I have to bore out a spare block to complete my build. The shop says i need to go at least 0.013" over. So if I go 0.02" which is 81.5mm i'll be good. Should i just go the full 0.04" or 82mm overbore. He told me he has gone over 82mm on several honda stock blocks and they have not had any problems with all motor daily drivers. He said as long as i don't spray i should be fine with 82.5 and even 83. So would it be safe to go 82 now and if i had to in the future go 82.5mm?
Build Specs: USDM ITR pistons, gsr block and head, bc3 cams, supertech valvetrains and flat faced valves. Comp about 11:1. 91 octane locally.


Modified by all-mtr-teg at 1:58 PM 8/5/2007

 

82mm is the limit you should go on stock sleeves

 

yes, typically, when you bore you only go as much as needed to get out any scratches on stock sleeves. The more you bore, the weaker the sleeve gets and the less material you have left to bore if you need to again. If you had your block sleeved you could bore it to whatever you needed then for the engine configuration you were building.

 

I run 12.1 compression on 81.5mm bore on 93 daily driving dont go 82mm unless you have to go 81.5 for now if you blow it later down the road you still can go 82mm after that you must MUST get sleeves...

 

i noticed you also wrote that u would be using usdm itr pistons. You will not find these in 81.5 or 82mm bore - only 81.25

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HAMOTORSPORTSUSA &raquo;</TD></TR><TR><TD CLASS="quote">i noticed you also wrote that u would be using usdm itr pistons. You will not find these in 81.5 or 82mm bore - only 81.25</TD></TR></TABLE>

Yes, you are correct but I think he was refering to the style of piston. RS machine or Nippon are tw manufacturers of this type of piston.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2001B18C1GS-R &raquo;</TD></TR><TR><TD CLASS="quote">I run 12.1 compression on 81.5mm bore on 93 daily driving dont go 82mm unless you have to go 81.5 for now if you blow it later down the road you still can go 82mm after that you must MUST get sleeves...</TD></TR></TABLE>

Why are people even going to 81.5mm when the bore limit specified in the helm is 81.25mm? You guys like asking for trouble? No wait, I know... Your neighbors buddy who has this friend did it and it worked like a charm, so Honda is wrong... am I right?

 

isnt helm maz service limit for head milling only 0.008" yet people mill 0.03" I see where your coming from.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid96EK &raquo;</TD></TR><TR><TD CLASS="quote">

Why are people even going to 81.5mm when the bore limit specified in the helm is 81.25mm? You guys like asking for trouble? No wait, I know... Your neighbors buddy who has this friend did it and it worked like a charm, so Honda is wrong... am I right?</TD></TR></TABLE>

I've run with 81.5 mm with no problems. In fact, plenty of people I know and helped on their rebuilds run 81.5 mm cast pistons on stock sleeves. It's really not a problem. If you know something different please share it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all-mtr-teg &raquo;</TD></TR><TR><TD CLASS="quote">isnt helm maz service limit for head milling only 0.008" yet people mill 0.03" I see where your coming from.</TD></TR></TABLE>

As long as you know where to set your cam centerline then that is not a problem.

 

plenty of 81.5 and 82mm builds...so why not?

im running 81.5mm without a problem? why? shop messed up and went 81.33 on a bore so I had to go next size up...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid96EK &raquo;</TD></TR><TR><TD CLASS="quote">

Why are people even going to 81.5mm when the bore limit specified in the helm is 81.25mm? You guys like asking for trouble? No wait, I know... Your neighbors buddy who has this friend did it and it worked like a charm, so Honda is wrong... am I right?</TD></TR></TABLE>

are you kidding me? hahahaha do you know how many people run 81.5mm without issue?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Casey &raquo;</TD></TR><TR><TD CLASS="quote">

are you kidding me? hahahaha do you know how many people run 81.5mm without issue?

</TD></TR></TABLE>

So you are telling me the bore limit specified in the Helm is just a "General guidline" then? Why do you think they put that limit out there? Do you think there could have been any reason/logic behind it?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all-mtr-teg &raquo;</TD></TR><TR><TD CLASS="quote">isnt helm maz service limit for head milling only 0.008" yet people mill 0.03" I see where your coming from.</TD></TR></TABLE>

Max milling on a head is a little different then messing with bore diameter in my opinion. Head milling will raise compression, put valves closer to pistons, etc. There are MANY reasons why Honda might specify the limit at .008. Keep in mind they are assuming people are using OEM components. Clearances are going to be different with aftermarket components.

Now with cylinder sizing, removing too much material will weaken the sleeve. While it might "work", there still has to be a reason why the decided they didn't want the sleeve any thinner then 81.25mm would make it. Wouldn't you agree?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hybrid96EK &raquo;</TD></TR><TR><TD CLASS="quote">

Max milling on a head is a little different then messing with bore diameter in my opinion. Head milling will raise compression, put valves closer to pistons, etc. There are MANY reasons why Honda might specify the limit at .008. Keep in mind they are assuming people are using OEM components. Clearances are going to be different with aftermarket components.

Now with cylinder sizing, removing too much material will weaken the sleeve. While it might "work", there still has to be a reason why the decided they didn't want the sleeve any thinner then 81.25mm would make it. Wouldn't you agree?</TD></TR></TABLE>

you answered your own question

they dont recommend over 81.25 because they assume youre using stock honda pistons

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Casey &raquo;</TD></TR><TR><TD CLASS="quote">

you answered your own question

they dont recommend over 81.25 because they assume youre using stock honda pistons</TD></TR></TABLE>

I don't think I answered my own question at all. More like they only offer .25 over because thats the bore limit. Ever look at D series pistons? Might be shocked to see that Honda offers them in sizes larger then .25 over. Its kind of lame to simply state that the boring limit came to be because the manufacture didn't want to offer anything over .25mm oversize.

 

yeah i guess youre probably right despite everyone having success even with boost on 81.5mm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by all-mtr-teg &raquo;</TD></TR><TR><TD CLASS="quote">isnt helm maz service limit for head milling only 0.008" yet people mill 0.03" I see where your coming from.</TD></TR></TABLE>

The manual says that because it's assuming you're only using stock cam gears which can't correct for much head milling. I would also say that their ultra conservative limit on boring might have something to do with trying to keep the engine in proper tune within emissions limits on a stock ecu.

 

Yeah, that makes sense, wouldn't boring a fairly new motor still in warranty limits void the warranty?

 

I'd say if it wasn't done for warranty purposes, than it more than likely would be.