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OPS .40 cylinder head

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timothy johnson

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Jul 9, 2011
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1,210
Yes mine came with aluminum .016 shim. Sounds like something is up with your bore!! also remeasured the bore and .866 is more like it. Sorry.
 
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Terry Keeley

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Jul 24, 2002
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6,239
I wasnt thinking when i said id get a measure on the rod. The engine is all buttoned up, besides the head. Im not taking it back apart, I hate cleaning loctite out of screw holes 😂 so i guess well never know. I did measure the bore though, it is .863; also, at TDC, the piston is .154 below deck, Terry, do you have one of these engines that you could compare with?
I ran the 45's back about 30 years ago, lol.

I remembered I had a book of old specs and the 45 had a 22mm (0.866") bore and 19.75mm (0.778") stroke, sounds like either the 40 and 45 had the same bore or the 45 piston/liner drops in and that's what you got.

Does your motor say "40" on the case? Can you measure the stroke?
 

MarkKing

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Sep 1, 2020
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I ran the 45's back about 30 years ago, lol.

I remembered I had a book of old specs and the 45 had a 22mm (0.866") bore and 19.75mm (0.778") stroke, sounds like either the 40 and 45 had the same bore or the 45 piston/liner drops in and that's what you got.

Does your motor say "40" on the case? Can you measure the stroke?
The engine casing has “40” cast into the side of it. From what Timothy said about his .45, id say ive got a .40 with a .45 piston and liner in it!
 

MarkKing

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Joined
Sep 1, 2020
Messages
23
I
I ran the 45's back about 30 years ago, lol.

I remembered I had a book of old specs and the 45 had a 22mm (0.866") bore and 19.75mm (0.778") stroke, sounds like either the 40 and 45 had the same bore or the 45 piston/liner drops in and that's what you got.

Does your motor say "40" on the case? Can you measure the stroke?
I could measure the stroke, but that would mean tearing the motor back down, I dont want to do that 😂 I suppose i could zero an indicator out on the top of the piston and turn it over once, but knowing the stroke really isnt going to help me any. Im just gonna solve my head clearance issue, and run it.
 

Terry Keeley

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Jul 24, 2002
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6,239
I could measure the stroke, but that would mean tearing the motor back down, I dont want to do that 😂 I suppose i could zero an indicator out on the top of the piston and turn it over once, but knowing the stroke really isnt going to help me any. Im just gonna solve my head clearance issue, and run it.
Pretty easy to get the stroke as you mentioned, that might solve the mystery of why the head is loose and hits ATDC.

Maybe you got a 40 head in a 45 motor? 😃
 

MarkKing

Member
Joined
Sep 1, 2020
Messages
23
UPDATE
Made major headway with the cylinder head for this little engine this morning; it should work! Chamber volume is right at .4 cc and squish will be .011 with a .020 shim. I have yet to tap the hole for the glow plug, tap should be in before the end of the week. Im still hunting for shims, if anyone has a few, i will buy them from you! I really dont want to have to make them 😂
 

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MarkKing

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Sep 1, 2020
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Thanks guys. Its coming together slowly. Should be able to run it by early next week
 

Terry Keeley

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Jul 24, 2002
Messages
6,239
UPDATE
Made major headway with the cylinder head for this little engine this morning; it should work! Chamber volume is right at .4 cc and squish will be .011 with a .020 shim. I have yet to tap the hole for the glow plug, tap should be in before the end of the week. Im still hunting for shims, if anyone has a few, i will buy them from you! I really dont want to have to make them 😂
What did you make it with?
 

MarkKing

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Joined
Sep 1, 2020
Messages
23
Well been awhile since ive given an update on this little engine. Progress halted with deer season, but my season came to an abrupt end so back to it! I sourced another exhaust pipe, I think it will work well, time will tell. Turned a short header for it, hopefully the divergent taper doesnt mess with exhaust pulses too much. Also made a flange to secure header in the coupler; all im waiting on now is the spring for header, and fuel to get to the lhs, and ill run it a bit to make sure all is well.
 

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