Differences in Headdesign 1275

[MMT1968]

Hi all,

Does anyone know if there have been differences
in Head design in 1275 heads, i.e. the positioning of water channels. I think I have read something about that somewhere and somewhen but I‘m not sure.
As the engine has been used in many different cars I can imagine that there have been changes over the years.

Chris

[Mr Spigot]

A lot of information here. You probably wish you had not asked!!
https://www.minispares.com/blog/2020/09/09/heads/

[MMT1968]

Puh! A lot of Information. Takes some time to read and understand.

Thank you!

Chris

[MMT1968]

Well, I read it. What I learned now is that 1275 heads fit any smaller engine. If it will work and be useful is written on a different sheet of paper. But water and oil channels are the same.
Thanks for this information!

The reason for me to ask is simple. In my tuned 1275 marina engine the head gasket has blown off for the 3rd time now and in each case it has lasted less than 500 miles. The damage was at the same place always: between 2nd and 3rd cylinder and we realy don’t know why nor do we find the reason. The head was torqued down to 68nm but we kept the head bolts an nuts. This time we‘ll use ARP bolts an nuts. Maybe that’ll be the winning step?
The engine has been rebuild from bits and pieces using the best new parts without compromises. The head has been professionally refurbished, ported and got bigger valves. Compression is rised to 10,7:1. Cooling system is cleaned throughout with new water cooler and bigger waterpump. An additional Davies Craig EBP 40 booster pump is installed to improve the coolant flow from the heater outlet to the water cooler inlet. Ignition has been set back a Little.
So we did everything I guess but have not found the reason for the blowing head gasket.

Chris

[les]

What a coincidence, I came across that site last Friday, before this thread was started. I tried to post a link as it was so comprehensive regarding heads. I couldn’t do it for some reason. So well done Mr Spigot.

[philthehill]

You do not mention if the top of the block or face of the head has been machined.
If you have not had those surfaces machined I would suggest then that is the problem.
Fitting ARP studs/nuts will not cure the problem if the basics are not right.
The basic Marina/Ital 'A' Plus studs and nuts are more than adequate for the spec of your engine.

[MMT1968]

Hi Phil,

The surface of the block and head have been machined each time the head gasket failed. That is standard procedure.
The engine as been rebuild after the last gasket failure by a very expierienced and good recommended professional engine builder, not by myself. The gasket had failed on a rolling road test that has been performed by a well known Test workshop. In that case it was not only the head gasket that failed but the piston of #3 was damaged as well as one inlet valve. That’s why the engine was completely rebuild. But now we do know exactly the same as before.

Chris

[philthehill]

Chris
My engine is based on a Marina/Ital with all the bells and whistles and in original form produced 145bhp.
All the engine building except for the professional machining is undertaken by myself so I have form in building and tuning 'A' Series engines. I am also a time served qualified BMC mechanic/technician.
Therefore based upon my 'A' Series experience I am going to give a qualified questimate on what I believe may have happened (or not ).
Were the valve guides reamed after fitting to 9/32" minimum?
A common fault with engines on rolling roads is that the process generates local hot spots. Was a external cooling fan employed to cool the engine as well as the engine fitted fan?
I think that what has happened is that a local hot spot has been generated, the inlet valve was in a tight valve guide, the valve picked up and stayed open in the wrong stroke so coming into contact with the piston causing damage to both piston and valve. If the head and block have been excessively machined the clearances will be very tight and will leave little room for the likes of a picked up/seized valve.
When I assemble a modified engine I always place a knob of plasticine on top of the piston fit the head with a used head gasket and when assembled turn the engine over several times. I then take off the head and see what has happened to the knob of plasticine. The process gives a very good indication of what clearances you have inside the cylinder/head.
That localised hot spot could and may have instigated the head gasket failure.
Unleaded fuel does not help with dealing with local hotspots as it has no lubricating qualities.
My advice is to make sure that the valve guides are reamed to give sufficient clearance and keep away from rolling roads unless there is a external fan employed.
Good luck and keep us informed on what you find and what you do to overcome the problem.
Phil

[MMT1968]

Phil,
Many thanks for your reply. To answer your questiones, yes the valve guides were reamed and yes an external fan was used. In the first case the shop had forgotten to switch on the fan and surprise surprise the head gasket was blown off. That’s why they had to pay for the engine rebuild. But in the actual case it happened on the road. I had just picked up the car from a paint job and was driving home. For the first 8km all was well, engine running perfectly, never exeeded 3500 rpm, temperature max 85°C. After 5 km on a motorway driving at 3800 rpm there was a sudden lack of power and as I stopped I heared it running on just 3 cylinders. Temperature was 85°C then.
So it was not on a rolling road this time and no overheating as far as I know so far. The car is now at the engine work shop again as they have to cope for the repairs.
The car is equipped with two electric fans instead of the normal two blade mechanical fan. These fans do work perfectly and there is a termal switch build in the watercooler next to the bottom.


