merc 59ci porting

[fs5]

i'm trying to get a few more revs out of my merc.is it worth while cutting the the port window in the sleeve on the intake side back up to the block casting?
thanks

[zul8tr]

Post a pic to see what you want to do.

[fs5]

like this mate
56190

[zul8tr]

Are you wanting to remove the small shelf of the top of the port that appears to be not lined up with the alum casting? That shelf will cause some restriction to the flow of the intake charge and I have read that removal could improve power, etc. However also from what I have read if the intake port opening sleeve removal increases the port timing by putting the top of the port opening closer to the spark plug that could effect low and midrange torque and lower compression could result? I tried this intake port streamlining on a Merc 200 22 c.i. and it resulted in reduced performance, the exhaust side port timing was the key. You need to discuss your plan with those that have tried it with your size and type engine.

[Fastjeff57]

..."You need to discuss your plan with those that have tried it with your size and type engine. "


Right! Unfortunately, those that know rarely share.

Jeff

[fs5]

my sleeve doesn't have that window cut in it,thats why I was asking.maybe some of the smack boat boys could chime in,i'd appreciate the help.
also another thing I noticed,when I put a bore scope down the bore .the piston travels about a good 4mm below the bottom of the exhaust port.what effect would lowering the bottom of the exhaust port have ?
thanks

[Lil' Blue Rude]

I've heard people talk about lowering the exhaust port like your talking about and one thing I've heard is it will expose more of the piston skirt to the exhaust gas causing more heat to enter the piston, but I wouldn't think that would be any different then raising or widening the exhaust port. Unless it would let gases slip by the piston skirt into the crank case while the pistons at the top of it's stroke. ??? I don't know just a thought. Good luck with the build.

[Fast Fred]

there is nothing to be had by lowering the sill of the exhaust window, it should match the crown at bdc. if it was mine i'd look at the boost port timin, bevel the top of the exhaust port

[LittleCharger]

there is nothing to be had by lowering the sill of the exhaust window, it should match the crown at bdc. if it was mine i'd look at the boost port timin, bevel the top of the exhaust port

Fred, I think what he is saying is the the sill of the exhaust port is 4mm above the crown of the piston at bdc.

[fs5]

Fred, I think what he is saying is the the sill of the exhaust port is 4mm above the crown of the piston at bdc.

yeah mate ,your spot on .the top of the piston is "about" 4mm lower then the bottom of the zorst port.

[Fast Fred]

i'd use dikum ink, paint up the cyl at the exhaust window, put the bullets, rods and crank back in, no rings, no rings on the pistons. set the next case on snug. then scribe each cyl at bdc. i'd also check the skirt at tdc to make sure she would be coverd.

[fs5]

i'd use dikum ink, paint up the cyl at the exhaust window, put the bullets, rods and crank back in, no rings, no rings on the pistons. set the next case on snug. then scribe each cyl at bdc. i'd also check the skirt at tdc to make sure she would be coverd.
thanks mate,i didn't think of that,an open zorst port at tdc ...
appreciate your help.