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OS max 12cv help

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Hardesty

Hardesty

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I have a OS max 12cv that you guys helped me free up I got it used my question is it looks like something is missing under head is there supposed to be a shim or something there. Does the head seat down into sleve or sit on top? This one is sitting on top of sleve.
 

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Last edited:
It's hard to tell, but it looks like the head screws are not tightened properly and the sleeve is sticking out.
 
ninnon said:
It's hard to tell, but it looks like the head screws are not tightened properly and the sleeve is sticking out.
Click to expand...
They are tightened down all way it seems like there is supposed to be something between head and block but I'm not sure. Could it be wrong cooling head?
 
google images of it to verify some of the images looked pretty similar to what you have.
 
It's hard to tell. Can you get it under a bench light without the flash, or try to get the flash to not light it up so much?

If there is a shim, it's only .01/.05mm, so it's not thick to eat up the gap you see there. To me, it almost looks like your sleeve isn't seated properly. Pretty much every engine I've ever had, the sleeve would be flush or almost flush with the crank case when installed properly, then the head shim (usually brass or aluminum) is there just to make a good seal (and to have proper compression) between the head button and sleeve.
 
olds97_lss said:
It's hard to tell. Can you get it under a bench light without the flash, or try to get the flash to not light it up so much?

If there is a shim, it's only .01/.05mm, so it's not thick to eat up the gap you see there. To me, it almost looks like your sleeve isn't seated properly. Pretty much every engine I've ever had, the sleeve would be flush or almost flush with the crank case when installed properly, then the head shim (usually brass or aluminum) is there just to make a good seal (and to have proper compression) between the head button and sleeve.
Click to expand...
Yeah just don't look right the sleeve is in the notch that it's supposed to be so I have no idea what's going on
 
olds97_lss said:
Does the head move at all? In the photo's, it appears there's a gap between the head button and sleeve, but is hard to see.
Click to expand...
No it's tight up against sleeve but it just don't look right it looks like something is missing I don't know enough about nitros to know

olds97_lss said:
It's hard to tell. Can you get it under a bench light without the flash, or try to get the flash to not light it up so much?

If there is a shim, it's only .01/.05mm, so it's not thick to eat up the gap you see there. To me, it almost looks like your sleeve isn't seated properly. Pretty much every engine I've ever had, the sleeve would be flush or almost flush with the crank case when installed properly, then the head shim (usually brass or aluminum) is there just to make a good seal (and to have proper compression) between the head button and sleeve.
Click to expand...
I guess what I need to know does the head seat down into sleve or sit on top?
 
I want to say it varies... you'd think with all the engines I've had apart, I'd remember better, but I don't. I want to say though, part of the button usually goes inside the sleeve a few mm, then along the rim is a shim to seal the button the the sleeve.

Like here is what I remember:
xtm28.webp


The brass/copper colored thing on the button head in his hand is the shim. The ring inside that shim goes into the sleeve a mm or 2, then the shim compresses between the button and the sleeve rim making the seal.
 
olds97_lss said:
I want to say it varies... you'd think with all the engines I've had apart, I'd remember better, but I don't. I want to say though, part of the button usually goes inside the sleeve a few mm, then along the rim is a shim to seal the button the the sleeve.

Like here is what I remember:
xtm28.webp


The brass/copper colored thing on the button head in his hand is the shim. The ring inside that shim goes into the sleeve a mm or 2, then the shim compresses between the button and the sleeve rim making the seal.
Click to expand...
Ok I know I'm missing shim then but my head is not seating at all down into the sleeve I really appreciate all the help
 
I wonder if you have the right head button. Is it a two piece head/button or one piece head with button milled into it? That varies too.

I used to run an OS 15 cv-r(x) in my xxx-nt and tried one in my t-maxx (underpowered for that).
 
olds97_lss said:
I wonder if you have the right head button. Is it a two piece head/button or one piece head with button milled into it? That varies too.
It's a one peice head
I used to run an OS 15 cv-r(x) in my xxx-nt and tried one in my t-maxx (underpowered for that).
Click to expand...
 
my main point was to show the OP how thick the lip is on the sleeve, and for them to look at both links so they can see several different images of the engine.
 

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