Port Matching

[spybot]

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.

[Dave S]

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.

[spybot]

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 ??

[Dave S]

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.....

[spybot]

Would a standard 85hp benefit from a bubble back ?
or are they just for the bigger engines ?
I will be grinding out all of the sharp turns and edges

[Dave S]

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.

[spybot]

If i have the engine down to bits i ill have the chance to cut out the rib anyways
If it cut and add it will it give a few more RPM ?
On the pistons is that the same a 1/2" radius ? Will i need to machiine the crank case ?

[Dave S]

do not cut the rib in the intake side as that will not give any improvement in flow. if any just grind it smotth...

[spybot]

the rib i was taking about is the lower rib on the exhaust side. So the bubble back fits/flows better.
Which one were you thinking on ?

[spybot]

If you had an 85hp and had only a die grinder and a 6" grinder what would you do to make it a fast but Reliable engine to push along a 660lb speedboat ?

[spybot]

Cut 1/4round cut of the piston scirt off on intake side for more flow... omc did it on race motors.

Do you mean 1/4 radius giving a 1/2" halfmoon ? Sorry iif im not getting what you mean.

[Forkin' Crazy]

Use the search function. There are several threads on this. Pages upon pages of reading.

[spybot]

Use the search function. There are several threads on this. Pages upon pages of reading.

On how much to remove from a piston >>????

[Umassot50]

Would a standard 85hp benefit from a bubble back ?
or are they just for the bigger engines ?
I will be grinding out all of the sharp turns and edges

You keep starting new threads asking the same questions about your 85 and the bubble back. And you keep getting the same answers.