What was inside the MS460 Raffle Saw

[blsnelling]

Keeping true to my mantra, here are the details of what I had in the MS460 I prepaired for the build-off.

I began by buying three pistons: 372BB, 064 Meteor, and 038 Magnum Meteor. The 372BB piston was not an attractive option to me at all. The skirts are no wider than the OEM piston, windows had to be cut, and it's not my favorite brand of piston. I went with the 038 piston. The 064 and 038 Mag pistons are very similiar. There are two main differences. The 064 has much longer skirts, and has thinner rings. I didn't realize until too late that the 038 rings were thicker. If I had it to do over, I'd go with a 064 piston. Both the 064 and 038 pistons have to be widened between the wrist pin bosses in order to fit over the rod.

Nik will have to clarify, but I we cut either a .030" or .035" popup. Because of the taller pin to crown height of the 038 piston, very little had to be taken off the cylinder base.

Once I had a piston to work with, I proceeded to porting the cylinder. I was able to go a full 70% of bore diameter on the intake and exhaust ports. I had to be very careful not to widen the very top of the intake port, due to the location of the ring locating pins. I did not raise the exhaust at all, since I wanted RPMs and torque. IIRC, the exhaust was around 102° at that point. Copmpression was 202 PSI.

I advanced the ignition timing about 8°. This is only about 1/2 the width of the key.

I also opened up the carb venturi about 1mm. Care must be taken to not thin the area where the nozzle comes through, or you're like to end up with it leaking.

I put it all together and headed to Andres, where he was testing the MS441 C-M. The 460 saw was VERY disappointing. It had VERY little more than a stock saw. I knew I had my work cut out for me at that point. No way could I deliver this raffle saw and build-off saw running like this.

I first tried putting the ignition timing back to stock. That didn't help.

So, I went back to degree my MS440/460 hybrid cylinder. It's an excellent running saw. I was shocked to find that it only has 14° of blowdown. It's a Mahle 046/460 cylinder, and that's how it came. Jeremy confirmed this by degreeing another early Mahle 046 cylinder and found it to only have 15°. I went back in the raffle saw and raised the transfers to 115°. It made a big improvement. I then went back in and raised the exhaust to 98°. I ended up with 17° of blowdown, with the exhaust at 98° and the transfers at 115°.

I still wasn't happy with it. I again advanced the timing 8° like I originally had it. It definately made a real difference.

I still wanted more. So, back in I went again, and did nothing other than remove the bottom ring. It suprised me by picking up several hundred RPMs in the cut. It was only after to talking to Jeremy again that I realized that the 064 had thinner rings. If getting rid of the bottom ring made that much difference, going to a thinner one could only help. This is why I'd go with the 064 piston if I had it to do over.

Are you thinking I'm crazy for going with that little blowdown and numbers that high? In talking with Jeremy about his build, he was experiencing some of the same frustrations. I finally talked him into raising his transfers, and he experienced the same improvement I did. He passed the info on to Randy, and you see where that got me Bottom line, this recipe works, and it works very well.

Is a popup and piston swap required for a great running 460? No. Some of the great running saws in this build-off had stock pistons and no popup. They may not make the winner at a race, but they're certainly not required to build a great running saw.

Here are the final numbers in this saw.

Exhaust - 98°
Transfers - 115°
Intake - 83°
Blowdown - 17°
Squish - .019"
Compression - 190 PSI

 

[komatsuvarna]

It definitely is a strong saw!! One question though. I've played with advancing ignition timing and you can really tell a difference,,, but Im scared to do it on a popup saw that pulling 180 to 200 psi. You ever had any problems running the timing higher with that much cranking pressure?

 

[young]

sharing is caring. *hugs* :wink2::wink2:

 

[blsnelling]

It definitely is a strong saw!! One question though. I've played with advancing ignition timing and you can really tell a difference,,, but Im scared to do it on a popup saw that pulling 180 to 200 psi. You ever had any problems running the timing higher with that much cranking pressure?

So far, I have not.

 

[Slamm]

So a "trick" that Dolmar uses is the one ring piston to drop the friction, in your opinion, how much of its HP over other 70-80cc saws is from this one thing?

