After doing a bunch of research I've read that your supposed to set the end gap at the product of bore * .00X. My question is - what is X? Some say .0045, some say .006.

I'm rebuilding a b20z back to OE spec for a mild b20Vtec build. The manual says that the top ring should be between .008 and .012 for this, but that would be the tightest X (around high .003x) that I've heard of.

This motor will never make more than 190whp but will see lots of the road course (I'm mentioning this because the heat the motor will see plays in to what X ends up being from what I've read).

Guru's what should my X be? What do you use for X when building your NA motors?

84.5mm, ~10.8 compression B20/GSR,

Thanks!

 

well first off there is no way in hell i would assemble that engine with. 012 ring end gap. roughly speaking i would try to have my gaps somewhere around. 018 and. 021. those numbers use multipliers around. 005 give or take. i have a suspicion though that u will have a ring that has more gap than the others out of the box and that will be the gap u make the others match up to.

what pistons and piston to wall are u using

 

Why would honda have .008-.012 as the spec gap If it shouldn't be?? All top rings have just about the same gap +\- .000x. The pistons/rings are stock b20z replacements - stock compression and all.

.005 is more along the line of what I've been reading but it seems arbitrary... Why .005? Why not .004?

Thanks!

 

Those specs do sound a bit tight. I'd be worried about butting ends and cracking a ring land. I personally would run then around .015 top and .018 bottom. Oil rings set the same as the top ring.

 

Set them on the higher side of what the manual says and you will be fine.

 

The high side is .012. The 2nd ring is a different story - I believe the range is .017-.022. This is straight out of the Helms manual.

 

roadrace or heavy load wot use, tends to generate higher temps in the components
(even if oil and water seem normal) so running a looser clearance is Ok on the top ring
than wat the manual says... after all the manual depicts grocery driving to and fro

the 2nd ring , ive gone way above 0.022 and there were no ill effects so that should be easier , you can increase gaps with a tool from summit

free bonus here is = u dont score the walls if u accidentally overheat (provded u shut down or coast)

and possibly less friction = less windage loss

 

Cool, thanks for the input.

For a road race motor that would never see more than 8k Rpms or 200whp would .016 top and .022 2nd be good? Or should I go wider?

 

that sounds like how id do them...

we've built a few, that runs production class and 200whp restrictor type class
bseries with 20-25 hotlap/heat , 5lap qualy and 10lap practice

if you're in that window of use.. then go for it

 

you don't need to go bigger, .018" and up is friendly for boosted cars that are not at extreme hp levels. no need to go bigger. large end of oem will be fine.

 

Awesome thanks! If anyone disagrees, speak up! Ring filer is coming in today and there's no going back once I open this gap up!

 

Can all the guru's explain why they run such large 2nd ring gaps ?

 

Bump. It's almost like no one builds honda motors anymore. Everything I find online is for v8's. maybe everyone has gone K.

 

what do you consider large second gap? i always have mine at 3-4 thousandths bigger than the top. as it was explained to me, any gas/pressure that passes the first ring goes past the second ring and is not trapped between causing ring flutter or excessive pressure on the ring/ringland. a good crankcase ventilation system will take care of the expended gas and any oil it may push.

additonally, ive personally lost a motor on the dyno when certain tolerances were too tight. ever since then i build them all a bit loose so i dont have a repeat performance.

 

I will attest to that. Rings are just like valves within reason. Slightly loose is always better than tight. You aren't going to lose anything performance wise, but gain insurance.

 

Guy I talked to at Childs and Albert said the same thing as well.

The gaps depend on material used as well as intention. Thermal expansion is different on cast iron rings to tool steel ones.