#360 free machining brass for a head button?

[hugh hargett]

you should be able to stick an arbitrary le pitch number in there all youre looking at is the difference of 5 mph. It wouldnt matter if it were 81 and 86 the rpm difference would be the same WOULDNT IT :huh: ?

 

[mtruex]

I have played with brass heads on and off for about 2 years, but i never did a back to back test comparing them.. I did a test today comparing an aluminum head to a brass head, they were both the exact same shape size etc, engine was a nova keep21 in my JAE 21.. the only difference was the alloy head had a turbo plug and the brass head had standard plug.. The aluminum head ran 81 the brass ran 76.. the head temp FELT the same when i brought it in, and both would come back on pipe the same after a few slow cooldown laps, neither head showed detonation.. the only thing im not sure on is how much the turbo plug is worth..

That was a good test Martin. But you may not really see a lot of increase in a 21 motor. And I will not say if the turbo head made that much difference. Where we are see the increase is in big motors that move a lot of fuel thru them.

Mark, the aluminum head was faster.

 

[hugh hargett]

looks like around 5300k to me

second that it WILL make a difference went back and used a half instead of one and the rpm difference reduced by that factor.

Everyone makes mistakes . Need the LE .

 

[dwilfong]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Then raise the nitro % and compare how much it will burn.

Would be interested in the results.

David

 

[Tim_Duggan]

It is the ability to raise the CR to make more power.

Most agree turbo plugs can get away with higher CR than a conventional and net an rpm gain in the same material.

So are you suggesting the CR with a brass button AND a turbo plug would run even higher CR without deto? I think you'd run into the area where the CR could actually limit upper rpm on smaller engines like 21's - but that may not be an issue on bigger displacement engines at all. Could be rather useful on low revving unpiped engines with excessive cooling areas attached to the back of the crankcase

 

[mtruex]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

 

[dwilfong]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

Can't answer that one. But if you take the plug out of the variables you would have a better comparison.

You have to test them apples to apples to see what is what. there may not be any difference.

Don't know till you try.

 

[dwilfong]

It is the ability to raise the CR to make more power.

Most agree turbo plugs can get away with higher CR than a conventional and net an rpm gain in the same material.

So are you suggesting the CR with a brass button AND a turbo plug would run even higher CR without deto? I think you'd run into the area where the CR could actually limit upper rpm on smaller engines like 21's - but that may not be an issue on bigger displacement engines at all. Could be rather useful on low revving unpiped engines with excessive cooling areas attached to the back of the crankcase

It is the ability to raise the CR to make more power.

Most agree turbo plugs can get away with higher CR than a conventional and net an rpm gain in the same material.

So are you suggesting the CR with a brass button AND a turbo plug would run even higher CR without deto? I think you'd run into the area where the CR could actually limit upper rpm on smaller engines like 21's - but that may not be an issue on bigger displacement engines at all. Could be rather useful on low revving unpiped engines with excessive cooling areas attached to the back of the crankcase

Remember torque curve. RPMs are not HP with out torque.

 

[Mike Rappold]

Earlier this year I was able to do some testing of a 360 brass head button on a MAC 67 engine running in a 67SG. I made several brass heads with different volumes. The first head button has the exact same dimensions as the stock aluminum head. The boat is a equipped with an Eagle Tree data logger. I am recording Cylinder Head temp, EGT, RPM, and GPS speed. The attached Word file has several screen shots of the data between runs. For any testing, I always get a "baseline" run and then start changing things from there. The first run example is my baseline. The second run example was everything the same except I switched the head button. Needle, head clearence, water flow were the same. The third example is when I richened up and increased water flow to bring the temps lower. There were more runs but these are just a few examples.

Some general findings from that day of testing were:

• Switching from stock aluminum head button to brass head button, with no other changes, causes the CHT to run 40-50 degrees hotter. EGT for same run was 20-30 degrees cooler.
  
