She's Almost Ready

[JUSTINROGERS]

Haha so much for the title. She's not as close to ready as i thought.

 

[timothy johnson]

Justin, get some blue plasti gauge at an auto parts store and recheck your Cl.

 

[JUSTINROGERS]

Thats what i used

 

[JUSTINROGERS]

With out the shim

 

[shoboat]

Justin,

I just finished you a 1445 and a reduced diameter 1450.

Try these and shorten your pipe a little more and see what happens.

Your package will ship out Priority Mail Service in the morning.

This Is A Late Christmas Donation,

Happy New Year,

Mark Sholund

 

[timothy johnson]

Justin, HC should be good! See you in Tampa.

 

[JUSTINROGERS]

Mark that is awesome. I can't thank you enough. I don't know if you have shirts or hat's but if you do and are willing to send one i can wear it at the race we got next week. Its the least I can do. Thanks again Mark.

See you there Tim!!!

 

[Terry Keeley]

Breaking the wire if usually always vibs, not fuel, prop, pipe etc.

Again, how's the motor mounted. Just a shot?

Would a more solid or more compliant mount be more likely to blow a plug?

Generally the "harder" the motor is mounted the more it pass vibs on to the hull, which (in my opinion) would be more abt to break the plug wire.

I tried partially captivating the rubber mounts on my boats and the hulls shook bad, went back to letting them float...

 

[Blackout]

Breaking the wire if usually always vibs, not fuel, prop, pipe etc.

Again, how's the motor mounted. Just a shot?

Would a more solid or more compliant mount be more likely to blow a plug?

Generally the "harder" the motor is mounted the more it pass vibs on to the hull, which (in my opinion) would be more abt to break the plug wire.

I tried partially captivating the rubber mounts on my boats and the hulls shook bad, went back to letting them float...

Thanks Terry. I'll keep this in mind.

Gonna try solid Delrin mounts in my .91 rigger that I am building this winter. If it doesn't work, I'll just go back to my traditional mounts.

 

[shoboat]

Justin,

Your late Christmas present will be in St Pete on Monday.

Let Us Know How They Work?

Mark Sholund

 

[JUSTINROGERS]

Mark thanks again. I will run them in open water Thursday and let you guys now and try to get some video too.

 

[Brad Christy]

Justin,

I'm with Dave on this. These .21's are very sensitive to head clearance. Too much, and you have to lean it down to get it to hit the pipe, and then it leans out at high RPM and takes out the plug. Too little and the compression ratio is too high, causing detonation and plug failure. You really want to be in the .005-.006" range.

Not to poo-poo on anybody's products or methods, but I've never gotten anything I'd consider reliable measurements on head clearance with anything other than depth mics. DO NOT USE CALIPERS. As I read on here once (and totally agree with), you might as well use a yardstick.

If you don't have them already, get yourself a decent set of depth mics. Most of us machinists already have them. If you're not one of us, and you don't want to drop the coin, surely you've got a machinist buddy who'll loan you his for the weekend. If you have to buy them, you don't have to blow the bank. Mitutoyo, Starret and B&S are nice, but there are many lower cost options that work fine for the hobbyist.

Remove the water jacket and drum housing. Use one of the drum housing bolts, with a washer or two, to lock the cylinder sleeve down to keep it from moving during measurement. Believe me, it will if you've got a well fitted piston. Roll the crank over to bring the piston to TDC. It will most likely kind of "click" into place. With the depth mic, measure from the top of the sleeve shoulder to the top of the piston and write it down. You might do this a couple times, taking the piston off TDC and then back up each time, to get an average, as there may be some minor fluctuation due to your piston fit. With the same depth mic, measure from the sleeve shoulder to the squishband of the head button. Do not include any shims in these measurements. Do the math and that's your head clearance. Hopefully, you're pretty close to zero, or even in the negatives, to give you some room to work.

Personally, I like for this number to be zero so that my shim stack-up IS my head clearance. I usually have to turn the top of the shoulder of the sleeve or the sleeve shoulder of the head button to achieve this, but this condition is not really required, so long as you can correct the head clearance with shims.

You can get head shims from Steve Wood or Dave Roach (if not others). You'll want to hit that .005-.006" range if at all possible, using whatever combination of shims required to get you there. I've been known to use a .0005" shim to nail that perfect .0055", but I'm goofy that way.

This may seem like a lot of work for something "so minor", but we all got into this hobby because we love to tinker, and when the effort pays off in the results we're looking for, it's all worth it.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

 

[JUSTINROGERS]

Brad thanks for the info on how to get a more accurate measurement. I wont have time to do it this way before the race. But i will have it done after. I am going to run it tomorrow with the head at .007 (measured with plasti gauge) and see how she go's. Its got to be better then the .011-.012 it was as. I hope.

