a little info needed

[Michael Costanzo]

hi guy's,looking for a few opinions on timing numbers for a cmb 67.just did not want to go overboard,i know we have to go slow and fast.going to run 50% and have a many pipes to chose from.also prop choice?have ran a prather 245&250.i know all hulls are different(mine is a muck hull) and just would like some other info.thanks for all the help.mike.

 

[FloridaScaleBoater]

Mike;

Which CMB 67 are we talking about here?

If it is the green head, the BEST pipe is the CMB black Fat Belly set at 11-3/4 to 11-7/8" from center of cylinder, along the length of the pipe. A Rum Racing Stinger muffler works well on them.

On all of my Scales, I'm running the AB 67 muffled pipe, which is the same as the CMB 67 muffled, same measurements.

The boys out in WA. state, say they are haveing good luck with the Mac's exhaust 11CC pipe, I've never tried one in a scale.

As far as props, if the boat is of average weight 15 to 18 pounds Octura X460 X560 & X462,

Prather 250 & 255 are good.

As far as modding the engine, if it's a green head???? Why!!!!!!!!!!!!!!!!!!!!!

B.T.W. What hull will the Muck Make?

You gonna have it ready for Hot-Lanta?

 

[jwo]

I agree. If it,s a Greeen head leave it alone. No need to mod it. Run a OS9B carb and a K67/AB67 or the CMB muffled pipe. You will be happy with it. I never had luck with the CMB Black carb. Some guys like them. Head clearance at 15-16 thousands. I run OD89 plugs and 60% with great results. John

 

[Glenn Gates]

hi guy's,looking for a few opinions on timing numbers for a cmb 67.just did not want to go overboard,i know we have to go slow and fast.going to run 50% and have a many pipes to chose from.also prop choice?have ran a prather 245&250.i know all hulls are different(mine is a muck hull) and just would like some other info.thanks for all the help.mike.

Hi Mike, Might try a X457/3 first. O.S. 9B carb, OD89 plugs. I just send my motors to Steve Wood and let him go thru em.

Glenn

 

[SayMikey]

hi guy's,looking for a few opinions on timing numbers for a cmb 67.just did not want to go overboard,i know we have to go slow and fast.going to run 50% and have a many pipes to chose from.also prop choice?have ran a prather 245&250.i know all hulls are different(mine is a muck hull) and just would like some other info.thanks for all the help.mike.

Hi Mike, Might try a X457/3 first. O.S. 9B carb, OD89 plugs. I just send my motors to Steve Wood and let him go thru em.

Glenn

It all sounds good, for me its a bone stock grenny,cmb/ab muffled pipe with a -410 stinger in it. Run a x457/3 run it stock then start trimming some tongue a little at a time. Pipe set around 11 1/8 to 11 1/2

 

[Michael Costanzo]

hi gang,first, thanks for all the replys.the hull is a "miller high life" 1988 u-31,and is about 13#'s..i have a a/b pipe or mac(nitro&muffled)pipes to try.the boat has been ran for years with a (red)ops 67 and macs 11cc muffled pipe with a pitched up 245 & 250 prop and ran very,vey well.looking foward to

running the cmb motor and some different pipes.yes,rick,i am going to be ready for atlanta.building 4 boats all at the same time,unfortunatly being a over the road trucker,time is a premium!! really do appreciate all the advice but the one thing i really need is time to test!PS,what is the story with the OD 89?? i use mc/9&K&B HP plugs. MIKIE.

 

[jwo]

Some may disagree. I have found that the OD89 is a superior plug. They are built better,Packaged better and last longer. They seem to run a little hotter than the mc9 but you can put more fuel to them. More fuel more power and less wear on the bearings. I was using the mc9 but tried the OD89 and wont go back. Had to many blow outs and burned elements. Not to mention the ones that had no element right out of the package. Oh ya they are cheaper than the mc9 as well. Check them out at tower.

 

[Glenn Gates]

Some may disagree. I have found that the OD89 is a superior plug. They are built better,Packaged better and last longer. They seem to run a little hotter than the mc9 but you can put more fuel to them. More fuel more power and less wear on the bearings. I was using the mc9 but tried the OD89 and wont go back. Had to many blow outs and burned elements. Not to mention the ones that had no element right out of the package. Oh ya they are cheaper than the mc9 as well. Check them out at tower.

Same here- best price I found was Phil's hobby. All I will use on my 45-80 motors.

Glenn

 

[moparbarn]

mike, i only run .21's, but od's have proven to be MUCH more durable that any other plug i've tried. even seem easier to needle on 65%.........od-9's are meant as a direct replacement for mc-9's B) . i like them better than od-89's, but this is in .21's. either way, try some odonnell plugs, i think you will be pleasently surprised with them - price, performance & durability !!!

 

[Michael Costanzo]

mike, i only run .21's, but od's have proven to be MUCH more durable that any other plug i've tried. even seem easier to needle on 65%.........od-9's are meant as a direct replacement for mc-9's B) . i like them better than od-89's, but this is in .21's. either way, try some odonnell plugs, i think you will be pleasently surprised with them - price, performance & durability !!!

i have heard alot of stuff with the newer mc9 that were burning up pre-maturly,still have a stash of old ones.i will try anything once,i will get some od's and give them a shot.what is the difference bewtween the od89 & the od9? thanks,mike.

 

[jwo]

You can go to the tower site and look up the plugs tech notes. I found them helpful. The OD9 is a medium plug designed for 21-45 engines. The OD89 is for 60-101 engines is a cold plug and runs with 50-65% nitro. I tried the OD9 last year in my 67 and cooked it right away. Run the OD89 2-3 races with testing then pull them and save for later. Great plug!!