• Brass head button requires more water cooling to bring CHT back to under 200 deg. Typically have found that the 150-180 CHT on aluminum button ran best.
  
• Brass head button does show detonation - just like aluminum. Could not tell if it delays it - not enough experience yet.
  
• As CHT was lowered through water cooling and richer mixture, the EGT increased.
  
• When mixture was taking out the glow plug, the GPS speed in turns would drop off - although the engine rpm did not appear to be dipping at the same time. Need to check again to verify.
  
• Boat is topping out on speed before the end of the straight away. The GPS speed is leveling off while steering still shows going straight.
  
• More Head Volume (head #7) resulted in average CHT (~150 deg) with EGT higher (~650+ deg).Closer to what Aluminum head runs. Did not sound clean though.
  

So for my application with engine, pipe, prop, hull combination, I have not unlocked the setup combination yet to determine if the brass head button is better than the aluminum. It defintiely runs hotter. The data clearly shows that. With the real hot head, I kept taking glow plugs out so I had to increase fuel and water cooling to stop. Looking back at it I should have just richened up more and not touch the water to see if that would have helped from taking the glow plug out.

 

 

For testing on the water, having a data logger is defintitely a plus. It helps show what is happening to the engine. More heads still to test - both brass and aluminum.

 

 

Mike

Brass vs Aluminum Head Button Run Examples for MAC 67.zip

 

[Terry Keeley]

Earlier this year I was able to do some testing of a 360 brass head button on a MAC 67 engine running in a 67SG. I made several brass heads with different volumes. The first head button has the exact same dimensions as the stock aluminum head. The boat is a equipped with an Eagle Tree data logger. I am recording Cylinder Head temp, EGT, RPM, and GPS speed. The attached Word file has several screen shots of the data between runs. For any testing, I always get a "baseline" run and then start changing things from there. The first run example is my baseline. The second run example was everything the same except I switched the head button. Needle, head clearence, water flow were the same. The third example is when I richened up and increased water flow to bring the temps lower. There were more runs but these are just a few examples.

Some general findings from that day of testing were:

• Switching from stock aluminum head button to brass head button, with no other changes, causes the CHT to run 40-50 degrees hotter. EGT for same run was 20-30 degrees cooler.
  
• Brass head button requires more water cooling to bring CHT back to under 200 deg. Typically have found that the 150-180 CHT on aluminum button ran best.
  
• Brass head button does show detonation - just like aluminum. Could not tell if it delays it - not enough experience yet.
  
• As CHT was lowered through water cooling and richer mixture, the EGT increased.
  
• When mixture was taking out the glow plug, the GPS speed in turns would drop off - although the engine rpm did not appear to be dipping at the same time. Need to check again to verify.
  
• Boat is topping out on speed before the end of the straight away. The GPS speed is leveling off while steering still shows going straight.
  
• More Head Volume (head #7) resulted in average CHT (~150 deg) with EGT higher (~650+ deg).Closer to what Aluminum head runs. Did not sound clean though.
  

So for my application with engine, pipe, prop, hull combination, I have not unlocked the setup combination yet to determine if the brass head button is better than the aluminum. It defintiely runs hotter. The data clearly shows that. With the real hot head, I kept taking glow plugs out so I had to increase fuel and water cooling to stop. Looking back at it I should have just richened up more and not touch the water to see if that would have helped from taking the glow plug out.

 

 

For testing on the water, having a data logger is defintitely a plus. It helps show what is happening to the engine. More heads still to test - both brass and aluminum.

 

 

Mike

There ya go, finally some DATA! Ain't the Eagle Tree great?

Sounds to me like the brass makes the head run hotter and therefore faster for those over-cooling their motors, alluded to that in another thread...

 

[RodneyPierce]

There ya go, finally some DATA! Ain't the Eagle Tree great?

Sounds to me like the brass makes the head run hotter and therefore faster for those over-cooling their motors, alluded to that in another thread...

Ive also heard this before....

