engine timing

[Geraghty]

I too have had good results with just raising the exhaust timing, and increasing CR but I will definately try shimming the sleeve as Rod has suggested. I have wanted to try this mod for a while but for me it has been difficult to locate the correct diameter and thickness of shim.

Once again if you have had success just raising the exhaust,you were not starting with 110 degree intakes.

It is difficult to try and locate shims pre made.I have a lathe and mill and a ton of aluminum and brass rounds so I just make what I need.

Listen guys,don't just start making shims and start installing them blindly hoping for the best.Spend your money on a copy of the Marty Davis E.A.P. program and learn how to use it.

These are great starting #'s for for any .21.Start by setting your intakes at 125,set the exhaust at 170 to 172 unpiped,180 to 182 piped.Leave the crank timing as it comes.Set the CR at 9.8- 1 and start from there.If the motor has good bearings,great crankcase compression[not a leaker],good P&S fit,a straight rod that has clearanced properly....the motor will run like hell if you let it.

For all you guys that know Ron Zaker and have seen him run......[126INT-182EXH "top hatted" and stock crank numbers are the numbers on all Zakers 3.5 hydro motors and he is running in the high 70's on 65% in heat race form.Believe me motors alone will not get you running fast.It is the total package.]

 

[Geraghty]

Rod,

I have a question and please straighten me out on this. I was of the impression that not all engines take to mods to make them high RPM power plants. i.e.: I always thought that the K&Bs and OS engines do better when mod'ed to be high torque work horses, not 40,K RPM buzz-saws like a Rossie or CMB (I'm talking .21)? :blink:

I took my older K&B 8906 and piped it for more torque (at least that was the attempt) so I'm swinging a x442 or x640 on it and now the fell'a seems to like those props more than an x440

... or have I missed the boat with my line of thinking??????

chunk t

Yes,you have missed the boat but I don't know why yet.

Call me 1-715-926-6096

 

[Jerry Wyss]

Ok Rod I've got the TT #'s

BORE: .654

STROKE: .630

ROD CtoC: 1.181

TDC to TOP of LINER: .116

TOP EX to TOP LINER: .535

TOP SIDE PORT to TOP LINER: .613

TOP BOOST to TOP LINER: .643

Also: I have custom buttons in the .17cc .18cc and .19cc

I think I remember cc'n the stock botton between .28 and .32cc (including the plug)

 

[Buckshot]

Hey Rod,

How crucial is it to match the Boost and Transfer ports? i.e. Should they have the same closing time from BDC?



-Buck-

 

[anthony_marquart]

Well after listening to Rod I got a very small cutter and opened up the transfers like he said. Fortunatley the P/S for the OStz12 is only 440 if it doesn't work. I think it wil lthouhg because it's real close to the numbers he suggested. If I can get this next kit built I'll let you guys know if it made a difference.

I love this site... Now I just need to get over this pnuemonia,... It's really bad,... but leaves me at home alone to tinker with my boats.

 

[chargerrc]

Just measured my boost and intake ports 125 geuss thats why it works on a AE.15 I still would like to try shimming the sleeve Thanks for the enlightment Rod that is probably why it did not make any noticable difference when I performed the same mods on a friends XTM .18

 

[Geraghty]

Hey Rod,

How crucial is it to match the Boost and Transfer ports? i.e. Should they have the same closing time from BDC?



-Buck-

I don't think that is crucial at all.

I have had motors where the transfers and boost have two different intake numbers and they run very very well.I have done motors that came with 110 degrees on the boost and transfers in stock configuration.The first generation CAM .45 with the "GoldHead" came this way.I raise the transfers to 130 degrees,straight cutting them across the top just like a K&B, and the motor becomes an animal.

Once again there is a big sweet spot in every motor and that spot is reasonably easy to find.

I never look for 100% of design effeciency or the last 5% of power.That last 5% willmake the motor very user un-friendly.I'll get the last 5% with set-up.......the total package is where it is at.

Remember.............In order to finish first,first you must finish.

 

[Geraghty]

Ok Rod I've got the TT #'s

BORE: .654

STROKE: .630

ROD CtoC: 1.181

TDC to TOP of LINER: .116

TOP EX to TOP LINER: .535

TOP SIDE PORT to TOP LINER: .613

TOP BOOST to TOP LINER: .643

Also: I have custom buttons in the .17cc .18cc and .19cc

I think I remember cc'n the stock botton between .28 and .32cc (including the plug)

This is what you have stock......

Intakes: transfers= 124 boost=105

Exhaust: 157

Compression Ratio with head clearance set at .012".... .17CC=11.5-1.... .18CC=11-1.... .19CC=11.5-1

This is where I would start..... raise the liner .013" with a shim.Cut a top hat in the center third of the exhaust port up .035" to an exhaust port height of .500" from the top of the liner.Set the head clearance @ .012" with the .19CC head

This would be the result........

Intakes: transfers=130 boost=120 Exhaust=175 CR with .19CC head set at .012"=9.6-1

This would be a great fit with the stock exhaust and a 12MM crank.The exhaust would also be good with an outboard pipe.

 

[Tim_Duggan]

Wise word's Rod as usual!

