piston ring gap positions ??

steptoe · Post by **steptoe** » Sun May 04, 2008 9:47 pm

the further I look the more variations I get

The Gregories is probably partly what I used in accordance to ring maker instructions last EA81 rebuild. This time I note ring maker says to have oil rail gaps 30 degrees above midline, either side with the locating pin facing the block centre for all boxer motors

Gregories says to have oil ring upper at the locating pin on the midline and lower rail gap 30 degrees below that point, with the lower comp ring sharing same position and the top rail 30 degrees below midline on the other side

EA82 FSM agrees with ring maker for oil rails (yet to see for comp rings) yet the same manual FSM on 1300 & 1600 engines sort of mimmicks the Gregories

I think I will adopt the EA82 FSM gap positions on the EA81's pistons with the expander ring gap on the opposite side of the locater pin, and also what is not mention but suspected necessary > so the piston pair in each half will be mirror image to the other gap location wise

any comments for those that follow

YouTube · Post by **El_Freddo** » Sun May 04, 2008 10:00 pm

Hey Steptoe,
With the rings I used I just followed the instructions that came with them. What exactly are you building to be worried about ring gaps? Are we talking guide clearances on old heads or the gap size when the rings are compressed in the bore?

Cheers

Bennie

steptoe · Post by **steptoe** » Mon May 05, 2008 9:57 am

EA81 bored out to suit new pistons, 1.00mm or the old 40 thou, crank linished, new 20/60 cam grind, followers reground, heads serviced and shaved and a speedi sleeve on the back of the crank using JAPAN made payen engine gasket kit with Japanese made seals too !!!

rings in the bore measure

Gregories also say follow ring makers instructions. I am going to say that in the Gregories they have diagrams for the EA81 and EA82 indicating a different ring gap position between the two similar engines ????? why ????

Ring maker says if it is a boxer the two oil ring rails are to be on the top half, the expander gap needs to be 90 degreesa away from any locating pin (which we have at gudgeon pin hole side facing inner side of block) so the expander gap will be either at the top or the bottom BUT instructions also say have expander gap 1 to 2 inches away from rail gap...SO......

if looking at piston the top side of the block nearest 12 O'clock is gonna be the expander gap, an inch either side will be the rail gap and the comp rings will go on the 4 clock and 8 clock positions

YouTube · Post by **El_Freddo** » Mon May 05, 2008 4:20 pm

steptoe wrote:if looking at piston the top side of the block nearest 12 O'clock is gonna be the expander gap, an inch either side will be the rail gap and the comp rings will go on the 4 clock and 8 clock positions

Yeah that sounds right, exept I think (going by memory here not the most reliable at times) my combustion rings were in the 10 and 2 o'clock positions. I'll try and verify this somehow

Cheers

Bennie

steptoe · Post by **steptoe** » Thu May 08, 2008 11:27 pm

and watching as the ring compressor wraps around the piston you could bet that the ring grips the inside and twists ever so slightly out of order anyway.

donk is together and in just waiting to stick manifold on and dizzy in.

littlewhiteute · Post by **littlewhiteute** » Fri May 09, 2008 6:03 am

I think you'll find that the compression rings will rotate in the bore during their service life.
I'd bet on disassembly they weren't in the places there were on assembly.

steptoe · Post by **steptoe** » Fri May 09, 2008 1:48 pm

my thoughts exactly

Matt · Post by **Matt** » Fri May 09, 2008 9:29 pm

I just pulled my pistons out and the compression ring gaps where lined up with each other...

discopotato03 · Post by **discopotato03** » Sat May 10, 2008 11:06 am

When rings are properly gapped they don't leak very much through the gaps anyway . I don't remember L ring gaps off hand but if they're typically 15-17 thou which is less than 1/2 a mm (1mm is just under 40 thou - 0.03937") then that's fine .

The REAL danger is having the gaps too small because the ends butt together and the ring binds in the bore and chops up it's and the bore surfaces .

Measure the rings by placing them individually in the bore and push them a little way down with an upside down piston to get it level . Then measure the gap with feeler gauges and alter if the gap is below tolerance .

Its the time taken to get all these things right that makes engine building expensive if your paying for it . I fully expect Ellies engine to owe me over 4 and that's with me supplying several engines and not the install . Mods to the heads/pistons/flywheel will add as will the fabed header .

Not a cheap exercise if you want it all nice , cheers A .

steptoe · Post by **steptoe** » Sun May 11, 2008 12:40 pm

yeah, I had forgotten the time involved in a careful rebuild keeping everything *clean, spotless and slippery at the same time. The motor is in and cannot get oil pressure (another post) it's Mothers Day and I make time for mine over the Brumby

FSM states 1.5mm gap is maximum ring gap so my 0.5 is fine

* an uncle (traitor) popped in the other day to show off yet another new car (traded his 2.5 Turbaroo with the works and only 7,000km for a 230kW 350Z , also the former owner of me white Brumby - looked at the engine and said "that's a new block ! "