Lotus Elan

Oil in exhaust

PostPost by: JohnMorin » Wed Apr 12, 2023 10:54 am

Hi

I recently had my cylinder head guides, seats, valves and springs replaced. All of the work including the machining was carried out by Vulcan Engineering near Brands Hatch. They pressure tested the head before commencing any work and the head was given a clean bill of health. The standard of workmanship is excellent and I am very happy with the result.

I refitted the head to the block the internals of which have covered probably less than 100 miles.

Initially the engine ran well but on starting it up last week it ran rough and there was a lot of smoke coming from the exhaust, light grey/blue in colour. On inspection I noticed black oil running down the block on the exhaust side by the rear face of the block. I suspected that despite my careful assembly the head gasket had failed. So I removed the head. All looks OK, the gasket shows no sign of damage, both the head and block face are are good. There is no evidence of leakage in the ports. No 4 piston had oil in the cutouts.

I think I know what the problem is but I would like some opinions from others before I start tearing things apart.

Thanks

John
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PostPost by: rgh0 » Wed Apr 12, 2023 11:07 am

How have you run in the block to get the rings seated ? With only 100 miles you may have excessivie blow into the intake which mainly gors into cylinder 4 or you may not have seated the oil ring in cylinder 4

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PostPost by: JohnMorin » Wed Apr 12, 2023 12:13 pm

Thanks Rohan

Maybe I should have given a bit more detail about the engine. It was built a long time ago but never run. On turning it over by hand I encountered sticking valves hence the head rebuild.

The bottom end is balanced, has a Tufftrided crank, polished rods and standard size Powermax pistons. I put the engine together very carefully having experience in this area in the past. I measured the bores with precision rollers and slip gauges and wear was less the 0.0015 in all bores - I put that down to the liners and the low mileage < 30K.

I don't have an airbox as this was originally a Stromberg engine but ow has twin DHLA 40s. The breather therefore goes into a catch tank, I fitted another breather goes from the front of the cam cover to the same catch tank. The catch tank vents though the air filter back plate. I have been running with the air filter off while setting up so the catch tank is not being positively vented.

I am suspecting the rings myself. I did notice an increase in compression after having the head rebuilt so I am wondering whether this has something to do with it.

Regards

John
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PostPost by: h20hamelan » Wed Apr 12, 2023 2:52 pm

Likely pulling the plugs and adding some atf or solvent if your draining oil could free them?
Mine was sitting 30 years, and it took a bunch of different soakings, agitating engine often during the day while filled with atf. Removed as much atf as possible with hand cranking and fuel transfer pump.
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PostPost by: JohnMorin » Wed Apr 12, 2023 3:40 pm

Hi h20hamelan

I have nothing siezed, the bottom end turns freely and the head is newly rebuilt?

John
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PostPost by: pharriso » Wed Apr 12, 2023 4:22 pm

JohnMorin wrote:Hi h20hamelan

I have nothing siezed, the bottom end turns freely and the head is newly rebuilt?

John


I think he's suggesting that the rings aren't moving freely & sealing fully...
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PostPost by: h20hamelan » Wed Apr 12, 2023 5:02 pm

Sorry, yes. Maybe rings?
Is it a lot of oil?
No chance its wet atmospheric carbon deposit or coolant??
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PostPost by: vstibbard » Wed Apr 12, 2023 8:51 pm

Check if there’s oil pooling around #4 exhaust bucket, late heads have a drain back to inlet side of head whereas early heads done.
If #4 guide is at larger end of acceptable range it can drain into exhaust port. Typically takes some time. If cars been left with front raised or on an incline it exacerbates the issue.
I had this occur on a S3 I rebuilt, I had head fully serviced new seats guides, new pistons rings, pulled and stripped it down again to measure everything again, all in tolerances, replaced oil rings with multipart oil rings and reassembled, it still kept smoking after sitting for few days.
We ended up making an external oil return line from back of head behind oil filler to chamber under inlet runners using 1/4” copper bundy, problem solved!! You can see the shiny copper bundy on back of the cylinder head in the picture below.
Here is a picture of the modification on an S2, I do them to all as a matter of course now:
oil drain back mod on early LTC.jpeg and
Oil drain back modification

Few locals thought the head was a development version!
Good luck
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Last edited by vstibbard on Fri Apr 28, 2023 5:52 am, edited 2 times in total.
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PostPost by: 2cams70 » Wed Apr 12, 2023 11:33 pm

I’d be a little concerned if the oil was black on an engine freshly rebuilt! You didn’t by any chance measure the compressions before you lifted the head?
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PostPost by: mbell » Wed Apr 12, 2023 11:36 pm

Worth just confirming it's not sucking brake fluid from a brake booster?
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PostPost by: JohnMorin » Wed May 24, 2023 9:09 am

Hi

After waiting for parts to arrive and the weather to settle down I finally got the head back on last week. Compression is up and there's no smoke from the exhaust.

Before fitting the head I made sure every head bolt went right to the bottom of their threads in the block easily by hand. I thought I had done that last time but maybe I used a spanner. After lowering the head onto the block, location studs used, I made sure again that all of the bolts went right down without their washers. I also ran a stone round the corners of the washers to prevent them digging in. When I torqued the bolts it felt like a little more effort than I remember last time.

Another thing I did was, as Miles Wilkins says, put Wellseal on both sides of the head gasket. The factory manual doesn't mention this so I had never done it before.

John
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