Hammerhead .21 Build

[mtruex]

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

David

its not good on small engines i know that

 

[dwilfong]

Yes but all the liners are different port dimensions.

All I am saying is if this liner has the correct blow down and good ports why not try it If dose not work gust add a shim.

This will also get you higher on the taper.

David

 

[dwilfong]

If that is the case then that is that.

Dose not matter if you can pull a bigger prop if you can't launch it.

David

 

[Ian Inverarity]

Yes but all the liners are different port dimensions.

All I am saying is if this liner has the correct blow down and good ports why not try it If dose not work gust add a shim.

This will also get you higher on the taper.

David

As mentioned before there is also a 35+ car liner that is lower timed and has otherwise the same port dimensions.

 

[Tim_Duggan]

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

The Nova 5 port and 7 port sport engines are good performers out of the box, cheaper and don't have the wild timing numbers - I'd reccommend those to the guys who don't have to have the last ounce of performance, are not interested in refining the internals, and want to have fun, over the 35+. These engines still have more torque than the drum valve induction engines in stock form and will pull a H7 in a rigger. I've got one of each & have tested and raced with them.

Having said that, The info on refining the 35+ is hardly a secret. I agree that it is too wild out of the box.

My experience with sub piston induction has that it has always robbed bottom end. A friend had a Certain Model Boat O/B powerhead on a tunnel that he just could not tune at all. Like you said - he was getting frustrated and was giving up. I noticed it had a small amount of SPI, so raised the sleeve with a shim, reset the head clearance, and presto - easier to tune and launched better. I doubt it was the higher timings or the pipe length that fixed it as we'd played with pipes / pipe length / props - which left the SPI.

 

[RodneyPierce]

Tim, you might remember me going round after round with a GO last year, couldnt get it a tune on it, couldnt get it to perform, wasnt consistent, sometimes wouldnt even launch. Almost pulled my hair out, and what was the culprit? Sub port induction. Shimmed it and it was night and day difference.

 

[Tim_Duggan]

First off - Sorry hammer-san for side tracking your thread like this!

RP,

Exactly the same phenomenon I had with the CMB. It was so minute it took a light under the piston to see it. Only a few thou. For me it's one of the last things I think of until I tear an engine down, so I appologise if you asked me about it and I didn't pick up on it being SPI. Not sure why it's not more prominent in my brain - maybe because it's uncommon - but it has been something that had me in a bind before. I recently had a friends rigger drop right off in performance and had to resort to tiny props and became a pig to tune - in that case it was a cracked skirt at the exhaust but the hole was quite large in comparison to that other case. If anything, the larger SPI seemed easier to deal with, but was still down on torque and rpm.

I've never been able to make SPI work positively for me with otherwise conventional timings. Maybe it works better with way over the top induction numbers so that you are cramming a lot more charge in plus capitalising on the return pulse from the pipe to stop the case venting thru the exhaust port under the piston at TDC?

 

[RodneyPierce]

First off - Sorry hammer-san for side tracking your thread like this!

RP,

Exactly the same phenomenon I had with the CMB. It was so minute it took a light under the piston to see it. Only a few thou. For me it's one of the last things I think of until I tear an engine down, so I appologise if you asked me about it and I didn't pick up on it being SPI. Not sure why it's not more prominent in my brain - maybe because it's uncommon - but it has been something that had me in a bind before. I recently had a friends rigger drop right off in performance and had to resort to tiny props and became a pig to tune - in that case it was a cracked skirt at the exhaust but the hole was quite large in comparison to that other case. If anything, the larger SPI seemed easier to deal with, but was still down on torque and rpm.

I've never been able to make SPI work positively for me with otherwise conventional timings. Maybe it works better with way over the top induction numbers so that you are cramming a lot more charge in plus capitalising on the return pulse from the pipe to stop the case venting thru the exhaust port under the piston at TDC?

Oh, no, I didnt mean it negativelly. You were on point trying to help me figure it out, like you always are B) . Was just one of those things neither of us thought about, and bam. That was the issue.

