engine timing

Schnuerle 114

boost 106

exhaust 155

induction 206

Any suggestions for each number? This engine has plenty o'torque need more rpm..

Usually when I talk I show just how dumb I am but here goes anyway what the heck! Those numbers are too low. The intakes need to be in the mid 120's the exhaust around 180 and rotor timing??? 110 or more.

Mark Hopper

htbboats said:

Usually when I talk I show just how dumb I am but here goes anyway what the heck! Those numbers are too low. The intakes need to be in the mid 120's the exhaust around 180 and rotor timing??? 110 or more.

Mark Hopper

Click to expand...

OK SO THAT MEANS

Schnuerle (the port right behind the carb) should be mid 120's

boost should be mid 120's

exhaust 180

and what is the rotor timing? My engine calls it "induction" I think and it's already at 206...

Am i all wrong here? Let me know before I waste a sleeve..

What make and size of motor is this? Greg :blink:

Your probably ok on the induction timing. The exhaust timing seems a little low at 155 it should be near 180 degrees of duration. Im not sure on the boost, or Schnuerle port timings. What size engine is it? Seems like port timings for .12-.15

You guys are good. It's a OS TZ 12. I'm running in a .12 size rigger. I've got my degree wheel out,... Ready to go to town...

A quick question before we go futher. I can't always run high nitro. Right now I'm running 30%. I'm assuming that these changes are not based on only running 50-60% fuel.

I run 210 induction and 180 exhaust on my AE.15 running 15% and it seems to work pretty good in a stadium truck. It improved power all the way around I would also sugest to set piston clearence at about .012 Not sure about running low nitro in a boat, I know in my boat when I switched from 25% to 40% it was like different engine. A much bigger, better, badder engine. Yea, just what the doctor ordered

anthony_marquart said:

You guys are good. It's a OS TZ 12. I'm running in a .12 size rigger. I've got my degree wheel out,... Ready to go to town...

A quick question before we go futher. I can't always run high nitro. Right now I'm running 30%. I'm assuming that these changes are not based on only running 50-60% fuel.

Click to expand...

I can't help but caution you on "cutting" the transfer ports Anthony, if at all possible get some sleeve

shim's to raise all the ports and cut your exhaust port when you have the other ports high enough.

Cutting some of those ports(especially on a small sleeve) can get outa hand real quick,,costing you another P/S.

You will have to have the head button turned to keep your headspace,, I don't know any other way around that.

Unless, Your Smarter Than I Am :lol: happens allot

Anthony,

The numbers you're getting from these guys are good. The suggestion of shimming the sleeve is a good one, too. If you find a sleeve height that works well, and there is enough material on the crown of the piston, you may be able to turn some of the piston crown off and eliminate thw sleeve shims, dropping the ports back where they should be in the case.

You have 206 degrees of induction, but when does the rotor open?

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

opens @ 34 after bdc

I opened the exhaust up to about 177 in the center 1/3 of the port. We'll see how this effects things.

anthony_marquart said:

opens @ 34 after bdc

I opened the exhaust up to about 177 in the center 1/3 of the port. We'll see how this effects things.

Click to expand...

Get ready to buy a new P&S......you just killed the one you cut.

Put a .030" shim under the new P&S and take all the ports up at once.

Nomenclature:The transfer intake ports are on the sides and the boost is in the back.

Machine a new or the existing head button to drop it down in the liner the .030" you raised the liner.

Set the head clearance at .012",throw in some 50 or 60% and go run it.

Leave the crank alone.It is just fine the way it is.

The motor will be user friendly and will make great power and rpm.

listen to what rod said and you need to do some homework, unless you like to spend $$$ top motor people don't use the 1/3 eyebrow mod anymore...just a tip

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.

This is for Rod Geraghty, would an engine of similar timings in the .21 (OB) size benefit from the same

mods you gave Anthony? .030in sounds like allot,,,I don't mean to question you,,I'm just really

intrested

I haven't tried that much shim yet,,I did put a stock crank back in my engine and it's about the same as

Anthony's, 55deg ATDC and 35deg ABDC

And a stock sleeve is about the same as Anthonys' too.

Jerry Wyss said:

This is for Rod Geraghty, would an engine of similar timings in the .21 (OB) size benefit from the same

mods you gave Anthony? .030in sounds like allot,,,I don't mean to question you,,I'm just really

intrested

I haven't tried that much shim yet,,I did put a stock crank back in my engine and it's about the same as

Anthony's, 55deg ATDC and 35deg ABDC

And a stock sleeve is about the same as Anthonys' too.

Click to expand...

Jerry,The thickness of the shim depends on the motor. With most of the .12's [for boating applications]I have dealt with the .030" will work very well.That will give you intakes of about 126 to 127 and let the exhaust fall where it may.

As for most .21's,it just depends on the numbers on the motor that you start from.

For example the old Picco P-5 Marine motors needed a .030" shim to really wake them up but a Nova Rossi,most of the time only needs a little exhaust work.The intakes are usually just fine right out of the box most of the time.[i just recently however had a new series Nova .21LS through here that needed a .030" shim.Go figure????]

Give me the following measurements on your TT.21OB and I will tell you "exactly" what size shim to make to get you some good numbers on the motor.

1.bore....2.stroke....3.rod length [centerline to centerline]....4.Top of piston to top of liner at TDC.....5.Top of exhaust port to top of liner.....6.Top of intake ports to top of liner[transfers and boost].....7.CC of the combustion chamber[i can fake this # and tell you exactly what size head button to make].As I recall the TT head button is about .18-.20CC.If so the head button will be just fine the way it is.

In laymans terms......What Anthony has done by cutting only the exhaust port is to move the intakes and exhaust even farther apart.That isn't the way to go.The only way to bring that liner back now is to also cut the intakes and that is a ***** on the smaller motors.I can do it because I have fixtures to do it but it is very time consuming.The shim is so much easier,even though you have to mess with the head a bit.The results are the same.Anthony can cut his transfers from the outside in a mill with a square top [i.E.Like K&B transfers] and just leave the boost alone and that will bring back the liner within 90+% that the shim would have given him.

P.S Your crank timing is just fine.

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

A question,

The piston moves in a tapered sleeve. If you move the entire sleeve up you move the highest point the the piston will reach in the sleeve down. Now the piston doesn't move as far up into the taper as it did. How with effect compression?

Obviously I'm no expert here but I've raised exhaust timing alone on engines before and had good results. I'm hoping I don't need a new P/S right away.

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.

Rod, All that stuff was left in the last computer in the e-mail,,it never got transfered.

I'll have to measure it all again The only info that I can find is the specs that I changed to.

I think this time I'm going to measure sleeve with a dial indicator, the calipers are a real

bit*h to do it with. I'll have to get back to ya with this.

You really gottem goin' now,,hehehe

anthony_marquart said:

A question,

The piston moves in a tapered sleeve. If you move the entire sleeve up you move the highest point the the piston will reach in the sleeve down. Now the piston doesn't move as far up into the taper as it did. How with effect compression?

Obviously I'm no expert here but I've raised exhaust timing alone on engines before and had good results. I'm hoping I don't need a new P/S right away.

Click to expand...

Re: Compression......Most tapers are between .0025" and .003" per "inch".Moving the sleeve up .030" means nothing to compression when you start with a new P&S.Probably less than .0005" bore diameter change in that .030".The motor will break in automatically taking that .030" of height into account.

Re:Raising your exhaust timing on motors before with great success......Did those motors start with 110 degrees of intake timing????I don't think so!