181 rebuild

[tolman_paul]

What started as a long overdo inspection and hmm maybe I should port this thing has turned into a rebuild. No before pictures, but everyone knows what a dirty saw looks like. I hadn't notice a lack of power cutting, although most of my cutting is small stuff. In hindsight I have noticed the saw is easier to start. Looking at the piston it was obvious why.

The top ring had completely lost it's spring, and there was definate blowby at the bottom ring gap

Turns out the folks at Northwood have great prices and had all the stuff I needed, and it arrived quickly

As a curiosity I took some measurements. I'm used to thinking in terms or port open duration, I know others post their readings differently

Stock saw
0.055" squish
ex 154 deg
trans 110 deg
intake 140 deg

Stock saw with base gasket removed
0.035"
ex 150 deg
trans 106 deg
intake 144 deg

My plan is to cut 0.030" off the cylinder base to tighten the squish to 0.025" and port as follows:
ex 158 deg
trans 118 deg
leave intake as is, should be 146 deg after cutting the base.

That should give me some leeway to play with base gaskets to fine tune the port durations.

The only real concern is the rod has more play than I'd like which makes me think I should put in a new crank. The main bearings are in great shape, but I might as well replace them if I'm swapping out the crank. But I hadn't put asside sheckels for a new bottom end so that might have to wait.

 

[srcarr52]

Fine tuning the port timing? 0.005" is only going to change the port timing 1/2 deg of duration. I don't think you'll be able to see any difference in performance in your testing.

The rods always feel loose when you move them side to side. Hold the crank at TDC or BDC and see if there is any vertical movement of the rod. If there is none you're good to go.

Is the new piston from meteor a thin ring like the stock piston?

 

[tolman_paul]

I know you can slide the rod side to side, but it's the rocking the concerns me. I'll put a dial indicator on it to see if I can measure any verticle movement.

The metereor piston is a single thick ring.

 

[srcarr52]

That is what I was trying to say is that they do have a lot of rock in them even when they are perfectly fine. It took looking at a few to realize how much rock is getting to be excessive. That is why I always tell people just to feel for any vertical play.

 

[mdavlee]

I would think it would run better with more intake. Maybe 156° for duration or 78° for the rest of us. It should have plenty of torque with the exhaust at 158° or 101°.

 

[srcarr52]

I'd probably go to 152-154 duration on the intake. These older non-quad port saws like to be a quite a bit under square.

FYI, I double checked my math notes on these saws... 0.010" port height is going to be around 1.7 deg duration +- a very small amount depending on where you're at. But 1.7 for all intensive purposes.

I have one of these torn apart but I hadn't measured it yet. Just looking at the stock numbers you can see why the 181 is about dead even with the 288 despite the displacement difference. The 181 was a little more aggressively ported with more intake and exhaust duration. Also a significantly smaller combustion chamber was the first thing I noticed when I pulled a 181 jug. Too bad you couldn't save the thin original piston with those wonderful low tension rings.

 

[tolman_paul]

I could probably re-use the piston, but I just can't find replacement rings.

I'll take the advice to drop the floor of the inlet tract and increase the duration, I'd just prefer to be conservative by a few degrees. Of course the other option is cutting the base of the piston. The upside of that tact is if you go too far, it's only a new piston to replace vs. an OEM jug with lots of hours of grinding.

What really chaps me is several years ago I bought a spare carb and several rebuild kits. I'd already rebuilt the carb and had it sitting on a shelf for when I needed it. Well, I know I laid my mits on it last winter, but for the life of me I can't find it! I recall clipping the bag to the set of 181 instructions I had and putting them "someplace safe" For the life of me I can't find that place.

 

[srcarr52]

Clipping the piston skirt is a good idea. Once you get it to where you like it... order up another piston and grind the port.

I spent several years working in a machine shop, you learn little tricks to keep things organized. Boxes and sharpies are your best friend. It works well until some jerkoff puts a box in front of the one you want, then you spend hours looking for a sleeper.

 

[tolman_paul]

I couldn't find my other thread, maybe a victim of cleaning up after our hackers.

Anyhow, I finally got a chance to put the rebuilt saw into some wood on Friday.

