Teaching An Old Dog New Tricks...

[Bob Kensill]

Right with ya Jack, glad to pass along what little I know.

As for rods, I chatted with Rod Geraghty just last week about rods for a older K&B 7.5 OB. Rod stated the K&B rods, after the move to Ca., are just as good as aftermarket ones. The ones to stay away from are those that look like "I" beems.

Are you referring to the "T" bone rods as some like to call them?

~Mitch

My HOT setup in 1981 used a Picco piston, sleeve, rod and wrist pin. Only minor machining of the K&B case was needed (The Picco sleeve was slightly thicker). This in combination with much Time/Area work, a well kept secret at that time, (My earliest graph that I can find now is dated 6-22-78). This set up won the District 19 points championship, ran within 1 MPH of the SAW record in a heat race boat and won the A_Hydro class at the Amarillo NAMBA nationals.

I also like to swap parts. I just finished a K&B 3.5 outboard with a Sirio .21 piston/sleeve. It was a very easy swap. I plan on "sneaking" it into B sport tunnel.

 

[oldlugs]

...I also like to swap parts. I just finished a K&B 3.5 outboard with a Sirio .21 piston/sleeve. It was a very easy swap. I plan on "sneaking" it into B sport tunnel.

Hey; that sounds like a hot tip... Which Sirio P/S #? Did the case need reaming or modifying?

Duane

 

[Marty Slater]

:blink: I my self cant do machining or take a dremel to a sleeve

a few weeks ago Rod G had pictures on aligning the prop shaft with scag i think i can handle that one what would another easy fix or are they mostly machine work an the man Jack G had articles on bearings an blue printing engines any other easy fixes for us less fortunet thank you for your time

Marty

 

[Jack Garcia]

:blink: I my self cant do machining or take a dremel to a sleeve

a few weeks ago Rod G had pictures on aligning the prop shaft with scag i think i can handle that one what would another easy fix or are they mostly machine work an the man Jack G had articles on bearings an blue printing engines any other easy fixes for us less fortunet thank you for your time

Marty

Thanks Marty:

I'm in a hog wallow when I'm passing on my experiences to boaters like ya'll and hopefully adding to your expertise.

 

[oldlugs]

Hey all, for how long did K&B offer a _disc_ rotor version of the 3.5 inboard? 'Till today, I wasn't aware of such a beast.... I imagine that parts aren't too easy to find for the rotor assy... Were they decent runners?

Duane

 

[oldlugs]

So call me crazy... As I was staring at my box of K&B 3.5 bits, it occurred to me that these things could actually run TWO intakes, one at each end. Since their intake timings are close to the same (and could be perfectly matched), can anyone see a reason why this shouldn't work?

Remember where you saw this first, if suddenly twin intake K&Bs (or other engines) start showing up at your local ponds... :lol:

Using the long pin outboard cranks, and turning the bearing case at a 90º like the old inboard will make the thing run in the right (left) direction for an inboard. The use of the outboard's long crankpin will drive the drum rotor... Two intakes! Since the drum rotor tosses the incoming mixture upward toward the piston, and the crank intake shoots it straight at the drum rotor, there shouldn't be too much interference; right? Wouldn't this give the ultimate in crankcase filling? I was thinking of trying it with the two venturi as pictured, but using a single 3rd channel needle tee'd off to both venturi, and controlling RPM with an exhaust throttle... Yes; just another wacky way to make a K&B boat grenade. Got a few other ideas too... :blink:

Duane

 

[Geraghty]

So call me crazy... As I was staring at my box of K&B 3.5 bits, it occurred to me that these things could actually run TWO intakes, one at each end. Since their intake timings are close to the same (and could be perfectly matched), can anyone see a reason why this shouldn't work?

Remember where you saw this first, if suddenly twin intake K&Bs (or other engines) start showing up at your local ponds... :lol:

Using the long pin outboard cranks, and turning the bearing case at a 90º like the old inboard will make the thing run in the right (left) direction for an inboard. The use of the outboard's long crankpin will drive the drum rotor... Two intakes! Since the drum rotor tosses the incoming mixture upward toward the piston, and the crank intake shoots it straight at the drum rotor, there shouldn't be too much interference; right? Wouldn't this give the ultimate in crankcase filling? I was thinking of trying it with the two venturi as pictured, but using a single 3rd channel needle tee'd off to both venturi, and controlling RPM with an exhaust throttle... Yes; just another wacky way to make a K&B boat grenade. Got a few other ideas too... :blink:

Duane

I took me awhile to find it but I dug this patience tester out of the sxxt pile for a photo...............We did this over 15 years ago with a 7.5 K&B with a disc rotor.

All I can say is .....get ready to start drinking very heavily........Good luck.

Rod Geraghty

 

[oldlugs]

I took me awhile to find it but I dug this patience tester out of the sxxt pile for a photo...............We did this over 15 years ago with a 7.5 K&B with a disc rotor.All I can say is .....get ready to start drinking very heavily........Good luck.

Rod Geraghty

Rod, I knew someone (likely you) had already tried it! I was just waiting for a reply... Honestly though; what were the biggest problems with it...? If/when it did work, was it working well?

Duane

 

[Geraghty]

I took me awhile to find it but I dug this patience tester out of the sxxt pile for a photo...............We did this over 15 years ago with a 7.5 K&B with a disc rotor.All I can say is .....get ready to start drinking very heavily........Good luck.

Rod Geraghty

Rod, I knew someone (likely you) had already tried it! I was just waiting for a reply... Honestly though; what were the biggest problems with it...? If/when it did work, was it working well?

Duane

As I recall,even with the small black K&B carbs there was a definite lack of fuel draw.

There just wasn't enough velocity across the spraybars to get a suffucient pressure drop to get a good fuel signal to deliver fuel.

I remember it kinda worked on the bench but was a miserable failure in a boat.

 

[oldlugs]

Hey all, was this K&B 3.5 drum rotor a short-lived production engine, or was this aftermarket stuff...? I know the throttle's aftermarket (most likely Prather), but I'm wondering about the rotor & bearing cases...

Duane

 

[David Homer]

I used to run K&B's pretty successfully in monos not too many years ago... It looks like that the engine in that pic there got a disc rotor from another brand of engine (I'm thinking maybe early CMB?) As far as I know K&B made just two inboard versions of the 3.5, the latter being a drum rotor. One tip I haven't seen anyone mention is you definitely have to restrict the water flow to these engines. K&B 3.5's run way too cold! I have used a watercooled exhaust header as a matter of routine, running the flow here first, then the head.. Even doing that I ran some significant restriction in the water flow. Aeromarine made a rod for this engine, don't know if they still do. Might be worth a check. Tried turbo cut on the inboard crank, ain't worth the hassle. Just throws everything out of balance. All I've ever done was skirt the piston, clean up the flow paths, and matched the sleeve with the case. Much more than that yer getting into green-ade territory....lol

Have had good success in the outboards doing just 3 things.. the Keeley head, water restrictions, and installing the K&B muffler. Those who have seen these OB's run can attest...

 

[Geraghty]

[quote name='David Homer' It looks like that the engine in that pic there got a disc rotor from another brand of engine (I'm thinking maybe early CMB?) As far as I know K&B made just two inboard versions of the 3.5, the latter being a drum rotor.

Thats exactly where this drum rotor came from.It was a from a mid '80s CMB .21.