Basic "Blueprinting" steps

[davefr]

I'm transforming my 034 into an 036 and have the new 036 cylinder and piston on the workbench. Before I put everything together is there any opportunity to take steps to improve performance.

I've ruled out timing/porting changes since I haven't learned the theory yet and don't want to blindly make design changes.


1. I notice the piston has lathe marks on the top. Would it be beneficial to have the piston top perfectly smooth/polished?
2. The exhaust gaskets are slightly smaller then the exit port to the muffler. Should I enlarge the exhaust port so there are no ridges or valleys where it get's connected to the muffler. (muffler's already been opened)
3. I've noticed somewhat rough casting texture inside the transfer ports. Would polishing the inner surface of the transfer ports be beneficial?
4. Intake port looks pretty good as is. Should I do anything. (I notice my old 034 cylinder had a little tit in the intake port where the 036 doesn't. Anyone know what this tit was for?
5. This violates my original goal but I though about taking a very modest amount off the cylinder base and compensating by chamfering the top piston edge by an equivalent amount. (however I doubt I'll do this).
6. Are there any other steps involved in "blueprinting" the top end? What steps does Madsen's do on the top end?

Or should I skip all of the above and put it together.

TIA

 

[timberwolf]

IMO, polishing the piston helps keep the carbon from sticking and building up on it, should reduce heat transfer into piston too. Dito for the exhaust port, a nice miror surfave helps it stay clean.

Matching the exhaust port outlet to the gasket and muffler is a good idea to maximize flow restrictions.

Transfer and intake port surfaces is debated, but removing any major casting flaws cant hurt.

A bit off the base of the jug may give a bit of compression but you need to mind the squish height too ensure .020 min (to be safe) from the top of the piston to head at tdc.

 

[thompson1600]

What methods do most of you use to "take a little off the base of cylinder"? I don't have a milling machine, and just wondered if any of you were using other methods.

Thanks

Tom

 

[rb_in_va]

What methods do most of you use to "take a little off the base of cylinder"?

That's what I was thinking. It would take a long time with a granite block and sandpaper to remove enough metal to make a real difference.

 

[bump_r]

Matching the exhaust port outlet to the gasket and muffler is a good idea to maximize flow restrictions.

minimize flow restrictions or maximize flow efficiency, right?

 

[Jim Mesthene]

The air entering the engine starts at 14.7 psi (atmopheric pressure). The exhaust exiting the combustion chamber starts at about 2000 psi.
The high pressure exhaust can easily overcome minor obstacles like a protruding gasket while the intake air has little energy to bypass restrictions.
Thus, gains on the intake side are far more significant than gains on the exhaust side. (Everyone wants some kind of supercharging; have you ever heard of an exhaust fan on an engine?)
I'm not advocating a restricted exhaust, but the real gains are made on the intake side.
So, spend more effort on the intake while not leaving any obvious restrictions in the exhaust. Exhaust restrictions are usually the easiest to make improvements on, but it's a mistake to say that they improve breathing; all they do is stop suffocating. After you've stopped choking (restricting) the exhaust by removing the obvious baffles etc. you've done all you can on that side.
Serious improvements on the intake side usually require a flow bench, and the know-how to use it. Getting rid of obvious choke points is always a good idea.
A dimple or post in the intake flow is sometimes done to promote swirl.
Polishing the piston top will reduce heat absorbtion and increase power; for a few minutes. Once the piston has again aquired a smooth, black coating of carbon, it acts like it was never polished; don't bother.

 

[timberwolf]

The flat surface and sand pape works quick enough, measure the thickness of the base flage at several points around the jug before you start and then take it down to what ever you are looking for.

As far as clean up, to give laminar flow as much as possible, as you say to minimize flow restrictions or maximize flow efficiency.

Note with intake and transfers, bigger and smoother does not consistantly = more HP (in some cases restriction is built in by design). But removing any major casting flaws should help to give the flow the engine was designed to have.


In some cases the gasket can be remove and gains found, but you will need to check the squish height and measure the gasket before deciding to do that.

 

[Lakeside53]

Nothing wrong with any of the suggestions above, but your gains will be quite modest and I wonder whether any of it is really worthwhile for normal saw usage. Sure, polish up your ports, but decking the cylinder - I wouldn't bother. Your biggest gain will come from modifying your 034 muffler into one that better matches your 036 cylinder. The 036 mufflers have much larger outlets and usually vent to the side rather than the front. You're probably going to have to change the muffler anyhow as your original 034 muffler casing may be 2mm too long.

 

[Crofter]

Anything that you do that can still use standard replacement parts at any point is not too bad. Any change that prohibits a routine repair with stock parts, might lower the resale value.

 

[Jim Mesthene]

I agree with Lakeside53, don't bother. If you do everything right, you could gain 10%, if you sharpen your chain two extra times you'll gain more.

 

[Lakeside53]

I agree with Lakeside53, don't bother. If you do everything right, you could gain 10%, if you sharpen your chain two extra times you'll gain more.

Heck, I was thinking maybe a 1 or 2%... excluding the muffler... but what do I know?

Yes, a sharp chain and a stock saw is what 99% (prove my number wrong ) of the world uses, and is happy with.

 

[Jim Mesthene]

Did you know that 76% of all statistics are made up on the spot?

 

[timberwolf]

I would agree with lakeside, the gains would likely be in the order of a couple % points, more could be found alone by improving the chain sharpening.

But a couple % gain on the engine is compounded by any gains made in the chain. If you have the time its a good way to get to know the saw and tools and put a bit of ownership into the saw and if it cuts a few hundredths of a second quicker all the better.

It takes a good bit of work in the engine to find 10%, the beter the engine is to start out the harder it is to find.

 

[Jim Mesthene]

The 10% was meant to include the muffler.

 

[timberwolf]

On new EPA saw 10% or more can be easily found in the muffler alone. I don't know that this is equal to 10% increased horse power, but in cut times which I assume work out close to 1:1.

 

[Mr.]

Did you know that 76% of all statistics are made up on the spot?

True about 50% of the time.


Fred

 

[Lakeside53]

The 10% was meant to include the muffler.

then we're in violent agreement!

 

[ozflea]

If your not going to get a really noticable increase in proformance then just screw it back together again in standard form and save yourself a lot of work.

Mc Bob.

 

[stihltech]

mods

And another well-intentioned amatuer modder gets shot down.:bang:

 

[Jim Mesthene]

He's increased displacement and he's hogging out the muffler, and he's ruled out porting. What's left that will produce significant gains? Nitro?