bath tub head

[dwilfong]

Here is the first test cuts on a new head design I will try on my RS 1.01.

I blame Dick most of the time for my hair brained ideas but this one is all Marty's fault.

I got this idea from some old tech notes he had on his web sight.

It cam out a little wide, about .080 too much and the cc are a little big at 1.09 with the plugs.

this should come in good when I adjust the width of the chamber and make it a little shallower.

It is at .160 deep now.

The final one will be in 360 brass

 

[SayMikey]

Lose a plug 2 of them just cost twice as much and dont help

 

[Roy Munoz]

I made one of these head buttons during the time Marty and John Ackerman were testing there's ..I found the engine developed a lot of power ,but I couldn't get the RPM I was looking for. I realy didn't give it a chance eather.and gave up on the project.. Good luck with yours..Will have to make another one some time and test some more or look and see if I can find my old one...

 

[dwilfong]

Roy did it make a difference how the chamber was orientated?

side to side or front to back?

 

[Roy Munoz]

Yes it did. You'll have to play with it a little to find the sweet spot' ..Mine had to be off center of the EX and Front intake port. I was thinking that my voleume might have been too much. don't remember how much it was.Been a long time..Should have wrote it down.

 

[DickJones]

Roy did it make a difference how the chamber was orientated?

side to side or front to back?

The orientation should be East and West, if U orient it North and South, " a "war" will brake out.JM2CW

dick

 

[Roy Munoz]

LOL good one Dick

 

[dwilfong]

thanks Dick
I sure don't want to start a war.

So what you think will happen if I stick a pair of MC-59's in it with 60%. :mellow:

 

[Roy Munoz]

Should run real good..I try that head button on a 67 and a 45..Still looking for them..LOL

 

[DickJones]

thanks Dick

I sure don't want to start a war.

So what you think will happen if I stick a pair of MC-59's in it with 60%. :mellow:

Assuming U are using the "bath tub" dual plug head button, I would try a little colder stronger element plugs, elements pulled, the first few runs and see if they hold up, because of the extra heat available with 2 plugs it is much easier to burn larger volume of fuel in the combustion chamber as opposed to a single glow plug, the extra heat also can be a problem when not enough fuel is available at critical peak lean conditions will cause detonation before peak RPM's are reached.Glow plug Orientation is a very interesting subject, first try plugs siting left and right at the transfer ports, and run the boat a few times to see how it launches and RPM's , then rotate the head 90 degrees, where the orientation is over the exhaust and boost ports and then scratch your head and let us know, HOW'S THAT WORKING FOR U!!!!!!!!!!!!

dick

 

[dwilfong]

Her is the finished head button.

Will give it a whirl this weekend.

Hope it don't start a war.

 

[Tom Foley]

Nice !! If it works you'll be getting orders !

 

[dwilfong]

Well gave it a try to day.

Runs different than the normal head. It has very nice manners as I would call it.

The power is more even around the course. There are no big changes in RPM with changing load conditions.

It might be that it detuned the eng not making it so critical.

I am not sure if this is a function of the two plugs or the chamber design.

It idles faster and smother and pulls the front end up from a slow start.

But it dose not rev as high on the unloaded conditions but then it dose not stall out after a over rev ether.

The MC 59 worked the best and the front to back orientation is the best for RPM's.

Would like to try some Rossi plugs in different ranges BUT thy are to pricey for me.

All and all I like the way it runs better with this head.

 

[Terry Keeley]

What volume did it end up at? How's that compare to what you were running?

 

[dwilfong]

both heads are the same at .92cc and .010 clearance giving a 9.3 CR with timing at 188EX.

The testing was done one right after the other with the same setup and needle settings.

Ran two gallons thew it testing. went back and forth with the heads to get a real feel for what was what.

The last runs I slammed the pipe in all the way to 10 1/2'.

The tub head did better on launch and throttling.

10 3/4" seams to be the best for heat racing setup.

Will go out tomorrow and try a longer pipe setting and see where the revs fall.

The testing was done with my modified RCMK H767ss prop with 4.1" lead in pitch.

It dose haul the mail!!!!!!!!!!!!!!!!!

 

[Roy Munoz]

I see that your getting the same results as I did.. I was able to go up a few prop sizes as well. Keep us posted.

 

[Terry Keeley]

both heads are the same at .92cc and .010 clearance giving a 9.3 CR with timing at 188EX.

The testing was done one right after the other with the same setup and needle settings.

Ran two gallons thew it testing. went back and forth with the heads to get a real feel for what was what.

The last runs I slammed the pipe in all the way to 10 1/2'.

The tub head did better on launch and throttling.

10 3/4" seams to be the best for heat racing setup.

Will go out tomorrow and try a longer pipe setting and see where the revs fall.

The testing was done with my modified RCMK H767/3 ss prop with 4.1" lead in pitch.

It dose haul the mail!!!!!!!!!!!!!!!!!

Good stuff!

 

[Ronald Van Wagnen]

Not that it mattered... but I used to run one hot plug and one cold plug, one or both would normally always survive 5 laps of WOT !

 

[dwilfong]

So let me get this strait.

The hot plug will get the burn rate up to rev the eng and if it blew. the cold plug would get you to the end of the race?

 

[Ronald Van Wagnen]

Absolutely correct. It can save you from a foul needle setting as well.