lotus twincam pistons in 1800 xflow

[DBU88Y]

can anybody make sense of these markings? have been told the pistons are lotus twin cam

[westwood35]

They look like Twin cam pistons. the 1.016 means they are +0.040" Oversize. (0.040" x 25.4 = 1.016mm)

[DVandrews]

Yup, they do look like twink pistons, the clue is in the reliefs for the valves.

Dave

[DVandrews]

Yup, they do look like twink pistons, the clue is in the reliefs for the valves.

Dave

[DBU88Y]

ok thanks guys, these are in a 711m block xflow so i take it the xflow and lotus twincam had the same bore as standard?

[westwood35]

Std bore in a X/Flow is 80.985mm. Std bore in Twin Cam is 82.55mm. Your engine is 2.58mm or 0.101" over std X/flow bore size!!!

[Sardonicus]

83.5mm bore in a x flow will get you 1700cc approx I used TC pistons in a X flow build many moons ago lovely light pistons IIRC

[Mr2Mike]

With the heron head don't you end up with a pretty awful combustion chamber shape using flat top pistons? (i.e. worse than the already not great design).

[Sardonicus]

Mr2Mike said:

With the heron head don't you end up with a pretty awful combustion chamber shape using flat top pistons? (i.e. worse than the already not great design).

I know but it does work and with the right BV head cam and CR with those pistons flies round the tacho like a 16 valve motor, a long time ago mind.

[DBU88Y]

im gonna have to try and find some vernier callipers, as when i measured it with a tape measure it came up at 84mm bore although i only did it quick so could have slipped a little!

the engine was sold to me as being a 1.6 dont worry, im far from disappointed! lol

heres the head, i believe it needs the ports opening up some more, i think the valves are 41mm and 36mm

Edited by DBU88Y on Sunday 22 June 14:16

Edited by DBU88Y on Sunday 22 June 14:37