Chris

[philthehill]

Thanks for the update.
Did you personally see the engineers machine the top of the block and face of the block or was it by word of mouth or appeared on the bill?
Personally even though it has been stated that the machining has been done I would be checking the top face of the block for flatness and hollows.
I would do the same with the cylinder head combustion chamber face.
I would go right back to basics and check everything.
Phil

[MMT1968]

The machining of block and head appeared on the bill and I‘m confident it has been done.
The company is going back t to basics surely as they don’t want to do those repairs for free. It’s a case of guarantee but they keep me informed on every step and in the picture.

Chris

[philthehill]

Make sure that you have clearance between the water pump and head. It is not unknown for the head to be resting on the water pump body especially if the head and block have been skimmed and a after market water pump used. The head resting on the water pump body does not allow the head to be fully pulled down leading to head gasket failure.

[MMT1968]

Good to know! Thanks

Chris

[ndevans]

Mine is a Marina 1275 bored to about 1293, with big valve head, though not tuned to anything near 145BHP. I had problems with head gaskets lasting 12-1500 miles, I went through 3 in the space of a year. I had the head machined square, and 12000 miles later that seems to have cured the problem *touches wood*. I also fitted a heater valve with bypass so there is always water flow to the back of the head.
Quality head gasket is worth paying for, I got mine from Minispares, although I can't quote off hand exactly which.

[MMT1968]

Good to know that I‘m not the only one…
But what drives me crazy is not finding the real reason for the head gasket blowing away.
Do only Marina engines have problems like these? Is it the same in transversal mounted 1275 engines? What about Cooper S 1275? Do these engines have similar problems?
Even if I think about much longer I can not imagine anything else I could do to prevent another head gasket failure after a few miles. I have done much more than others but with no changes. If I‘ll have to scimm the head again and again the compression rises each time. Now we are at 10,7:1 so there is not much room for further scimming actions I‘m affraid.

Chris

[philthehill]

Marina engines properly modified/built do not have problems.
The same cooling/head gasket problems may be found throughout the 'A' Series range.
Skimming the head is limited to the thickness of the metal between the face of the head and the horizontal oilway feeding the rocker gear.
Saying that it has been known for a horizontal transfer pipe to be silver soldered into the face of the head when too much has been skimmed off the head which results in breaking into the horizontal oil way. If you have a very expensive modified head it may be cheaper to fit the horizontal pipe instead of starting from scratch.
You must have a minimum of 0.040" between the bottom of the vertical oil transfer passage and the head face.
To determine the depth of metal between the head face and the bottom of the vertical oil transfer measure the depth of the hole from the top face of the head and take that off the overall depth of the head and that will give you the depth of the remaining metal. Less than 0.040" then you may/will have problems.
The standard depth of a 'A' Series head is 2.75" so anything less than that will give you a good indication of how much has been previously skimmed off the head
My advice to you is that when you rebuild the engine check and measure everything yourself - do not rely on what you are told.
Phil

[les]

[quote=philthehill

My advice to you is that when you rebuild the engine check and measure everything yourself - do not rely on what you are told.
Phil
How true that is.

[panky]

If you use the Minispares OEM or Victor Reinz composite gaskets they need to be 'conditioned' once fitted. The engine should be run for a couple of minutes without coolant to get things warm and activate the coating on the gasket. Once cooled fill with plain water for a couple of hundred miles as the gasket absorbs the water to expand the fibres, it's been found in the Mini community that filling with anti-freeze immediately will cause the gasket to 'weep'. Remember to re-torque after the first heat cycle.
I was blowing copper gaskets on my Mini Cooper and Morris Traveller but since fitting the Minispares gasket, and following that procedure, I've had no issues since. Engine in the traveller is a 1098 with 12G940 head with 1 1/2" SU and 'sports' exhaust.

[ndevans]

If you use the Minispares OEM or Victor Reinz composite gaskets they need to be 'conditioned' once fitted. The engine should be run for a couple of minutes without coolant to get things warm and activate the coating on the gasket. Once cooled fill with plain water for a couple of hundred miles as the gasket absorbs the water to expand the fibres, it's been found in the Mini community that filling with anti-freeze immediately will cause the gasket to 'weep'. Remember to re-torque after the first heat cycle.
I was blowing copper gaskets on my Mini Cooper and Morris Traveller but since fitting the Minispares gasket, and following that procedure, I've had no issues since. Engine in the traveller is a 1098 with 12G940 head with 1 1/2" SU and 'sports' exhaust.

Are they the green ones that look like they are made from fibreglass?

[panky]

This is the one from Minspares described as OEM





So far so good.