New Manic Mechanic High Comp Billet Head

Discussion in 'Spare Parts, Tools & Product Developement' started by 210061741, Feb 9, 2010.

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  1. 210061741

    210061741 Guest

    Here is the new high compression head from Jim at Creative Engineering.
    Currently there are only 2 of them and i have 1.
    These will be available at Pirate Cycles only.
    Very Very soon.









    Heres a video of how it sounds.
    Notice i am running an 18mm Dellorto Carb now too.
    Last edited by a moderator: Feb 9, 2010

  2. AussieSteve

    AussieSteve Active Member

    Looks different. It's very tall.
    Again, what's the compression in psi?
    That's more important than the sound, which is really the carb & pipe, not the head.
    Also, what is the clearance, head/plug to piston?
    And, does it bolt straight on with standard 107-108mm studs?

    ... Steve
    Last edited: Feb 9, 2010
  3. 210061741

    210061741 Guest

    Yes it bolts right on.
    It's for the PK motors only at this point.

    I will have to figure out the psi and get a compression tester.
    However my PSI will be slightly lower than on a stock motor due to my porting arrangement.

    I will get both measurements soon as i have some time.

    The chamber with the dome piston is cut down to 4cc.

    You have to set the clearence to exactlly .020 inches.

    The squish is perfect.
  4. AussieSteve

    AussieSteve Active Member

    This is another one that's quickly losing me.
    You guys are designing a high-compression head, but you don't even have a compression tester?
    I'm a beginner backyard mechanic and it was one of the first things I bought.
    You say high compression, but then say combustion chamber pressure will be lower than a stock engine?
    20 thou clearance, with lower psi than a stock engine?
    Mine is a measured 142psi, (17psi higher than stock), and has 0.044", (1.1mm) clearance, measured and not from spec.
    And why so tall? My RSE billet head is plenty cool enough, with much more meat than a stock head.
    Maybe I'm off track, but I'm not quite keeping up with this. something doesn't add up with the 'hi-comp' head. Maybe I'm misunderstanding what you're saying.

  5. swifty

    swifty New Member

    steve,when you do a compression test you are measuring dynamic compression.from where the piston seals the exhaust port to the top. if you port & raise the exhaust port you will have less dynamic compression.this is not to be confused with static compression ratio which takes into account the total swept could have an engine with low cranking pressure yet still have hi comp ratio if it has a very high exhaust port. hope this helps.
  6. AussieSteve

    AussieSteve Active Member

    Swifty, I follow what you're saying, but isn't the aim of a high compression head to raise the gas pressure at the point of firing, regardless of compression ratio.
    If the measured gas pressure is lower than that of a standard head, isn't that a low compression head?

    ... Steve
  7. swifty

    swifty New Member

    as the engine revs higher the percentage of loss becomes less & less to a point where with a properly tuned expansion chamber it will start to increase.this is when a 2 stroke comes "on the pipe".the engine with low cranking pressure, due to port timing will out perform the std port engine in the mid & hi rpm.given that the static comp ratios are the same. you dont ride your bike at cranking speed.
  8. AussieSteve

    AussieSteve Active Member

    I was only originally trying to find a way to compare the Manic Mechanic head with my Rock Solid Engines one, in some useful fashion. I guess it's not that easy.
    Also, originally I thought the new MM head was a bolt-on performance accessory for a standard HT engine, rather than being specifically for a ported PK.

    I've avoided porting, apart from a tiny bit of widening, to keep my bottom end.
    (I'd love to be able to ride my bike at cranking speed, although that's less important now, with a shift kit.)

    Compression ratio measurement always had me wondering, on a 2-stroke, since it's not just a matter of the swept volume : compressed volume. As you say, it's dependent on the position of the (top of the) port.
    I thought that psi measurement at cranking speed was a fair comparison, but obviously not.
    And therefore it follows that measuring psi has been a waste of time, except for future comparisons to see if I've lost any.

    Not that I was planning to change, but from the sound of things the head I have suits my purpose best.

    ... Steve
  9. 210061741

    210061741 Guest


    I am not the only person working on this project.
    I am not the one who designed the head.
    It was done by Manic Mechanic and BRENDON POWERS.....
    Brendon powers builds F1 Racing Engines professionally.
    So i don't allways have all the figures at my fingertips.

    I do things mathematically and then verify it all in the cad system.

    Obviously Rock Solid didn't tell you what the PSI of there head is or you guys wouldnt be testing with compression gages.

    The high performance engine is much higher than stock.
    greater than 9:1.

    Now to clarify things.

    The high compression billet head will produce higher PSI on a stock PK.
    Much higher.
    It also produces higher psi on my engine.
    All i was saying is due to my porting the PSI reading i get will be slightly lower than what you will get.

    I will model everything in CAD and tell you the exact compression ratio and the exact psi of the head.

    Also we will be producing an even higher compression head for the ported Performance Motors.

    I'm sure Jim at Creative Engineering can tell you what the Exact PSI is as well.

    The stock cc chamber is 8cc.

    The billet chamber is 7cc.

    The piston also consumes around 3cc.

