OMC Cross Charge Mod questions

[930turbo]

I'm considering massaging a '77 140 and I'm looking for some advice/photos of mods I'd seen many years ago. Does anyone have photos of the CCC transfer port area where it appears an end-mill was used to remove a portion of the cylinder (upstream at the bottom) and near matching crescent cut out of the piston skirt? (to improve transfer flow). Any advice on total timing advance with the OEM heads and 93 octane pump gas? (removing melted piston now)

[EMDSAPMGR]

You may be referring to an old document which was created by Racer. I believe it is referred to as the "9 pages." It got posted here a few years ago. You may be able to do a key word search for it.

[Lockjaw]

Off topic, but I wish someone would post pictures of each of these ports on OMC, yammie and merc engines, along with what they do. You know, boost, transfer, intake, exhaust. Be interesting to have it all in one place.

[perfmarine1]

You talking about this. http://www.screamandfly.com/showthre...w-Thread/page2 9 page in this thread

[EMDSAPMGR]

Yes, that's the thread.

[930turbo]

How do you know if your pack has a limiter? 1977 140

[Fullthrottleguy]

What is the consensus for the end horsepower of an old 235 cross flow after the mods in the "9 pages" are completed?
....just planning for the future.

[Riverman]

How do you know if your pack has a limiter? 1977 140

No limiter.

[930turbo]

I appreciate your feedback. What was your set-up? I have a Viper II. I'll apply the 9 pages during the rebuild of my 140. The rig came with a 14X30 Chopper I, I hope it'll turn it.

[Riverman]

I'm running 5" of setback with the prop about 1/2" above the pad and a 14 X 30 cleaver. I have been to 80 with this setup.

[930turbo]

The ports are square...



Piston skirt and cylinder base machining are next......

[Lockjaw]

Man that looks GOOOOOOOOOOOOOOD!!!!!!!

[racer]

I hope you have a good chamfer on the top and bottom of each port, The corner radius is tight. The 9 page deal is for race engines, I would recomend using 5/8 to 3/4 cutter on lake use engines for better life. We down to as small as 3/8 and the power difference is minimal.

[Riverman]

I don't understand the mod to the bottom of the transfer area - it's not clear to me where the 1.375 dimension is measured from, and at what angle.

[BarryStrawn]

Jeff - The section cut across the bottom of the cylinder inside the transfer port is specified to be 1.375" from the block parting surface. If you were using a vertical milling machine you would setup with the block on its back with the cylinders pointed down at a 45 degree angle. Then use an endmill to remove the top section of the cylinder inside the transfer port until it is 1.375" below the parting surface. Since the cylinder is on an angle the section cut off forms a curve. People do this to any number of other dimensions and shapes.

The "9 pages" intake and exhaust porting both specify a 1/4" diameter cutter. When I first saw this I wondered if that was supposed to specify a 1/4" radius for the port corners which would be made with a 1/2" cutter.