Inspecting an engine with the cylinder head off

[svenedin]

I am planning to swap the cylinder head on my 1098cc A-series (10 MAU-H) engine.

A suitable 12G202 cylinder head is away at the machine shop at the moment to have hardened valve seats fitted, new valves, new valve guides, better top-hat oil seals etc. The complete rocker assembly is also going to be refurbished at the same time.

The reason I am doing this swap is that I have a slow ooze of oil from the head gasket; my current cylinder head is not modified for unleaded petrol and I have the old, not very effective O-ring oil seals which are way past it.

I do not have specialist tools like an external micrometer (to measure bores) but I am wondering what I can usefully learn about the condition of my engine when I have the cylinder head off? What should I look for?

Any advice gratefully received.

PS: An upper body restoration is planned for my car in the next 18 months or so. At this point the engine will come out and the bottom end can be worked on.

Stephen

[Sleeper]

Stephen
Before you remove the head a leak-down test and a compression test would be useful..

John

[svenedin]

Stephen
Before you remove the head a leak-down test and a compression test would be useful..

John

Ok. I can do a compression test. I do have a compression tester. I can’t do a leak down test.

[philthehill]

The easiest way of determining the condition of the bores/engine is to run your finger nail up the bore. if the nail catches on the bore ridge than the engine is in need of a re-bore new pistons and rings.

[svenedin]

The easiest way of determining the condition of the bores/engine is to run your finger nail up the bore. if the nail catches on the bore ridge than the engine is in need of a re-bore new pistons and rings.

Excellent Phil. I will do exactly that.

Stephen

[JOWETTJAVELIN]

Nope, a ridge does not always necessitate a re-bore. There are/were 'ridge-dodger' piston rings available for worn engines which can take up bore wear. It all depends on how severe the wear is.

[oliver90owner]

PS: An upper body restoration is planned for my car in the next 18 months or so. At this point the engine will come out and the bottom end can be worked on.


Unless there is an obvious problem, wait for the engine overhaul, if you are determined to carry out something that may, or may not, be necessary.

Compression (loss past the pistons) and excessive oil consumption, likewise, are the obvious signs. Both likely better assesed after improving the top end.

You are currently changing the ‘top’ end. If the ‘bottom’ end is performing adequately leave it alone is my advice - that includes pistons and bores. BTW, you would need an internal micrometer to measure the bores, not an ‘external’ one!

An improved top end (head, valve gear - including cam - can stress the bottom end in a well-worn engine.

I could feel a ridge, only on one bore, when I dismantled my engine. Luckily it was fairly easily removed - it proving to be a carbon ring, not bore wear.

[svenedin]

PS: An upper body restoration is planned for my car in the next 18 months or so. At this point the engine will come out and the bottom end can be worked on.


Unless there is an obvious problem, wait for the engine overhaul, if you are determined to carry out something that may, or may not, be necessary.

Compression (loss past the pistons) and excessive oil consumption, likewise, are the obvious signs. Both likely better assesed after improving the top end.

You are currently changing the ‘top’ end. If the ‘bottom’ end is performing adequately leave it alone is my advice - that includes pistons and bores. BTW, you would need an internal micrometer to measure the bores, not an ‘external’ one!

An improved top end (head, valve gear - including cam - can stress the bottom end in a well-worn engine.

I could feel a ridge, only on one bore, when I dismantled my engine. Luckily it was fairly easily removed - it proving to be a carbon ring, not bore wear.

Thank you. Yes I would need an "internal" micrometer to measure the bores. I do not have one and I am not going to buy an expensive tool for one job.

I know there is a slow oil leak from the head gasket and I do not know whether the gasket will suddenly fail or go on with a slow leak for ages......

Getting a head refurbished means that the cost of a total engine rebuild is spread out and also deals with the head gasket.

I am not intending to do anything with the bottom end at this stage but I thought I should have an idea of what the condition is like because I will probably not see it again. If it is terrible, which I have no reason to think it is, I do have 2x short blocks on my garage floor. Either of these could be refurbished but I am not at all keen on that idea because I want to keep the car and its original engine together. If the car had an engine that had a different number to its Heritage Certificate that would bother me excessively. However, at a real push, it could have a different engine as a temporary measure but that is an expense I would rather avoid.

So in summary, I just want to get an idea of the bores with the opportunity of having the head off.

Stephen

[philthehill]

As regards an internal micrometre - unless you are going to do the re-bore yourself and need to determine what size re-bore and pistons is/are required there is absolutely no need for an internal micrometre.
Any engineering shop worth its salt will measure and determine what minimum size re-bore and pistons is/are required and re-bore accordingly.

[svenedin]

As regards an internal micrometre - unless you are going to do the re-bore yourself and need to determine what size re-bore and pistons is/are required there is absolutely no need for an internal micrometre.
Any engineering shop worth its salt will measure and determine what minimum size re-bore and pistons is/are required and re-bore accordingly.

Yes. I will do your fingernail test and look for any scoring or other damage.

Is there any truth that a refurbished head on a worn engine can cause the engine to overheat?

[philthehill]

There is no truth in the statement that a re-furbished head on a worn engine will cause the engine to overheat.

[svenedin]

The promised 2-3 weeks for the 12G202 head to be refurbished has turned into 2-3 months with an August eta.

The oil leak is getting worse. It is mostly down the right hand side of the engine (if looking from the front). The tappet chest cover side. The leak seems to be coming from the front right hand side but is also all along the right hand side and slowly dripping off the bottom of the engine. It is not a huge leak in terms of speed of the leak. It's a few drips really but has made that side of the engine very oily.

Quite a few people looked at the leak at 2x shows I was at recently. Everyone who commented thought the leak was actually tappet chest cover(s) even though I have replaced the gaskets and the seal that goes around the bolt inside the cup washer. I am not convinced because the leak seems to be above the tappet chest cover at the union with the head. I thought this was a fairly common leak point from the head gasket because there's an oilway supplying oil to the rocker gear near the front of the engine?

For now I have ordered new neoprene tappet chest gaskets and I will take off the manifold so that I can access the area better. I can also clean up that side of the engine and get a better idea of exactly where the leak is coming from.

On a totally unrelated note that might be of vague interest, I nearly did not get to a recent show. Suddenly the engine started to run extremely rough and would only idle with a lot of choke (mixture very lean). We limped home (a short distance). I took out a spark plug to find the electrode a pale white and then found the breather hose with a huge split in it. I bought that hose, which was described as "breather hose" from a well known supplier but it was utter rubbish. I have replaced with much better hose which is actually fuel hose with internal reinforcement.

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