Stihl 044 timing numbers?

[Brock Mayo]

I'm about to start grinding on the old 044 and was hoping someone can give me some advice. I think I'm sticking with the stock squish (came in a bit too tight with no gasket).
The squish is .03
Exhaust opens at 102 ATDC (156 duration)
Transfers open at 117 ATDC (15 blowdown)
Intake opens 70 BTDC (140 duration)
Not planning on messing with the upper transfers, but was wondering what you pros would do with the Exhaust and Intake heights? You don't have to worry about me taking anyone's business, it took me three weekends to replace the bearings Thanks!

Brock

 

[lxskllr]

@Al Smith might have something useful for you.

 

[stikine]

@huskihl to the rescue?

 

[stig]

Are you going to show it at Pebble Beach when it is finished?

 

[Brock Mayo]

Hmm, Pebble Beach?

 

[Nutball]

From what I remember they have good stock numbers, so stay conservative: just a healthy muffler mod, lower the intake to around 72 or 74. Dont widen the ports further than 33-34mm, though they may already be a smidge wider than that. Raising the exhaust and lowering the intake makes peak power at higher rpm, and reduce low rpm torque such that it can stall in the cut at a higher rpm than stock. Raising the intake is relatively easy if you find you went too far compared to lowering the exhaust.

A high flow air filter can help a lot too.

I'll have to check sometime if I have any notes on a 044.

 

[Brock Mayo]

I really appreciate the help. Thanks!!!

 

[Nutball]

I just checked my notes. I'd try 75 on the intake, and 101 on the exhaust.

 

[huskihl]

I wouldn’t raise the exhaust because you haven’t increased the compression. You can widen the exhaust to within 1MM of the edge of the skirts. With cylinder on, trace the exhaust port onto the piston so you know how far you can go on each side. You need to leave at least 1MM of skirt wider than the port so the piston can seal the port. I’d take the intake down to about 76 and widen the intake a little bit with the same rules as the exhaust port. Stay 1MM narrower than the edge of the intake skirt.

 

[huskihl]

Make sure the exhaust port has a slight arch to it so you don’t snag a ring. And bevel the ports with a diamond ball and finish with sandpaper when you’re done

 

[Brock Mayo]

I like that method for knowing how wide you can go by tracing the port onto the piston. I haven’t run across that in a video that I can remember. Thanks guys!

 

[huskihl]

Not an 044, but you want about this much arch in the exhaust roof. Flatter will deliver more power, but you don’t want to snag a ring. The arch will ease the rings back in

 

[Nutball]

I cheated and got both flat and arched

 

[Brock Mayo]

Great pictures! I’ve seen some domed pistons, but nothing like than. Is that a common option, or just something you’ve tried?

 

[Nutball]

I've only done it 3 times and I don't have a picture of just the piston to show what it looks like. It's not a full dome, just a little off the edge on each side of the exhaust port.

 

[Brock Mayo]

Well, I got a little gun shy on my grinding. Ended up smoothing out the lower transfers and widened the intake and exhaust slightly. Timing numbers ended up about the same.
What do you'll like to do with your muffler mods? Bark box, another port on the opposite side, or both?