Just wondering.

Sam

 

[Stumpys Customs]

Nice Brad, conferms the theory's I had about how to make the one I built Better. Talkin With Randy & readin this thread answers a few ?'s I had about the port timing on these saws. I was afraid to raise the uppers any more than back to stock since they were already kinda high.

I also didn't mess with the ign timing. I wanted too after I noticed how big of a diff it made on a 288 I built, but the 460 was already on it's way to Terry's.

Also wanted to thank you & Randy fer tryin to help my saw out after the race.

 

[blsnelling]

A significant amount. With that single change I picked up several hundred RPMs in the cut. It was very noticeable.

 

[Stumpys Customs]

A significant amount. With that single change I picked up several hundred RPMs in the cut. It was very noticeable.

I noticed the Same on the last few 372's that I've buit with raisin the uppers. These 460's already had real high uppers so I chickened out on raisin them. Live and learn. I know that the 372's I build now are prolly closer to a top 5 saw in a buildoff. Not try to start anything just pointin out how much I learned about the 372's after the build off. I feel the same will happen with the 460's.

How do you come up with yer intake opening #'s?? ATDC, ABDC?? What is the Dur. of the intake of the saw?

 

[DSS]

Keeping true to my mantra, here are the details of what I had in the MS460 I prepaired for the build-off.

I began by buying three pistons: 372BB, 064 Meteor, and 038 Magnum Meteor. The 372BB piston was not an attractive option to me at all. The skirts are no wider than the OEM piston, windows had to be cut, and it's not my favorite brand of piston. I went with the 038 piston. The 064 and 038 Mag pistons are very similiar. There are two main differences. The 064 has much longer skirts, and has thinner rings. I didn't realize until too late that the 038 rings were thicker. If I had it to do over, I'd go with a 064 piston. Both the 064 and 038 pistons have to be widened between the wrist pin bosses in order to fit over the rod.

Nik will have to clarify, but I we cut either a .030" or .035" popup. Because of the taller pin to crown height of the 038 piston, very little had to be taken off the cylinder base.

Once I had a piston to work with, I proceeded to porting the cylinder. I was able to go a full 70% of bore diameter on the intake and exhaust ports. I had to be very careful not to widen the very top of the intake port, due to the location of the ring locating pins. I did not raise the exhaust at all, since I wanted RPMs and torque. IIRC, the exhaust was around 102° at that point. Copmpression was 202 PSI.

I advanced the ignition timing about 8°. This is only about 1/2 the width of the key.

I also opened up the carb venturi about 1mm. Care must be taken to not thin the area where the nozzle comes through, or you're like to end up with it leaking.

I put it all together and headed to Andres, where he was testing the MS441 C-M. The 460 saw was VERY disappointing. It had VERY little more than a stock saw. I knew I had my work cut out for me at that point. No way could I deliver this raffle saw and build-off saw running like this.

I first tried putting the ignition timing back to stock. That didn't help.

So, I went back to degree my MS440/460 hybrid cylinder. It's an excellent running saw. I was shocked to find that it only has 14° of blowdown. It's a Mahle 046/460 cylinder, and that's how it came. Jeremy confirmed this by degreeing another early Mahle 046 cylinder and found it to only have 15°. I went back in the raffle saw and raised the transfers to 115°. It made a big improvement. I then went back in and raised the exhaust to 98°. I ended up with 17° of blowdown, with the exhaust at 98° and the transfers at 115°.

I still wasn't happy with it. I again advanced the timing 8° like I originally had it. It definately made a real difference.

I still wanted more. So, back in I went again, and did nothing other than remove the bottom ring. It suprised me by picking up several hundred RPMs in the cut. It was only after to talking to Jeremy again that I realized that the 064 had thinner rings. If getting rid of the bottom ring made that much difference, going to a thinner one could only help. This is why I'd go with the 064 piston if I had it to do over.

Are you thinking I'm crazy for going with that little blowdown and numbers that high? In talking with Jeremy about his build, he was experiencing some of the same frustrations. I finally talked him into raising his transfers, and he experienced the same improvement I did. He passed the info on to Randy, and you see where that got me Bottom line, this recipe works, and it works very well.

