Teaching An Old Dog New Tricks...

[oldlugs]

OK; so I know the K&B 3.5s are far from modern, and I don't expect the same kind of reliable power that the MACs, CMBs, and NovaRossi are making...

BUT since there are SO many of the old dogs out there (K&Bs), I thought it may be fun to pick brains about modding the K&B 3.5s... Old timers (er...experienced racers), please feel free to pitch in your thoughts (yeah, I know; pitch out the K&B...).

Who's got a list of the "magic parts" that make a K&B 3.5 really go?

Best case to use, best style of piston/sleeve, best head button, bearings...?

Any favorite or well established port measurements and massage techniques? How about which cranks to run, and how best to mod them (both older inboard, and outboard)?

And finally, what about the late/last/current(?) drum rotor version...? Can they go zoom or just KaBoom?

With all the good-guy parts, can any K&B inboard ever run even sorta close to modern .21s, and still live a season..?

Is this a ridiculous thread idea?

Thanks!

Duane

 

[Boatshop]

OK; so I know the K&B 3.5s are far from modern, and I don't expect the same kind of reliable power that the MACs, CMBs, and NovaRossi are making...

BUT since there are SO many of the old dogs out there, I thought it may be fun to pick brains about modding the K&B 3.5s... Old timers, please feel free to pitch in your thoughts (yeah, I know; pitch out the K&B...).

Who's got a list of the "magic parts" that make a K&B 3.5 really go?

Best case to use, best style of piston/sleeve, best head button, bearings...?

Any favorite or well established port measurements and massage techniques? How about which cranks to run, and how best to mod them (both older inboard, and outboard)?

And finally, what about the late/last/current(?) drum rotor version...? Can they go zoom or just KaBoom?

With all the good-guy parts, can any K&B inboard ever run even sorta close to modern .21s, and still live a season..?

Is this a ridiculous thread idea?

Thanks!

Duane

-OLD DOG'S OLD TIMERS?

I am offended, who do you think you are

Byte me, HAHAHAHAHAHAHAHA :lol:

Hey, just kidding.

Skirted piston all but exaust area,

RPM con rod.

out board engines 3.5

Keely turbo head.

Used thunder tiger carb, because of mid range needle.

Could get completely off the throttle milling, and get rite back up, no problem.

Oh RPM con rod.

Improved flow on sleeve, filed bypas, boost port area, of sleeve, to improve fuel flow.

Been a while, but if I think of any more I'll post again

Dave Hobson

 

[Dan_Cousin]

I spoke to Gary Perusse at G&M models about this on the inboards and one of his suggestions was that to NOT use the standard two piece motor mounts we use today. You'll break that K&B in two. Octura had a mount that both mouting sides were connected under the motor. you can attach the bubber buttons to that to keep the two sides level and not put stress on the case.

You might give him a call.

 

[Boatshop]

By the way.

head clearence 0.006 -0.008 3.5 ob

K&B 45 drum rotor head 0.008

RPM con rod, Improve flow boost bypass ports

skirt piston, same all but exaust port.

seemed to work good for me.

Dave.

60% red max

 

[oldlugs]

OLD DOG'S OLD TIMERS?

I am offended, who do you think you are

Byte me, HAHAHAHAHAHAHAHA :lol:

Hey, just kidding.

Skirted piston all but exaust area,

RPM con rod.

out board engines 3.5

Keely turbo head.

Used thunder tiger carb, because of mid range needle.

Could get completely off the throttle milling, and get rite back up, no problem.

Oh RPM con rod.

Improved flow on sleeve, filed bypas, boost port area, of sleeve, to improve fuel flow.

Been a while, but if I think of any more I'll post again

Dave Hobson

Cool Dave; thanks. No offense intended; but the engine has been around forever, and who but the wise, experienced racers would know them better...?

The first one I played with was in an Associated R/C car.... around '78 or so. I had no idea what I was doing, and traded it off without getting it running well.

