CMB101RS Head Vol & clearance

[Ian Inverarity]

I am after good figures for head volume and clearance for a mod CMB101RS running 50% nitro in a mono. Is the stock volume okay, what head clearance works with the stock volume?

Ian.

 

[BigChuck]

Ian Stock heads!!! 17-19 on 50% 19 -21 on 60% If the temps are in the 90's pull the pipe back 1/4 to 1/2.

 

[Ian Inverarity]

Thanks Chuck, I will try that! B)

 

[Piston1]

Here's another way, 1cc volume, .014" clearance. 50-55% Nitro. B)

 

[mark voorhies]

I am after good figures for head volume and clearance for a mod CMB101RS running 50% nitro in a mono. Is the stock volume okay, what head clearance works with the stock volume?

Ian.

Ian,

Wish I could give you some good numbers , but I have not reached a point yet with this engine to tell ya.

last race I was here; 192 exh, 135 boost, 130 trans., hd button .83 cc vol., hd clr., .018., 9.2 comp. ratio.

That has a .015 sleeve shim., Macs 15cc pipe @ 11.5 " to center of band, X467 prop from Sholund as stated before.

I need to test some more with this. Was runnin 60% with 12% oil, that has went to 18% oil as of last run which all

added oil is castor.

 

[BigChuck]

What MARK failed to mention is the reason he was having issues is the heat index at the lake the weekend was 106*

Oh yes I do know, was there last year had the same problem in open water. Made two changes and raced the weekend. OH and was swinging waaayyyy more prop than the X467.

 

[Ian Inverarity]

Ian,

Wish I could give you some good numbers , but I have not reached a point yet with this engine to tell ya.

last race I was here; 192 exh, 135 boost, 130 trans., hd button .83 cc vol., hd clr., .018., 9.2 comp. ratio.

That has a .015 sleeve shim., Macs 15cc pipe @ 11.5 " to center of band, X467 prop from Sholund as stated before.

I need to test some more with this. Was runnin 60% with 12% oil, that has went to 18% oil as of last run which all

added oil is castor.

Mark,

Is 0.83 a stock volume? On the engine I measured the volume was 0.92 but I am not sure if this head button has been modified or not.

 

[Ian Inverarity]

There seems to be a few approaches to this, larger bowl volume or stock bowl with more squish clearance. Personally I make my own head buttons but after much trouble trying to get consistency without detonation on 50% nitro I gave up and went down to 25% nitro and have been happy with that ever since. But a friend wants me to make a head button and cooling jacket for his 101 that he runs on 50% in a Seaducer.

I found that my engine, which was perfectly happy on 50% in a rigger, would detonate badly on 50% in a mono. When I fitted a larger bowl volume (with the same squish clearance) I lost too much torque and couldnt throttle well with the same props. After making a mess of a few pistons and head buttons I gave up and now run a higher rpm/lower torque setup on 25% nitro. On 50% the needle setting was a knife edge, too rich and it was slow, a click too lean and it took the plug element or even blew the centre clean out.

So I am after a head setup for 50% on a modified engine that doesnt have the above problems. Has anyone compared more volume and lower squish clearance to stock volume and more clearance?

Ian.

 

[mark voorhies]

What MARK failed to mention is the reason he was having issues is the heat index at the lake the weekend was 106*

Oh yes I do know, was there last year had the same problem in open water. Made two changes and raced the weekend. OH and was swinging waaayyyy more prop than the X467.

Yep is was HOTTT at E-ville, share your 2 changes if you will? What prop?

 

[mark voorhies]

Ian,

Wish I could give you some good numbers , but I have not reached a point yet with this engine to tell ya.

last race I was here; 192 exh, 135 boost, 130 trans., hd button .83 cc vol., hd clr., .018., 9.2 comp. ratio.

That has a .015 sleeve shim., Macs 15cc pipe @ 11.5 " to center of band, X467 prop from Sholund as stated before.

I need to test some more with this. Was runnin 60% with 12% oil, that has went to 18% oil as of last run which all

added oil is castor.

Mark,

Is 0.83 a stock volume? On the engine I measured the volume was 0.92 but I am not sure if this head button has been modified or not.

Ian,

mine was stock @ .83, the piston dish may get it to .84, .85, not sure.

 

[mark voorhies]

There seems to be a few approaches to this, larger bowl volume or stock bowl with more squish clearance. Personally I make my own head buttons but after much trouble trying to get consistency without detonation on 50% nitro I gave up and went down to 25% nitro and have been happy with that ever since. But a friend wants me to make a head button and cooling jacket for his 101 that he runs on 50% in a Seaducer.

I found that my engine, which was perfectly happy on 50% in a rigger, would detonate badly on 50% in a mono. When I fitted a larger bowl volume (with the same squish clearance) I lost too much torque and couldnt throttle well with the same props. After making a mess of a few pistons and head buttons I gave up and now run a higher rpm/lower torque setup on 25% nitro. On 50% the needle setting was a knife edge, too rich and it was slow, a click too lean and it took the plug element or even blew the centre clean out.

So I am after a head setup for 50% on a modified engine that doesnt have the above problems. Has anyone compared more volume and lower squish clearance to stock volume and more clearance?

