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Oil in inlet manifold 
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Post Oil in inlet manifold
My Rossa has a 1275A+ with 30 thou rebore and what I believe is a Piper BP270 cam (it has 270 stamped in the end of it). Other than through the breathers or down the valve guides are there any circumstances where oil could find it's way into the inlet manifold? Could it get up from the cylinders through the valves? That might sound like a daft question but I'm completely baffled with this one :?

My engine has given problems with oil in the cylinders since it was rebuilt (previously discussed without successful conclusion in another thread) and has already been removed and stripped to check bores, pistons, rings etc and all found to be bang on. I recently removed the manifolds to fit a GTM stainless exhaust and oil ran out of the inlet ports/manifold with signs of it in the exhaust ports as well although No 4 seemed ok. I cleaned all this out, fitted the exhaust, left the breathers off and the engine ran quite well. The breathers were 'puffing' away so obviously not blocked with a very slight oil mist coming from the flywheel end one. A few days later I started the engine again and it was back to being lumpy with oiled up plugs again. I removed the manifolds again and more oil ran out so with the breathers off I presumed that it had to be coming from the valve guides which my machine shop had previously pronounced ok. I removed the head and there were signs of oil in the exhaust ports at the bottoms of the guides but No4 was clean as before.The inlets were a different story and the ports were really well coated with oil. I stripped the head and took it back to the machine shop who said that although there was a little wear in the guides it wasn't bad enough to justify fitting new ones :? :? I invested in a digital vernier caliper (great tool) and measured the valve stems which are all exactly the same at 7.09mm which is the minimum size in the specs. I don't have a size for the guide IDs so I added the minimum valve stem diameter to the maximum allowed clearance in the guide and they are all just within it so the guides and valves are worn as much as they can be and still be within tolerance. The valve stem oil seals are the top hat type as they should be and I had them on all 8 valves - they are also a nice tight fit. The vent in the rocker cover cap is clear and the cam timing has been checked to make sure that everything is at tdc when it should be.

So. The head is sitting on the bench all cleaned up and I haven't a clue what to do next hence my question - is there any other way that oil could get drawn up into the cylinder? Apologies for the long story but this has been going on for a long time....

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Fri Aug 31, 2012 9:44 pm
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Post Re: Oil in inlet manifold
Quote:
- is there any other way that oil could get drawn up into the cylinder?

Well there is annother way oil could get down into the port...
If the ports are opened up sideways as is normal on a modified head you can break through into the pushrod channels, it's possible the casting has gone porous in this area.


Fri Aug 31, 2012 11:19 pm
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Post Re: Oil in inlet manifold
I opened up the ports slightly myself so that they matched the gasket and just tapered them in but not by nearly enough to break through the push rod holes. I should have mentioned that I have also checked this but thanks for the reply.

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Sat Sep 01, 2012 10:57 am
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Post Re: Oil in inlet manifold
What oil spec are you using :?:

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Sat Sep 01, 2012 9:47 pm
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Post Re: Oil in inlet manifold
To begin with I had Halfords 20/50 but after starting the engine a few times and letting it idle in the garage I began to worry a bit about glazing in the bores before I got it run in so I changed that for Miller's running in oil in anticipation of a few road miles on trade plates which hasn't happened yet because of the oil problem and also the bluddy awful weather that we've had this summer. The problem is just the same on either oil. There is no smoke on start up and none until it gets really hot when there is just a wisp from the exhaust.

As I said above it ran pretty well after I fitted the exhaust, cleaned the plugs and wiped out the ports but the next time it was back to square one. I do wonder if the guides are 'leaking' slightly and letting enough oil down to collect so that it fouls the plugs as soon as the engine's started. I suggested to the machine shop that it wouldn't do any harm to replace the guides anyway - they're only £12 a set approx - but they insisted that it wouldn't make any difference. I'm still not convinced, though, but mainly because I can't think of anything else!!

