eng622 wrote: ↑Tue Dec 19, 2023 8:46 pm
OK made a mistake as bracket will be raised by thickness of nut say ~ 12 mm.
On my car the rear stud as two nuts one for the head other for stab. bar which is a full nut and does protrude from the end of the stud. Thinking of replacing the steel pipe with a rubber hose with metal inserts at each end, won't look very pro. though.
Are the head nuts 9/16 AF.
That's exactly what I did on my 1275. Pic below:-
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The right hand pipe goes from the heater valve to the radiator bottom hose, connecting via a short pipe adapter. I have a non-standard heater valve, one that permits coolant flow around the rear of the head with the valve closed and heater out of the circuit. This helps keep the rear of the head cool.
Points taken but I'm curious why my gasket suddenly failed, maybe the PO's did not re torque the head on the new engine. I have an oil leak on the manifold side which may be from the head gasket.
I am going to look at torque when undoing each nut. Need to find the problem if I can lift the head off. So will be looking at the pipe issue after I know what needs doing next.
eng622 wrote: ↑Wed Dec 20, 2023 12:01 am
Points taken but I'm curious why my gasket suddenly failed, maybe the PO's did not re torque the head on the new engine. I have an oil leak on the manifold side which may be from the head gasket.
I am going to look at torque when undoing each nut. Need to find the problem if I can lift the head off. So will be looking at the pipe issue after I know what needs doing next.
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It could be a poor quality gasket, it could be that the head has got too hot and warped slightly, it could be that they just don't last forever. Mine went through about 4 head gaskets in 3 years, I was getting less than 2000 miles from each one. I had the head skimmed slightly, just enough to square it off, and haven't had a problem since.
eng622 wrote: ↑Tue Dec 19, 2023 10:32 pm
The issue is if you need to replace the thermostat you cannot get the housing off without removing the heater pipe which means undoing two heads nuts, not a good idea.
Earlier 948 engines look to have a copper pipe on the manifold side, assume can be fitted to the 1098. Just missed one on ebay. Guess they are hard to come by.
Yes, it isn't ideal but, as 'svenedin' has pointed out, countless cars have had thermostats replaced requiring the two head nuts to be removed over decades, so it really shouldn't be an issue. If you are still concerned, then my advice would be to replace the existing thermostat as a precaution whilst the head is off. They are hardly expensive.
As to why your head gasket failed, my answer is that they do fail from time to time. Its not uncommon, nothing lasts for ever. Having said that, I have only had one head gasket go in nearly 40 years of continuous Minor driving. You may pick up some tips from this rather lengthy thread, which records my experiences, and advice from members on this forum (although the pictures seem to have disappeared ): viewtopic.php?t=63980&hilit=cylinder+head+nuts
eng622 wrote: ↑Wed Dec 20, 2023 12:01 am
Points taken but I'm curious why my gasket suddenly failed, maybe the PO's did not re torque the head on the new engine. I have an oil leak on the manifold side which may be from the head gasket.
I am going to look at torque when undoing each nut. Need to find the problem if I can lift the head off. So will be looking at the pipe issue after I know what needs doing next.
We are assuming that your engine problem is definitely the head gasket. This does seem increasingly likely especially as you also have an oil leak. Other possible sources of oil are leaking from rocker cover gasket or tappet chest gasket.
Hard to say why it failed. Seems unlikely but maybe a dud gasket or perhaps the previous owner had done some work and hadn’t properly torqued the head down. Ivor Searle engines have a good reputation and the miles are low since rebuild but we do not really know how the engine was treated. Maybe it was thrashed!
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
That's what I would do IF I was concerned about it. In reality, although the later design seems to be a backward step in a way, it doesn't trouble me really. It is still a joy to work on such a simple and well designed car
Head off, copper gasket very bad between 1 & 2, looks to have melted away, pic attached
Not a good advert for an Ivor searle on 10k miles, unless it has been tampered with.
Block looks ok slight scarring between 1&2, bores good no lip at top, pic att.
Now I cleaned the head face all straight no light showing under straight edge. The bad news between 1 & 2, as there are what look like two tiny cuts across where the minimal surface is, so guess skimming is needed. May see in pic att.
The metal water pipe will still fit the rubber hose when the brackets are on top of the head nuts, so will attach with lock nuts.
I'm wondering why the head failed. Have done around 300 mile since purchase and it performed with perfection, never raced max 60 mph, no coolant loss or overheating. Perhaps just bad luck but I recon the head is a duffer and the cuts were there from the start and the gasket did its job until now.
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Oh dear! Well, now you know why you had no compression from the front 2 cylinders. That gasket is certainly blown away.... The head looks to have quite a crack in the same position too? That may not be worth trying to repair. Cylinder heads are not difficult to source though. Impossible to see how deep that damage is but I'd probably think about a replacement?
I don't think it's any good blaming Ivor Searle without knowing how the engine was set up and used for the 10,000 miles it has covered. They have a decent reputation as engine reconditioners but who knows how the engine was set up? Ignition timing, carburetion etc and what fuel has been used and/or how driven prior to your recent ownership. It is just bad luck and hopefully at least the bottom end can be rescued
It looks like a crack in the pic but in reality appears to be a very shallow mark. If I take it to a skimming company they should know the best approach.
The whole gasket does not look great not just the total failure between 1 and 2. I would be cautious about another skim on that head as it has almost certainly been skimmed already. Can that mark be felt with a finger nail? This is a surprisingly sensitive test.
I’d also suggest that’s been leaking for a while.
Stephen
Last edited by svenedin on Thu Dec 21, 2023 12:09 am, edited 1 time in total.
1969 1098cc Convertible “Xavier” which I have owned since 1989.
How can you tell if the head has been skimmed can you measure the thickness.
The mark can be just felt running my finger nail over, I guess that is bad news.
eng622 wrote: ↑Thu Dec 21, 2023 12:07 am
How can you tell if the head has been skimmed can you measure the thickness.
The mark can be just felt running my finger nail over, I guess that is bad news.
I’m no expert but you can tell by measuring the volume of the combustion chamber. A skim reduces the volume of the combustion chamber and this increases the compression ratio. An experienced machine shop person can also tell just by examining the head (a general idea at least). They measure the depth of the combustion chamber. A burette measurement of volume is more accurate.
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
A standard unskimmed 'A' Series cylinder head is 2.75".
The amount that can be skimmed from a 'A' Series cylinder head is limited to 0.040" below the horizontal oil way that runs from the N/S front of the head to the base of No: 1 rocker pillar.
0.060" can safely be removed from the combustion chamber face of a non skimmed head. But it is always best to measure the thickness of the head before doing so.
Having just enlarged the photo of your block I would be looking at more than just the head? No2 piston looks like it's been attacked internally bits of the edge of the piston look to be missing and all the register marks in the crown suggest something had entered the bore.
chrischris59 wrote: ↑Thu Dec 21, 2023 12:18 pm
Having just enlarged the photo of your block I would be looking at more than just the head? No2 piston looks like it's been attacked internally bits of the edge of the piston look to be missing and all the register marks in the crown suggest something had entered the bore.
Very well spotted! You’re right. Piston 2 is damaged.
Could the OP post a picture of piston 2 at the very top of its stroke and also at the very bottom looking for scoring of the bore?
Stephen
1969 1098cc Convertible “Xavier” which I have owned since 1989.
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