372/385 Hybrid

[TBrown]

You can buy sae threaded rod and bolts made from aluminum from Mc Master

 

[blsnelling]

What's the stroke difference? Bolting it up is only one piece of the pie.

 

[Mattyo]

Thanks for letting me know about the aluminum rod. .

Brad ....the diff is only 1 or 2mm stroke. Easy to account for by milling the case down

 

[strtspdlx]

I wish I still had my saw and my parts saw. I'd definitely donate to the cause. The jug I have right now I couldn't donate. I'm saving it for a special project if it doesn't sell. Now you have me thinking of the Stihl hybrid. 460-660


Regards-Carlo

 

[Mattyo]

Might it be better to slot the bolt holes in the cylinder as opposed to drilling and tapping new holes in the case? Also, could another piston of the correct diameter with a 12mm wrist pin be utilized to save having to make bushings?

Joe

Ok, spoke to Homelite410 this evening for a total of 5 minutes and he was a wealth of information, and suggested just what you suggested Joe, to consider using another piston, or consider wrist pin caps that act as bushings. I want to do my homework and have all my ducks in a row before I cut anything, but I'm kinda hung up on this.

stock height from top of wrist pin to top of piston is 16.5mm according to one of bailey's pistons for a 372. it seems to me like I could use a 660 piston with a 12mm wrist pin, as it has a 17mm stock height (taller is good, will make up for stroke differential), but the piston is windowed. Anyone know if this is going to be an issue? Seems like this would be the simple fix if it would work.

http://www.baileysonline.com/Chains...6-MS-660-Chainsaws-Replaces-1122-030-2005.axd

once I have the piston sorted, I can mod the jug/case assembly to fit without issue I think.

 

[mdavlee]

You would have to raise the transfers on the bottom some tI feed them. There's also 288 pistons, 7900 BB, jonsered 910-930

 

[Mattyo]

Need a 12mm wrist pin stock
....288 has 13mm...I think

 

[Mattyo]

The 7900 is too short I think

 

[bplust]

066?

 

[bplust]

066?

Never mind, I missed your previous post regarding this.

 

[Mattyo]

Maybe messing with the wrist pin might be the way to go

 

[idiotwithasaw]

dude i want to see this so bad, there was a post a while back that i read where someone put a 385 carb on a ported 372 xpw. it required the 385 boot and carb, and the gutted intake horn off a 372 xtorq. not sure if you could just use the 385 filter and intake.

http://www.arboristsite.com/communi...r-your-hopped-up-372-375.195586/#post-3530386

 

[idiotwithasaw]

my next question tho is why stop at 385, why not a 390?

 

[mdavlee]

Real small case capacity is one reason. There's 52mm big bore kits already. Maybe boring one of them out if the walls are thick enough and having a Wiseco piston made would be the longest lasting.

 

[Mattyo]

Sounds exotic. I think I'm going for proof of concept here but still expect a runner. I saw weimedog's video showing how thin the walls on the hutzl 52mm big bore are... not sure thats the way to go...plus plating would be what, $200 alone? I can get a meteor 385 kit for like $135.

The 385 has 54mm and the 390 has 55mm bore. I'm a big fan of bigger if possible, but if I was going to change out the piston there are more options at 54mm. If I am not going to change the piston then i'll go to 55mm if possible.

So far it seems like changing the piston is... involved, mostly due to the windowing. It ends up being compromise onto of compromise. If I can build a wrist pin with end caps, that would likely be the ticket, because I can expand a 12mm to 13mm wrist pin and accommodate a stock 385/390 piston. Then I just have to drop the jug enough to account for the stroke, and/or take some off the piston. popup? 1mm = 39 thou...

here's a question, if the stroke is 2mm longer on a 385, does that mean I only have to drop the cylinder 1mm due to the stroke being a circular motion? and then just account for the transfers timing somehow?

 

[mdavlee]

55 mm bore isn't but a 390 and an old dolmar. I would think you could find a drop in piston.

 

[Mattyo]

#1, you and I need to go to bed,

#2, you are WAY more experienced at this than me, so if you could point me in a direction to find a drop in piston, thats great. need 12mm wrist and 16.5+mm top of pin to top of crown height, non windowed.

 

[Mattyo]

I've looked now, a lot. I don't see anything that will drop in. Seems to me I have to machine the wrist pin at this point. I'll pick up an AM 385/390 kit and machine a wrist pin/ piston to fit a 12mm needle bearing and con rod on the 372.

 

[mdavlee]

I'm on night shift.

Sometimes the bearings can take up the difference. Like with the 288 and 066. Different pins but the rod end is the same size. Use the bearing for the piston.

 

[Marshy]

Go for it, if you succeed it will be awesome. If it fails, then it will be awesome. Either way I will be awesome!

Fixed that for ya.