Hybrid clonesaw 365 with a 390 topend - aka the "86'r from youtube"

[Woodwackr]

 

[Rich Fife]

 

[Mad Professor]

View attachment 452481View attachment 452482

Are those pictures at BDC and TDC of the stroke?

 

[Woodwackr]

Are those pictures at BDC and TDC of the stroke?

Yes
Here's BDC, intake side

 

[Woodwackr]

I’m curious as to where the piston will wind up in this hybrid build.
I know things can be manipulated via matching the cyl but to what degree? Just wondering what types of things will be “adjusted”. Just the cyl, piston as well?

 

[upstateamish]

It's a custom build... its normal to assemble and disassemble multiple times. Unkess, you do all of the calculations prior... but, Setup bearings make it a relatively painless process.

Yup... I know but just had my false sense of hope going that I had nailed it right out the gate... turns out I'm still bad at math...

I’m curious as to where the piston will wind up in this hybrid build.
I know things can be manipulated via matching the cyl but to what degree? Just wondering what types of things will be “adjusted”. Just the cyl, piston as well?

Good question and I'm not sure, I had step away to go run some errands after I got the case back together and rotating freely. I'm hoping I can use the 390 piston that came with the cylinder but I'm not 100% on where that'll land with the larger stroke of the 395 crank... which reminds me I need to figure out a way to cut my squish band (I lack a 4 jaw chuck for my lathe so will ponder a bit... may end up doing the sandpaper on a piston approach for now.

But that'll probably become apparent if it's needed or not once I get a chance to get a piston on the connecting rod we'll see where it ends up. (I imagine we'll have some interference in a variety of places...)

Here's what the cylinder will looked like with the lower transfers/case openings matched up.






I may do some minor port work on the cylinder but only if the numbers are wicked off out the gate. The goal of this second prototype will be to see if I can get this crank with the larger wistpin combo working... I plan to do a third itteration which I guess I would call "the lessons learned build" (maybe build that with a 390 big 57mm bore top end... but lets not to get to far ahead just yet)

 

[upstateamish]

Good news - Piston clears the bottom of the case.
Expected news - Piston hits the top of the cylinder




Top of piston at BDC does not fully clear the exhaust port


I'll work on figuring out how to get clearance to get a full rotation and then some timing numbers

 

[Woodwackr]

Good news - Piston clears the bottom of the case.
Expected news - Piston hits the top of the cylinder

View attachment 452538
View attachment 452537

Top of piston at BDC does not fully clear the exhaust port
View attachment 452536

I'll work on figuring out how to get clearance to get a full rotation and then some timing numbers

Mine doesn’t look so bad now

 

[Mad Professor]

Good news - Piston clears the bottom of the case.
Expected news - Piston hits the top of the cylinder

View attachment 452538
View attachment 452537

Top of piston at BDC does not fully clear the exhaust port
View attachment 452536

I'll work on figuring out how to get clearance to get a full rotation and then some timing numbers

How bad is it hitting the top? Maybe a shim/spacer between the case and the jug. Get the piston below the ex port at BDC. Could make up a plastic one to see how thick you need, or some small washers held by the case bolts just to see where squish is.

 

[Woodwackr]

How bad is it hitting the top? Maybe a shim/spacer between the case and the jug. Get the piston below the ex port at BDC. Could make up a plastic one to see how thick you need, or some small washers held by the case bolts just to see where squish is.

Start stacking gaskets till it clears? Measure and adjust the combustion chamber as needed?

 

[upstateamish]

How bad is it hitting the top? Maybe a shim/spacer between the case and the jug. Get the piston below the ex port at BDC. Could make up a plastic one to see how thick you need, or some small washers held by the case bolts just to see where squish is.

It's a pretty solid hit, but I didn't measure the exact height last night.

Start stacking gaskets till it clears? Measure and adjust the combustion chamber as needed?

I'll have to dig in a bit here to see how large gasket / shim may be needed

 

[Rich Fife]

What about tossing on a degree wheel, zero it and then see what degree the interference is at? Should be able to calculate how much needs to be removed.
What MM piston?
That exhaust will be choked with the crown height.

 

[Mad Professor]

It's a pretty solid hit, but I didn't measure the exact height last night.

I'll have to dig in a bit here to see how large gasket / shim may be needed

I was thinking you could just shim it up with small washers on the cylinder screws until it clears/rotates, that would be quick to do if you have the washers.

 

[Powerstroke Cowboy]

What if you went back to the shorter rod?

 

[Ketchup]

Start stacking gaskets till it clears? Measure and adjust the combustion chamber as needed?

^This

It's a pretty solid hit, but I didn't measure the exact height last night.

I'll have to dig in a bit here to see how large gasket / shim may be needed

Lower the piston crown first rather than raising the jug or cutting squish. The piston is heavy. Lighten it up as much as possible.

That exhaust will be choked with the skirt hanging that low.

You mean the crown that high? Not necessarily. It all depends on the roof height.


Where is the intake landing? That will indicate whether you want to raise the jug or not. Also if Ex and Trans are super low, of course.

 

[upstateamish]

Intake opening:

What about tossing on a degree wheel, zero it and then see what degree the interference is at? Should be able to calculate how much needs to be removed.
What MM piston?
That exhaust will be choked with the skirt hanging that low.

yup, just got back from doing this. This is the stock 390 piston (55mm) & agreed on the blocked exhaust

I was thinking you could just shim it up with small washers on the cylinder screws until it clears/rotates, that would be quick to do if you have the washers.

yup did some quick and dirty washer stacking (I don't have any other shim stock in hand)



But I do have DynoJoe's digital degree wheel (which works great, if anyone was on the fence on getting one. shout out to @Red97 thanks! )


With a 4.33mm washer high stack (no gasket) it clears the full rotation and puts things at:
Intake - 79,5
exhaust - 96.5
transfers - 123.5
Squish is 0.40mm

In theory (if my math is correct, which I am not sure is so correct me please) 4.1mm(ish) would be the distance needed to be removed/taken off the piston & squishband (or shimmed up) to get a .20mm squish.

 

[upstateamish]

What if you went back to the shorter rod?

I'll be ordering another 390 crank, so that could be a possibility if I can't get this working (I wasn't planning to go with the stroker crank but I'm still learning how to machine with my old iron )

^This
Lower the piston crown first rather than raising the jug or cutting squish. The piston is heavy. Lighten it up as much as possible.

yup, I plan to machine off some of the piston crown, I haven't weighed it yet but with the counterweights machined down the piston will need to lose weight as well.

You mean the crown that high? Not necessarily. It all depends on the roof height.

Where is the intake landing? That will indicate whether you want to raise the jug or not. Also if Ex and Trans are super low, of course.

See above post (should have refreshed prior to me posting

 

[Rich Fife]

You mean the crown that high? Not necessarily. It all depends on the roof heigheight

Yes, Thank you... I'll correct it.

 

[upstateamish]

I'm wondering (since I have a spare piston) perhaps machining off the top ring of the piston to make it be a single ring is an option? Could be a way to get a bit of the needed clearance & I've read it would be less parasitic drag.

 

[Woodwackr]

I'm wondering (since I have a spare piston) perhaps machining off the top ring of the piston to make it be a single ring is an option? Could be a way to get a bit of the needed clearance & I've read it would be less parasitic drag.

The piston crown isn’t thick enough to do that.