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Thread: Port Matching
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10-08-2017, 04:49 PM #1
Port Matching
Is port matching a good or bad thing to do on a standard 85hp V4 johnson crossflow?
Im about to rebuild an 85 johnson
I have the tools and ability to carry out the port matching but don't know if this is a good or bad thing to do to a standard engine.
I know it will help with whole intake and exhaust flow but will this harm a standard motor ?
Is it best carried out on a race / tuned motor ?
I understand t will take a lot of hours but i don't mind that if at the end my engine runs really smooth.
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10-10-2017, 03:20 AM #2Screaming And Flying!
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Being your across the big lake and parts are hard to get. I would just clean up the reed area where it is sharp air turning.The exhaust chamber can be cleaned up w/out playing with the ports. That is simple stuff that you can't go wrong with. Real power is to be had with exhust port rasing and tighter squish cutting of the block... not heads. Blend any sharp air flowing corner.
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10-10-2017, 03:42 AM #3
Hi Dave
I have all the parts to turn this in to a 140
Crabs Reed stuffers Bubble exhaust cover and manifold pluss the exhaust stuffers but the hard part is getting the machining done with out a reference point for the ports. So im going to stick to the 85hp but to tune her the best i can Hence the port matching. I will be balnacing the rods and pistons and will be adding the reed stuffers and the carbs. Also a set of CCSM reeds. Hopefully once i have smoothed out the flow and added he items i have she will be a fast reliable motor.
Any thoughts on what else i can do to the engine ??
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10-10-2017, 04:09 AM #4Screaming And Flying!
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IMO the bubble back is fine.But there are lots of points that can be made to get more flow. Just grind the sharp turns.....
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10-10-2017, 04:15 AM #5
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10-10-2017, 04:43 AM #6Screaming And Flying!
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I think a 85 is the same 99cid. Put your block together and check piston to block hight. Cut to get .ooo clearance. The gasket will stop piston from hitting. Cut 1/4round cut of the piston scirt off on intake side for more flow... omc did it on race motors. Bubble back gives more resons to grind the v4 exhust chest.
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10-10-2017, 04:51 AM #7
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10-10-2017, 05:09 AM #8Screaming And Flying!
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do not cut the rib in the intake side as that will not give any improvement in flow. if any just grind it smotth...
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10-10-2017, 05:14 AM #9
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10-10-2017, 05:16 AM #10
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10-13-2017, 05:50 PM #11
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10-14-2017, 05:16 PM #12
Use the search function. There are several threads on this. Pages upon pages of reading.
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10-14-2017, 05:24 PM #13
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10-15-2017, 05:02 AM #145000 RPM
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