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Sun Sep 02, 2012 9:33 pm
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Post Re: Oil in inlet manifold
Still plugging away with this.... I've had the valve guides replaced, seats recut and valves refaced. The valve stems are fine. After lapping in the valves the whole lot was rebuilt with Viton oil seals on all 8 valves and refitted to the car with the correct MG Metro inlet manifold replacing the Mini Spares one which has thinner flanges than the MG metro exhaust manifold. While the head was off I replaced the alternator because the ignition light has always been very reluctant to go out and also the distributor for one with all the correct numbers on it so the damned thing has cost me a packet again :roll: Anyway, I started it up and it ticked over roughly and no amount of fidling with timing or mixture made much difference to it, in fact the mixture screw could be turned almost fully in or out before it made much difference so I wondered if it was drawing air from somewhere it shouldn't be. I've just had the carb and manifold off to check that out and guess what - oil in the inlets again :x :x Th inside of the inlet manifold is fine but the inside of the ports is covered with oil again and a small puddle was beginning to form at the mouth of each port :? I just can't understand what is going on here and haven't a clue what to do next. One thing I did notice is that the oil in the damper on the carb has gone down a lot - I filled it to half an inch below the top of the damper rod and after 20 minutes or so of running it's more than half empty. That oil must be going somewhere and I wonder if that's what is causing the problem. Surely the damper oil shouldn't go down as fast as that and does it mean that the carb is knackered too? The piston certainly feels much looser in the chamber than I remember it being in the HS types that I used to be familiar with - any suggestions?

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Fri Oct 05, 2012 9:20 pm
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Post Re: Oil in inlet manifold
as I was half way through reading your last post above I was thinking "Damper oil" :roll:
Are you using Damper oil or just engine oil :?:

If it has had it you can get a rebuild kit or just send it to southern carbs........ http://www.sciperformance.co.uk/ :wink:

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Last edited by turbocox on Mon Oct 08, 2012 10:57 pm, edited 1 time in total.

Sat Oct 06, 2012 12:20 pm
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Post Re: Oil in inlet manifold
Hi. I originally had engine oil in it and when I refitted it after doing the valve seats I used 3 in 1 which is probably too thin but I've used it quite successully in the past so thought it worth a go as it might not foul things up so much. I've drained it so that there's just enough oil in it to cover the damper piston and hopefully I'll get it started this afty and see what happens - I tried to start it last night but the battery was flat :roll:

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Sat Oct 06, 2012 1:40 pm
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Post Re: Oil in inlet manifold
When ever I play with su or stromberg caburators I use caburator oil, my dad had a tin of it allways performed well, 3in1 is too thin.

I will admit I have not tried to get any for a while

Neil

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Sat Oct 06, 2012 6:13 pm
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Post Re: Oil in inlet manifold
I got the car started and it ran not too badly. I fiddled about with timing etc for a while and it settled down a bit but was still a bit rough with traces of smoke from the exhaust after it got up to temp - the breathers were not connected but it still has thin running-in oil in it which might help to explain it. After switching off I removed the plugs and the centre two were very slightly oily but nowhere near as bad as I've seen them before (this was with a very low oil level in the dashpot) and the outer two were dry but sooty. I removed the dashpot assembly and there was oil in the bottom of the piston and also, looking through the carb, the inlet manifold was coated when it had been dry before. It seems, then, that the oil may well be coming from the damper but why? I checked the suction chamber properly and it is a much better fit than I thought it was - it moves up and down smoothly on it's bearings and there are no signs of it rubbing on the side of the dashpot which would indicate wear. The carb was pretty rough when I got the car so I stripped it, cleaned it thoroughly and rebuilt it using an SU rebuild kit but I've never been totally convinced that it's 100% although I don't know why - it's just a gut feeling I suppose. Ideally I could do with another carb to see if it makes any difference before getting mine overhauled or buying another one. There are a few on ebay but the reasonably priced ones might not be any better than mine and the overhauled/vgc ones are not cheap. Any suggestions as to why the damper oil is getting sucked out would be much appreciated! (I don't know what viscosity proper damper oil is but I seem to remember having seen some on sale somewhere not too long ago but as usual I can't remember where :roll: For what it's worth the Haynes manual says to use 10/40.) At least I now have another avenue to explore 8)

