How Much is To Much When doing Sleeve Work

[steve wood]

DO NO HARM.

the cmb 67 need very little done to the sleeve.use a degree wheel or the eap(my choice) to find your numbers,don't touch the transfers,then try for 30° blow down,with about 188° exhaust. you can skirt the liner below the boost a little if you want. .012 head clearance. the engine loves more carb too.

 

[John Seybold]

Hi, are there any articles explaining how to modify engines? I'd like to learn how to do this and understand that there is a lot that goes into having a fast boat besides just the engine. Someone had mentioned blueprinting an engine, how do you know what the settings sound be for a stock engine (timing, head clearance, etc...)? And once you know what the numbers should be, how do you make those changes? I'm not asking for everybodies secrets,lol, those I know don't come free, just trying to find a place to start.

John

 

[moparbarn]

find some of john finch's books B) . talk to rod geraghty B) . 2 of the best in the hobby, imho. both very willing to help teach & share what they have learned.

 

[RonShaw]

I always used CeeBee marine carbs but I am not sure of Carl's status or if someone has continued his legacy. His carbs gave you the ability to exchange barrel opening adapters to help establish the perfect carb for any size boat. I still use them on many of my boats today.

 

[dwilfong]

The first thing you need is a eng program so you can see what dose what. Marty's is very good lots of info and all the help you would ever need.

Not trying to sell any thing here just the facts.

Well worth the investment!

David

 

[Tom Foley]

and one of the biggest things you can do to WAKE up that engine is use a good carb.. the carb that comes with that motor don't cut it in my opinon

And would you care to fill us in, on what would be a GOOD carb?

I can handle that question though I just might be a little prejudice.

I do not know about the GOOD carb but the BEST carb is the ZOOM.....

Charles

**** ..I knew that would be the answer !! I have yet to try one but have heard great things about your product and would like to know more about one for a MAC 67 so i can kick Jeremy's arse at the next race !! :lol: :lol:

 

[JeremyEdge]

LoL,I am so ready to race it will be 2 months since I raced.Bring the speed buddy I'm ready

 

[Jim Allen]

I would like to know how much work on a sleeve is to much.

Intake,Exausht,And transfer ports.

And witch angels work best for Riggers on these areas.

And what dremel bits are being used to achieve the cleanest work.

Also what needs to be done on a drum intake.

Thanks,

Jeremy

The modification & building of a reliable high HP 2 cycle engine is greatly influenced by first making all the mechanical features of the engine as correct as possible. The elimination of unecessary friction & drag will do more to increase the engine's HP than changes to window geometries. A good carburetor & tuned pipe working together could possibly break most engines presently available on the market.

With these things in mind; 1) increase the blow down time area without increasing the exhaust timing 2) look for induction systems that will increase the induction time area without very late closings 3) use a tuned pipe system that will develope at least 100+ in of water at wide open throttle 4) use a very large bore fuel metering type carburetor, .625" bore for a .90 size engine 5) build some type of a reliable test stand.

There is no one single thing that will make a "super engine".

Jim Allen

 

[mark voorhies]

Thanks Rodney

What will I lose in the transfer ports when shimming the liner?

You really need to try Marty Davis EAP, engine analysis program, it will give the

answers your after, you measure certain points of your engine, feed those into

the program, and it gives you timing numbers per your changes, It's a must,

if you want to play with engine timings.

Here is a link; http://rc-engine-analysis-software.com/

 

[Joe Warren]

I would like to know how much work on a sleeve is to much.

Intake,Exausht,And transfer ports.

And witch angels work best for Riggers on these areas.

And what dremel bits are being used to achieve the cleanest work.

Also what needs to be done on a drum intake.

Thanks,

Jeremy

Jeremy the angles @ the top of the boost & transfer need to be maintained. You can lower the tranfers & boost windows without too much trade off. Got to be careful not to waste blown down time. the Piston cannot move the fuel upwards if some port is opened too long.. Widening the existing ports helps increase flow. However with the increase of flow you loose velocity so dont over do it on the small engines. Most modified engines Only gain 5-7 MPH over a well set up stk engine with the correct prop & pipe on it..

 

[mark voorhies]

I have run the CMB .67 with great results just using a bigger bore carb, like.550, I'm sure the Zoom

carb is a good choice, just haven't tried one. If you want to play with your timings on any engine

you need to try the EAP engine program.

http://engine-analysis-software.com/