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Bummed with my cross 359 cylinder. Would you run it? Updated!!!

XP_Slinger

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Tough to say.

The plenum does come to mind, so does air and fluid flow dynamics. Also, vacuum flow and pressure flow are different.

On a V8 Big Block Rectangular port Chevy, would anyone in their right mind make the intake manifold area the same size as the carb venturis? Never.

There's a balance that occurs and where that lies is the mystery.

Sometimes it's clear by theory, and at other times we stumble upon it by accident and scratch our heads.
Funny you use the V8 example, that’s where my mind draws the plenum “theory” from. Different air pump but still a pump. Thanks Doc, as always I learn a lot from you

:beer-toast1:
 

Stevetheboatguy

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Ok here goes. Last night before anything fully set on the saw. I swapped out the oem jug for the cross.

Today I got out of the shop early and tried it out. The results were not good. Would surprisingly tach 13200 no load. But wouldn't hold 7000 in the cut. Had to be very very light on it. Regardless of the carb screws fat or lean it was a total dog. My poulan 5020 easily out cut it.

I got back to the house and all my kids were napping. So rather than wake them. I went into the garage and swapped the oem cylinder back on.

Went back out and made a few cuts. Night and day difference. Didn't try to tune it for max rpm yet, but I did throw the tach on it and it's four stroking at 10500 in the cut. Needs leaned out a little bit more.

Same 16" bar and chain. Same piston and ring in both cylinders. Same material for the base gaskets. Only difference was the cylinder.

That's all I have for now. It's what I have spent the last three hours doing.

Hopefully this info helps someone down the road.



Steven
 

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Thanks for taking the time to do the experiment Steve! I wonder if that small intake is why it won't maintain well under a load. Did it seem like it was lean under a load?? Or just plain couldn't pull it??

Good cylinder to experiment with, one change at a time. First thing I would probably do is either give the intake more area, or give it more time by lowering the floor.
 

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@tree monkey piped 066 has a smaller diameter pipe exit (stinger?) than the size of the Ex flange. He says making it bigger will kill the saw.

Does any of this make sense?

I say run the AM jug. See what happens. My guess is that it will be a dud.

Good post Doc :)

Tuner pipes definitely bring more to the game. No you are using the exhaust header shape to maximize scavenging. I'm no tuned pipe expert/designer, but in all of the time I have spent in 250r world hopping up my trikes, a common theme I have seen said by the industry's best 250r builders is that stinger diameter and length does have an effect and there is always a sweet spot for the stinger dimensions for a given expansion chamber design and cylinder port layout. It all works together
 

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Thanks for taking the time to do the experiment Steve! I wonder if that small intake is why it won't maintain well under a load. Did it seem like it was lean under a load?? Or just plain couldn't pull it??

Good cylinder to experiment with, one change at a time. First thing I would probably do is either give the intake more area, or give it more time by lowering the floor.

It just couldn't pull it. I tried for a while playing with the tune but it just didn't have any guts at all.


Steven
 

Stevetheboatguy

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Did you measure squish clearance?

I believe it was .028. With the thin gasket I made. I didn't write it down. Gasket material is .013 before it's crushed.

Haven't checked the oem squish yet. But I made a gasket from the same material for it. (Don't know why I didn't just reuse the first one. Damn ocd).

Steven
 

Stevetheboatguy

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Squish clearly is not the problem. The problem is in the casting itself. That cylinder is useless as is.

Not totally useless. I'm going to experiment grinding transfer's or secondaries on it. I've done plenty of intake and exhaust, but never the uppers.

And if it's not a successful learning tool. It will meet the 7mm for some extreme port work/vaporizing whatever you want to call it :para:


Steven
 

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Not totally useless. I'm going to experiment grinding transfer's or secondaries on it. I've done plenty of intake and exhaust, but never the uppers.

And if it's not a successful learning tool. It will meet the 7mm for some extreme port work/vaporizing whatever you want to call it :para:


Steven
That would be video worthy!

Thanks for running this experiment. It’ll be interesting to see where you find the most gains in grinding. Having the OEM cylinder to compare will be an asset in your first time grinding on the upper transfers.
 

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Too many variables to determined which part of the experiment lead to the suck-as-ness of the AM jug.

For any real determination, both jugs need to be timed, both degreed, both squish measured, and both given a quick compression check.
 

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Too many variables to determined which part of the experiment lead to the suck-as-ness of the AM jug.

For any real determination, both jugs need to be timed, both degreed, both squish measured, and both given a quick compression check.
Yes sir they do. Get it all on paper and start from there. I doubt this will be a one port fixes all endeavor.
 

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Too many variables to determined which part of the experiment lead to the suck-as-ness of the AM jug.

For any real determination, both jugs need to be timed, both degreed, both squish measured, and both given a quick compression check.

Yes sir they do. Get it all on paper and start from there. I doubt this will be a one port fixes all endeavor.


Bingo.

This one is going to be pushed way back in the project list. But when It makes it's way to the front again. I will measure and check everything before I go nuts with a grinder. Probably experiment with one port area at a time. See where the most gain is. And definitely see where the port timing is before I start. I have a feeling it's not even close. But no time for playing right now.

I didn't really like the 357/359 saws until recently. But now I'm hooked. Have three runners and a couple needing work. I am in need of a recoil and at least one more set of cases for sure. But eventually they will come my way. Cool thing is. All three of my runners are G models.


Steven
 

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Bingo.

This one is going to be pushed way back in the project list. But when It makes it's way to the front again. I will measure and check everything before I go nuts with a grinder. Probably experiment with one port area at a time. See where the most gain is. And definitely see where the port timing is before I start. I have a feeling it's not even close. But no time for playing right now.

I didn't really like the 357/359 saws until recently. But now I'm hooked. Have three runners and a couple needing work. I am in need of a recoil and at least one more set of cases for sure. But eventually they will come my way. Cool thing is. All three of my runners are G models.


Steven
My 357 is one of my favorite saws, puts a smile on my face every time I run it.
 

GCJenks204

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Bingo.

This one is going to be pushed way back in the project list. But when It makes it's way to the front again. I will measure and check everything before I go nuts with a grinder. Probably experiment with one port area at a time. See where the most gain is. And definitely see where the port timing is before I start. I have a feeling it's not even close. But no time for playing right now.

I didn't really like the 357/359 saws until recently. But now I'm hooked. Have three runners and a couple needing work. I am in need of a recoil and at least one more set of cases for sure. But eventually they will come my way. Cool thing is. All three of my runners are G models.


Steven

No love for the J-Red any more?
 

Stevetheboatguy

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No love for the J-Red any more?


Love the j-red but.......

Honestly I haven't even started it yet. I may get a chance to give it a once-over on Monday. Just to make sure it's ready to go. Because Tuesday -Friday my dad and a friend may come over and help me drop, cut haul next year's start. It's going to be nice having all heated saws this time. The jred from you, the 357 from @laslabjohn , this 359 that @jockeydeuce got me set up with the g parts. And my walkers 372xpg. Should make fast work out of it.

I'm running a good three months behind. That darned surgery on my leg held me up. Right now I'm just enjoying the time with our new baby girl. So that hasn't helped me get ahead, but she is worth it. And I'm enjoying every minute of it.




Steven
 
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