 

[Tim_Duggan]

Remember torque curve. RPMs are not HP with out torque.

The key word there is CURVE. And curve ties in to application.

 

[mtruex]

There ya go, finally some DATA! Ain't the Eagle Tree great?

Sounds to me like the brass makes the head run hotter and therefore faster for those over-cooling their motors, alluded to that in another thread...

BINGO !

 

[Andy Brown]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

Years ago when I tried the std. plug/ turbo plug comparison back to back in the boat, the turbo was worth 3 mph in a set-up that was running 70 mph. In that test I used identical CNC'd heads and a turbo plug & std. plug of the same # from the same glow plug manufacture. It was definately an Apples to Apples, Oranges to Oranges comparison. I'm sure the turbo plug gave the aluminum head the big boost.

 

[mtruex]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

Years ago when I tried the std. plug/ turbo plug comparison back to back in the boat, the turbo was worth 3 mph in a set-up that was running 70 mph. In that test I used identical CNC'd heads and a turbo plug & std. plug of the same # from the same glow plug manufacture. It was definately an Apples to Apples, Oranges to Oranges comparison. I'm sure the turbo plug gave the aluminum head the big boost.

Thanks Andy,

I figured the turbo plug was the reason for the speed difference, I also used Od77 plugs in both.. Im thinking if they both had turbo plugs there would be no difference..

I want to add that i was only posting my results to add to the discussion, not debating that the brass heads have worked well for some others.. its all in the combination.. But i do think if you are trying to hide detonation with different head material you can still have it, and are hurting performance IMHO

 

[Andy Brown]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

Years ago when I tried the std. plug/ turbo plug comparison back to back in the boat, the turbo was worth 3 mph in a set-up that was running 70 mph. In that test I used identical CNC'd heads and a turbo plug & std. plug of the same # from the same glow plug manufacture. It was definately an Apples to Apples, Oranges to Oranges comparison. I'm sure the turbo plug gave the aluminum head the big boost.

Thanks Andy,

I figured the turbo plug was the reason for the speed difference, I also used Od77 plugs in both.. Im thinking if they both had turbo plugs there would be no difference..

I want to add that i was only posting my results to add to the discussion, not debating that the brass heads have worked well for some others.. its all in the combination.. But i do think if you are trying to hide detonation with different head material you can still have it, and are hurting performance IMHO

Martin,

I agree that there probably would have been no difference based on your results for your boat. Not saying others are not getting gains from the brass. I suspect your set up is already optimized to work best with the aluminum. A whole different set of variables would be needed for the brass to work better. In the case of the CMB 101's, the brass is matching to the set of varibles that are built into that engine.

We could have this same type of discussion around dual plug heads. Several of us had big gains with them. Others did not. Again, it is a matter of what matches the particular engine best.

 

[hugh hargett]

76 to 81 is approx a 6.6% increase, assuming the prop efficiency doesnt change too much in that range it would also be a 6.6% increase in RPM. Assuming the RPM was 30000 for 76mph, this would become 31980, ie almost 2000 rpm more.

yes its the same thing(error) I made youre taking an arbitrary rpm instead of arbitrary pitch same deal for example theres a difference between 6.6percent of 25000 rpm which would be 1650 and 6.6 percent of 30000 which is 1980 so you really need the LE to determine the appropriate rpm from which to take your 6.6 percent

unfortunately knowing the props LE pitch is important for making this calculation :angry:

apples to oranges is the enviroment a boat on the water "dyno" creates just like differences in sea level.Now its not a fair test ?

Sounds like I need to buy a turbo plug for aluminum head instead of a brass button??

 

[Jim Allen]

Earlier this year I was able to do some testing of a 360 brass head button on a MAC 67 engine running in a 67SG. I made several brass heads with different volumes. The first head button has the exact same dimensions as the stock aluminum head. The boat is a equipped with an Eagle Tree data logger. I am recording Cylinder Head temp, EGT, RPM, and GPS speed. The attached Word file has several screen shots of the data between runs. For any testing, I always get a "baseline" run and then start changing things from there. The first run example is my baseline. The second run example was everything the same except I switched the head button. Needle, head clearence, water flow were the same. The third example is when I richened up and increased water flow to bring the temps lower. There were more runs but these are just a few examples.

