motor help

[warlokboats]

i have done some testing today. i need more torque on the launch. the motor is a 45, pipe at 9 in., prop is 1657 backcut (1655 not quite enough on the top end). i like the exhaust timing where it is at. what i need to know is can i drop the intakes to get what i want?

thanks jon

 

[Norm Doerr]

i have done some testing today. i need more torque on the launch. the motor is a 45, pipe at 9 in., prop is 1657 backcut (1655 not quite enough on the top end). i like the exhaust timing where it is at. what i need to know is can i drop the intakes to get what i want?
thanks jon

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What engine, what kind of boat, (outrigger,) and how much does the thing weigh?

 

[warlokboats]

cmb crapshooter about 6 lbs

 

[Lay26]

this summer i had a 2004 cmb 45 stock in a crapshooter if i put the pipe that short it would not run, the best set up that i found was the ops 60 pipe@ 9 3/4 wuth a 1460@55mm it would run with that all day, with a 1657 the pipe had to be at 9 3/4 i feel that those engines need alot of work to run as fast a my picco with a parabolic pipe @9 1/4-9 1/2 with the same prop. what pipe are you using. the pipe migh be too short for that big prop. stock cmb 45 sucks!!!!!!!!!! it eventuall broke and they sent me another that i haven't used at all

 

[warlokboats]

lay26 parabolic quiet pipe. it runs like a rape ape after it launchs.

timing is stock on the sleeve. the drum,carb,spraybar, headbutton is another thing.

but no one has answered my question yet.

 

[Norm Doerr]

this summer i had a 2004 cmb 45 stock in a crapshooter if i  put the pipe that short it would not run, the best set up that i found was the ops 60 pipe@ 9 3/4 wuth a 1460@55mm it would run with that all day, with a 1657 the pipe had to be at 9 3/4 i feel that those engines need alot of work to run as fast a my picco with a parabolic pipe @9 1/4-9 1/2 with the same prop. what pipe are you using. the pipe migh be too short for that big prop. stock cmb 45 sucks!!!!!!!!!!

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CMB that is internally balenced? Try pulling the pipe out. The OPS pipe is a good idea. Just reduce the stinger to around .....I think .330". There are several ways to get the thing to pull and everyone has an opinion. Here are some options that my mentors and myself have found to work.

Lowering the sleeve is good for the south and finding a needle. But .... you have to cut the underside of the liner and cut the exhaust to make up for it.

Running HIGHER compression will make it launch. Soooo you have to mess with the head buttom after you set the exhuaust.

Do you know the numbers now? (exhaustm, transfers, boost and rotor timing.

Is the thing stock AND since it is CMB, How did you break it in?

 

[warlokboats]

norm i thought about lowering the head clearence. i looked at the piston at the end of the day and no sign of any problems. so you are saying the i can lower the boost and transfer ports to increase low end torque?

and yes i know all the numbers on this motor.

 

[Lay26]

basic answer.... lengthing the pipe will give you more torque

#2 lowering the head clearance will help too if you have the shim that it came with the the head clearenc is too hi set it @.011 hopes this help this is what i experienced with my shooter

 

[warlokboats]

the question was can you lower the boost and transfer ports to get low end torque.

this may seem a dumb question but does someone need to know all this other stuff to answer the above question?

 

[TimD]

the question was      can you lower the boost and transfer ports to get low end torque. 

this may seem a dumb question but does someone need to know all this other stuff to answer the above question?

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Jon,

The blowdown will effect the torque. I don't know the stock numbers on those engines so I don't know what the figures are. Dave Marles would be the person to ask about CMB's and timing numbers and the effect on torque.

Also, what bowl volume are you running in the head button?

 

[Norm Doerr]

the question was      can you lower the boost and transfer ports to get low end torque. 

this may seem a dumb question but does someone need to know all this other stuff to answer the above question?

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I usually start with the exhaust timing then plug in the other numbers. So yes that is important .

The exhaust should be at around 185 to 188 Machine the squish band flat or if you don't like a rough idle, machine half of the squishband flat and angle the inner half at 1 to 1.5 degrees Set the CR at 10.5 to one, the bowl will be around .35 cc. Use 60 percent nitro. I don't know for sure weather lowering the intakes will gain torque, but you will find the needle easier.

 

[Preston_Hall]

Jon,

Lower numbers will should work but why do that? Seems like it is only going to slow you down on the top end. I say lower the head clearance.

BTW, Picco 45 + Crapshooter + parabolic @8-8.5" + 1657 = 88mph, very easy to launch and excellent low speed

 

[warlokboats]

preston whats a picco 45 :unsure: nice to have but no parts. all i want to do is lower the boost and transfer ports. the exhaust will stay the same. as for speed i had a picco i used for a buddy and my cmb is just as fast(on radargun), but needs some help on the launch.

jon

ps hows the 21 running?