Ian.

Will be tryin 50% soon, the numbers I have run so far shows no detonation on 60% , but with 18% oil. Not quiet there on performance, but will sqeeze it

down more with the 50% and see?? Still not sure on volume, squish, hd. clr. , more testing needed!

 

[Tom David]

What MARK failed to mention is the reason he was having issues is the heat index at the lake the weekend was 106*

Oh yes I do know, was there last year had the same problem in open water. Made two changes and raced the weekend. OH and was swinging waaayyyy more prop than the X467.

Did you Win???? :huh:

 

[Tom David]

Ian,

Wish I could give you some good numbers , but I have not reached a point yet with this engine to tell ya.

last race I was here; 192 exh, 135 boost, 130 trans., hd button .83 cc vol., hd clr., .018., 9.2 comp. ratio.

That has a .015 sleeve shim., Macs 15cc pipe @ 11.5 " to center of band, X467 prop from Sholund as stated before.

I need to test some more with this. Was runnin 60% with 12% oil, that has went to 18% oil as of last run which all

added oil is castor.

Mark,

Is 0.83 a stock volume? On the engine I measured the volume was 0.92 but I am not sure if this head button has been modified or not.

Ian,

mine was stock @ .83, the piston dish may get it to .84, .85, not sure.

Ian,

I agree with Mark, stock bowl is .83. But my measurement on the piston dish shows approximately 1/10 of a cc (0.1).

That would give total volume of .93 cc excluding squish clearance.

Tom

 

[mark voorhies]

Ian,

Wish I could give you some good numbers , but I have not reached a point yet with this engine to tell ya.

last race I was here; 192 exh, 135 boost, 130 trans., hd button .83 cc vol., hd clr., .018., 9.2 comp. ratio.

That has a .015 sleeve shim., Macs 15cc pipe @ 11.5 " to center of band, X467 prop from Sholund as stated before.

I need to test some more with this. Was runnin 60% with 12% oil, that has went to 18% oil as of last run which all

added oil is castor.

Mark,

Is 0.83 a stock volume? On the engine I measured the volume was 0.92 but I am not sure if this head button has been modified or not.

Ian,

mine was stock @ .83, the piston dish may get it to .84, .85, not sure.

Ian,

I agree with Mark, stock bowl is .83. But my measurement on the piston dish shows approximately 1/10 of a cc (0.1). That would give total volume of .93 cc excluding squish

clearance.

Tom

Tom , thanks for clarification on piston dish, have not mearsured that yet, I was way off , I believe you are correct.

I need to re check my #'s on that. And that gets me at 8.6 on CR .

 

[BigChuck]

No Tom..........I did not win. Charlie walked out of there with the trophy because I did not keep my head in the game. And gave away 300 when it was only me and sammy on the water. But you your self stood in the pits and saw me unlap and pass Mark for the win in the first heat. So, do I know how to get my 101 to run strong in the heat? Yes. Do I know what the limits of the motor is as far has how much prop it can pull? Yes. How much testing was done to know this.................Priceless Welcome to the WARS. I will be back, might even be the fall race. But I have a few test session to go before I even consider racing my Rs motors again. B) B)

 

[Tom David]

No Tom..........I did not win. Charlie walked out of there with the trophy because I did not keep my head in the game. And gave away 300 when it was only me and sammy on the water. But you your self stood in the pits and saw me unlap and pass Mark for the win in the first heat. So, do I know how to get my 101 to run strong in the heat? Yes. Do I know what the limits of the motor is as far has how much prop it can pull? Yes. How much testing was done to know this.................Priceless Welcome to the WARS. I will be back, might even be the fall race. But I have a few test session to go before I even consider racing my Rs motors again. B) B)

Mark and I were runing CMB 80's that season. Yes, we have joined the 101 club this year and are making progress everytime we

test at lake. Come on up this fall and will try and give you some competition.

Tom

 

[Joe Warren]

Well. I`am running 60 Techonology fuel & Will be running 65 percent in the fall races...... Low Nitro is NOT the direction for POWER!!!

 

[SayMikey]

Will a hydro have the same burning issue? I have a new 101 and can switch to a 91 hr if its going to eat pistons

 

[Ian Inverarity]

Mike,

I havent specifically tried a stock button in a 101 in a hydro, but my experiences with several engines is that they are more tolerant than monos when it comes to detonation, as I said in an ealier post my setup worked fine on 50% in a rigger but not a mono.

 

[BigChuck]

Well. I`am running 60 Techonology fuel & Will be running 65 percent in the fall races...... Low Nitro is NOT the direction for POWER!!!

FullY agree with "He of Tall TROPHY!!!" Have been Running 60% for years, Did see the numbers up when I test the 65% also. But like the 60% for all round friendly use.

Mikey, 101 on stock head @ .021 thou. Romanos single in the video is just that. The Gold & White single. If you remenber that last heat in the fall race last year he was "Haulin the Mail"

Tom..........You had a 42 SD with a K&B in it that left me for dead............how many year ago in Huntsville??? You showed me them what it means to be out side the box.

Just not outside the paramaters. Have fun testing.