To say I'm pleased with how it runs after the fresh piston/ring, base gasket delete, porting and improved muff mod is an undestatement. It's a beast and you can bury that 20" bar and it just flings saw chips like a fire hose. I still don't have a tank of gas through the engine yet. I can feel the already stiff compression is building slightly. Can't wait to get my 288, give it the same treatment and fit a 30" bar on it :hmm3grin2orange:

Unfortunately I managed to get my truck stuck! I backed in over a log that ran diagonally under the truck but was covered with just enough detrius that I didn't see it when backing in. The driver side front tire broke through the duff and starting digging a nice hole in the mud. Long story short, I unloaded all the wood to lighten the truck, jacked up the back to cut the log out from under the drive line and differential and took multiple forward and backward passes that made my driver side mud hole into a trench. Then I took a couple of the smaller logs I'd cut and some branches and filled the trench.

After spending more time getting the truck unstuck than cutting wood, filling the bed and emptying the bed the rain had soaked me through, I was wet, cold and tired. I wasn't real keen on carrying that wood the 50-60 feet to where the truck was parked after I got it unstuck, so it's left neatly stacked. It's been raining for almost all of September so perhaps if we get a dry and cold early October I can get back to it when the ground firms up but before it gets snowed in. Either that or with a bit of snow on the ground I can bring some kids sleds and slide it down the hill to the edge of the road.

Free firewood never is, and sometimes instead of warming you, it can chill you. In a sick perverse way I had a great time and can't wait to go back for more. Next time I'll put some effort into scouting out where I'm going to park. Diesel trucks are great for hauling a load on pavement, they are not so fun when they get stuck.

 

[heyduke]

Diesel trucks are great for hauling a load on pavement, they are not so fun when they get stuck.

my f250 powerstroke can get stuck in the walmart parking lot on a dry day.

 

[tolman_paul]

my f250 powerstroke can get stuck in the walmart parking lot on a dry day.

When we moved to AK I had a toyota 4X4 truck, the predecessor to the Tacoma. As I recall in the 10 years I had it up here I never got it stuck once in mud or snow and all I ran on it were A/T tires.

I got the Ram in November and managed to get it stuck 3 times within the first month of owing it. The factory tires suck, I got a set of studded winter tires and a new set of A/T's. I think I need to invest in a good set of chains. I had two pairs of cable chains but have managed to break one pair, one of which was on this adventure. The other chain broke when pulling a police cruiser out of a ditch.

 

[RedFir Down]

Nice load of wood tolman! To bad you got stuck, that really sucks!!! I know how it goes... One time I had to leave my truck on the mountain over night, (becuase of the rain) I couldn't pull out of this nasty hole with all 4 tires chained up. (Walked 8 miles to get cell service)

What kind of wood is that? Spruce maybe?

Oh did that new oiler fix your oiling issue?

 

[tolman_paul]

It was a nice load of spruce. There was a big project this summer upgrading power transmission lines and I was in the cleared right of way of the power lines. In theory a nice drive a couple hundred yards off the highway, but as you know there is no such thing as getting just a little stuck. The whole area is open to cutting standing and fallen dead wood and there is still quite a bit from beetle kill over the years. The key is finding wood that you can drive to, and not get stuck. In years past I've had no problems driving off the shoulder of the road, but those years didn't include nearly a month straight of rain to soften everything up.

Even though I was just a couple hundred yards off one of our busiest higways, I was probably 8-10 miles from cell service, and 60 miles from the closest tow truck. Somehow I had a feeling this trip was going to be an adventure, but not exactly what I'd expected.

I finally got the oiler issue figured out. I ended up stripping the original plastic gear and modified a 288 gear to work but need to do a bit more work on that as it seems to be binding up the clutch.

 

[RedFir Down]

Yeah days like that turn into an adventure in a hurry dont they?... At least you didnt get hurt or break something. Think about it this way, it will give you something to talk about down the road.

Im glad to hear your getting your oilier issue figured out.

 

[o8f150]

10000 pd wench would come in handy

 

[tolman_paul]

I prefer my wenches to be bit more slender :jester:

 

[pioneerguy600]

I prefer my wenches to be bit more slender :jester:

Remember,...Scott likes his Snackies large.