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7 Port cylinder head install. Oil now in combustion chambers
https://www.ausmini.com/forums/viewtopic.php?f=2&t=97297		 Page 1 of 2
Author:  TommyK [ Sat Jun 02, 2018 2:01 pm ]
Post subject:  7 Port cylinder head install. Oil now in combustion chambers
Hi there.

Recently i installed a brand new MED 7 port cylinder head onto my 1380cc motor. Head was installed with ARP studs and is running minispares roller tip rockers.

The motor was built about 4 years ago with occasional use on weekends etc, so i consider the motor to still be quite fresh.

After installing the head and getting it running, the engine started to blow white smoke. On further investigation all 4 cylinders had a considerable amount of oil in them (even amount of oil in the 4)

Ive since changed the head gasket and valve stem seals. Also a machine shop had a quick look and tested the valve seats and stems, both being fine.

Just wondering if anyone has had any issues like this with the 7 ports or has any theory's as to how the oil is getting in the cylinders.



Cheers, Tom
Author:  Goldbrocade_62 [ Sat Jun 02, 2018 5:09 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
White I thought was brake fluid do you have a booster
Author:  Ian_B [ Sat Jun 02, 2018 5:32 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
Can you give us a picture of this head
Author:  justfanginaround [ Sat Jun 02, 2018 6:01 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
" The motor was built about 4 years ago with occasional use on weekends etc, so i consider the motor to still be quite fresh"

Maybe not run in enough and now glazed the bores so the rings don't seal, might need a strip and rehone / rering.

other than guides there's really no other way { maybe 4 mis-machined bores or loose ring gaps } for oil to be in all 4.

my 7 port had an oil leak from the feed through the head. leaked on a copper gasket, a bk450 and now runs a mls gasket from MED.

Oh and Ian ... my head studs are arp's and pushrods are MED ones but thats prob not going to help as my head is from Pierce.
Author:  Ian_B [ Sat Jun 02, 2018 8:31 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
Are you running webbers and not enough highway into it stuff.
Author:  68Rusty [ Sun Jun 03, 2018 7:01 am ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
Has your carburisation changed, meaning do you still have adequate crankcase pressure breathing or vacuum. I have found I must have vacuum in engine to prevent oil usage through inlet valves regardless of age of motor. My motor is modified which I imagine aggravates the blow by and crank case pressure problems.


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Author:  TommyK [ Sat Jun 09, 2018 3:04 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
Thanks for the replies guys.

@Ian_B

I haven't got any handy, was there something in particular you wanted to see?
And yes i'm running Webers, 2x 40 DCOE set up to be rough enough to drive to rolling road by WeberPerformace.com.au

@justfanginaround

Bores do seem a little shiny/smooth for my liking, how much oil would you expect to find past the rings. There are pools of oil filling about a quarter of the dish in the pistons. I feel as though i have driven it plenty to bed the rings in.

I had some sealing issues with the MED mls gasket, leaked between 2 and 3. bk450 fixed this though. SO i was leaning towards possible un even surfaces for head and block mating, which might still be causing an issue with the oil. But was thrown off by how even the oil was in cylinders.

@68Rusty

Yes by switching the head I've gone from a 1 3/4 Hif44 carb to 2 40mm Webers. Are you saying if i have too much pressure in the rocker cover that it will push oil past the valve seals and guides? Currently it has only got a 1 inch transfer case breather.


There are a lot of potential issues and i'm getting to the point where i don't want to play the trial and error game. The head is currently off and i'm thinking the best bet is to give the whole motor a freshen up. (Rings, hone, deck block, skim head if it needs, make a proper breather/catch can system.

If anyone else has any ideas or things i should do/check when i'm freshening it up that would be greatly appreciated.
Author:  drmini in aust [ Sun Jun 10, 2018 12:25 am ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
What pistons are they?
Recent UK 21253 ones have narrow, low force oil rings. Reduced friction but poor scraping performance.
Solution- machine them for wider twin scraper rail rings, or replace with Hypatec or Russell pistons.
Author:  68Rusty [ Sun Jun 10, 2018 7:24 am ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
If you have the head back on, setting up crankcase vacuum is worth your while to try. Cooper s had vacuum PCV systems set up for a reason on these old motors. Might be other issue but regardless imo these old motors should have crank case vacuum so no or negative pressure can be achieved.


