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998 To 1275 Plumbing Question


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#1 Seato65

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Posted 31 December 2016 - 06:15 PM

I have just got hold of a low mileage 1986 1275 metro engine which I am going to put into my 1990 mini checkmate 998. I think I am ok with all the mods I need to make apart from the plumbing.

I think I need to drill the head so I can use the heater outlet hose from the 998 and use the themostat from the 998 instead of the metro sandwich unit.

Is that all I need to do? I'm a bit confused by comments on other posts about holes in thermostat and lack of return hoses.

If I drill the head (top left) is that something I need done by a pro or is it just a plug?

Any advice gratefully received but can we stick to the plumbing as I'm ok on the rest.

#2 neal

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Posted 31 December 2016 - 07:12 PM

I have just got hold of a low mileage 1986 1275 metro engine which I am going to put into my 1990 mini checkmate 998. I think I am ok with all the mods I need to make apart from the plumbing.

I think I need to drill the head so I can use the heater outlet hose from the 998 and use the themostat from the 998 instead of the metro sandwich unit.

Is that all I need to do? I'm a bit confused by comments on other posts about holes in thermostat and lack of return hoses.

If I drill the head (top left) is that something I need done by a pro or is it just a plug?

Any advice gratefully received but can we stick to the plumbing as I'm ok on the rest.

This is quite a straight forward job and can be done easily if you have basic tools, but before you drill, centre punch the blanked portion on centre then use a small pilot drill about 2.5- 3mm.

 

Then in stages go up in drill bit sizes until you drill out the blanked off portion, If I were you I would probably use the vacuum cleaner at the same time to remove the bits of swarf so they don't go into the water jacket.

 

The threads should already be tapped (1/4" unf) so you don't need to worry about that, but I would give the threads a clean out and use a little oil or grease on the threads when installing the heater take off pipe, oh and don't go too bonkers tightening them up as they will shear and then you will have problems.



#3 Seato65

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Posted 03 January 2017 - 04:47 PM

Thanks Neil. That sounds straightforward enough. Do I still need to drill the thermostat or will this mod negate that requirement?

#4 neal

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Posted 04 January 2017 - 11:55 PM

Thanks Neil. That sounds straightforward enough. Do I still need to drill the thermostat or will this mod negate that requirement?

Good question.... the answer will depend on who you talk to, but a thermostat should, or at least they used to have a little hole with a jiggle pin or sometimes a bleed notch instead.

 

Either way, a jiggle pin or bleed notch allows trapped air in the cooling system  (hot spots in the water jacket causing bubbles) to pass through the thermostat and be released from the system into the top of the radiator.

 

The jiggle pin/bleed notch helps in pressure equalisation below and above the thermostat and aids a smoother operation of the thermostat to open and close. The operating temp will be stamped on the thermostat, different operating temperatures can be purchased to suit different applications.

 

I would probably avoid drilling the thermostat and buy a good quality item, if I remember correctly the summer stat is 74 degrees C and the winter stat is around 82 degs C. It might be worth purchasing both to see which one suits your car best.



#5 Seato65

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Posted 08 January 2017 - 08:09 AM

Thanks again Neal, I'll get both and give it a go. Drilled the head yesterday - all pretty straightforward.




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