Any "turbo" mod on the crank, or do they fall apart afterwards? Years ago, I remember seeing outboards with no carb, a radiused carb opening (BIG I.D. venturi where the carb would mount), and a needle & jet in the set screw holes. They were run with ex throttles... Here's what I'm talking about, but on an inboard (I haven't tried it out yet):

Anyone know how well that mod worked? Lose too much intake velocity at low engine speeds?

Duane

 

[Boatshop]

WOW

Don't know what that is haven't seen a K&B drum roter 3.5

seen some exaust throttle engines, inthe past;.

Don't know much about them.

No offense taken, just joking sorry

 

[Boatshop]

WOW

Don't know what that is haven't seen a K&B drum roter 3.5

seen some exaust throttle engines, inthe past;.

Don't know much about them.

No offense taken, just joking sorry

WOW Again

Not a drum roter

Dave

 

[oldlugs]

WOW Again

Not a drum roter

Dave

No, that's not the drum rotor version, but an example of the front case made into a venturi, for use with an ex throttle. That engine's from just prior to the drum rotor version. Been wanting to try it for years, since seeing others done like that some 15-20 years ago. I never saw those run either... I'll probably take the needle off this, plug the hole & run a 3rd channel needle. Need more room for the ex throttle.

Great info so far! I was thinking to help with case strength, I'd scrub one up well & JB Weld the backplate in place. I'm sure that would help strengthen it a bit.

Duane

 

[MarkScott]

First off, I enjoy ET's. Question has been asked in years past. Reasons given back were but not limited to: they waste fuel (inboards catch all) spitting out the venturi, hard to set needle, current carbs are working better..

Here's my K&B 3.5 OB, Gardner XXL Exhaust Throttle & Garcia pipe. The lower was sold off to Gener.

Keeley Turbo head

Swiss bearings - Racecraftbearings

RPM Conrod (also have a titanium conrod)

Non turbo crank (have one though)

Slight grove cut on piston side.

Sleeve mods can be seen: Sleeve mods

When I got a boat to handle the motor, it was never radar'd. Don't know the top speed it would give. Plan on working on that this year.

 

[[email protected]]

The problem w/the venturi is there **** messy. Plus I'd put some sponges to asorb water around that venturi so it doesn't splash inside of it.

 

[SayMikey]

The problem w/the venturi is there **** messy. Plus I'd put some sponges to asorb water around that venturi so it doesn't splash inside of it.

If you are talking about that early crank inducted motor in the pic,without a McCoy crank its trash can material. It will break the crank in short order been there done that. I have a handful of drum motors id sell cheap.

 

[oldlugs]

...If you are talking about that early crank inducted motor in the pic,without a McCoy crank its trash can material. It will break the crank in short order been there done that. I have a handful of drum motors id sell cheap.

Talk to me... I'm interested in the handful. I'll send you a PM.

How well did they run in comparison to the crank inducted versions on HP/RPM? I'm sure they were a bit more reliable.

Duane

 

[oldlugs]

Hey all; does this look about right for a "turbo" mod, or should more be cut? Thanks!

 

[jaxracer]

First off, I enjoy ET's. Question has been asked in years past. Reasons given back were but not limited to: they waste fuel (inboards catch all) spitting out the venturi, hard to set needle, current carbs are working better..

Here's my K&B 3.5 OB, Gardner XXL Exhaust Throttle & Garcia pipe. The lower was sold off to Gener.

Keeley Turbo head

Swiss bearings - Racecraftbearings

RPM Conrod (also have a titanium conrod)

Non turbo crank (have one though)

Slight grove cut on piston side.

Sleeve mods can be seen: Sleeve mods

When I got a boat to handle the motor, it was never radar'd. Don't know the top speed it would give. Plan on working on that this year.

What lower is that? Looks kind of like the lower sold by hyperprod.com.

~Mitch

 

[Marty Slater]

Beautiful Duane i hope this 1 stays at the top for a while

3.5 inboards an outboards do you do the same things or are there mods for just in or outboards

an speaking of old where is the G man :lol: sorry Rod shouldn't have said that before getting your $1.95 input what is the 1st thing to do an please use a lot of pictures for us less fortunate

thanks for all of this INFO

Marty

 

[MarkScott]

What lower is that? Looks kind of like the lower sold by hyperprod.com.

