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Classic Mini fitting 1275 cylinder head to 998 / 1100 A-series engine everything you need to know
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- เผยแพร่เมื่อ 28 เม.ย. 2020
- Everything you need to know about fitting the 1275 cylinder head onto a 998/1098 small bore A-series engine block. A complete how to guide. It's not always necessary to pocket the block to clear the exhaust valve as this video explains, watch on to see how.
Classic Mini, Classic Mini Cooper.
Oil gangway between head and block for the rocker shaft never lines up the hole in the head needs stretching over
Great video and very helpful for doing the head conversion. Another option for the waterways is to dry deck, either with something like MED's gasket or plugging the water ways in the block deck.
Thanks for the positive comment. Yes that’s an option and something I covered in this video:
th-cam.com/video/t3TESvji4Ts/w-d-xo.html
Unfortunately I forgot to mention it in the 1275 head conversion video.
Great video, lots of great information in one place 💪🏻
Mini Matt TV thanks mate.
Excellent stuff- thanks Phil 👍🇬🇧
You're very welcome.
Mate, what a great summary of all the important points! ^^
This video was suggested to me today, I did not know your channel before. With such good content, I could only subscribe to your channel directly and also activated the bell, so I do not miss anything!
Keep up the good work, greets from Germany. :o)
Thank you for your kind comment. I’m really glad you like the channel and found the video useful it’s much appreciated. Regards. Phil.
top stuff Phil!
Harry Palmer thanks mate.
Buy How To Modify Your Mini by David Wizard, or one of his later books Tuning The A-series and you'll get plenty of info about how much valvelift various camshaft will give you. If the 1275cc/12G940 head havent been skimmed at all there should be 7,2mm from heads face to face of the valve, add another 0,7-0,8 for the head gasket and you will be able to work out it will work with the factory camshaft with 7,1mm valvelift fitted to pre A+ engines. Did this to a Mini about 25-30 years ago and gained 15mph top speed just by changing the 998 head and gasket to the 1275cc ones. Didn't make any valve pockets at all. Calculated a gain in compression from 8,3-1 to 9-1 by this. This at a total cost of a tenner back then. Value for money!
Yes it can certainly work out a pretty cheap conversion compared to buying a modified small bore head.
It's always best to measure everything though as rocker ratios, valve depths etc can all vary. Better safe than sorry.
Another great video Phil, thank you. For a fast road mini would the overall results be similar if a 12G295 head was to receive larger valves, say a 33/27 valve combination with back cut mods, three angle valve seats, leave the porting as is and skim the head to increase the compression a bit?
Thank you. A 295 as modified in this video would give better results.
th-cam.com/video/mA3iIG1ddSY/w-d-xo.html
Though fitting a standard 1275 head is usually far cheaper so for the cost involved is usually the preferred option.
@@TurboMinicom Thanks Phil.
Thanks for this Phil. I can't seem to find dyno figures anywhere for this setup running on the road with a mild cam anywhere. Seems to be conflicting opinions about loss of torque low down, or not?
adam beckett there will definitely be some loss in torque low down due to the large ports on the 1275 heads promoting poor velocity. That’s why I mention in the video keep the ports standard size and keep the smaller 33mm inlet valve for best results on the road.
But the improvement in airflow will give decent gains higher up.
Good vid would u be able do a more in depth how to on measure valve lift please
liam wallace I’m not sure there’s enough to make a full video of just that. It’s pretty simple, using a DTI gauge on one of the exhaust valve top caps, zero the dial when the valve is fully closed and simply rotate the engine until the valve is fully open and read off the measurement on the DTI. Hope that makes sense.
liam wallace check out Adam Campion he has just released part 1 and 2 of him fitting a 127( head on a 998
Turbo-Mini.com it does cheers :)
Mini Matt TV ive seen them mate cant wait for next vid :)
On a road goin 1293 in hot climate is an electric water pump better or useless? Great videos!
Used in conjunction with an intelligent controller to vary the speed according to the engine temperature, a decent electric pump works really well, but isn’t cheap & is unlikely to have the lifespan of a good mechanical pump.
There’s a lot to be said for the reliable simplicity of a good mechanical pump.
Glad you’re enjoying the videos & thanks for commenting and subscribing. Much appreciated.
Great video mate but if you sink the ex valve wont it start opening sooner effecting compression or does it not matter as its on ex stroke?
Hi Sean. The cam controls the opening/closing of the valve, so sinking the valve won’t alter when it begins to open or close.
can you link that measuring tool for the lift distance?
It’s called a depth mic. Just search eBay etc and you should find one.
@@TurboMinicom cheers
So is it possible just fitting to the block without pocketing the block!?
Just sinking the valves 40 thou !?
As it explains in the video, It all depends how much clearance you need. If sinking the valves gives you enough, then it’s certainly an option.
what's difference between 1098 moggy head n 1275 head?
It’s a completely different casting, so the porting is larger as are the valve sizes on the 1275.
Don't like that concept of block pockets....it must destroy the headgasket sealing of combustion chamber?
The 998/1098 bores are much smaller diameter than the 1275 blocks & as you’re using the 1275 gasket to match the head, the gasket fire ring sits outside the diameter of the pockets. So there’s no issues with the gasket being undermined.