Stihl 038 AV Super to Magnum Conversion

[Cloudfeather]

I've had my Stihl 038 AV super for some time. She's been a good saw for felling, cutting firewood, and milling. I've decided to convert it from a Super to a Magnum...

I ordered a cylinder and piston kit and know, from creeping some other posts, that I will need to slot the Mag cylinder and gasket to get it to line up with the holes in the crank case. Using the gasket from the super as a guide. I'm pretty savy with fabrication and my two brothers are both gear heads so it shouldn't be a problem. I've just got a couple of random questions.

1. I had planned on doing a very light porting on the new cylinder, mostly to just clean up imperfections and whatnot, not so much to get a lot of extra power from it. I've got a dual port muffler on it now. Should I leave it be or open it up a bit?

2. I've read a couple places that you should eliminate the cylinder gasket to add compression. Is this something that's recommended? And, if so, should you use any kind of sealer or just mate the two surfaces together?

Any little tidbits of info would be appreciated. Thanks.

 

[drf255]

Welcome to the site.

You MAY need to modify the base holes in the jug. I've seen conflicting data on that depending on whether or not you are converting an AV/Super to a Mag.

You need to measure the squish with lead solder that's the closest size larger to your desired squish. Only then can you tell if it's safe to eliminate the base gasket. Shoot for .018-.025. If it's too tight, you'll need to find gasket material to make up the difference. If it's too loose without a gasket, you'll need machine work to correct it.

You need sealant between the case and jug if you're not intending on using a gasket. It has to be a type specified for gas resistance. I use Dirko myself. Some use loctite anaerobic gasket maker-it only sets up it the absence of air, so it will seal the jug, but it will rinse off inside the saw if there is an excessive amount applied.

 

[Adam08ski]

I am currently part through a rebuild on a seriously dead 038 super that came my way into a magnum. I ordered two cylinder kits and sent one back (had zero luck with finding a 52mm OEM cylinder) So I settled on a Hutzl/farmertec cylinder kit. They must have upped their game on parts since their MS660 have been so successful as it was far cheaper than a Hyway cylinder kit and in my opinion the port beveling etc was on a par. If it does not last I will hold out for a used OEM 52mm as this saw is not one that I will need or use more of a fun project.

So from doing this I found that the later crankcases do not need rework at all to do the swap. The cylinder holes needed barely any slotting, I did all mine with a chain file. However the cylinder clearance holes from the top to the base needed enlarging. I think I used a 0.5mm bigger drill than the existing holes to give clearance for the torx drive. then it was just a case of dremelling out a bit of clearance for the bolt heads on the outside of the cylinder wall to allow the bolts to seat down when properly when tightening. I found that this farmertec cylinder even with a base gasket delete has more than .020 squish, I am guessing as it is AM they will differ from manufacturer to manufacturer etc. The whole job was really easy to do.

My 038 had been fitted with a Bing carb which is the one used on the magnums I think and I believe it is larger.

I am part way through modding the muffler. The muffler inlet is smaller on an av and super than the magnum exhaust port so will restrict flow. Also I am matching the overall exhaust outlet size to the cylinder exhaust port size so that there is no restriction, this included opening up the restrictor in the actual muffler when it is unbolted.

So far it has had a fairly large amount of used OEM and new AM parts and seems to draw fuel, crank smoothly etc. It will probably cost more than an 038 mag on ebay but I am doing it for fun

Hope this info helps and makes sense???



- Adam

 

[Cloudfeather]

Thanks for the info, fellas. I wasn't aware of the clearance for the bolt heads but it shouldn't be an issue. I don't think I'm going to mess with removing the gasket because it's a bit more in depth than I want to get. I'm not trying to eek every bit of power out of it, just want a little leg up since I'm swapping the cylinder anyway and figure I might as well port it a bit while it's fresh.

I had read about the exhaust port to the muffler inlet variation and will take care of that with my dremil and files. For opening up the restrictor, I planned on drilling a few 5/16" holes in it and maybe opening the port a bit where the screen is. I'll try and take some pics to post when I get off of work later on. Thanks again, fellas.

 

[Adam08ski]

I don't think I'm going to mess with removing the gasket because it's a bit more in depth than I want to get. I'm not trying to eek every bit of power out of it

You might find though that if you are using an aftermarket cylinder then the squish might be larger than OEM due to casting differences and the compression will work out lower than stock giving inferior gains(no-one wants that), well this is what I am 100% sure would have happened had I used a supplied standard gasket with the Farmertec cylinder I used. My theory is these 038's were built tough and will handle it although the squish of mine is not particularly low still. I believe different thicknesses of manilla envelope prepared properly have helped make that perfect thickness gasket.

