Thunder Tiger 3.5 engine

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rcboats2@aol.com

[email protected]

Well-Known Member
Joined
Nov 6, 2002
Messages
4,025
Guys,

I saw a brand new in the box 3.5 Thunder Tiger engine at my LHS for $179.99, tax is another 8.25%. So it'll be near $200. Is this the going rate? Cheap? Or expensive?

I've read that everyone on this board is very pleased w/the way they run if you mod them soI'm considering it.
 
from Rodney"I've read that everyone on this board is very pleased w/the way they run if you mod them soI'm considering it."

Yeah, All Two Of Us!

OOP's, I left out "JD" and Mike Bontoft said they ran well,,,

That's "Four" of us :rolleyes:

The price is right if the motor is made in this decade. (red box)
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Jerry,

yeah, I must have been considering your word as good as 4 people.... :lol: :lol:

It is the red box version. They have the original water cooled 3.5 K&B w/a gold carb for $235, an SS for $255 and the SX for $289....many options, many options.
 
Hi Rodney, Ya know? I just don't see any K&B's runnin' in mod class(3.5) up here anymore. I think Kip McKay may still run one in my local club but he's been gone raising a son for a few years.

The Tiger's take a fair amount of work to make'm really go but I mildly mod one for a club member and it cooks. It's just a matter of taking material off the bottom of the button until you get .005 headspace, 180degrees Ex port and Turbo the crank. Run a hot plug, "MC59"and 60% nitro with a small prop(637 or 438) and I don't think many K&B's will catch you. I use to run the same and they will run for several seasons. They seem to like the old Irwin "J" un-muffled and stinger sleeved(or spud) to .250in :)
 
Rodney,

Raise the exhaust timing, slap on a pipe, a new head button and sleeve shim and it will serve you very well (for a low buck engine - it's surprising how well) B) B) B)
 
Well, There Ya Go,, and I'm SURE Tim will Make-up a "Small Fleet" of button's for Ya :p No Problem,, Right Tim?? :D
 
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Tim_Duggan said:
I don't mind telling the specs for the buttons  :lol:
109605[/snapback]

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He wouldn't know what to do with it,,,but Terry Keeley, Might :huh:
 
[email protected] said:
It is the red box version.  They have the original water cooled 3.5 K&B w/a gold carb for $235, an SS for $255 and the SX for $289....many options, many options.
109594[/snapback]

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I was wrong on the prices. K&B 3.5 w/gold carb $189.99, SS $209 and the SX $219 even better.
 
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Hi there,

Well the Thunder Tiger can be competitive if you follow Jerry advices on timings and head clearance. Remove as much material as needed from the sleeve to achieve at least .007 head clereance ( I did not try .005). Then it is a becomes another engine. It will give great power till you will be too lean... (Common problem with that engine.)

I noticed that it starves (transfers size is too small) and needs a big work on the crankshaft and on the sleeve to bring more air/fuel to the combustion chamber.

I do not know if you got this problem but I have some air leak with the front bearing. I changed the front bearing fot an OS one but there is still a small air leak. It seems that the tolerance on the crankshaft is wrong and air seems to flow between the shaft and the bearing, ?!? :eek:

Jerry, did you try to change the carb for a bigger one ?
 
Howdy Tony! I've been messin' with the Tiger's allot lately,, much more than what I decribed in that post to Rodney.

With the help of TimD and a machinist in Ohio We made up some head button's in the .17 , .18 and .19cc volumes.

Along with those, I cut the crank induction to 214 degrees (open 30deg ABDC and close 65deg ATDC) and have cut the custom head buttons to allow up to a .010in sleeve shim to raise all the ports and still have .008 headspace.

Also found a GadgetCraft Carbon Pipe from a fellow boater

like you were using and that "combo" will really light them Tiger's Up :eek:

There is a new "learning curve" using the low volume button's as I found out. It involves running the motor "fairly rich" and restricting the waterflow to get things hot enough to use all that fuel,,and when it does,,YEEHA!

Oddly enough the engine likes 184deg exhaust port timing with this set-up and I've tried many, all the way down to 175deg.

The "front bearing leak" you mentioned is not something I've noticed,, I do use a Swiss bearing in there and and change them in mid season.

I also put two ounces of "castor" in a new gallon of 60% fuel it will help with the poor seal in the crank rotor.

I've only used the carb that comes on the "newer re-introduced" motor, it has a different carb than the earlier models. But I did find out that it was hard to get the engine "rich enough" for the new mods with out the needle falling out. TimD suggested cutting the tip of the needle off (about "1" to 1.5mm)and I promptly did.

