Crankcase compression??

[H2OPERF]

Agree anything nosub posted you can bet is noteworthy, Chaz is a wealth of info too...

[Chaz]

Read the other thread, nosub knows his stuff...

With archives dating back to 2001, that narrows the search down to a couple hundred thousand threads to search through ...

You are correct about flow-thru crankshafts. The "widow" is only so wide and any corner of the counterweight that hangs out in the airflow will cause the charge to tumble.

The good news is that the crankpin, big end of the rod and part of the beam is in the way in one way or the other for only 360* of the circle ..

[powerabout]

With archives dating back to 2001, that narrows the search down to a couple hundred thousand threads to search through ...

You are correct about flow-thru crankshafts. The "widow" is only so wide and any corner of the counterweight that hangs out in the airflow will cause the charge to tumble.

The good news is that the crankpin, big end of the rod and part of the beam is in the way in one way or the other for only 360* of the circle ..

the other thread as in the one linked in this thread, post #3 that should narrow it down...


https://www.screamandfly.com/showthr...on-for-experts

[H2OPERF]

I have several different injector timing values i wanna run back to back some day and see how much difference it makes trying to keep away from a direct shot to the the big end and another after reeds close ect. will only work when you are below an RPM where the pw value is low enough though.

[Jay Smith]

During any and every JSRE engine build I ALWAYS cut front case half to increase crank case compression I had a customer quoted “with a cut front case half raising crankcase compression verse stock changed his bottom end and mid range power on his motor was like stepping on a grape verses stepping on a firecracker “

Good luck !!!

Jay @ JSRE

[powerabout]

During any and every JSRE engine build I ALWAYS cut front case half to increase crank case compression I had a customer quoted “with a cut front case half raising crankcase compression verse stock changed his bottom end and mid range power on his motor was like stepping on a grape verses stepping on a firecracker “

Good luck !!!

Jay @ JSRE

How much do you knock off Jay?
Is the distance uniform on a Merc from new?

[Instigator]

One thing w/the OMC Loopers is they’re easy to improve.

I cut .100” off the front half, fill the voids around the reeds and use nylon rod to fill the main bearing bores that are in the crankcase.

As Jay says, it makes throttle response much more crisp, similar to adding compression.

Added to porting it becomes dramatic.
Then add compression.......

[Instigator]

This was different a place when we had the knowledge of him, ProffeserOB etc.

Read the other thread, nosub knows his stuff...

[H2OPERF]

Gary it would be nice to know how much cutting and filling changes the actual ratio... and what the diff is between the old and etec front. we know it all helps but is it near the ratios from Jennings.

[H2OPERF]

I have 1/4 bar same material as the reeds glued in and sanded to shape in this one to fill it up.

[Chaz]

the other thread as in the one linked in this thread, post #3 that should narrow it down...


https://www.screamandfly.com/showthr...on-for-experts

2002 , yea that would narrow it down a bunch ..

The fongus thread .. I'm suprized you didn't catch the "disc drop" .. First time I watched it I saw that ..

The most accurate and meaningful statement in that whole thread was that "If you stuff the crankcase you will need to recontour the transfer roof angles to compensate for the increased port velocity".

Clipping a front half aprox 4 cc off of a 1500 cc crankcase will leave you at 1496 cc Yea , I see where the major improvement "lies" at ...
Chaz= thinkin, 1500/1496 is 99.73% ... or .27 of 1% change ... gotta be night and day difference ... LMAO @ how math has a way of finding the truth ..
It takes serious work to actually make a difference in volume and a

quantifiable change in working pressure

..

Chaz= wunderin, H2O, is that splash-zone, zink-cromate, inside the reed block area, or a temp barrier coating ..

[ChrisCarsonMarine]

We make crankcase stuffers for almost all modern outboards. These are a few of the popular ones.

[ChrisCarsonMarine]

Adding these before the reed block results in the same advantage,usually more,than milling the crankcase...without removing the crankcase and milling it. Economical,fast and easy to install while changing reeds,usually with more space taken up than milling allows,and with no external changes so linkages stay the same. Chris

[RBT]

This was different a place when we had the knowledge of him, ProffeserOB etc.

Nosub and standpat were head and shoulders out front

[RBT]

2002 , yea that would narrow it down a bunch ..

The fongus thread .. I'm suprized you didn't catch the "disc drop" .. First time I watched it I saw that ..

The most accurate and meaningful statement in that whole thread was that "If you stuff the crankcase you will need to recontour the transfer roof angles to compensate for the increased port velocity".

Clipping a front half aprox 4 cc off of a 1500 cc crankcase will leave you at 1496 cc Yea , I see where the major improvement "lies" at ...
Chaz= thinkin, 1500/1496 is 99.73% ... or .27 of 1% change ... gotta be night and day difference ... LMAO @ how math has a way of finding the truth ..
It takes serious work to actually make a difference in volume and a

quantifiable change in working pressure

..

Chaz= wunderin, H2O, is that splash-zone, zink-cromate, inside the reed block area, or a temp barrier coating ..

Exactly, math isn’t your friend it tells you the truth. Add, moving the flutter valves closer to the crank and tightening the radius is counter intuitive