Dominant V4 Piston for the 372

[Ronie]

I tuned it richer but it didn't get any better, just slower. Maybe if I ground on the transfers it would gain some torque, I don't know. If you have to grind on the cylinder you might as well go with a cheaper Meteor piston. I'll be taking it out of my saw. If they got rid of the exhaust cutout it would be a better piston but I still wouldn't pay $119 for it. I tried it richer and leaner and made a video of it turning 13560 rpm, I gave up after that.

 

[huskihl]

I tuned it richer but it didn't get any better, just slower. Maybe if I ground on the transfers it would gain some torque, I don't know. If you have to grind on the cylinder you might as well go with a cheaper Meteor piston. I'll be taking it out of my saw. If they got rid of the exhaust cutout it would be a better piston but I still wouldn't pay $119 for it. I tried it richer and leaner and made a video of it turning 13560 rpm, I gave up after that.

Too much blowdown maybe.

 

[Ronie]

Too much blowdown maybe.

I guess, I don't know enough about transfer timing to know.

 

[Ronie]

Maybe I can cut that exhaust cutout out of it and still use it.

 

[huskyboy]

I tuned it richer but it didn't get any better, just slower. Maybe if I ground on the transfers it would gain some torque, I don't know. If you have to grind on the cylinder you might as well go with a cheaper Meteor piston. I'll be taking it out of my saw. If they got rid of the exhaust cutout it would be a better piston but I still wouldn't pay $119 for it. I tried it richer and leaner and made a video of it turning 13560 rpm, I gave up after that.

Man that thing has a great exhaust sound if anything.

 

[Ronie]

Man that thing has a great exhaust sound if anything.

It's got a 1" pipe.

 

[beaglebriar]

I tuned it richer but it didn't get any better, just slower. Maybe if I ground on the transfers it would gain some torque, I don't know. If you have to grind on the cylinder you might as well go with a cheaper Meteor piston. I'll be taking it out of my saw. If they got rid of the exhaust cutout it would be a better piston but I still wouldn't pay $119 for it. I tried it richer and leaner and made a video of it turning 13560 rpm, I gave up after that.

Doesn't seem like it will hold RPM worth beans if you lean on it. I think you should check the port timing. Small changes can get some big gains. If you haven't done anything to cylinder you can't expect a huge improvement. Essentially the only thing changed is the exhaust height and that might have a negative effect.

 

[Ronie]

Doesn't seem like it will hold RPM worth beans if you lean on it. I think you should check the port timing. Small changes can get some big gains. If you haven't done anything to cylinder you can't expect a huge improvement. Essentially the only thing changed is the exhaust height and that might have a negative effect.

I might reduce the blow down and see what happens.

 

[huskihl]

Maybe I can cut that exhaust cutout out of it and still use it.

Not sure if there’s enough crown thickness

 

[huskihl]

Doesn't seem like it will hold RPM worth beans if you lean on it. I think you should check the port timing. Small changes can get some big gains. If you haven't done anything to cylinder you can't expect a huge improvement. Essentially the only thing changed is the exhaust height and that might have a negative effect.

I’d bet the farm that it would run better if there was a 5* notch over the primaries and a 1* notch over the secondaries with nothing on the exhaust side

 

[Ronie]

Not sure if there’s enough crown thickness

Your probable right. I'll pull the cylinder Monday and go from there. I wish there was something I could do with it, it's a nice looking piston.

 

[Funky sawman]

How about if you were to do what kevin said with the notches and then cut cylinder base, then turn piston at the squish band to remove exhaust slope? Sounds like alot of crap, but that's were I would have gone if there was a machine shop in my back yard lol

 

[beaglebriar]

I’d bet the farm that it would run better if there was a 5* notch over the primaries and a 1* notch over the secondaries with nothing on the exhaust side

I agree but that would be taboo...and that don't sell pistons. Lol

 

[Funky sawman]

Well not necessarily in that order

 

[beaglebriar]

How about if you were to do what kevin said with the notches and then cut cylinder base, then turn piston at the squish band to remove exhaust slope? Sounds like alot of crap, but that's were I would have gone if there was a machine shop in my back yard lol

Might as well adjust the ports. That piston can run well as is, if the port timing is brought to where it should be.

 

[huskihl]

I agree but that would be taboo...and that don't sell pistons. Lol

Can’t give out all the secrets at once. Gotta work their way up to v5. Or 4.1. Whichever

 

[Ronie]

Might as well adjust the ports. That piston can run well as is, if the port timing is brought to where it should be.

I think your right, I'm going to go ahead and port it. After I widen the exhaust I'll cut that notch to match it.

 

[huskyboy]

You’ll probably gain torque when you lean it out a touch more too, after break in of course.

 

[NSEric]

If I had that piston I'd grind/file a notch into the top of the piston like the one by the exhaust port beside the transfers to get the blow down in the 20 degree range.
This would give ported saw like port timing without grinding on the cylinder.

I ground the top of the piston by the transfers to adjust blowdown on the Chinese saws I ported because I don't have a tiny angled grinder that will do the tops of transfers, they work fine.

 

[Ronie]

If I had that piston I'd grind/file a notch into the top of the piston like the one by the exhaust port beside the transfers to get the blow down in the 20 degree range.
This would give ported saw like port timing without grinding on the cylinder.

I ground the top of the piston by the transfers to adjust blowdown on the Chinese saws I ported because I don't have a tiny angled grinder that will do the tops of transfers, they work fine.

I may end up doing something like that for the transfers. I think that if the transfers are ground up as high as they need to go then they might be too high if the piston is ever changed out.