An idea for the head oil leak

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Volker_P
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An idea for the head oil leak

Postby Volker_P » Fri Jan 14, 2011 2:39 am

Well, guess you all know what I am talking about. Considering why only the top O-Rings leak but never the bottom ones I thought the problem might be related to the fact that the larger bottom rings have bushings for inner support while the upper O-Rings are free to escape towards the oil line and get flat and leaky that way.

So I think it might be worth a try with support rings like that below (shown with an old O-ring). Dimensions are 5x4.7x2mm, made by a friendly mechanic with a drilling machine and two old hondas. I'll probably install them in the next days when I go to replace my valve stem seals.

I hope it is centered well enough, will play around with spare engine parts later. A better solution might be to drill a step and make a longer bushing that is guided by the oil line a bit for say another 3mm of length but I am unwilling to remove the cylinders and fight with tensioner and piston rings just to avoid filings falling in. And I think I should not drill the head as upside down is a risk during assembly.

Please let me know your comments or suggestions.
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tmorgan0630
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Re: An idea for the head oil leak

Postby tmorgan0630 » Fri Jan 14, 2011 10:48 am

Which support rings are you using? The same ones from the bottom of the motor? I am very interested. I am having to do the samething now. I am looking foward to your success in this endeavor.

helmet hair
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Re: An idea for the head oil leak

Postby helmet hair » Fri Jan 14, 2011 5:06 pm

Volker, while you have the head and barrels apart can you post some close up shots of the oilway joints (head & barrels) and some dimensions of the oilway bore diameter, depth of the 'O' ring recess and the outside diameter of the sleeve.
If I was going down this route I would have it done on a properly set up vertical milling machine rather than risk it with a hand held electric drill or a large pedestal drill.
Looking forward to seeing and reading your results

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Volker_P
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Re: An idea for the head oil leak

Postby Volker_P » Tue Jan 18, 2011 2:17 am

The lower O-Rings are 10mm diameter, so these 5mm support rings are hand made parts.

The oil line diameter is 4.7mm, the O-ring recess is only at the barrel side (and in the gasket) and I think depth was 1mm. Can measure that at an open engine. What is maybe more important, I just found two old, hardened O-Rings which should have conserved the exact gap together with the head gasket. Will measure them, too.
If you put the whole thing into a milling machine, traces at old O-rings indicate that it might be a very good idea to polish the O-ring recess bottom surface, too. This is my second main concern besides the inner support.

What I really want to do is to replace the valve stem seals. If I can manage that without removing the head (and moreover the carbs) I'll probably postpone the support rings as the head does not leak significantly yet. Even then I'm not going to remove the cylinders for machining the hole/recess now.

It was warmer and dry this weekend but I used the opportunity to go for a ride and with these preferences it may take some time until I start with work. :)
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wingman
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Re: An idea for the head oil leak

Postby wingman » Sat Jan 22, 2011 6:56 pm

Volker_P wrote:It was warmer and dry this weekend but I used the opportunity to go for a ride and with these preferences it may take some time until I start with work. :)



Yep my sentiments exactly !! Had a nice ride today too...

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Volker_P
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Re: An idea for the head oil leak

Postby Volker_P » Tue Jan 25, 2011 1:49 am

So finally here are the data:
O-Ring recess: diameter 10mm, depth 1mm (quite exactly in the accuracy of my caliper)
The old, compressed, hard O-Rings have a thickness of 2.05-2.1mm.

During that I found seven valve stem seals (I just ordered a set some weeks ago) and that I still have a quite acceptable set of pistons and cylinders. :D Maybe I'll try them in my first engine that I set out of duty due to heavy oil consumption.
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Pinhead
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Re: An idea for the head oil leak

Postby Pinhead » Tue Feb 01, 2011 2:26 pm

That is a genius idea!

Am I right to assume that the height of the support is going to be determined by the thickness of the head gasket?

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Volker_P
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Re: An idea for the head oil leak

Postby Volker_P » Wed Feb 02, 2011 2:32 am

The head gasket and the recess at the cylinder barrel side add up to the required thickness. The head side is flat. I measured old, hard O-rings being slightly above 2mm and decided to get 2mm rings which still might be grinded down to 1.9mm.

I suppose this solution being only second best, but it allows to leave the cylinders, bottom gasket and tensioner in place. I only urgently want to do the valve stem seals and only remove the head if I cannot manage that without removing it. Only in this case I would install these support rings. And I don't want to break down further than the head in any case.

The better solution is probably making a longer ring/bushing of identical ID and OD and drill a guide into the cylinder side oil line. Again one would need the bushing look out 2mm from the recess bottom or 1mm from the flat cylinder surface for the gasket thickness. Due to the filings, one better won't do that drilling with the cylinders installed, of course. That's why I have these short rings.

I think the recess will center the O-Ring and support ring quite satisfactory, I am not sure if the camshaft oil bores are straight to allow for a visual check. As the camshaft oil flow seems to be controlled by the calibrated bores in the bottom gasket bushings, I would assume that a slight misalignment is probably no real problem.
In any case a drilled guide seems more precise and reliable and less susceptible during installation. And it would look more professional.
Although I am the guy that prefers somehow the tiny and simple but effective things. :lol:

So far the theory, but of course it still waits to be proved working in practice at all. :)

BTW, I recently successfully used a plastic bushing instead of an O-Ring in a high pressure cleaner (~150bar).
Last edited by Volker_P on Wed Jun 15, 2011 4:35 am, edited 1 time in total.
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feelo
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Re: An idea for the head oil leak

Postby feelo » Fri Jul 22, 2011 2:58 pm

Great idea, creating support for the O ring.
Too bad these need to be custom made.

MiGhost
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Re: An idea for the head oil leak

Postby MiGhost » Thu Aug 01, 2013 4:27 pm

Just to be clear on this.

The o-ring sits in an approx 10mm dia. x 1mm deep? recess in the top of the cylinder, and the oil gallery is 4.7mm dia.

To extend the support ring into the cylinder to act much the same as the dowel pins do to locate the head. Drill a guide hole 5mm dia. x 3mm deep to enlarge the oil gallery to hold the support ring. This would make the dimension of the support guides 5mm OD x 4.7mm ID x 5mm H.

A jig could be made up to easily align the drill to keep the hole straight.

My concern would not be getting chips into the cylinder so much. Those can be covered, or cleaned. The oil gallery though is a different issue if the engine was still assembled.

I would pack the oil gallery with grease before drilling the guide hole. Once the holes are drilled. You can turn the engine over to use the oil to flush the grease, and chips up out of the hole.

I agree that there should be no reason to drill into the head as the dowel pins are used for the head alignment. The support guides only need to be held in place on top of the cylinder.

I like the idea!! :D

Anyone interested in making a kit (jig, guides, bit) for these supports?
Let me know! I am interested in getting some.

Ghost
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