~Mitch

Design Graphics I believe. No option to put a cavitation plate on it. Water pickup needed to be created also.

 

[oldlugs]

Beautiful Duane i hope this 1 stays at the top for a while

3.5 inboards an outboards do you do the same things or are there mods for just in or outboards...what is the 1st thing to do an please use a lot of pictures for us less fortunate

thanks for all of this INFO

Marty

Hey Marty, since the in & outboards are pretty much the same engine, I figure the mods would be more or less the same for both.

Now, that turbo mod for the crank would have to be angled differently on the outboard, 'cause it's spinning the opposite direction.

The most recent version outboard uses a bigger/stronger/better breathing crank than the older engines used, and the most recent inboard used a better induction system (drum rotor) that allowed for both better breathing, and a less flexy crank. I imagine that piston and sleeve mods could be the same for all versions, depending on your desired RPM... I think that moderation is the key here; the K&B is pretty unlikely to see 35,000+ RPM more than one time. I doubt that the professional engine tweakers will have much to say here, but you never know; they may throw us a bone yet...

I figured that this may be a good thread... So many folks who just want to play, and don't need (or can't afford) the latest & greatest all-out race engines yet still want to go fast... and they may have K&Bs sitting around. I'm going to mod a few & see for myself what seems to work, and what helps them to not go KaBoom. I seriously doubt that I can make one go as fast as say, a MAC or NR, but I think I'll have some fun trying...

Duane

 

[Dr Hydro]

Hey Marty, since the in & outboards are pretty much the same engine, I figure the mods would be more or less the same for both.

Now, that turbo mod for the crank would have to be angled differently on the outboard, 'cause it's spinning the opposite direction.

The most recent version outboard uses a bigger/stronger/better breathing crank than the older engines used, and the most recent inboard used a better induction system (drum rotor) that allowed for both better breathing, and a less flexy crank. I imagine that piston and sleeve mods could be the same for all versions, depending on your desired RPM... I think that moderation is the key here; the K&B is pretty unlikely to see 35,000+ RPM more than one time. I doubt that the professional engine tweakers will have much to say here, but you never know; they may throw us a bone yet...

I figured that this may be a good thread... So many folks who just want to play, and don't need (or can't afford) the latest & greatest all-out race engines yet still want to go fast... and they may have K&Bs sitting around. I'm going to mod a few & see for myself what seems to work, and what helps them to not go KaBoom. I seriously doubt that I can make one go as fast as say, a MAC or NR, but I think I'll have some fun trying...

Duane

Hey Duane....I'm an old K&B man from way back when. Used to run them in hydros back in the 80's. Never raced but had a ball with my podnuhs. I'm still wondering what a Keely turbo head is. If someone could post some pics I sure would appreciate it. Good luck and God bless!

 

[oldlugs]

...Hey Duane....I'm an old K&B man from way back when. Used to run them in hydros back in the 80's. Never raced but had a ball with my podnuhs. I'm still wondering what a Keely turbo head is. If someone could post some pics I sure would appreciate it. Good luck and God bless!

I think the "turbo head" just uses a tapered seat "turbo" plug, but not sure... Are the Keely heads currently available?

Duane

 

[Marty Slater]

hay Duane i under stand about a bone i have been know to take any thing I'm hungry about KBs 3.5 mostly

an some thing about the first picture you posted Jack Garcia? wrote an article about KB 3.5 out boards titled California Hop ups in an old RC boat modeler that talked about that set up you took out the carb an put in aKB speed needle in its place but you had to drill the block for pressure an then a exhaust throttle in i will try to rattle his chain if no bones from him i will try to find that article.

is the mods for piped engines that work for 1 an not the other or most mods just help an engine breath better any how an as for that OBNut guy goes i just wish i could a 100000000000 of the stuff he does on a computer very help full on tunnel boats too thanks again Mark an Duane for starting this post

Marty