Jerry, Time to tell Rod the whole truth about what you have been testing......

Greg Mortlock and I just built a TT with a .010 sleeve shim and modded head in "stock" guise - hopefully it will get wet this weekend.

 

[Jerry Wyss]

Ok Rod I've got the TT #'s

BORE: .654

STROKE: .630

ROD CtoC: 1.181

TDC to TOP of LINER: .116

TOP EX to TOP LINER: .535

TOP SIDE PORT to TOP LINER: .613

TOP BOOST to TOP LINER: .643

Also: I have custom buttons in the .17cc .18cc and .19cc

I think I remember cc'n the stock botton between .28 and .32cc (including the plug)

This is what you have stock......

Intakes: transfers= 124 boost=105

Exhaust: 157

Compression Ratio with head clearance set at .012".... .17CC=11.5-1.... .18CC=11-1.... .19CC=11.5-1

This is where I would start..... raise the liner .013" with a shim.Cut a top hat in the center third of the exhaust port up .035" to an exhaust port height of .500" from the top of the liner.Set the head clearance @ .012" with the .19CC head

This would be the result........

Intakes: transfers=130 boost=120 Exhaust=175 CR with .19CC head set at .012"=9.6-1

This would be a great fit with the stock exhaust and a 12MM crank.The exhaust would also be good with an outboard pipe.

Thanks for all That Rod, Don't have much of the 12mm crank stuff left (case's and cranks) and I haven't ran an "unpiped" Tiger in about 10 years.

I have a "Ton" of 13mm crank engines and parts,,when I found out that TT omitted the motor I bought up

about every part I could find,,close to $2000 worth over a few months.

I have quite of an array of pipes,, the "Gadget Craft" carbon unit has gave the best performance with the

mods I'm currently using.

I can put together a 12mm engine and see what this info does, but I think Grim and others have been down this road themselves,,,They're report was,,well, grim....Anything wrong with the 13mm engine??

 

[Jerry Wyss]

Wise word's Rod as usual!

"Jerry, Time to tell Rod the whole truth about what you have been testing......"

I don't think we gotta'nuf paper here!,,Tim :lol:

Ahh,, I thought Rod knew,,Most, of what I,,And you Tim have been doing. I talked to Rod before

about some of this stuff,,namely the opening of the induction window to 65ATDC and 30ABDC,

I remember him saying He didn't like the idea,,that it would render the engine "unfriendly",,which

it actually did to a certain extent.

The "growing" of the piston in a ceramics oven was in a topic a while back where Rod had some

input in that discussion.

I was on here continually "crowing" about gettin some low volume buttons made for the Tigers.

There's always a reason why Rod says what he does,, I can put together a 12mm engine

with his specs and see what's there.

Anyway Rod,, TimD and I have put our abilities together and came up with the following

The low volume buttons mentioned above,, button cut to accept .010" sleeve shim @ .008 H/S

C/R I believe 10.70:1

Crank opened to the above specs

I have cut the Ex port to 184deg,, (plugging my ears now) TimD recommended 178deg

Engine has ran extremely strong,,alot of rpm's, But shortcomings in an array of props and a learning

curve in how to use the buttons, pipe length , how much water and needle setting have been a bit much for me.

I do have a 3rd channel needle now and plan to back the EX timing off a little.

The suggested method of running the needle rich and pinching (nipping in Oz) the water Way down

has been a real eye opener for me,, man it actually works.

 

[Geraghty]

....Anything wrong with the 13mm engine??

Absolutely nothing.I didn't know you had the 13MM stuff.

I would still start with the same #'s.

 

[anthony_marquart]

How do I reach Kevin Bulifant? Ron, I was wondering what the carb cost you. Can you P.M. me on that?

Get rid of the carb and put a larger one on it. Use one from the OS .18 or get Kevin Bulifant to cut down one of his Nova Rossi .21 carbs to fit in the 13mm throat. I'll bet that I gained 5 MPH easy with just that one change. That 5.5mm hole in the carb is choking it.

 

[Tim_Duggan]

How do I reach Kevin Bulifant? Ron, I was wondering what the carb cost you. Can you P.M. me on that?

PM "izitbrokeyet?" on this forum - KB is always very helpful.

Tim.

 

[Saugling]

put a .18carb on your .12 TZ and leave timings as they are, this engine (at least my one) screams like there is no tomorrow with a .18 carb, a V937/3 and 30% nitro

have a look at the diagramm I attached...the bhp curve's peak is at 33.000 rpm and starts falling at about 35.000 rmp, you still have 1 bhp at 37.500 rpm...isn't that enough??? :blink:

Robert

 

[anthony_marquart]

is it ever enough? Good question. I found an os 21 carb I'm going to try on it. I didn't want to spend the $70 on the TZ18 carb. I need a new v937 too.

put a .18carb on your .12 TZ and leave timings as they are, this engine (at least my one) screams like there is no tomorrow with a .18 carb, a V937/3 and 30% nitro

have a look at the diagramm I attached...the bhp curve's peak is at 33.000 rpm and starts falling at about 35.000 rmp, you still have 1 bhp at 37.500 rpm...isn't that enough??? :blink:

Robert

 

[Saugling]

not enough...put in the .18 TZ