tue Jan 18, 2022 4:24 pm

Oil smoke normal on cold startup. As previous post, no valve guide seals installed. The oil in the head weeps down the stem/guides and burns at startup.

Drive and enjoy!
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PostPost by: alanr » Tue Jan 18, 2022 4:36 pm

You mentioned valve guide seals...There are no valve guide seals fitted as standard on a twink engine!...edit..others beat me to it!

However, something else for you to try which can give the impression that you have an engine problem when you actually don't. Have you thought that the smoke could be brake fluid being sucked into the engine?
With the engine running and being revved at a couple of thousand revs try pumping the brake pedal and see if the smoke gets worse?
If it does it means the seals have gone in the brake servo filling the canister and then brake fluid is being sucked back into the engine and so causing the smoke.

Alan.
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PostPost by: elans3 » Tue Jan 18, 2022 4:41 pm

If the smoke is blue, it's oil, white is brake fluid, (suspect servo as above), and black of course is fuel.
Of course you will also get white smoke if the head gasket is gone around a water jacket hole, where water is getting into the cylinder.
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PostPost by: Slowtus » Tue Jan 18, 2022 5:47 pm

jasper2347 wrote: Do these motors have problems with valve guide seals?


No but they do have 'problems' with valve guides themselves which is what we have here, assuming it is oil smoke.
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PostPost by: jasper2347 » Tue Jan 18, 2022 9:01 pm

Thanks for the info. He says the guides were replaced and new valves fitted when the motor was rebuilt.
Servo was apparently new last year due to the problem mentioned of leakage. Wasn't smoking then though, just using fluid.
It's certainly oil burning, it has that smell and is blue. There is a bit of black when flooring the pedal when stood, which is just the carb pump jets over fuelling for a second.
The guy did say he could have got more cranking psi by oiling or WD40 down the bore first, but prefers to do them dry as such.
I know the old Escort engines were very particular about being over the max mark on the dipstick. Used to smoke quite a lot till it was drained to the max or just under. I will get him to check that.
Our own sprint and climb car has a performance engine and it does smoke a bit on cold start. Never bothered us a lot. He's just a bit fussy about his car. Or maybe just concerned about the haze?
Thanks again for the information and your thoughts. :D
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PostPost by: 2cams70 » Tue Jan 18, 2022 11:32 pm

jasper2347 wrote:I know the old Escort engines were very particular about being over the max mark on the dipstick. Used to smoke quite a lot till it was drained to the max or just under. I will get him to check that.


Yes that is one thing to definitely look out for - i.e dipstick indicating correctly the actual oil level. If dipstick is non original or tube not pressed in correctly, etc. it may not be correct. I've had that problem before in an Escort. If the crankshaft webs are striking the oil at the bottom of the pan you'll get heaps of smoke!
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PostPost by: rgh0 » Wed Jan 19, 2022 12:50 am

Oil smoke on startup only is generally a problem with the engine having the earlier heads without the cross drilling that help oil drainage from the rear of the head. With the engine stopped oil seeps down the rear valve guides and then produces smoke on starting. The heads with the cross drilling have a plug above and to the right of No4 exhaust port. The oil pooling and smoking is generally worse if the car is parked on a slope with the front higher than the rear.

Oil smoke on startup and when accelerating after Idling for a short time is generally an indication of worn or incorrectly set inlet valve guide clearances and port vacuum when the throttles are closed sucking oil down into the inlets.

Oil smoke on higher engine loads and revs but not so much on idle and startup is generally a problem with ring sealing and ring wear / piston / bore wear. This can cause excess blow by and oil carryover back into the engine and this can be made worse by to high oil level. It can also result due to the oil ring effective being worsened by wear, fouling and blow by so the are not effectively scraping the bores of excess oil on the down stroke leaving oil in the cylinder to burn. .

These are all general statements and each engine is different given they all usually have a different and complex maintenance history over the last 50 years :)

cheers
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PostPost by: jasper2347 » Thu Jan 20, 2022 3:47 pm

P1020103.JPG and
I like your picture rohan. Here's a couple more interesting ones for you.
Back to the smoking Elan, It seems it only started after he changed the oil for the first time since the build. Used the same stuff as the builders put in it as they gave him it, along with the spare from the original fill. Said it was showing a bit low on the stick before changing, around 3 to 4mm below max. wonder if the stick is a bit out of whack? Oil is spot on level now. What we might do is drain it off in to a clean can and refill to the spec amount in the manual and see where it is on the stick at that point. As I said before these Ford engines don't seem to cope well when there is too much oil in there. The cranks must be pretty close to the level. Too cold at the moment. :D
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