61x Ported cylinders

Req

Req

Location
SW Tenn
From what I have read 83mm is safe and 84mm is too thin for a lot of peoples comfort. I hear they are like paper at 84.

Correction.... 84.5 seems to be safe.
 
Last edited:
Req

Req

Location
SW Tenn
Are they big bore sleeves? You may have a set of sleeves dropped in for BB applications. If thats the case its like 86.5 or something for max bore.
 
Req

Req

Location
SW Tenn
I guess my local guy is even more conservative, He was scared of the thought of going to 84. That is great info, it means I will have an extra bore or two on my 83mm motor I am building. I was thinking it was going to be game over for it if ever needed a bore. Sorry for passing along bad info.
 
bored&stroked

bored&stroked

Urban redneck
Location
AZ
I actually asked groupK about it. On the 701 mods page they talk about 84mm being max bore. But on the project square nose rec boat they built they state they bored to 84mm leaving 2 more oversizes to 84.5mm for later. They said the rec boat was lower compression and lower RPM so thats why they felt safe going that far. I have 84mm 61x cylinder and its holding up fine so far on its second season.
 
J

joelake

Location
Australia
I actually just purchased a cylinder from a guy on here (good dude) that was questionable at 82 or 83mm. My machine guy said that it might not clean up at 83mm, so go for 83.5mm. no dice, couldn't find an 83.5. so next option was an 84mm, that's a stock 760 BTW. He reckons it was A ok at 84mm, but said care would be needed by the machine operator to not break the bottom of the sleeves off while doing the bore/hone work. 61x cylinder. Standard sleeves.

Will be getting it machined tomorrow.....
 
Blue

Blue

Judging your cheapness
Location
St Cloud Florida
84mm is not a problem on a 61x cylinder. I have done many at 84mm and a few at 84.5 but thats the max. The cylinder gets very thin around the tapered intake ports windows so extra care is used when chamfering the ports but other than that is fine. If you bore to 84 dont forget to replace your head domes with the larger 760 domes which fit 84mm to 86mm bores instead of the 701 domes which fit 81mm to 83mm bores.

Sent from my SM-N950U using Tapatalk
 
bored&stroked

bored&stroked

Urban redneck
Location
AZ
joelake said:
He reckons it was A ok at 84mm, but said care would be needed by the machine operator to not break the bottom of the sleeves off while doing the bore/hone work. 61x cylinder. Standard sleeves.
Click to expand...

When you port the cylinder you cut the bottem of the sleeves off on the intake side anyways.
 
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