Sheepers other MS75 crown coupe

[sheepers]

Ive been continuing to pick away at the 7M motor.

@Roman dave made me some prototype pistons to try out some things.

with my big cams and increased lift there is still a million rooms between the valves and the pistons. im never going to keep this a non interference engine if im aiming for 11 to 1 so i might as well re-think the whole piston dome situation.

all those years building stupid two stroke engines might just pay off after all........

upshot is that i can run bigger valves without any clearance issues - only thing limiting this really is the 5M head's fondness for cracking between the valves and the spark plug hole.

the other thing ive done is to sort out the cambelt/front pulley drive on the front of the crank.

5Ms have a stepped crank at the front and the cam pulley has a larger internal diameter than the crank pulley, 7Ms do not, the 7M crank pulley is larger internal bore than the 5M.

 

so i machined the front of the crank and cut a new keyway in the crank so i can run the 5M pulleys on the 7M crank.

i did spend 2 hours machining the crank only to find that it was bent and the middle journal was running out by half a millimeter. i had a spare crank so i just used that in the end.

 

2022-04-10_04-22-50 by sheepers, on Flickr

 

2022-04-10_04-23-10 by sheepers, on Flickr

 

2022-04-10_04-22-58 by sheepers, on Flickr

 

2022-04-10_04-22-44 by sheepers, on Flickr

 

2022-04-10_04-22-30 by sheepers, on Flickr

 

 

2022-04-10_04-22-37 by sheepers, on Flickr

 

2022-04-10_04-22-22 by sheepers, on Flickr

 

2022-04-10_04-22-14 by sheepers, on Flickr

 

[sheepers]

fucking 10 years latter....

we were trying to sell our house and that fucked up many things including any progress on this engine.

 

anywho,

here we are. ive been doing many measuring and many modeling of things and i am 99% sure i have a piston shape that clears the bigger valves and the increased lift but yields 11.5 to 1.

i figure if the CR is too high i can remove material but if its too low that's a bit harder to fix...

so yea now i need to do a final check of piston clearance and then find someone to make a set of them to my drawing.

ill start the ball rolling with getting the head work done too.

with the head sorted and the pistons under control the rest of the project seems like its achievable.

however we shall see. 

still got a whole ITB system to craft for this as well as many other things.