Some general findings from that day of testing were:

• Switching from stock aluminum head button to brass head button, with no other changes, causes the CHT to run 40-50 degrees hotter. EGT for same run was 20-30 degrees cooler.
  
• Brass head button requires more water cooling to bring CHT back to under 200 deg. Typically have found that the 150-180 CHT on aluminum button ran best.
  
• Brass head button does show detonation - just like aluminum. Could not tell if it delays it - not enough experience yet.
  
• As CHT was lowered through water cooling and richer mixture, the EGT increased.
  
• When mixture was taking out the glow plug, the GPS speed in turns would drop off - although the engine rpm did not appear to be dipping at the same time. Need to check again to verify.
  
• Boat is topping out on speed before the end of the straight away. The GPS speed is leveling off while steering still shows going straight.
  
• More Head Volume (head #7) resulted in average CHT (~150 deg) with EGT higher (~650+ deg).Closer to what Aluminum head runs. Did not sound clean though.
  

So for my application with engine, pipe, prop, hull combination, I have not unlocked the setup combination yet to determine if the brass head button is better than the aluminum. It defintiely runs hotter. The data clearly shows that. With the real hot head, I kept taking glow plugs out so I had to increase fuel and water cooling to stop. Looking back at it I should have just richened up more and not touch the water to see if that would have helped from taking the glow plug out.

 

 

For testing on the water, having a data logger is defintitely a plus. It helps show what is happening to the engine. More heads still to test - both brass and aluminum.

 

 

Mike

Excellent post Mike! The info about how to hold the piston for machining is in the photo album under 7+ HP motor. How's the work coming on the dyno?

 

[dr gary turner]

I have been reading the comments on the brass head button and it has been vary interesting. Mark and I have been running them for about 2 yrs on the 101's. After talking with Martin Davis about his on I believe it was his 21 in Charleston about 2 yrs ago, I felt like we should try them out. Mark made one and I tried in my single 101 C/S. We used Naval Brass. This was not a scientific study[DOUBLE BLIND PROSPECTIVE WITH DOUBLE CROSS OVER] but my experience. I did not see a significant increase in speed. What did occur is the ability to NEEDLE motor. There was a smooth transition from being rich to about right with the third channel. Also we are not seeing the detonation as before with the aluminum heads. BTW the architecture and volume were the same with the same plugs with both heads. We have not had holes in the top of pistons since, with the 101's. I think also the water temperature became less of a factor due to the consistency of the temperature that is held in the brass material. The detonation maybe better because ot the brass being harder,less poris, and seems to be a purer material. The stuff will ring like a bell when "raped". The Naval brass will really shine when polished. I guess that is why it is called NAVAL BRASS

 

[Jack ODonnell]

Apples to apples the brass will not make the difference.

It is the ability to raise the CR to make more power.

Make two buttons with smaller chambers same plug and compare it.

Would be interested in the results.

David

Not disagreeing, but why was the brass so slow. 5mph is a lot on a 21! I have made/tried tons of heads and never seen + - 5mph.

Years ago when I tried the std. plug/ turbo plug comparison back to back in the boat, the turbo was worth 3 mph in a set-up that was running 70 mph. In that test I used identical CNC'd heads and a turbo plug & std. plug of the same # from the same glow plug manufacture. It was definately an Apples to Apples, Oranges to Oranges comparison. I'm sure the turbo plug gave the aluminum head the big boost.

Hi Andy; You say you are sure the turbo plug gave the alum. head a big boost. Can you tell me how you arrived at that. or why you think the the turbo plug is better. I/we have not seen that kind of difference between the std. and turbo seat. Most preference problems we see are in the stem seal's