I was looking at different cylinder heads and noticed that the one from 72-73 actually "looks" a bit better with some squish thing. Does anyone know if the volumes are equal and could I actually have some benefit of mounting a 73 head on my 75 or could it be used as an replacement at least?
GT 550 cylinder head difference
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Roos
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GT 550 cylinder head difference
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Allan k
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Re: GT 550 cylinder head difference
What the f.. 
I have 3 heads from the later engines, they are all domed.
These squish head should make it possible to run a higher compression without detonating problems..
Wanna sell?
I have 3 heads from the later engines, they are all domed. These squish head should make it possible to run a higher compression without detonating problems..
Wanna sell?
2-strokes are full of speed,
4-strokes are full of parts!
4-strokes are full of parts!
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tz375
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Re: GT 550 cylinder head difference
I was thinking the same thing. The 72 I just sold had the usual "open" no squish head on it. Were those welded and re-machined by any chance and are the ports stock or is that motor a bit special.
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Alan H
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Re: GT 550 cylinder head difference
Never seen squish heads on a 550 - and ~ I've seen/got a few!!
Can you post a pic of the complete head - top and bottom so that we can have a better look?
Can you post a pic of the complete head - top and bottom so that we can have a better look?
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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Vintageman
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Re: GT 550 cylinder head difference
Two pics at same scale?
If not maybe GT380 head? Just recently a couple were posted on ebay as GT550 heads and were really GT380.
If a GT550 that is awesome.
+1 post couple complete pics of it both sides please
If not maybe GT380 head? Just recently a couple were posted on ebay as GT550 heads and were really GT380.
If a GT550 that is awesome.
+1 post couple complete pics of it both sides please
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Roos
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Re: GT 550 cylinder head difference
Here are some more pictures:
So that could be an 380 head, I guess that one wont fit so well I guess?
So that could be an 380 head, I guess that one wont fit so well I guess?
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Alan H
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Re: GT 550 cylinder head difference
That's not a 550 head. It looks like a 380 head.
Here's a pic of an early (1972 K) head. Look at the differences in fins etc. The centre of the head (middle cylinder part) protrudes where the 380 is 'flat' all the way across.
Must admit, I've never stripped a 380 so I don't know what the inside of the head is like.
Here's a pic of an early (1972 K) head. Look at the differences in fins etc. The centre of the head (middle cylinder part) protrudes where the 380 is 'flat' all the way across.
Must admit, I've never stripped a 380 so I don't know what the inside of the head is like.
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Roos
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Re: GT 550 cylinder head difference
Yes I think so to, after a little google for 380 then this type of head pops up.
380 is 54x54mm (?) so fitment on a 550 would be hard, to bad!
380 is 54x54mm (?) so fitment on a 550 would be hard, to bad!
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tz375
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Re: GT 550 cylinder head difference
How close is the bore spacing? I don't suppose there's any chance it could be used is there?
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Roos
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Re: GT 550 cylinder head difference
I don't have it (its on ebay). It's rather low priced so maybe I should buy it and see if it can be modified but it would be good if the square measurement is at least close to the 550. Piston is 3.5mm radius smaller so that should be in the range of doable modications..
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old racer
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Re: GT 550 cylinder head difference
So long as the cylinder stud spacing are the same maybe devide it by three.
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Craig380
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Re: GT 550 cylinder head difference
It certainly looks like a 380L/M/A head.
For what it's worth, the spacing between the centres of the stud holes on a 380 head is 57mm. The bore is 54mm, of course.
For what it's worth, the spacing between the centres of the stud holes on a 380 head is 57mm. The bore is 54mm, of course.
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Roos
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Re: GT 550 cylinder head difference
Stud spacing on 550 is 62mm so it will get a bit tricky, made a very simple cad model (please tilt head)
As seen it will be a bit narrow close to the studs and I guess the outside square is to small as well.
The outer ring would need some work (57->61) and even after lot of work this would not be so good after all.
As seen it will be a bit narrow close to the studs and I guess the outside square is to small as well.
The outer ring would need some work (57->61) and even after lot of work this would not be so good after all.
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Suzukidave
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Re: GT 550 cylinder head difference
Easy .. machine out the 550 head and put in squish inserts 
the older i get the faster i was
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tz375
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Re: GT 550 cylinder head difference
^^+1^^
Or weld up the head and machine it to a new shape.
Or weld up the head and machine it to a new shape.