-Adam

 

[Cloudfeather]

How do you recommend measuring squish? Can I compare the new cylinder measurements to the old? Thanks.

 

[a. palmer jr.]

I don't have a compression release on my 038 Magnum but I can tell you I wouldn't want it to have more compression. Hard enough to pull it over the way it is.

 

[Adam08ski]

If you have the stock cylinder and piston and gasket you can bolt it all back up and feed a length of solder wire through the spark plug hole until it touches the side of the cylinder/piston wall and pull it over. The soft solder will squish to the gap. Then measure the thickness of the solder with some calipers. Then match this with the new cylinder by repeating the process with different thicknesses of gasket paper.

My 254xp with minimal squish rips my arm out sometimes when the pull cord is feeling stroppy and that is only a 54cc saw.. HA HA

 

[bulletpruf]

I had read about the exhaust port to the muffler inlet variation and will take care of that with my dremil and files. For opening up the restrictor, I planned on drilling a few 5/16" holes in it and maybe opening the port a bit where the screen is. I'll try and take some pics to post when I get off of work later on. Thanks again, fellas.

CF - what is the exhaust port to muffler inlet variation that you speak of? Is that just port matching the muffler to match the port?

Would like to see your pics of opening up the restrictor, too.

And what did you end up deciding on porting? I have an 038 Magnum that I'm going through and I'm interested in doing some basic porting.

Thanks

Scott

 

[Gypo Logger]

There are a few variations in the different models of the 038. I don't recall them all, but after mixing and matching several parts I ended up with a stock triple port muffler on an 038 Mag.

 

[Cloudfeather]

I opened up the muffler port to match the exhaust port on the cylinder, opened up under the screen a bit and drilled some tiny holes in the second port. The baffle was already drilled out when I bought it.

As for porting the cylinder, I just cleaned the intake and exhaust ports of imperfections and whatnot. Nothing too fancy. No pics of the cylinder, but got some of the muffler.

 

[bulletpruf]

There are a few variations in the different models of the 038. I don't recall them all, but after mixing and matching several parts I ended up with a stock triple port muffler on an 038 Mag.

From what I can tell, only the Magnum (W. Germany) or Magnum II (Brazil) came with the triple port from the factory. I believe Stihl gets about $100 for an OEM replacement. For that price, I'll buy an aftermarket dual port and get out the Dremel. Thanks

 

[bulletpruf]

I opened up the muffler port to match the exhaust port on the cylinder, opened up under the screen a bit and drilled some tiny holes in the second port. The baffle was already drilled out when I bought it.

As for porting the cylinder, I just cleaned the intake and exhaust ports of imperfections and whatnot. Nothing too fancy. No pics of the cylinder, but got some of the muffler.

Thanks for the details. That's what I plan to do with mine - mod the muffler and do some basic cleanup in the ports. Thanks, Scott

 

[a. palmer jr.]

Anybody got a stock picture of that triple port muffler that comes on the Magnum? I'm just checking to see if mine has what it's supposed to have on it..mine just looks like a couple of little vents with a shield over them.

 

[Cloudfeather]

I've still got to break her in a bit, but she started up easily and seems to run like a beast so far. I let her idle for about 5 minutes, adjusted the carb and ran a couple cuts with it. Definite difference between the mag and super cylinders. I'll try and post some pictures and a cutting video as soon as the weather here warms up a little bit. Hopefully now, I can leave well enough alone and just put her to use.

Though, I can't lie, the artist side of my brain wants to think I can convert it to side adjuster on the chain tensioner with parts and some fabrication work. I think I'll abstain for now though. Lol

 

[a. palmer jr.]

I don't plan to modify mine, it seems good enough and besides that I may sell it eventually.

 

[Adam08ski]

I don't plan to modify mine, it seems good enough and besides that I may sell it eventually.

I struggle to sell a saw, I get too attached

 

[a. palmer jr.]

I struggle to sell a saw, I get too attached

Me too and I'm not actively trying to sell right now.

 

[Cloudfeather]

Got a video of her in action today. She's still breaking in and I need to adjust the carb a tad when I'm done, but I'm just tickled with the results. Any critique is welcome. Thanks.

 

[Adam08ski]

Got a video of her in action today. She's still breaking in and I need to adjust the carb a tad when I'm done, but I'm just tickled with the results. Any critique is welcome. Thanks.

What bar and chain are you running? Is this full chisel? Base gasket delete? Muffler mod? And is this oak? Upload one when you are leaning in the cut when you get a chance if you could? I am keen to see. I am waiting on a coil and a few bits and bobs and then mine will be up and running. Looks good. Is this an AM or OEM cylinder?
-Adam