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Thread: Looper exhaust porting
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12-23-2013, 12:23 PM #166Scream And Fly VIP
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First I agree with 6 you dont need/want to increase the boost/transfer port area . Also making rpm is not the issue its getting them to have power at the rpm, the more you go up on a stock engine the faster the power drops. We ran them 75 to 7600 when we raced mod vp on stck ported engines but the tune was always on a razors edge.
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12-23-2013, 12:26 PM #167
I'm getting more and more interested in those fingerports... Just need to make myself a jig in order to not mess up the bore. I would like a piece of steelpipe in the same size as the cylinderbore, cut myself a slot in the pipe in size of the fingerports, slide the pipe in place inside the bore, start the grinder and cut. Anyone tried the idea I described? Any thoughts on how deep to cut the slots without risk?
Another thing; would cutting the lower above the cavplate sound more than a Bobs snout?
I want to clear the tuner fast when hitting it going from idle.Last edited by Captain75; 12-23-2013 at 12:32 PM.
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12-23-2013, 12:38 PM #168Screaming And Flying!
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NC mill would be the way to go so they are all the same
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12-23-2013, 02:44 PM #169
Did some searching on fingerporting, found this;
http://forums.everything2stroke.com/...ding-old-ports
"One of the old tweaks for adding a tiny (possibly inconsequential) amount of port area to a two-stroke having this old layout was to grind or mill little "finger-ports" into the cylinder wall on either side of the boost port. Finger ports were nearly always fed through two matching holes drilled into the piston, just below the ring. People had various ideas (swags!) as to how to aim the upper edge of the finger ports; do you angle them up, or to blow straight across, or what? I never heard any before-and-after dyno figures on these gizmos; ours was and is an utterly amateur sport with no prize money or sponsor interest. I think it would take a pipe with a strong suction effect to get any real benefit from finger ports."
some other thread stated "You should have to turn some big rpms to benefit from fingers"
If I decide to go fingers, will I benefit from them through out the rpm range, all the way from idle?
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12-25-2013, 06:53 AM #170
To the top...
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12-27-2013, 04:30 PM #171
two small questions; the thin slot at the bottom of the fingers, what are they?
How did you cut the right side(from pic)hole in the pistonskirt, I'm asking because of the wristpin housing is in the same area...
ok a third question; at what angle did you cut the fingers?Last edited by Captain75; 12-27-2013 at 04:39 PM.
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01-03-2014, 08:54 PM #1725000 RPM
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Att: 6 killer
Got a friend who has made dome inserts for merc v-6 & PWC heads, so dome installation should not be an issue
Would like to use custom domes in the v4 heads, any suggestions for combustion chamber shape ?
Have read where Baja200 converted a 3.3 piston to a flat-top, so, would a merc 2.5 or 3.0 drag style chamber work ?
Would this end up as a behind the liner set-up ? not a lot of experience w/ 3.3 stuff. most my experience is crossflow & 49Cui loopers.
machine work will be no problem, got access to really great machinist.
any mods recommended for the 3.3 sleeves , angles? timing ? etc.
would like to build first pwhd as a budget beater to learn, then go all out later.
Any help is GREATLY appreciated.
Lawrence Thornton
South Carolina melon belly associateLast edited by thornl01; 01-03-2014 at 09:32 PM.
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01-04-2014, 01:42 AM #173
Yes Beefs "mutt" has 1,xxx hour factory DI pistons we chopped the dome off to make them flat. We know exactly nothing about what is best for timing, angles etc. but there are a few that pointed us in the right direction and we have broke plenty of parts finding out the hard way... Just cause they will twist doesnt mean they make power up there.
Anyway we took an "educated" guess on porting since it was a blown up POS FICHT block with holes in it, short rods and factory brand-new-used pistons Just cause our junk is alive doesnt mean yours will live!
We figured we better break it in easy.
https://www.youtube.com/watch?v=jhK4b0TEjN0
https://www.youtube.com/watch?v=SHFHt2Zdz5I
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01-04-2014, 10:00 AM #174
Buy your pistons from "Monty", they are flat top with the higher wp heights. (you can use stock rods).
Leave heads stock, use 1.8 heads if you want a larger bump in compression.
Weld up the outside of the block if you want behind the liner, this will twist the flange. Machining the block mating surface will be required, then recut all of your sealing ring surfaces and main surfaces. Or you can use epoxy on the outside of the block if you could find something that can stand the 450* heat required to install the sleeves.
You can do the welding without the machining, but this will require the block to be assembled with RTV. (MY first motor was that way)
Or........you can have Jeff @ Advance Sleeve make some customs where the two outer boost ports are deleted then you can cut fingers with a mill and run a 2.2 finger port.
Anything is possible, how much "Snap" do you have........Last edited by 6Killer; 01-04-2014 at 10:06 AM.
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01-04-2014, 12:31 PM #175
Depending on what kinda RPM and fuel your aiming for you might want to consider different heads. Right now we are running 2.7 heads but since its a 3.854 bore we are going to run the larger chamber open deck 3.0 heads cut to the same CC for pump gas. Should make more power since we ported it to peak in the mid 6k range and we didnt want it to turn over 8k because the short rods will pummel the piston skirts off.
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01-06-2014, 05:04 PM #176
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91 charger stv thanked for this post
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01-06-2014, 05:52 PM #1775000 RPM
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I drilled three 1" holes in my lower. It's stupid loud. If you drill any size holes, it will be louder. 10mm isn't very big, but it sure it will make noise
Last edited by NosBoss; 02-06-2014 at 10:37 PM.
1975 Hydrostream Ventura II
1987 evinrude 200xp
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01-06-2014, 07:21 PM #178
I drilled three 1" holes in mine then conected all three as an oval. It's very loud, but most of the guys I boat with have mercs with offshore mids so I I don't stand out so bad.
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01-06-2014, 07:26 PM #1795000 RPM
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01-06-2014, 07:31 PM #180
Oh yeah. But im not the one obnoxiously loud boat in the crowd, so it's not a problem.