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12G295 HEAD
Posted: Wed Apr 09, 2003 10:22 pm
by stormin
Hi people,
I am new to MMOC and MOGGIES, I have just aquired one of the above and wondered if anyone could tell me what the correct height of the head should be.
I dont know if the head has been machined before and so I need a 'benchmark' to start from.
The engine I am rebuilding is going into a Traveller/pickup conversion project. All comments/info gratefully accepted.
Thanks
Posted: Thu Apr 10, 2003 7:47 pm
by les
The head thickness is normally 2 3/4 inches.(2.75). If u use the head on a 1098cc minor it will need to be skimmed as the chambers have more volume than the standard item.
12G295 Head
Posted: Thu Apr 10, 2003 8:32 pm
by stormin
Thanks for that Les. I know the head needs skimming but I didnt want to End up taking 0.1 or more off when allI wanted off was 0.060! or even worse!!
Posted: Thu Apr 10, 2003 9:09 pm
by les
The think the amount u can remove is largely dependant on the depth, horizontally, of the oil feed hole to the rockers. As you probably know it's quite a good head, without much need for modification.
Posted: Thu Apr 10, 2003 10:17 pm
by Daddsie
I've put a 12G940 on my 1098, should I have skimmed it before fitting as performance is nothing to write home anbout.
Posted: Fri Apr 11, 2003 8:38 pm
by les
You sure it's a 12g940 daddsie!
Posted: Fri Apr 11, 2003 10:11 pm
by Daddsie
Why?
Posted: Fri Apr 11, 2003 10:12 pm
by Daddsie
Its a huge valve, ported ex metro head.
Posted: Fri Apr 11, 2003 10:42 pm
by rayofleamington
12G940 - nice one!
That's what used to be on my first 1098. It was rather good! (I checked the casting number recently after another thread suggested the Midget 1275 head would not be OK for a 1098 Minor)
And I checked the nymber on my midget 1275 cylinder head - Also 12G940, so fromk thatr I would conclude that a Midget 1275 head is OK on a 1098 Minor engine.
anyway, the 12G940 has very big valves so I was going to check valve lift on a standard minor cam to see how much the valves actually clear the block.
My first 1098 also had a 1.5" carb and a larger exhaust, and it really had some guts.
Posted: Fri Apr 11, 2003 10:46 pm
by les
Becauce I thought the cylinder spacings were different on large bore heads. Have you seen the number 12g940 on the item?
Posted: Fri Apr 11, 2003 10:58 pm
by rayofleamington
the big valve head from my first Minor says #G 94# as the first and last digits were machined off.
I checked it by eye with a plastic ruler (dead accuracte...) and it was identical to the Midget one where the 12G940 is fully visible.
The cylinder spacings may be different so I'm going to make a cardboard template to check the valve overlap with the block.
There's 2 possiblilities:
A)
the valves do overlap, but the lift on a standard cam may not push them far enough to hit the block?
Therefore for the second part of my test I'm going to measure how far the valve moves based on the standard cam.
or
B)
the valves do not overlap the 1098 block. ?!?
Once I've looked at it I'll be happier to know the limitations for recommending the 12G940 head - as it may only be suitable with standard valve lift and with a limited amount of skimming, it may be a bad move if someone already has a high lift cam / high ratio rockers.