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(Not*) Mediocre 242

I did another compression test when the engine was hot. Same numbers, so I pulled the head and finally got some good news. Pistons look great. What I thought was pitting was just carbon buildup.

m1iyNiRl.jpg


xQggzyel.jpg


Cylinder one piston moves significantly in the bore relative to the other pistons, which explains the lower compression in cyl 1. Based on this I'm pretty sure new rings would fix my blowby and low compression.

Here's cylinder 1:

https://youtu.be/VyCsI97eEuw

<iframe width="560" height="315" src="https://www.youtube.com/embed/VyCsI97eEuw" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Here's cylinder 4:

https://youtu.be/ERzqbJQ8jhE

<iframe width="560" height="315" src="https://www.youtube.com/embed/ERzqbJQ8jhE" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>
 
I hate to say this but piepers 244 was the same way with those rods and pistons. Lots of side to side and back and fourth movement. Rsi internals?
 
Huh. That kinda sucks. Do you think replacing the rings is worth it? Anything else I can do to reduce blowby?

I would pull the plugs and measure the ring end gap. Also what you pull them out check the orientation. Who knows maybe the rings are a super loose fit on the pistons and they shifted too much and are causing the consumption.
 
Would be good to verify the piston to wall clearance, the bore might be too loose to fix with rings.

I was thinking about measuring the bores today since I haven't pulled the pistons or oil pan yet. I was going to just use a bore gauge and micrometer, then measure the pistons at the skirt when I pull them. That's the way to do it right?
 
Just did some quick measuring with a telescoping gauge and a micrometer on cylinder 1 in different spots and orientations and got the following:

3.8003"
3.8017"
3.7986"
3.7964"
3.7963"

Using this sheet from Simon through Kenny, my bore size should be a max of 3.8027".

0hDzbmdl.jpg


My measurement technique wasn't perfect, but it should be a pretty good estimate. Based on my measurements it seems like my cylinder 1 bore is ok.
 
Just did some quick measuring with a telescoping gauge and a micrometer on cylinder 1 in different spots and orientations and got the following:

3.8003"
3.8017"
3.7986"
3.7964"
3.7963"

Using this sheet from Simon through Kenny, my bore size should be a max of 3.8027".

My measurement technique wasn't perfect, but it should be a pretty good estimate. Based on my measurements it seems like my cylinder 1 bore is ok.

You've got .004in difference in diameter throughout the cylinder. That's a lot. Like A LOT a lot.

If it's bore taper, then the block could be honed straight. If it's run like that for too long, the rings can eat away the ring lands since they're opening and closing .013" every single revolution
 
You've got .004in difference in diameter throughout the cylinder. That's a lot. Like A LOT a lot.

If it's bore taper, then the block could be honed straight. If it's run like that for too long, the rings can eat away the ring lands since they're opening and closing .013" every single revolution

I would guess the variation is mainly from my measurement method. I plan on taking the block to the machine shop for a hone and for them to put the rings in. But I'll definitely check the ring lands.
 
It definitely takes some practice with snap gauges and a mic.
Are you using studs or head bolts?
If the machine shop can hone with a torque plate, that might be best if you're using bolts.
You can immediately see the low spots at the top of the bore (that are caused by the head bolts deforming the cylinder) when you run a cylinder gone through them.
 
I bet. The first two measurements were freehand. The last three were with the snap gauge resting on the piston. But it's mostly my inexperience with it surely.

I'm using studs, so hopefully I won't have much distortion if any.
 
Just called up wiseco and ordered some new rings based off of this spec sheet:

an7yIzul.jpg


It's a little different than this one I got from Kenny (below), but it's newer and more likely the actual pistons I have.

m4sfw9Ql.jpg


If you want to order some new rings from Wiseco, just tell them the part number of the pistons (I used ASC-00317) and they can look it up from that. They're XS style and like $34 per piston.
 
So what's your game plan, are you pulling in rings and anticipating replacement?

Engine is totally stripped. I'm taking the block and pistons to the machine shop probably tomorrow to have them check the piston to wall clearance and probably a tiny hone.

I already have new rings, so if both pistons and block check out, I'll reassemble everything and put it back in. Bearings look pretty good, I don't think I'll have to replace any.
 
I have next to no experience from this, other than building my B23, but why wouldn't you just replace the bearings no matter what if it's apart?
 
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