Is a popup and piston swap required for a great running 460? No. Some of the great running saws in this build-off had stock pistons and no popup. They may not make the winner at a race, but they're certainly not required to build a great running saw.

Here are the final numbers in this saw.

Exhaust - 98°
Transfers - 115°
Intake - 83°
Blowdown - 17°
Squish - .019"
Compression - 190 PSI

AHA!!!!

I knew that hillbilly from upper buttcrack, TN, couldn't have won that buildoff on his own. There's one mystery solved.


:monkey:

 

[blsnelling]

Nice Brad, conferms the theory's I had about how to make the one I built Better. Talkin With Randy & readin this thread answers a few ?'s I had about the port timing on these saws. I was afraid to raise the uppers any more than back to stock since they were already kinda high.

I also didn't mess with the ign timing. I wanted too after I noticed how big of a diff it made on a 288 I built, but the 460 was already on it's way to Terry's.

Also wanted to thank you & Randy fer tryin to help my saw out after the race.

Not a problem. I learned a ton on this build myself. I've always preaching on sharing, and that's what I'm trying to live by here.

How do you come up with yer intake opening #'s?? ATDC, ABDC?? What is the Dur. of the intake of the saw?

It's 83° BTDC, for 166° of intake duration.

AHA!!!!

I knew that hillbilly from upper buttcrack, TN, couldn't have won that buildoff on his own. There's one mystery solved.

Lol. Like I told Randy before the cuts were made, even if it costs me a place or two, it's about having fun and making friends MORE than it's about winning. That Randy is some kind of nice guy. I really enjoyed meeting him We're all in this together.

 

[mtngun]

Thanks for the info, Brad.

I again advanced the timing 8° like I originally had it. It definately made a real difference.

What method are you using to indicate the timing ?

Asking because I've been tempted to play around with ignition timing, but haven't figured out an easy way to measure it.

 

[Outlaw5.0]

Any photos of the build?.

 

[wheelman]

Brad shared much of this with me at the lunch table on saturday,and I must say it was very enlightening. I am going to be back inside my saw soon to try out a couple of the tricks learned there.
I must give props to Brad for his willingness to share info like this with everyone. A lot of sweat goes into learning the little stuff and not everyone would be so eager to share.

 

[blsnelling]

Any photos of the build?.

I was too busy taking the saw apart and putting it back together!

 

[FATGUY]

there were a few pics of the machining operations in the original thread.

 

[parrisw]

That sounds good Brad, its very close to what I did on my build, only I didn't raise the uppers much at all, I cleaned them up thus raising a little, it took out some of the bevel then I re beveled a bit more. I used the 064 piston. I'd like another shot at a 460.

 

[blsnelling]

Thanks for the info, Brad.


What method are you using to indicate the timing ?

Asking because I've been tempted to play around with ignition timing, but haven't figured out an easy way to measure it.

I just thin by half the part of the key that sticks out of the keyway in the crank. You can see how much you move it by holding a degree wheel of the same size over the flywheel. It's not an exact method, but it gets the job done. It's accurate within 1° though.

 

[komatsuvarna]

I just thin by half the part of the key that sticks out of the keyway in the crank. You can see how much you move it by holding a degree wheel of the same size over the flywheel. It's not an exact method, but it gets the job done. It's accurate within 1° though.

Same way I do mine, about the hardest part is trying to get the nut snugged down without the flywheel spinning......need an extra hand and a piston stop to make it easier.....or I did anyways.

 

[wheelman]

I always put a socket down around the end of the crank against the flywheel and give it a pretty good whack with a hammer to seat it in place before I put the nut on. This has always worked well for me.

 

[blsnelling]

Same way I do mine, about the hardest part is trying to get the nut snugged down without the flywheel spinning......need an extra hand and a piston stop to make it easier.....or I did anyways.

I hold the flywheel down by hand, tighten the nut slightly, rotate the piston up against a piston stop, then tighten it down, all the while holding it down.