Porting Stihl 038 - The intake hump???

[Brewz]

Hi Folks.
I have a couple 038 Magnums here that I am rebuilding and was going to do a bit of grinding on them for the friends I am rebuilding them for.

What are peoples opinions on the hump in the intake port?
I assume the idea behind it is to direct the charge towards the transfers but I am thinking if the feature was discontinued, it may be worth getting rid of.

I also have an 084 with the same hump.

what do you recon...... leave it, grind it out, or smooth and reduce?

 

[Mastermind]

It's actually a support for the ring at BDC. I just thin it and streamline it a bit.

 

[Brewz]

Problem solved in one post!

Thanks mate

 

[jb-chainsaws]

I notice on the 038 mag the intake hole at the boot side isn't a full circle but rather has the bottom and left side square and the rest round. Seems a lot area is lost here and it feels like it'd impede flow a lot.

What's your opinion on grinding on this?

 

[Mastermind]

I notice on the 038 mag the intake hole at the boot side isn't a full circle but rather has the bottom and left side square and the rest round. Seems a lot area is lost here and it feels like it'd impede flow a lot.

What's your opinion on grinding on this?

If you open the jug, and it no longer matches the boot, what have you really gained?

 

[jb-chainsaws]

If you open the jug, and it no longer matches the boot, what have you really gained?

Good point, 044 boot it is then! Now onto the carb, do you think the bing would flow enough to allow the new boot and opened jug make any difference?

 

[Mastermind]

Good point, 044 boot it is then! Now onto the carb, do you think the bing would flow enough to allow the new boot and opened jug make any difference?

If you are going that far......use a bigger carb.

 

[Canadian farm boy]

Good point, 044 boot it is then! Now onto the carb, do you think the bing would flow enough to allow the new boot and opened jug make any difference?

The 044 intake boot won't work due to the impulse passage. I'm sure it could be made to work with enough determination. You would have to figure out an alternative way for the impulse line.

 

[Chainsaw Jim]

The little uvula hump can be completely ground out to match modern cylinders.
Look at what you're working with and you'll see that the intake is not any wider, nor are the ring pins any narrower on the piston. Keep the shape of the intake roof in mind so it matches the shape of the exhaust to give the rings trouble free travel.

Are we positive it is for ring protection or is it done to splash mix downward to the bearings to keep them wet?

 

[Chainsaw Jim]

The 044 intake boot won't work due to the impulse passage. I'm sure it could be made to work with enough determination. You would have to figure out an alternative way for the impulse line.

You should be able to drill a passage through the carb body to match the impulse hole.
For example if you have access to two wj carbs from a 394 and an 066 you'll see how the impulse in the wj39 is through the carb body where the wj69 is plugged and routed through the cover plate. Either can be easily made to interchange with the other with one drill bit and jb weld. You just swap the plates after drilling or plugging holes.

 

[Mastermind]

Right on Jim. You are right about being able to remove it........I've done just that on 084s. I just err on the side of caution when sharing info with other people.

Good stuff on the carbs.

 

[Chainsaw Jim]

Right on Jim. You are right about being able to remove it........I've done just that on 084s. I just err on the side of caution when sharing info with other people.

Good stuff on the carbs.

The last thing I want to be responsible for is leading someone to ruin their equipment. That's exactly why I deleted certain info I posted about carb modding. a modded carb will work awesome on one saw but not at all on any other saw. I flat out destroyed a wj39 carb for my 394 experimenting with it. The 394 wouldn't run right no matter what. Before junking it for parts I decided to try it on my 075 and it made that saw run better than it's ever ran before. lol

 

[Brewz]

If you are going that far......use a bigger carb.

If your going that far, sell it and get an 044.
I am not interested in extreme porting these 038's, just a bit of flow and directional work to help them along

 

[Mastermind]

I've built some 038 Mag IIs that will make a feller pretty happy. With the stock carb and boot.....

 

[Chainsaw Jim]

If your going that far, sell it and get an 044.
I am not interested in extreme porting these 038's, just a bit of flow and directional work to help them along

A stock 038 mag II running right will cut side by side with a stock 044/440.
And when Randy says happy he's being very modest.

 

[Brewz]

Oh I believe it.
I will be keeping the stock boot and carb and intake shape, just adding to it a bit,

The ports look really good stock to be honest

 

[drf256]

You should be able to drill a passage through the carb body to match the impulse hole.
For example if you have access to two wj carbs from a 394 and an 066 you'll see how the impulse in the wj39 is through the carb body where the wj69 is plugged and routed through the cover plate. Either can be easily made to interchange with the other with one drill bit and jb weld. You just swap the plates after drilling or plugging holes.

Good Stuff Jim.

Was thinking of doing just that in an attempt to add a 44 carb to an 036. Figured the passage had to be there.

BTW, no one has mentioned that the flat wall of the boot and intake port matches the flat side of the Bing Venturi in these saws.

 

[Brewz]

Will anyone dare to offer help with port timing advice for the older shorter stroke saws like 038?
I have not measured the 2 x 038 magnums I have here but I am wondering where they like to run best?

 

[drf256]

Funny how it's short stroke but reported to be a torque Saw.

Randy has to have numbers, for sure.

I'd bet 102/124/74 myself. That intake uvula may allow you to safely raise the intake roof for more time/area without sacrificing case compression.

 

[Chainsaw Jim]

If I were going to port an 038 mag I'd raise the exhaust by one degree and modify the intake to match an 066 or 372oe intake boot. A carb upgrade may not be necessary. I wouldn't touch the transfers since they're already larger than a slant fin 044.