Stihl 038 Super to ported 038 Mag build -Part #3 - case and cylinder prep - (pick heavy)

Here's part 1 & 2.

Stihl 038 Super to ported 038 Mag build -Part #1 (pic heavy)

Stihl 038 Super to ported 038 Mag build -Part #2 - Muffler Mod - (pick heavy)

I decided to hold off on grinding till next week since I have a bunch of stuff to do between now and then. I want to take my time.

To start off I had to do some cleaning of the casing on the case so the 52mm cylinder would fit. There was a small ridge on the both sides.

Needed to slot all of the cylinder mount holes to match the 038S holes. Fun fact - the diagonals are 62mm. You will be able to see the holes a couple pics from now.

Mounting bolt heads had to be ground down in diameter by 1mm so they would fit against the outside cylinder wall. Wrapped the threads with masking tape so I was still able to hole them when they heated up. They were just spun on a small grinder. The bottom right one is not done in the pic. They are just set in the cylinder for the pic. They mount from the other side.

 

The casting in the squish band was not the cleanest with high areas so had to clean it up a bit with sand paper and a piece of 1 x 2.

My final squish with the gasket (.020 thick) was 30 so sanded .008 ish off the gasket for a final squish of .022 - went .002 high because the gasket was getting too thin and if I was off a hair when sanding there would be room.

Pre grind timing numbers now are 1 degree less the whole way around.
Exhaust 104
Intake 71
Transfers 124

Went with the numbers that another builder did for my markings.
101
75
122

Set the exhaust using a ring as my guide put the crank to 101 held the crank in place and pushed the cylinder on then marked with a sharpy. For the width of the exhaust and intake I went with 36mm =70% of the diameter running the cylinder wall. I cut a piece of card stock to 33mm and made my markings and will take them off.

As for the intake did the same thing with a ring BUT pulled the piston and sat in on the ring to make my mark for when it opens on the skirt. The 2 small black marks are my ring pin markers for reference so I do not grind too wide and end up catching a ring when it is running. I will grind only half way to the parallel mark on the left and to the line on the right. For the port height - will only grind to the lateral line to reach the 75.




The transfers need cleaned up on the casting and only need about 0.5 mm to reach the 122 so only taking about half the line off should do the job.


The last pic in the 1st post shows the unfinished squish also. The pic above shows what I ended up with. It's not perfect like a milling but will suffice and is much cleaner than prior.

Before I grind next week do everything sound / look correct?

 

Found a couple more pics in a different camera file.

Pic of cylinder mounting hole prep with reference of the 50mm cylinder.

Knowing that I would bump the timing wheel a time or 2 or take it off to do stuff. A little trick I did when I was going to set the timing wheel to TDC was pull the connecting rod straight up and parallel with the top of the case then mark the case and crank with a sharpy. No matter what I did I always had that for reference to reset the timing wheel. As long as the marks lined up the timing wheel could be anywhere. I would just move the wire back to TDC.

 

Here's a pic of the ridges along the side of the case I had to grind off to make the cylinder fit and how I prepped so no aluminum shavings would fall in the case. The ridge is only about 1mm wide just outside the tape left and right. Kinda hard to see.

 

Good idea on that.

 

Nice thread and pics... wonder what comp and rpm you'll get out of this one.

These saws are absolute tanks and are fun to run.

 

It is good to see a build thread on here. Thanks for taking to to share the pics.

 

Looks like your doing a great job there Mark. I look forward to your completed project.

 

Don't know - first build. Don't even have a compression gauge - I'll find out when I pull the rope for the first time. No tach either - I'm pretty sure I can get a close max tune by ear and performance.

 

The custom stickers came in today!!! I designed and formatted them in Microsoft Word and emailed them to a local sign/sticker shop. They were able to put the word document in their system print and cut with exact measurements.
I got 2 sets/ 6 stickers for $13.84 mailed to my door in one day!!!

The wood chips in the background of the sticker that I had was a bit darker but pixelated so they had to go with a wood chip background that they had on file. I still think they look bad azz!

 

Porting complete. I keep it in this section so you can scroll up and down to see before and after pics. App porting was done with a dremmel and tungsten carbide burs, no 90 degree tools. I had a rough start trying to figure out how to hold angles and adjusting the speed of dremmel. It kept taking off on me and hit a few places on the first transfer that I attempted. The take off scratches look much deeper than they are. You cab barely feel them. I do not think it will cause any problems. I have seen worse scored cylinders run like crazy. I just saw this in the pics- the little dots on the cylinder wall are not defects it is drying cleaner after porting.

2nd transfer looks a bit better.

Exhaust and muffler with gasket port matched.


Intake


All inner edges beveled so a ring does not catch. Maintained a nice small curve to the exhaust and intake to help prevent ring wear and catching. I did not go crazy on really polishing everything. Even though they may look rough they are pretty smooth in comparison to after market and OEM castings. Hardly touched the intake with final sanding - rough is OK for fuel / air mixing. The intake boot actually has little dimples inside.

Here's my final numbers.
Exhaust 100
Intake 75 1/2
Transfers 122

I think those should be OK. Final assembly probably this weekend. I hope it runs...

Thanks for tagging along with my thread on my first build!!! I will post a few more pics down the road.

 

There are better pics of the transfers. Wow hard time getting in there with just a dremmel. The exhaust and intake took 1/3 of the time.

 

Is it running yet?

 

Hopefully tonight or tomorrow. I have a nice 12-14" test log.

 

Nice!