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Author:  WasabiPimpNinja [ Mon Jun 11, 2018 2:56 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
Although you've had your stem seals and guides checked, pop the carbs off after it starts to smoke (mostly after extended idling in my experience) and look down the inlet ports to see if there is oil above the valve/around the guide/in the intake. I'm unsure of the MED 7 Port as I've not seen one, but the style sold by Minisport have the valve stem seal constantly sitting in a pool of oil and can leak into the intake area.

This style:
Image
Author:  TommyK [ Mon Jun 11, 2018 4:59 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
@drmini in aust

They are Omega die cast 73.5's

@ 68Rusty

So you're thinking vacuum from the manifold is better than neutral crankcase pressure? Could be worth a try.

I just feel all in all oil shouldn't be getting into the combustion chambers at idle.

@WasabiPimpNinja

Yup, its that style just machined by MED. Did wonder why there is limited oil passage from the valve "wells" But assumed that a high end machining company wouldn't sell products that all leak oil due to a machining issue that could be fixed.
Author:  simon k [ Mon Jun 11, 2018 5:29 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
sounds like there is too much oil for it to be an issue with carbs or venting...

Quote:
Although you've had your stem seals and guides checked, pop the carbs off after it starts to smoke (mostly after extended idling in my experience) and look down the inlet ports to see if there is oil above the valve/around the guide/in the intake. I'm unsure of the MED 7 Port as I've not seen one, but the style sold by Minisport have the valve stem seal constantly sitting in a pool of oil and can leak into the intake area.


If I was in to betting, I'd have my money on this one. It's a bit sh*t if the oil can't drain away - is that channel there just not deep enough?

I would also be looking for oil sitting on the back of the valves...
Author:  Ian_B [ Mon Jun 11, 2018 6:07 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
How much oil is in the rocker cover Is it getting too much (flooded)
What pushrods are you running Too large diameter restricting oil drainage.
I have a mate restricted oil to rocker assembly and is running standard rockers
Author:  TommyK [ Mon Jun 11, 2018 7:50 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
I think there might of been a bit of oil on the valve guides but can’t remember exactly I’ll have another look.

In reference to the picture over the head above, do you think if you milled oil channels to all valves and a bit deeper to mimick the kind of oil drainage that a stock head would have that you would open up and galleries in the head?

I don’t know why they only have channels going to half of the valves?

I’m running standard push rods, they are the ones that were installed when I bought the motor (rebuilt 1100 S motor.
Author:  simon k [ Mon Jun 11, 2018 9:15 pm ]
Post subject:  Re: 7 Port cylinder head install. Oil now in combustion cham
I'm no expert, and I may be talking out of my arse, but having enough oil to pool in the dish of a piston without burning away would seem like it'd be from dripping in there, rather than come in as vapour or up past the rings - so if that is the case, then the only place it can come from is through the carbs or valves.

You do want to look at the exhaust valves too - you might invest in an inspection camera or one of these - https://www.jaycar.com.au/usb-inspectio ... m/p/QC3373 Jaycar's is expensive, they're really cheap on ebay etc. but will take a while to get here from China/HK.

It should be a reasonably reliable test to take the extractors and carbs off and squirt the back of the valves with a little bit of injector/carby cleaner to thin out any oil that's on them (assuming they're not dry already), and then poke a rag in there on a stick to soak it up - basically get the ports as clean and oil-free as you can. Then take the spark plugs out (no compression) and turn it over on the starter motor for a good minute or so - really get oil pressure in to it so there would be plenty of oil coming up to sit in the "valve wells" and the valves giving a good old pump up and down on the guide seals working.

What sort of seals are you using by the way? nice viton/metal seals that work properly?

TommyK wrote:
In reference to the picture over the head above, do you think if you milled oil channels to all valves and a bit deeper to mimick the kind of oil drainage that a stock head would have that you would open up and galleries in the head?

I don’t know why they only have channels going to half of the valves?


each pair of valves should only need one channel - assumption being that there is a little channel from the exhaust valve across to the inlet

If it turns out that oil pooling is the culprit and it can't be fixed with better valve stem seals or lifting the stems a little bit so they're above the pool, then it may be your only fix - but you'd want to be sure there isn't a water or oil gallery under there. Aluminium is easy to weld repair, but I'm sure you'd rather avoid that
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