Hammerhead .21 Build

[RodneyPierce]

and the man speaks.

 

[mtruex]

Mr hammerhead,

As Tim said once you get it right you will not want any other engine.. Drop the sleeve till the ex is 189, take .012 off the squish band to reduce volume, set clearance at .006, put an od77 plug in it, and reduce water cooling to make some heat and you will be screaming. Only thing I'm not sure on is your pipe, I've never run that pipe before. Good luck.

 

[dwilfong]

The blow down is what I would try and get at 30% first then set the transfers at 126. A little sub port won't hurt as much as the wrong numbers. It is a trade off to the good. You can always shim it back up if it dose not work. Brass head button and higher CR you will never no it was sub porting.

Like I was told but had to learn on my own. there is noting up there if you are heat racing.

David

 

[dwilfong]

It is 60deg 30% 126 trans 186 ex.

Real easy to remember. trans at 125 ex 185, trans at 124 ex184 ect, ect, ect.

Start low and work your way up. can do it at the pond with liner and head shims.

You will find there is a point that the revs will no longer go up. so why go higher.

But the needle and throttle will fall off.

When the transfers get to high it will load up with fuel sooner in the striates. this can be resolved with more cup on the tip but this is a band aid.

You can go around in circles tuning.

Start low with a short pipe and land on a good prop like a H7 stock. then raise the liner till the reves don't go any higher. step back one and cup.

Just my thinking on tuning.

David

 

[Tim_Duggan]

If memory serves me correctly, the 35 Plus M sleeve is already at 30 degrees blowdown (194ex, 134 tr) before lowering. After lowering 0.013" it's at 190 / 130 and still maintaining the 30 degrees blowdown and port area/shape.

The stock bowl volume in the head + the dish in the piston was about 0.24cc. After taking some off the squish face it drops to better numbers volume wise but I can't remember the exact number. (head clearance needs adjusting anyway after dropping the sleeve!)

Frank Orlic makes a higher CR turbo plug button for these engines if more compression + Turbo plug is wanted than what decking the stock head provides, but plenty of fast guys find the NR head decked 0.013" to be working well. I have both. Haven't tried one in brass yet as I want to stick with turbo plugs, rather than introduce another change by going back to conventional plugs. One change at a time wherever possible I find is the best way to learn. However if someone who is good at machining turbo plug seats that actually seal wants to make me one in 360 brass, I'd be willing to try it! :lol:

 

[aaron alberico]

Ain't no problem running real FAST with the lowered 35plus sleeve....

 

[dwilfong]

Remember the higher the timing the smaller the eng thinks it is. Unless you have a custom pipe to load the cylinder.

Lower timing will let you run the pipe shorter.

High timing dose not alway give you RRRRRRRRRRRRRRRRRs but it will take the bottom and mid range out of the eng.

Higher timings do not make a good heat race eng.

I didn't listen when it was explained to me but I found out the hard way.

Thanks for sharing Marty it finally sunk in.

You will find more power in the "pipe" and button lastly once you settle on the lower timing.

Try a out board full tapered pipe from the spigot it will help.

surprised no one has made one for a nova in rigger yet.

David

 

[Ian Inverarity]

Try a out board full tapered pipe from the spigot it will help.

surprised no one has made one for a nova in rigger yet.

Who says it hasnt been done already? B)

 

[mtruex]

Remember the higher the timing the smaller the eng thinks it is. Unless you have a custom pipe to load the cylinder.

Lower timing will let you run the pipe shorter.

High timing dose not alway give you RRRRRRRRRRRRRRRRRs but it will take the bottom and mid range out of the eng.

Higher timings do not make a good heat race eng.

I didn't listen when it was explained to me but I found out the hard way.

Thanks for sharing Marty it finally sunk in.

You will find more power in the "pipe" and button lastly once you settle on the lower timing.

Try a out board full tapered pipe from the spigot it will help.

surprised no one has made one for a nova in rigger yet.

David

David,

im not saying you are wrong, but what happens if you have high timings AND a short pipe and can still pull a big prop !!

 

[dwilfong]

Remember the higher the timing the smaller the eng thinks it is. Unless you have a custom pipe to load the cylinder.

Lower timing will let you run the pipe shorter.

High timing dose not alway give you RRRRRRRRRRRRRRRRRs but it will take the bottom and mid range out of the eng.

Higher timings do not make a good heat race eng.

I didn't listen when it was explained to me but I found out the hard way.

Thanks for sharing Marty it finally sunk in.

You will find more power in the "pipe" and button lastly once you settle on the lower timing.

Try a out board full tapered pipe from the spigot it will help.

surprised no one has made one for a nova in rigger yet.

David

David,

im not saying you are wrong, but what happens if you have high timings AND a short pipe and can still pull a big prop !!

Then you got a real fast boat!

 

[Ian Inverarity]

Oh Yeah!! B)

 

[aaron alberico]

Mmmmm

That is what I have been doing wrong!!!!

Better lengthen my pipe, or lower my exhaust timing....

 

[Tim_Duggan]

Mmmmm

That is what I have been doing wrong!!!!

Better lengthen my pipe, or lower my exhaust timing....

Please do - in fact do both and change your prop also - you're too fast. :lol: :lol:

 

[Ian Inverarity]

Mmmmm

That is what I have been doing wrong!!!!

Better lengthen my pipe, or lower my exhaust timing....

I'll send you a special liner, pipe and prop.

 

[dwilfong]

You know it is funny how those that have it all figured out to the knife edge with many hours of testing can say that this is the way to go.

but what about those gust trying to have a good running boat and go to a few races to have some fun.

thy will do what all the top guys do to get the last little bit out of the eng. Only to get frustrated and give up.

val-la one less nitro boater to go to a race.

I give advice to help some one get a consistent run not a tuning nightmare that thy may not wake up from.

So tell me did you all just raise the timing to the moon shorten the pipe and throw a H7 on it and it was golden?

David

 

[LarryConrad]

Ain't no problem running real FAST with the lowered 35plus sleeve....

I know mine is no slouch. Steve Wood dropped my sleeve a bit and re machined the button. Engine pulls better at lower rpm's without effecting the top end performance. Mine is a 2007 Novarossi 35+M version of the engine.

 

[Ian Inverarity]

You know it is funny how those that have it all figured out to the knife edge with many hours of testing can say that this is the way to go.

So tell me did you all just raise the timing to the moon shorten the pipe and throw a H7 on it and it was golden?

David

No one in the above discussion is saying to raise the timing.

 

[dwilfong]

But has any one ever gone lower and sub port the ex to see what hapens?

David

 

[dwilfong]

Yes he did. tried some things on my RS 1.01 last weekend. very interesting results.

Do not want to say as the testing is not done yet.

Not sure where it will lead.

David

 

[Ian Inverarity]

But has any one ever gone lower and sub port the ex to see what hapens?

David

That is not needed, other liners with lower timings go into the same case. I have run the 7M liner quite a bit.