    1 more thing as well.

    Engines with different strokes and different porting will have different Readings.

    Hope this helps.

    I will post the data soon.
  10. 210061741

    210061741 Guest


    The head is currently being produced for stock unported motors.

    A new one will be produced for the ported motors.

    Also my porting and the addition of the Dellorto drastically increased the bottom end as well as the top end.

    It pulls hard and fast.

    You just wouldn't believe it.

    I allmost fell over when i got it ported spot on.
  11. AussieSteve

    AussieSteve Active Member

    It's obviously a little more involved than I thought, but in terms of combustion chamber size, they can be easily compared.

    Along those lines, they could be compared with a comp gauge on a given engine, just as my stock head and billet head can be compared. 115psi vs 142psi

    My questions have only been for the benefit of others, as a comparison between mine, (RSE billet) and the new one. Mine suits me, as I said. My only drama, as you remember was stud length, hence that question.

    Does it need quite as much fin area? Mine is pretty meaty and runs at a pretty good temp. I'm thinking overhead clearance issues with some frames.

    Tony doesn't give a psi figure, quite rightly it seems, but he does give a CR figure of 16:1.

    I've never delved deeply into this stuff in the past, beyond shaving about 0.040" off a few heads when I was younger, with no idea of any figures when I was done.

    I learn more every day here.
    And potential customers know a lot more about the impending head.

    I was a bit blunt earlier and owe a bit of an apology. Maybe even a whole one.
    Wouldn't be the first time and probably won't be the last.

    ... Steve
    Last edited: Feb 11, 2010
  12. Pirate Cycles

    Pirate Cycles New Member


    Lots of hours went in to the development of this head. Here are some more detailed pics of the process..


    Pirate Cycles
    Last edited: Feb 12, 2010
  13. gothicguy64

    gothicguy64 Member

    have any speed results in kmh of what ur 66cc bike would do both b4 and after jack drive conversion .

    it a pity i dont have a compression tester i wonder what my 50cc rse hp1 motor with ceramic piston an billett parts all ova ......its ported an goes to 64kmh not bad with a 44 rear ...

  14. AussieSteve

    AussieSteve Active Member

    I don't doubt that, Justin. Looking pretty good, overall.
    I'll wait until someone (with a comp gauge) bolts one onto a stock 66cc motor to find out a direct psi comparison. Only out of curiosity.
    My remaining minor point is the height, which will prevent fitting this head to some engines, due to clearance issues. Otherwise, the extra meat and fins will help with cooling.
    Love the workshop and bench, I use my dining room table for my engine work.

    Brad, if you have 26" wheels, (I allowed for 25.6" under load), then at 64kph, (40mph), you're pulling about 9470RPM. Not too shabby.
    Probably not good to hold those revs for too long at a time, though.

    ... Steve
  15. Steve,

    Good evening from sunny Florida. Here are a few answers to your questions, from the manufacturer.

    "Looks different. It's very tall.
    Again, what's the compression in psi?
    That's more important than the sound, which is really the carb & pipe, not the head.
    Also, what is the clearance, head/plug to piston?
    And, does it bolt straight on with standard 107-108mm studs?

    ... Steve"

    The overall height is decieving to the's actually only 1/8" taller than the cast piece measured vertically. If the engine is mounted at the typical 45 degree angle, the builder will need to allow an extra 1/2" for frame clearance. As Rich stated, the psi, relative to a compression gauge test is not accurate. Porting will affect the gauge reading. The cylinder head that I make has a chamber that is 1cc smaller than the factory head. Obviously, without any other modifications, the cylinder head that I make will show a higher reading on a compression gauge. This has been done for the current factory run of PK80 engines. Yes I know they aren't actually 80cc. Yes...of course I made it to fit as a direct replacement...The stock stud length was taken into consideration when designing the product.

    Tony at Rock Solid is a friend, a customer, and a pro engine builder...I'm not making cylinder heads to compete with him. I'm making them for a specific engine that Pirate Cycles sells.

  16. AussieSteve

    AussieSteve Active Member

    Thanks, Jim, for such a comprehensive reply.
    That 1/2" for frame clearance can be a lot on some frames.
    Having said that, in my case, the air cleaner is closest to the frame, with only 10mm vertical clearance. (SBP low profile air filter and the RSE head isn't very tall.)

    I'm not sure how much smaller in cc the RSE head is compared to the stock one, so as mentioned, I'll wait until someone bolts your head on a stock 66cc engine to compare compression pressures, just out of interest.

    The stud length was a major issue for me with Tony's head. If it wasn't for the boys at Sick Bike Parts, I might still be trying to get 112mm x 8mm x 1.0mm studs.

    Any idea of price yet, even a ballpark figure?

    ... Steve
  17. Pirate Cycles

    Pirate Cycles New Member


    They will sell for $42.00. Shipping will be $5.00 for a 2-3 day priority USPS service.

  18. AussieSteve

    AussieSteve Active Member

    Good price for all the work that's gone into this.
    You won't get any complaints in that department, I wouldn't think.
    Even here in Oz, with shipping, the price is comparable to Tony's.

    ... Steve