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Sat Oct 06, 2012 10:00 pm
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Post Re: Oil in inlet manifold
I've been doing some Googling and found some more interesting info. This site gives a very good explanation of how these carbs work http://www.zparts.com/zptech/articles/m ... 11601b.htm and the following extract explains what has been happening to my damper oil

'Too often people use light duty (sewing machine or general purpose) oil in the dash pot assembly. This type of oil does little if anything to impede the upward movement of the piston as the throttle opens.
Engine oil can be too viscous (depending on climate). After 2 hours of driving it ends up in the bottom of the piston, the majority of it sucked into the engine. This happens because it is too thick to pass through the damper as the piston falls causing the oil to flow out of the top of the dashpot.'


That explains how my 20/50 ended up in the bottom of the suction chamber and then into the engine.I have also read on another site that very thin oil can be sucked out in little droplets into the engine. It also ties in with the very first time I started the car when it was fine for for the first few seconds and then poured smoke out of the exhaust after a blip on the throttle. The remnants of that oil have then lingered in the engine because it hasn't had a good blast up the road to burn it off.

Pukka damper oil is SAE20 and is available for £4.39 from SU themselves so I'll be ordering some pdq :wink:

If this solves the problem I'll be more than pleased but I'm not so pleased that I've gone to so much hassle and expense when the answer is so simple :x Still, it's all part of the fun and everything's easy when you already know the answer :roll: Thanks for your help gents.

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Sun Oct 07, 2012 8:00 pm
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Post Re: Oil in inlet manifold
RaymondH wrote:
If this solves the problem I'll be more than pleased but I'm not so pleased that I've gone to so much hassle and expense when the answer is so simple :x Still, it's all part of the fun and everything's easy when you already know the answer :roll: Thanks for your help gents.


Hey, life would be so easy with hindsight. We've all had one of these moments. Spent ages & £££ on trying to sort a problem, then it turns out to be something relatively simple. i know i've pulled my hair out at times trying to sort similar.
Anyway hope that this does sort the problem. You'll just feel so good when its sorted, you'll forget the frustration & hassle its caused you. Fingers crossed for you.

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Sun Oct 07, 2012 10:09 pm
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Post Re: Oil in inlet manifold
Thanks for your kind remarks - a little encouragement goes a long way :mrgreen: The damper oil should be with me tomorrow (£8 delivered for 125ml on good old ebay) and hopefully that will solve the problem. That means that I can turn my attention back to the brakes which I think I will redo (with a servo this time) for the third time :roll: :lol:

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Mon Oct 08, 2012 9:22 pm
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Post Re: Oil in inlet manifold
It is all positive progress then, doing the brakes now has to be easier then when they have some road grime one, and before you really need them with how some people seem to drive.
Im sure this will be the best built rossa when it is complete


Neil

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Tue Oct 09, 2012 10:44 am
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Post Re: Oil in inlet manifold
WEST wrote:
Im sure this will be the best built rossa when it is complete


Thanks for your sentiments :D I don't know about that, though, but it won't be for want of trying :lol:

I totally agree with what you say about the brakes - there are some real numpties on the roads these days and I'm not taking the Rossa out there until I'm 100% satisfied that it will stop on a sixpence when I want it to. My philosophy is that as long as I can steer it and stop it then it doesn't really matter what else happens. I'm trying to decide whether to go for the twin servo mentioned by Alan Rossabitz at an eye watering £300 or two Mini servos for £200 but needing much more space and I have to say that I'm tempted by the twin one just to be different but, then again, I might never be able to use it because my wife will kill me when she sees the cost :lol: And there's also the Mini 8.4" disc setup that's in a box in the garage - all I need is driveshafts and a handbrake mechanism.... It never ends, does it :roll:

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Tue Oct 09, 2012 8:46 pm
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