 

[Tom Foley]

Brad thanks for the info on how to get a more accurate measurement. I wont have time to do it this way before the race. But i will have it done after. I am going to run it tomorrow with the head at .007 (measured with plasti gauge) and see how she go's. Its got to be better then the .011-.012 it was as. I hope.

We can check it and change it in 5 minutes at the lake . Set it at .006 and run that 1445 and i think you will be surprised . I also have a CMB (muffled) pipe you can try if you like along with other pipes as well as a muffled Mac (AB ) fat pipe

 

[dwilfong]

The CMB high nitro pip is a great all around pipe for the .21.

If you don't have one I have a extra one I can bring for you to try.

Also have a bunch of props.

 

[JUSTINROGERS]

Tom and dwilfong i might take you up on your offers. I was just running it and it is still eating plugs. Not to where it dies while running but every time i come in the plug is broken. I think i need to make the pipe longer???

 

[dave roach]

Justin

Are the bearing good.With the head clearance set at .007 and on the 3280 pipe set it at 8.00 inches it should not be taking out plugs.Are you running the engine on the rich side.the MAC likes fuel.How much Nitro are you running.

Dave

 

[JUSTINROGERS]

The bearings are brand new. Im running 60%. Its real needley. First needle setting takes about a lap to get on the pipe. I go one click in and its on the pipe instantly. Thats with a fine thread os needle. Changing the clearance to .007 definitely helped with milling

 

[Terry Keeley]

Breaking the wire if usually always vibs, not fuel, prop, pipe etc.

Again, how's the motor mounted. Just a shot?

Would a more solid or more compliant mount be more likely to blow a plug?

Generally the "harder" the motor is mounted the more it pass vibs on to the hull, which (in my opinion) would be more abt to break the plug wire.

I tried partially captivating the rubber mounts on my boats and the hulls shook bad, went back to letting them float...

Thanks Terry. I'll keep this in mind.

Gonna try solid Delrin mounts in my .91 rigger that I am building this winter. If it doesn't work, I'll just go back to my traditional mounts.

Try it but I'm quite you won't like it...

 

[Terry Keeley]

Justin,

I'm with Dave on this. These .21's are very sensitive to head clearance. Too much, and you have to lean it down to get it to hit the pipe, and then it leans out at high RPM and takes out the plug. Too little and the compression ratio is too high, causing detonation and plug failure. You really want to be in the .005-.006" range.

Not to poo-poo on anybody's products or methods, but I've never gotten anything I'd consider reliable measurements on head clearance with anything other than depth mics. DO NOT USE CALIPERS. As I read on here once (and totally agree with), you might as well use a yardstick.

If you don't have them already, get yourself a decent set of depth mics. Most of us machinists already have them. If you're not one of us, and you don't want to drop the coin, surely you've got a machinist buddy who'll loan you his for the weekend. If you have to buy them, you don't have to blow the bank. Mitutoyo, Starret and B&S are nice, but there are many lower cost options that work fine for the hobbyist.

Remove the water jacket and drum housing. Use one of the drum housing bolts, with a washer or two, to lock the cylinder sleeve down to keep it from moving during measurement. Believe me, it will if you've got a well fitted piston. Roll the crank over to bring the piston to TDC. It will most likely kind of "click" into place. With the depth mic, measure from the top of the sleeve shoulder to the top of the piston and write it down. You might do this a couple times, taking the piston off TDC and then back up each time, to get an average, as there may be some minor fluctuation due to your piston fit. With the same depth mic, measure from the sleeve shoulder to the squishband of the head button. Do not include any shims in these measurements. Do the math and that's your head clearance. Hopefully, you're pretty close to zero, or even in the negatives, to give you some room to work.

Personally, I like for this number to be zero so that my shim stack-up IS my head clearance. I usually have to turn the top of the shoulder of the sleeve or the sleeve shoulder of the head button to achieve this, but this condition is not really required, so long as you can correct the head clearance with shims.

You can get head shims from Steve Wood or Dave Roach (if not others). You'll want to hit that .005-.006" range if at all possible, using whatever combination of shims required to get you there. I've been known to use a .0005" shim to nail that perfect .0055", but I'm goofy that way.

This may seem like a lot of work for something "so minor", but we all got into this hobby because we love to tinker, and when the effort pays off in the results we're looking for, it's all worth it.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

If I try to run that low I get that tell tale ring around the piston letting me know it's been growing & hitting the head. I do like to get good heat in the motors tho and run very little cooling but lot's of fuel. I run 0.010 - 0.012" on 21's to 90's.