Smokey engine

Post by **mgcjag** » Thu Dec 15, 2011 12:08 pm

Hi All.....Just looking at a friends US import 1970 S2 ots, fully converted to RHD with tripple Su,s. engine No is -9 so assuming 9:1 compression. Engine was rebuilt in 2003(9:1 pistions used & approx 4k miles since) car runs fine & engine quiet.....when lifting off after accelerating smoke comes from the exhaust near side......I was thinking valve stem oil seals? Dry/wet compression test shows as follows, engine hot.

6 140/175
5 140/162
4 145/175
3 153/185
2 140/170
1 145/178
The Plug on 5 is always oily. Questions. am i correct in thinking that the Comp for the 4.2 should be 180, if so are the wet results indicating rings/bores?
No 5 being lower wet, indicating valve? Your thoughts please, Steve

paulsco · Post by **paulsco** » Thu Dec 15, 2011 1:26 pm

Hi Steve,

I think there is a significant difference between the wet and dry figures which to me indicate ring/bore wear.

Paul

Post by **1954Etype** » Thu Dec 15, 2011 1:58 pm

How about glazed bores? That mileage is pitiful for 8 years!

christopher storey · Post by **christopher storey** » Thu Dec 15, 2011 6:24 pm

Although I would not be dogmatic about it , I feel that there is a huge amount of hocus pocus talked about so called wet and dry compression comparisons . I have never yet seen a standard 4.2 which would produce a 180lbs reading dry, and the more typical reading is in the 140 - 150 lbs/sq.in range , precisely as you are getting . Pouring cold oil into a hot engine is bound to affect the result even where the rings are perfect for the simple reason that the combustion chamber volume is diminished by precisely the amount of oil put in , and this is much more critical than the corresponding diminution in swept volume : the effect of introducing as little as 10cc increases the nominal CR by about 1.15 . As a result, I doubt whether there is anything seriously wrong with the bores, although as has been said they could be a bit glazed. If it were bore wear, then you are much more likely to see blue smoke at times other than high vacuum conditions. Overall, I suspect worn guides with no 5 probably being in very bad shape

Post by **mgcjag** » Fri Dec 16, 2011 10:42 am

Hi All thanks for the input. is there any way of checking for guide wear? I was thinking of removing inlet & exh manifold & cams & tappets & pouring oil around valve/spring area, if there was no wear would the oil seap down the guides & be seen through the manifold if i then push the valve open ? Just trying to look at all options before pulling the head. thanks Steve

christopher storey · Post by **christopher storey** » Fri Dec 16, 2011 10:58 am

When my Cooper S ate its valve guides and did 50 miles per pint I could see that the inlet valves were wet with oil . If you have already taken the inlet manifold off, I should have a look at the valves ( you can see them easily with a torch ) and if there is any sign of wetness , you have your answer . In any event, if the guides have been leaking for any length of time, it is likely that the valves will be encrusted with a gooey black mess. If not, you could try anointing them on the stem , having removed the cam and tappets, and see what happens. Without wishing to teach my grandmother to suck eggs, remember no rotation of engine unless both cams are completely removed .

Steve : just another thought. If you are getting leakage down the guides , the result is often a big blue cloud immediately on a cold start in the mornings, far worse than at other times. Is this happening?

Post by **mgcjag** » Fri Dec 16, 2011 5:38 pm

Hi Christopher......Thanks for the input....No dont get a blue cloud on startup....will try the oil down the valves & try to see if any is seeping by looking throgh the inlet ports.....Its a friends car & he,s reluctant to pull the head becaus it can then swowball into another rebuild....Steve

christopher storey · Post by **christopher storey** » Fri Dec 16, 2011 6:35 pm

Steve : another thought which might save a lot of time. I understand that fibre optic endoscopes of the type ( but not quality ) used for examining the hot section of turbine engines can now be bought for relatively modest sums ( someone told me 80 or 90 quid) . With one of these through the plug hole you could examine not only the valves of each cylinder but also the state of the pistons and indeed the cylinder walls

PeterCrespin · Post by **PeterCrespin** » Fri Dec 16, 2011 7:19 pm

mgcjag wrote: Engine was rebuilt in 2003(9:1 pistions used & approx 4k miles since) car runs fine & engine quiet.....when lifting off after accelerating smoke comes from the exhaust near side......I was thinking valve stem oil seals? Dry/wet compression test shows as follows, engine hot.

Remember there ARE no valve guide seal on that engine - unless non-stndard parts have been fitted. If seals were fitted without correct guides and valve spring retainers they will not work correctly.

If the wet cylinder communicates with the smoking cylinder then the two issues are obviously linked. Could be a stuck/broken ring rather than a glazed bore but it's nothing mega-major with those compression numbers.

I'm not too convinced about oil seeping down the guides at standstill as I don't believe the oil level in the valve chest exceeds the height of the valve guides in a stationary engine in a level car. Pooled oil around the tappets in the cam box obviously has no leakage effect on the valve stems.

