84mm bore on 61x top end???

[slickrick22]

Have a 61x topend ported and bored to 83mm. Have light rub on one of the side walls of the cylinder. I was told I may be able to bore it to 84mm. Is this an acceptable size to go?? I've heard mixed answers to this.

 

[augustaf]

I had a 61X cylinder bored to 84mm a few years ago, widened exhaust ports too. The sleeve walls look scary thin, but it's been holding up quite nicely. I often wonder if the "mixed answers" folks have actually done it and with what results.

 

[Nuklear6]

I've bored dozens of 61x cylinders to 84mm. So has @powerhouseperformance I know for a fact.

 

[Pro-pulsion]

I am currently working on a blaster with 61x cylinders bored to 84mm. I believe you need 760 domes or a stock 760 64x head and gasket though to run it.

 

[X2Kid]

Group K claims safely 83 mm on a 61X and 84 mm on a 62T. I think 83 mm is the limit on a 701 head gasket.

 

[stefan]

I have seen a couple off 61x bored too 84 hade a 62t my selv bored too 86, Group K is a bit conservativ but have lots off great info.

 

[slickrick22]

I am currently working on a blaster with 61x cylinders bored to 84mm. I believe you need 760 domes or a stock 760 64x head and gasket though to run it.

So I can't put my ada head back on this top end if I bore it out to 84mm?

 

[Pro-pulsion]

You sure can, you just need 760 domes now. ADA makes these heads compatible with only needing a change of domes. From what I have been told, you can also run 760 domes on a 701 bore. If you want a pair of nice condition 31cc 760 domes shoot me a pm, I have a pair I will never use.

 

[Quinc]

I am on my third season 61x @ 84mm with 701 37cc ada domes on my blaster with no issues.

 

[bored&stroked]

GroupK claims 83mm in one place [701 tech info] but then claim 84mm in the restomod square nose build using a 61x cylinder.

 

[JetManiac]

I've bored dozens of 61x cylinders to 84mm. So has @powerhouseperformance I know for a fact.

As have we at JetManiac, Blue has built many for us with 84mm bore on stock sleeves. As said above, you should swap to 760 domes for use with 84mm bore.

 

[Nuklear6]

Can also machine the 701 ada domes on the lathe to accept the 84mm or larger bore. Cost is $12 each. Much cheaper then buying new domes. Just FYI.

 

[tomski]

Clean up the sleeve and check the bore. Use it at 83mm if possible.

 

[tntsuperjet]

I have done a few and I have had several customers bring them with the skirts broken off at the base as the 61x steps down.
62t has more meat on bottom of sleeves.
I believe 83.5 is pushing limits for anything I will build with my name on it.
There are heavy sleeves that don't have step cut in bottom that hold up at 84mm in 61x