Learn Me GT380s

[Vintageman]

Craig380,

I think you said you measured straight across in the cylinder. I did a paper trace then laid the paper flat. So I was thinking that is why mine shows longer.

Is that true

For a paper trace I covered just the port I wanted so I could tape it in place on the cylinder wall so it won’t move. Them just use a soft pencil.

Update: Oops I did mess up the exhaust numbers as I looked again. repeated intake

I accidently found if you take tape (I used a black duck tape like stuff) and put it in the cylinder and rub over port and top of liner with your fingers it make a perfect sharp line in glue to measure from
Exhaust:

Top 1.280”/32.5mm 1.295”/32.893mm
Bottom 2.173”/55.19mm
Width 1.574”/39.98mm 1.426”/36.22mm widest

Intake:
Top 2.572”/65.33mm
Bottom 3.340”/84.84mm
Width 1.574”/39.98mm across both windows

Transfer:
Top 1.667”/ 42.34mm
Bottom 2.217”/56.3mm * Tried to exclude long factory chamfering
Width` 1.260”/32mm

[markush]

Hi !
I took some values, too.
Some are equal as posted above, some are different.
All my cylinder ports were in stock condition.
Bore 54,5mm, all.
all measures in mm.
width = chord (not circumferential).
Distances from cylinder top surface.

GT380B
average values of 3 cylinders. (one set of Left+Center+Right)
Outlet
width : 33,7
top : 33,4
bottom : 56,2
(heigth : 22,8)
Inlet
width: 36,8 (over all)
(center bar width : 4,5)
top : 65,5
bottom : 84,4
(heigth : 18,9)
transfers (measure for one)
width : 27,5
top : 43,4
bottom : 56,4
(heigth : 13)


GT250L/M
Shown values are averages of 4 cylinders. (two sets of Left+Right)
The range off differences between cylinders was max. 1 mm.
Outlet
width : 33
top : 32,5
bottom : 54,5
(heigth : 22)
small additional Outlets (measure for one. Lying at the same heigth/position as transfer ports)
width : 6
heigth : 12
Inlet
width: 36 (over all)
(center bar width : 3)
top : 66,8
bottom : 84,7
(heigth : 17,9)
transfers (measure for one)
width : 26
top : 43,3
bottom : 55,3
(heigth : 12)

Shapes of outlet ports of 250/380 are a bit different.

Auslassschlitz_GT250_380_dr.jpg