Hammer, yes, sorry brother for getting this side tracked. I didnt even pay much attention there, just got into the conversation, and now its a few pages deep and nothing about the original. Sorry man.

 

[Hammerhead]

Don't you guys worry about side tracking this thread. I'm enjoying it.

Lots of great info.

 

[LarryConrad]

Hammerhead, Your boat turned out awesome, and your Maple stand and starter box look killer. When you get that 35+ dialed in, hang on.

 

[Hammerhead]

Will do, Larry!

 

[57fairlane500]

Well, Marty's motor is starting to run real strong. Jim work some magic and that thing is starting to run good.

 

[Hammerhead]

Yes!!! After a year of pulling my hair out, It finally runs. I don't know exactly what numbers he got it down to though. Maybe he will get in here and share the info. He did say the boost and the transfer were still a little bit higher than normal. For being as big of a boat that it is, It has no problem pulling a Props4U custom 1450, so I'm happy with the way it is.

 

[Glenn Quarles]

Yes!!! After a year of pulling my hair out, It finally runs. I don't know exactly what numbers he got it down to though. Maybe he will get in here and share the info. He did say the boost and the transfer were still a little bit higher than normal. For being as big of a boat that it is, It has no problem pulling a Props4U custom 1450, so I'm happy with the way it is.

Marty, did he lower the sleeve?

GQ

 

[Hammerhead]

Yes. I'm not exactly sure how to explain it, but he said the sleeve was cut wrong. So he had to take off 0.0017 off the bottom. of the lip.

The way the sleeve was originally, the exhaust timing was at 201 degrees. It's now down between 186 and 187 with no SPI.

 

[Jim Mamaril]

Yes!!! After a year of pulling my hair out, It finally runs. I don't know exactly what numbers he got it down to though. Maybe he will get in here and share the info. He did say the boost and the transfer were still a little bit higher than normal. For being as big of a boat that it is, It has no problem pulling a Props4U custom 1450, so I'm happy with the way it is.

Marty, did he lower the sleeve?

GQ

Yes I lowered the sleeve, the problem was there was a problem with the machining on the undeside of the lip. It was tapered and had a burr left on it that was about .005 high. I removed a total of .017(including the burr) to get the underside of the lip perpindicular to the bore, that brought the exhast down to 187 and the transfers to 136 if I remember correctly. Then I machined a shim to set the head clearence at .007. which left the head button in its original configuration. It seems to run really strong so now I have really be on my A game to stay in front of Marty..

Jim

 

[RodneyPierce]

Jim, Im betting those transfers are now closer to 127

194/134 out of the box. Minus .012 off the underside of the sleeve (not including the burr) should have netted around 187/127 or there abouts.

 

[Jim Mamaril]

Jim, Im betting those transfers are now closer to 127

194/134 out of the box. Minus .012 off the underside of the sleeve (not including the burr) should have netted around 187/127 or there abouts.

Yes Sir I believe you are right, I couldn't remember off the top of my head and I didn't right it down, I was more worried about the Exh, and SPI if I went to far.

 

[Tim_Duggan]

Sounds like a good result in the end! Time to test some pipes on that beast Marty-san, and see what really turns it on!

 

[Hammerhead]

Yes!!! After a year of pulling my hair out, It finally runs. I don't know exactly what numbers he got it down to though. Maybe he will get in here and share the info. He did say the boost and the transfer were still a little bit higher than normal. For being as big of a boat that it is, It has no problem pulling a Props4U custom 1450, so I'm happy with the way it is.

Marty, did he lower the sleeve?

GQ

Yes I lowered the sleeve, the problem was there was a problem with the machining on the undeside of the lip. It was tapered and had a burr left on it that was about .005 high. I removed a total of .017(including the burr) to get the underside of the lip perpindicular to the bore, that brought the exhast down to 187 and the transfers to 136 if I remember correctly. Then I machined a shim to set the head clearence at .007. which left the head button in its original configuration. It seems to run really strong so now I have really be on my A game to stay in front of Marty..

Jim

I don't think you need to stay on your A game, Jim. Your B game will be just fine