Also took the boat and engine to a District race to test it (Not Recomended) but finally found it and it did help allot,,(didn't lose anymore needle's)

It's Great to here from You,,We need to talk more :) Jerry
 
Tonymods said:
Hi there,
Remove as much material as needed from the sleeve to achieve at least .007 head clereance ( I did not try .005). Then it is a becomes another engine. It will give great power till you will be too lean... (Common problem with that engine.)

109814[/snapback]

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Tony,

you will find, as Jerry did, that a new head button is a far better approach. Factor in the head clearance when making the new button. make the bowl smaller and the squish completely flat.

Tonymods said:
I noticed that it starves (transfers size is too small) and needs a big work on the crankshaft and on the sleeve to bring more air/fuel to the combustion chamber.

109814[/snapback]

​
Click to expand...
It's a combination of a poor needle valve in the carb, and the stock timings are too conservative. A sleeve shim and carb mods will do the job, as well as opening up the crank window to better numbers. The port area's are reasonable on the transfers / boost. No need to seriously modify the sleeve other than raising the exhaust and cleaning up the edges of the ports. The piston fit is not the greatest and improving the fit is worth doing also.

Tonymods said:
I do not know if you got this problem but I have some air leak with the front bearing. I changed the front bearing fot an OS one but there is still a small air leak. It seems that the tolerance on the crankshaft is wrong and air seems to flow between the shaft and the bearing, ?!? :eek:
109814[/snapback]

​
Click to expand...
Not the bearing, but the crank to case fit is poor. Hard fix - have the case bushed. Easy fix - run more castor oil. I ran as much as 15% in my tiger!

Tonymods said:
did you try to change the carb for a bigger one ?
109814[/snapback]

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The 9mm ID carb form the inboard engine can work well after mods! A remote needle is the best option.
 
[email protected] said:
[email protected] said:
It is the red box version.  They have the original water cooled 3.5 K&B w/a gold carb for $235, an SS for $255 and the SX for $289....many options, many options.

109594[/snapback]

​
Click to expand...
I was wrong on the prices. K&B 3.5 w/gold carb $189.99, SS $209 and the SX $229 even better.

109711[/snapback]

​
Click to expand...
Hii Friend!!

Where you found K&B engines for this price??

See ya
 
This note is to "Tonymods", Tony, you can "grow" the size of the Thunder Tiger piston by putting it in a small "ceramics oven" or "kiln". The temperature I used was 675degrees F,, for two hours and turn off and let cool in oven. The first two I did this to, "grew" a little and the second two "grew" alot,, I cooked the second two an hour longer. The second "batch" had to be lapped in by hand in the engine, it took about an hour,, plenty of oil and I kept the engine warm with a heat gun while doing this.

The other method is to resize the sleeve with a special tool, that I don't have.

There's also the "tubing" cutter method but I'm avoiding that one for my own reasons :huh:
 
Thanks Jerry,

I ve never tried to "cook" the piston of my TT. Actually I changed once the sleeve and the piston because I ran too lean and my crankshaft broke. I really noticed a great difference with the head clearance reduced to .007. I use only 33% nitro so I do not know if I need to change the Head for different volume. Concerning the carb I use the original one but I reshaped the needle, made and big venturi shape on the bottom and corrected the barrel which was not perfectly inline.

I ran the TT against my bittburger cat with CMB 21 LSI yesturday and the TT was not slower. I worked a lot on the sleeve, crankshaft and carb on the TT but the compression is defently the way to go. Sure that the new heads you've tried must give amazing results ;) .

I am stil using O.S 8 and the glow seems to be "sucked" into the engne. I think this means that I can shortened the pipe. The engine is still running cold, even with a water restrictor.. :unsure: . need to go for air cold head.
 
Hi Tony, The high compression buttons gave the engine the ability to turn larger diameter props than before and the "sleeve shims"(rasing all the ports) allowed the engine to go into RPM area where more "pitch" could be used.

It's a totally new power delivery, I call it "passing gear". I'll have to install a "third channel needle control" to get the engine to "hit" passing gear more consistantly.

I have some "sleeve shims" for you to try if you give me you mailing address at

<[email protected]>. I'll also throw in some hotter plugs

I have used as much as .010in sleeve shims in the engine and the exhaust port cut to 184deg with the shims in place. Also a hot plug like a McCoy "MC59", "MC8"

or the "K&B 1L" with .008 head space. Any less head space with this set-up could

cause you some other problems,, .008 gives you a safety margin and is close to being the correct compression ratio with the .18cc headbutton(of which I'm not able to supply at this time)

You can cut (in a lathe) the "bottom" of the "largest" diameter section of the "stock

button" down to .083in thick. Then start removing the "squish band" face until that section is .124in thick (the section that goes into the sleeve)

.008 to .010 sleeve shims should get you to .008 head space in most of these engines from what I've seen.
 

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