Lotus Elan

LOTUS ELAN S4 new member

PostPost by: mar083 » Sun May 07, 2023 1:10 pm

Hi all. My name is Christian,
I am French, already has 2 English TR3A from 1959 and AUSTIN 998 from 1970. I also have 2 Italians: FIAT 500 GIANNINI (700cm3) from 1970 and a LANCIA Fulvia 1.3S rally from 1970. I just bought a 1970 LOTUS ELAN S4. Identification 7011220073K. With engine completely redone (photo and complete invoices attached) and 5000Km only since the works. It runs well, does not smoke, but after a strict control of oil consumption, I see 1,250 liters per 1000Km. So I'm a bit in dispute with the seller. To support my observation I would like to have your opinion on this consumption figure. A French friend who owns 3 tells me it's way too many. Could you give me your opinions (as many as possible) specifying for each the mileage of the engine and its oil consumption. I do not find on the lotus documentation a theoretical oil consumption.
Thank you all for your help
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PostPost by: rgh0 » Sun May 07, 2023 1:47 pm

Hi Christian and welcome to the forum - love the Lancia Fulvia one of my all time favorite cars, after Lotus of course :)

Many factors can influence oil consumption in a Twincam, which after all it is a 50 year old design even if it an excellent one for the time and even today.

VW and other modern manufactures consider 1 litre per 1000 km "Normal" and will not take warranty action until it exceeds that !!

So for a twincam the starting questions are

1. How does the oil consumption show itself ? a large puff of smoke after idling, a continuous blue haze when driving, large puddles of oil under the car ?

2. what grade of oil and type are you using

3. What driving style for the car - pottering around town, country cruisiing, sporting road driving, track use, serious track use hard on the rev limit and throttle

4. When was the engine last rebuilt and buy who and how


The most common cause of excessive oil consumption in a twincam is worn or incorrectly toleranced valve guides as it has no valve stem seals. This shows up especially as a large puff of smoke on resumption of driving from a period of idling. But many other possible causes.

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Rohan
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PostPost by: mar083 » Mon May 08, 2023 1:15 pm

Hello ROHAN,
Thank you for your reply. I know that in modern cars some brands advertise 1liter per mile Km. But others like TOYOTA have Zero Oil consumption vehicles. The engine was completely redone in 2014 and traveled only 5000Km. It was sold to me with this argument, photos and invoices in support. I use ELF HTX 20W50. I carried out a consumption check with experts (weighing the introduced oil and weighing the remaining oil) by doing 500Km on the road, neither mountain nor winding and at authorized speed!. So cool. As I said, I want to have the average consumption of the greatest number in order to have arguments to possibly obtain a discount on the price I paid. A liter and a quarter seems excessive to me for a just run-in engine? Finally as an external sign I have nothing. No oil on the floor in the garage, no blue smoke in the exhaust.
Sincerely Christian
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PostPost by: rgh0 » Tue May 09, 2023 2:01 am

The consumption is at the top end of what I personally would consider an acceptable range.

What do the plugs and the top of the pistons look like if you put a borescope down the plug hole ? Is it just dry black carbon or wet and oily carbon?

From the photos it looks like a lot of care went into the egine build but that does not guarrantee machining accuracy of things like the cylinder bores.

If no smoking especially after accelerating after idling or on start up it is probably not the valve guides and more likely the oil rings. Modern synthetic oils generate a lot less smoke than the earlier mineral oils so a slight continuous oil consumption from piston rings not sealing correctly may not show any noticeable smoke.

Rings not seating can be caused by poor quality bore machining and honing or not running in the engine correctly.

Do you any details of the bore machining and measurements that confirm bore size accuracy with no taper or ovality in the bores and correct honing done ?
Do you know how it was run in ?


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Rohan
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PostPost by: 2cams70 » Tue May 09, 2023 3:04 am

The cylinder bores on that engine still look shiny and polished from the pictures. It may have been fitted with new rings and pistons without the cylinders having been properly honed or deglazed. The nature of the cross hatching pattern on cylinder walls after they are honed is quite critical. Correctly done it’s designed to retain oil on the cylinder surface for ring and piston lubrication

Sometimes it’s hard to properly test for blue smoke from the exhaust whilst you are in the driver’s seat. I’d suggest you get a friend to travel behind you in another car and observe whilst you drive and test it under different load conditions.

A good test is to travel at speed down hill on a trailing throttle whilst in gear. When you reach the bottom of the hill give it full throttle. If you get a cloud of blue smoke then you know you have a problem.

Travelling on a trailing throttle down hill results in a high vacuum condition in the cylinder which will draw oil past suspect areas like valve guides. When you then open up the throttle the collected oil will burn and produce the blue smoke
1970 Ford Escort Twin Cam
1972 Ford Escort GT1600 Twin Cam
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PostPost by: 512BB » Tue May 09, 2023 8:14 am

Hopefully the plain nuts on the camshafts were changed to nylocks at some point, or oil consumption could be the least of your worries.

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PostPost by: mar083 » Tue May 09, 2023 8:29 am

I thank you all and I will give it a try according to your advice. I just had a compression check done, but just with a hand-held pressure gauge. I just found a garage with a device that records the result. See you on Thursday. LESLIE could you tell me more about camshaft nuts. ?
Thank you Christian
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PostPost by: rgh0 » Tue May 09, 2023 9:42 am

I, like many, when building the engine use plain nuts on the cam caps as they have to come on and off a number of times and the engine is assembled and clearances checked. Once all that is done I replace the plain nuts with nyloc nuts on the cama bearing capsand torque them to the specification

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PostPost by: 512BB » Wed May 10, 2023 8:39 am

' LESLIE could you tell me more about camshaft nuts'

Whilst looking at the pictures you posted Christian, I noticed that your cam caps were secured with plain nuts. That is fine for setting up the valve clearances, but they MUST be changed for nyloc nuts after that, with washers, as plain nuts may come undone even if used with spring washers. You can check if they were changed by undoing the oil filler cap and observing if no.10 cam cap still has them fitted.

In my formative years with Elans, I fitted a brand new set of Weber carburettors to a car, and just used plain nuts with thackery washers. I set up the carbs and went for a long run. When I got back, I popped the bonnet to see that the carbs were only held on with just 3 of the original 8 plain nuts. I never made that mistake again!

Welcome to the board, by the way.

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PostPost by: mar083 » Wed May 10, 2023 1:55 pm

Yes my cam caps were secured with plain nuts with planes washers. What is diameter for nuts?
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PostPost by: 512BB » Wed May 10, 2023 2:23 pm

5/16" UNF thread size, 1/2" AF spanner size. If who ever built the engine can make such a fundamental mistake as to use the incorrect fasteners for the cam caps, I would be very concerned for the rest of the build of the engine.

FYI, a twin cam engine I rebuilt 5k miles ago does not use any oil between services now. Not discernable anyhow.

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