Resurrecting an 038 Mag II

[jacob j.]

Thank you for the build thread. Is this 038 now a super magnum?

I reserve the title of super magnum for something else. I think I’ve sent you a picture or two of my “super magnum”

I'm guessing the wife was in on that build...

 

[GoBigBlue1984]

I'm guessing the wife was in on that build...

Bahahahaha

 

[Bodell0]

Sent from my iPhone using Tapatalk

 

[Terry Syd]

It’s sporting a Bing 48

I wonder how much of the grunt of these old saws is related to the pre-EPA mandates on emissions. If so, those old carbs could be golden on a newer saw.

 

[drf256]

Nice work Brett, as always. Thank you for taking the time to do a thread.

Talk about Band width...

 

[Al Smith]

The Brazil Mag I have is the one I souped .It came from "Rocky J " in Florida .The German Mag is a stocker that survived 20 years for a tree service and literally grenaded a piston .JJ was kind enough to send me an OEM piston and it probably runs as well today as it did brand new .That thing spent another 8-10 years in service before it was given to me .I'm a little bit kinder to it than the trees service was .
I've ran 32" bars on both of them but obviously the modified does better .That one the exhaust opens at 96 after as opposed to the stock 101 -102 4 cycles at around 14,500 or so .Original piston/deck clearance around 45 thou taken down to 23-25 now--D-handle obviously .

 

[GoBigBlue1984]

Sent from my iPhone using Tapatalk

Gorgeous Ryan. Thank you for sharing.

 

[GoBigBlue1984]

The Brazil Mag I have is the one I souped .It came from "Rocky J " in Florida .The German Mag is a stocker that survived 20 years for a tree service and literally grenaded a piston .JJ was kind enough to send me an OEM piston and it probably runs as well today as it did brand new .That thing spent another 8-10 years in service before it was given to me .I'm a little bit kinder to it than the trees service was .
I've ran 32" bars on both of them but obviously the modified does better .That one the exhaust opens at 96 after as opposed to the stock 101 -102 4 cycles at around 14,500 or so .Original piston/deck clearance around 45 thou taken down to 23-25 now--D-handle obviously .

Do you happen to have the port timings for each Al? I’d be curious to see the difference in the two.

 

[Al Smith]

The only thing I remember was the stock exhaust opening which was around 101-102 stock on the Brazilian .I doubt the German was any different but I never checked it because I never changed it .
What you have is two different trains of thought on this exhaust opening thing .Some hold it longer to attempt to get a little more torque and some raise it up to get more RPM's .I do the later but also take it wider and it appears to work but I'm not going to get in a three page argument about it .It works for me but that's with a pop up up piston too .
I did basically the same deal on an 038 AV except that was a factory hemi domed piston which I did not cut .It runs good too but I think I only raised that one to maybe 98 after opening .

 

[GoBigBlue1984]

Completely agreed Al. I too like a low exhaust for a work saw. But I’ve vowed to try a couple things outside of the norm for me. If nothing else, I’ll learn something.

This 038 is a good candidate to see if I could raise the exhaust to 95-96 and see if the wide band and tight squish would negate the compression loss of the exhaust opening sooner. The smaller chamber and less blowdown (raising the uppers even more) could be the ticket.

High compression, high exhaust without building a head.

 

[Al Smith]

There 's really no actual wrong way to do it if done within reason .Which is not saying it can't be really f---d up if done completely incorrect .I can't remember everything but as an example a Stihl 200T probably the hottest little trim saw ever made has huge transfers and I think around 96 after right from the factory I think around 35 thou piston deck clearance .They can be improved also unless you really go bonkers and do something really nutty . Same deal,pop up,cylinder shaved but keep at 96 ,muffler cleaned up for flow .Bottom muffler not the best design for flow .Elasto start on that one,it will snap back .You have to work with what you have .

 

[drf256]

Completely agreed Al. I too like a low exhaust for a work saw. But I’ve vowed to try a couple things outside of the norm for me. If nothing else, I’ll learn something.

This 038 is a good candidate to see if I could raise the exhaust to 95-96 and see if the wide band and tight squish would negate the compression loss of the exhaust opening sooner. The smaller chamber and less blowdown (raising the uppers even more) could be the ticket.

High compression, high exhaust without building a head.

Raising the exhaust roof reduces cranking compression less than one would think. To me it’s more about not bleeding off mid rpm cylinder pressure from combustion too soon. Leaving the roof physically lower creates a hybrid of sorts, smaller case/swept volume ratio. It’s all about how much you can fill that swept volume column with the correct stoichiometric charge. If you can fill it completely at a given rpm, you shouldn’t lose anything.

How can 2 outa 3 Al’s be wrong?...

 

[Al Smith]

How can 2 outa 3 Al’s be wrong?...

Oooh,I'm not going to touch that one . Depends on the thought pattern I suppose .The whole thing adds up to the sum of the parts .Never the less you can't just pull the base gasket and cut another hole in the muffler and call it a hot saw .Rather than get in 15 page BS session I'l just say the subject saw,Stihl 038 Magnum is and was a damned good saw worthy of some restoration if it needs it .They will hold their own with anything made today EPA regulations be damned .

 

[GoBigBlue1984]

Raising the exhaust roof reduces cranking compression less than one would think. To me it’s more about not bleeding off mid rpm cylinder pressure from combustion too soon. Leaving the roof physically lower creates a hybrid of sorts, smaller case/swept volume ratio. It’s all about how much you can fill that swept volume column with the correct stoichiometric charge. If you can fill it completely at a given rpm, you shouldn’t lose anything.

How can 2 outa 3 Al’s be wrong?...

Al, you are truly the man. I learn something from you often. Thanks so much for commenting/sharing.

I’m just a hack, but you my friend....are the real deal. Your knowledge and understanding of engines in general is infinitely higher than mine.

 

[GoBigBlue1984]

Oooh,I'm not going to touch that one . Depends on the thought pattern I suppose .The whole thing adds up to the sum of the parts .Never the less you can't just pull the base gasket and cut another hole in the muffler and call it a hot saw .Rather than get in 15 page BS session I'l just say the subject saw,Stihl 038 Magnum is and was a damned good saw worthy of some restoration if it needs it .They will hold their own with anything made today EPA regulations be damned .

Well said Al

 

[Al Smith]

I think people get hung up on cookie cutters and real work saws .You can raise them up to maybe 92 after with a big carb and the head deck so close it has almost diesel compression .Pot licker will rev up like a model airplane engines and cut 9" poplar cants lickity split .Take it to the woods and try it out on some white oak. Isn't worth a hoot .Too damned perky ,won't lug very good .Have to keep it in specific RPM range to keep the power .Having said that I think the cookie cutter popularity went the way of the passenger pigeon .Fun maybe but not real practical .

 

[drf256]

Al, you are truly the man. I learn something from you often. Thanks so much for commenting/sharing.

I’m just a hack, but you my friend....are the real deal. Your knowledge and understanding of engines in general is infinitely higher than mine.

Not sure I am right, but thank you for the kind words.

And you are far from a hack.