piston ring gap size

[skabrock5]

i have a quick question. Does the ring gap requirement stay the same as stock when installing hi comp pistons? (WISECO 86MM 10:1-10:9-1) This is my first full build from block and up.

[KE20Rally]

Ring gap should be as per the piston spec sheet from Wiseco, not the toyota specs, from the Wiseco FAQ page:

Wiseco 4-cycle Powersports piston rings are designed with the proper end gap for most applications. Because 4-cycle engines contain two and three rings, the end gaps do require different values depending on the ring. This chart will help illustrate the minimum ring end gaps:

Top ring 2nd ring Oil rail
Most standard engines 0.004 0.005 0.015
Modified engines or Nitrous Oxide 0.005 0.0055 0.015
High performance racing 0.0055 0.0053 0.015
Racing with Nitrous / Turbo 0.006 0.0057 0.015
Blower / Forced induction 0.007 0.0063 0.015

Multiply your bore size in inches times the value on the table (to convert metric bore to inches, divide your metric bore x 25.4. For example, 77mm divided by 25.4 = 3.0314”, multiply this times the value on the chart).

Note: If your piston contains only a top ring and oil set, simply omit the second ring requirements

http://www.wiseco.com/faqs.aspx


Sorry the text in the table above does not line up correctly (looks good in my edit box), have a look at the link for a beter view

Cheers,

Pete

[skabrock5]

thanks KE20Rally, looks like I have a bit more research as well as buying a few more tools before I start assembly. thanks again.

[KE20Rally]

You don't need any special tools to check and adjust ring gap, you place the ring in the bore and measure with feeler gauges, I use a sharpening stone to then adjust the gap.

http://www.laskeyracing.com/shop/ringgap.htm

Have a read here then do a bit of a search and you will get the idea.

Cheers,

Pete

[mikealike]

gap them correctly so the rings doesn't butt up together

[skabrock5]

I still have to purchase the ring grinder tool, bolt stretch gage, bore gage set, o.d. micrometer set for checking bearing gap clearances. I've read that plastigage is not accurate enough.

[KE20Rally]

All those tools are great, but can be costly, depending upon your budget, rpm/hp you are expecting, time and skills you can cut that list of tools dramaticly to the following:

1, Ring grinder: a very fine file as per the link above, or I used a sharpening stone.
2, Bolt stretch gauge: this depends upon your rpm more than anything, if you are regularly doing 8000rpm+ yes, if not a good tourqe wrench is fine. (high rpm and rod bolts don't like each other!)
3, Bore gauge set: a set of telescope bore gauges is the cheapest option in combination with your micrometer.
4, Micrometer: Spend your money here, a good quality 100mm micrometer is what you want, and will do all your bearings, pistons, botes etc.

Yes plastigauge is not perfect, but I always use it to double check my calculated clearance before final assembly.

Be paitent with your measurements, from experiance to do this correctly should take several hours to complete properly, each measurement should be taken in 3 axis, 12 o'clock, 2 o'clock and 4 o'clock. Each bore should have 9 measurements, top, mid and bottom x 3 axis, piston x 3 axis, crank should have 9 x 3 axis, assemble each rod with bearing and measure x 3 axis and finall assemble the main caps with bearings and there is another 5 x 3 axis. Most importantly, double check and write all this down when you are doing it.

As my machinist always says, "always measure everything, we are human and make mistakes, no good complaining about machining when you have a broken engine"

Enjoy,

Pete

[skabrock5]

Thanks for the measuring technique info. I took quick measurements of two cranks and both have undersized rod journals on number 3. What might have caused this trend and why on number 3 only ? All the other journals are at the bottom of the tolerance. One crank was .005 under tolerance and the other crank was .019 under tolerance @ 1.8695"