Porting information, specifically intake

[drf255]

You don't have a right angle piece, so you're stuck with your transfers, is that correct?

It sounds like you don't mind playing, so I'd JB weld the intake to 75. I find it simple to use paper or aluminum foil with a slightly looser piston as a dam for the messy epoxy. Keep the jug tilted so that the epoxy stays about level at the entry angle you are looking for. Don't forget to fully degrease the port, and make a few divots in the floor for the JB to hold onto.

You can progressively lower the floor and always raise it back with not much work.

The ways I see it, you want more pressure cause your transfers are physically a bit lower than you want. You can raise either their intake floor of the transfers, but you can't do the transfers because of lack of tooling.

It won't ruin your jug or do anything bad to your saw, so why not give it a shot? If it's worse, just grind it out.

Again, is this a quad or dual transfer saw and what CC displacement ?

 

[blsnelling]

After screwing around with that dumb wheel I think that my intake duration is 162 which means it opens at 81, right? I have raised the intake slightly to a duration of 158-160..... It is 158 looking through exhaust and 160 through the spark plug. I think that means it opens at 101-100, right?

I think we have some misunderstanding here. Intake is measured at the bottom of the intake port as the piston skirt opens it while moving upwards. This cannot be measured any other way than through the intake port. If you have raised the intake port, along with lowering the jug, you need to make sure you're not dropping the ring end into the intake port! That's a deal breaker right there.

The ways I see it, you want more pressure cause your transfers are physically a bit lower than you want.

I don't see the transfers as being low. He only has 15° of blowdown the way it is.

We actually need to drop back now and wait to find out what his intake timing really is.

 

[AK jonsered]

It is a quad and displacement is 59cc. Pretty much a husky 359 with a 357xp top end. The upper transfers are bigger than stock and lowers look like a 357xp. The bore is the same as the 359. The combustion chamber is smaller than stock...

I would like to see how she runs now, but the epoxy idea is still on the table for later. We will see if I can work it in with all the other projects. It is sorta how I unwind after work.

No, the intake has been raised less than I dropped the jug. When I said raised the intake, I meant exhaust, will fix

Next project is making an aluminum backed timing wheel. Then more port messing.....

 

[Chris-PA]

The ways I see it, you want more pressure cause your transfers are physically a bit lower than you want.

You lost me there - if the transfers are low then they open later, which means there is inherently a longer case compression angle. If you raised them you would reduce case compression. The case (primary) compression angle is between when the intake closes and the transfers open, as shown below:


You can increase case pressure by reducing intake duration too of course, but I don't see the connection to lower transfers - it would seem to be the other way around.

 

[AK jonsered]

I think it was more a flow issue then compression? I think that widening the transfers would increase flow enough that the extra intake could flow better. Because I have no way of adjusting the transfers, I have to increase case compression to increase flow...

Should probably buy another tool... Are right angle grinders like $400? Maybe after vacation


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[drf255]

I didn't know it was a Quad Brad.

I actually like his numbers betterer now.

 

[drf255]

You lost me there - if the transfers are low then they open later, which means there is inherently a longer case compression angle. If you raised them you would reduce case compression. The case (primary) compression angle is between when the intake closes and the transfers open, as shown below:
View attachment 504711

You can increase case pressure by reducing intake duration too of course, but I don't see the connection to lower transfers - it would seem to be the other way around.

I'm not gonna get into an argument. Part of why I don't post here as much any longer.

The transfers need to be a certain height to fully fill and scavenge a cylinder. If they are too low, even with a high intake and lots of case comp angle, they aren't gonna fully evacuate burnt charge. If they are too high, they can backfill and/or push so much in that they eject fresh charge out of the exhaust port unburned.

I'll bow out now guys.

 

[Chris-PA]

I'm not gonna get into an argument. Part of why I don't post here as much any longer.

The transfers need to be a certain height to fully fill and scavenge a cylinder. If they are too low, even with a high intake and lots of case comp angle, they aren't gonna fully evacuate burnt charge. If they are too high, they can backfill and/or push so much in that they eject fresh charge out of the exhaust port unburned.

I'll bow out now guys.

So you see a discussion as an argument? It's not like I attacked you, I merely disagreed with your comment and presented an alternate view. A continued discussion could lead to better understanding by all, but instead you are offended. Why such a thin skin? I agreed with some of your thought in your second comment. Except this:

or push so much in that they eject fresh charge out of the exhaust port unburned.

I've read this before but never seen anything to support it, and I don't think it really happens. We had a long discussion of case compression and Delivery Ratio over on chainsawrepair a few months ago that is sort of relevant.