I'd be tempted to try a water spray decoke on a hot engine. If you were going to whip the manifold off anyhow it might even be fun to try it on cylinders 5/6 and maybe 3/4 to see if it helped and to provide a comparator with 1/2 when looking down the ports either with a flexible borescope (good idea) or with the manifold removed.

Post by **mgcjag** » Fri Dec 16, 2011 7:32 pm

Hi Peter....Please expand on the water spray dekoke? what do you do? Thanks for the heads up on the stem seals, i was just assuming they were fitted as standard..Steve

PeterCrespin · Post by **PeterCrespin** » Fri Dec 16, 2011 8:35 pm

mgcjag wrote:Hi Peter....Please expand on the water spray dekoke? what do you do? Thanks for the heads up on the stem seals, i was just assuming they were fitted as standard..Steve

Well, on your own head (or your friend's) be it - 'scuse pun...)

It is acceptable (preferably just before an oil change) to do a water spray decoke on old-tech engines, but it has risks and not everyone agrees with it. It isn't very environmentally sound i have to say...

Basically, you get the engine thoroughly hot and then whip the plenum off. You can do it without the plenum and ram tubes fitted if it doesn't run weak like that.

Anyway, once the engine is thoroughly heated through, you can hold it at something like 3000 rpm and using a handheld spray bottle squirt some atomised water into one of the carb throats. There will be clouds of smoke out of the relevant exhaust pipe and the steam effect will clean carbon from inside the engine. Do it to each carb in turn and then go for another decent run to make sure there's no water in the carb bowls etc.

Bear in mind, this operation has to be done carefully. Pointing a hosepipe down the carb could result in hydraulic lock and a bent rod, or worse, but IMHO you'd have to be a plonker to squirt that much down. Wafting the tiniest whiff like a scent spray won't do much, if anything. Somewhere in between lies a clean engine the old tech way, though today's fuels and injection system, oils and running clearances, mean decoking is ancient history.

Changing the oil afterwards is good timing to remove any stuff that gets in there (theoretically anyhow).

If it's someone else's engine you might want to check their attitude, or maybe use of of the modern engine cleaners like BG44 or Techron if you can find it and follow their instructions.

By the way, I meant to say in the other post that if the wet plug cylinder corresponded to the smoking exhaust side then it was obviously a link...

Pete

Post by **mgcjag** » Fri Dec 16, 2011 8:46 pm

Hi Peter....sounds GREAT...But cant see my mate wanting to give it a try. never heard of it before......Will keep it in reserve for my next project....Ps the oily plug 5 does correspond to the smoky(near)side exhaust...Thanks Steve

Post by **1954Etype** » Fri Dec 16, 2011 9:02 pm

Another way of solving the glazed bore issue was to park in a field and introduce Vim into the inlet manifold. A mate of mine did it on his Aston Martin DB4 (no other choice) and swore it made the engine use less oil.

christopher storey · Post by **christopher storey** » Fri Dec 16, 2011 10:06 pm

no!No!NO!NOOOOOOOO!

Post by **1954Etype** » Fri Dec 16, 2011 10:25 pm

christopher storey wrote:no!No!NO!NOOOOOOOO!

Yep he did! Engine was stuffed and burning oil so it was either strip it down and hone it or use Vim. He chose Vim and sold the car for a fortune later to a Japanese collector.

Post by **mgcjag** » Sat Dec 17, 2011 9:47 am

Hi All.....Thanks for all the replies, will investigate further over the next few weeks.....But to be quite honest wont be using the Vim.....or any products!! What ever the problem is once identified, will use a more traditional method.........ie strip down & rebuild...Steve

Post by **1954Etype** » Sat Dec 17, 2011 11:26 am

mgcjag wrote:Hi All.....Thanks for all the replies, will investigate further over the next few weeks.....But to be quite honest wont be using the Vim.....or any products!! What ever the problem is once identified, will use a more traditional method.........ie strip down & rebuild...Steve

Where's your sense of adventure man! I say do it and report back here - I mean, what could possibly go wrong?

andy303 · Post by **andy303** » Sat Dec 17, 2011 3:48 pm

Go to the jag-lovers forum and use "Bon-ami" as a seach term. You will get results such as this: http://forums.jag-lovers.org/av.php?155316n15
There are probably many, many more.

I have never done it, so I can't vouch for the technique. Many have heard of it, few have tried it. If the choice comes down to tearing the engine apart, perhaps a pinch or two down the sparkplug hole of the offending cylinder, followed by an oil change, might do the trick. If you put the stuff through the carbs you would be adding wear needlessly to the other cylinders.

Mark Gordon · Post by **Mark Gordon** » Sat Dec 17, 2011 6:41 pm

I give up! What is "Vim?"

Mark

e-bygum · Post by **e-bygum** » Sat Dec 17, 2011 7:34 pm

Mark Gordon wrote:I give up! What is "Vim?"

Mark

It's the same stuff as Ajax but from a different maker.

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