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Thread: Looper exhaust porting
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01-17-2014, 06:54 AM #211
I use a homemade jig. 89mm steelpipe(appx 3,5") The desired portmap is cutted out. On top of the steelpipe I have welded an "ear" in which I fixate the jig in desired position.
I start grinding a shallow slot using a small beltgrinder(can be done without)
The shallow slots... These are used to steer a standard air-grinder equipped with a burr of same specs as the desired portwidth. Due to the jig you don't need to worry about messing up the bore, you can push hard...
The final result...
Hope this will help! I think steelpipes in right dimesion can be found in a hardware store.
God luck!
//Anders
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01-17-2014, 08:51 AM #212
Thanks for the step by step and the great pictures ! Glen
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01-17-2014, 01:05 PM #213
Did you raise the transfers to the boost port height?
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01-17-2014, 04:55 PM #214
No, the transfers open before the boostport stock.
I timed the fingers to open at the same time as the boost (the black line)
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01-17-2014, 07:33 PM #215
Hmmm. I can measure a ported block tomorrow but it's too late to matter now. I'm no porting genius by no means but I the way I understand it is the higher the target rpm range the closer the transfers should be to the boost port and the fingers should match the transfers. I saw the line but I guess from the angle of the picture it looked like all three were at the same height.
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01-18-2014, 01:33 PM #216
Its the picture angle, transfers open before boost and fingers
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01-18-2014, 03:48 PM #217Junior Member
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You mean that the boost port is slightly higher than the transfers and transfers, right?
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01-18-2014, 04:04 PM #218
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01-18-2014, 04:17 PM #219Junior Member
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Ok. Have you read Graham Bell´s Two Stroke Preformace? If not, i recomend it. Page 51/52 is about transfer port timing. I know that the boost is lower in a stock engine, but today most tuners agree that there its bettrer with the boost port 1-1,5mm higher. And the transfers aimed lower, over the piston crown.
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01-19-2014, 12:04 PM #220
Here is the complete portmap from cyl #5, all transfers open about the same, mains a touch before.
I don't want a high revving motor, boat is mainly used for skiing and tubing, for that reason I've avoided raising any durations.
Exhaust is widened, all sleves are matched to surrouding casting, rodslots are cleaned, exhaust cavity grinded and polished from port to prop.
Next up is cleaning the whole block with detergent, hot water and toothbrush before ballhoning and another round of cleaning.
Tomorrow after picking kids up from hockey, I will try to drill the piston windows and order new pistonrings.
A couple of questions for you guys;
-Jetting, any thoughts? Stock compression, fuel equals appx 91oct US (in Sweden its called 95, containing 10% ethanol) Right now jetting is stock; main #62D, mid #14, idle #48.
-Power output? What kind of hp do you guys think these mods and a fresh honed bore would give me? I'm still using the stock airbox with baffel, intake is cleaned up. Reeds are stock steel since I have had big trouble with the aftermarket ones, when I took motor apart plenty were open more than you want.
greateful for advice!
//AndersLast edited by Captain75; 01-20-2014 at 12:08 AM.
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01-19-2014, 07:17 PM #221New Member
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Nice port work
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01-20-2014, 05:31 AM #222
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01-20-2014, 01:06 PM #223
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01-21-2014, 06:06 AM #224
My problem is that I'm having trouble to decide where "rich" starts...
If stock is 62D, what is the definition of rich, 65, 67, 72? Since the fuel I'm using contains 10% ethanol 62D can't really be considered stock because the ethanol contains less energy?!
250-260hp, hope thats true, in that case all the work seems to make sense!
Again I'm hoping get some replys to get this thread to stay alive, and hopefully get some of you guys to post pictures of your projects!
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01-21-2014, 07:31 AM #225
Nice work, Captain! How deep are your finger ports? They look like they barely break through the iron sleeve in the picture, so I'm guessing they're about 1/8" (3mm).
Most of the finger ported blocks I have are about .400" deep (10mm) in the finger ports.
Great idea with the little belt sander! I tried that out on some scrap cast aluminum yesterday using a 36 grit 1/2" wide belt on a sander meant for 3/8" wide belt. It cut a beautiful slot .200" deep x 2" long in about 5 minutes. Straight as an arrow and nice flat bottom.
I've already pulled the sleeves out of my project motor, so I only have to grind aluminum. I'll slot the sleeves in the mill, and end up with about .300" depth, total.
Keep the progress reports coming!Last edited by Tony Brucato; 01-21-2014 at 07:38 AM.