2.4 Block mods

[Gmcviper]

I'm looking for opinions of exhaust chest mods, specifically rounding the lower edge of the port where it meets the chest or should I leave it sharp?

I milled the chest out and cut the ports in a mill, so far I haven't done much more that clean it up a little with a belt sander.

[Mrzip]

.. I tk They All Need To Match

[nitro_rat]

It looks like you took out a whole bunch of "stuffing" amd did nothing to increase flow...

Definately radius the bottoms of the ports "down!"

Here is one that has had the bottom radiused without removing the "ant trails:"



Something like that is what you want if you don't have a really light hull...

Taking out the "ant trails" removes a lot of volume or "stuffing" and really kills the bottom end in most applications!

[Merc 2.5]

Here is a pic of just cleaned up pretty much, I'm with nitro, u took alot of material out with out "smoothing" the flow, also when removing lots of chest ,will kill bottom end in most cases , what is this mota being built for? Uses?

[dwiggl]

Those pix are great info! Thanks for sharing. Have been wanting to do the same thing and now have a better understanding.
Gmcviper; Have you looked up the thread "Cherry 2.4" ? Very good info on how to build HP without making the engine uin-tunable. I never took on the project as the photos were old technology and not very clear. I forget who wrote it all up but he was a really nice guy that shared a lot of info. The new tech makes the photos so much better.
On another note; be ready to do some rejetting - a whole nother learning curve.
Don

[SS Minnow]

Correct me if I am wrong, but it looks like you are trying to aim each one a little further back? They are different but consistent port to star, like a header/collector effect?
If that is true, would love to see how that works. If it ended that way by chance.............still want to know.

[Merc 2.5]

The "cherry 2fo" is a t-rex mota and dude is a one of greatest , if u do exact same thang ,u will have very strong mota

[Gmcviper]

I knew I was going to have to be smoothing everything out, I was looking to see what you thought about leaving that bottom of the port sharp instead of rounding it over. I have seen blocks where it was left sharp. This is going on my Hydrostream vulture, petty much just a lake hotrod. I know I'm going to have to get into jetting , but it's nothing I'm scared of.

[Gmcviper]

The ports are very close to the same, I tilted the head on the mill and cut them. The end mill was about 1/4" short of the full port length so I had to grind that out with the belt grinder.

[Merc 2.5]

The sharper the ports , my guess will have better bottom end , more round the less , so, I would just round it sum for smooth transition and cut heads for extra compression and it.will make up any bottom end loss and add power thru out power band , someone with more experience on chest work could guide u n rite direction, this is just my experiences

O and if u dont have 1 already , get yourself a die grinder , money well spent for porting

[Gmcviper]

10-4 I was going to cut the heads To 32cc like wrenchin2 on chateneuga fishing forum. Probly cut the front .050" too. I'm trying to think of a way I can build a jig to make all of the piston ports the same.
Thanks for your help

[Merc 2.5]

He is the one that did my block work, James is very good, did I say very gud! If he tells u it will work it will work, genius

[FORBESAUTO]

I’ve always smoothed and blended the bottom ends of the pocket exits to the chest floor, that’s the way Rex done it and I picked it from him and believed in his work. The ones I’ve seen from Eaves(another that I respected highly for making power), he worked the pockets in same manner as I do, (and James from pics above) but he leaves a little edge at the end instead of blending smoothly, it’s still laid back just has an edge. I feel the advantage of this is to lift the flow up off the floor a little and help it jump over the next guy in line, which I like and am planning on trying on a future build. I doubt it’s a big difference, and will probably take a dyno to see. As far as tuning for rpm I feel it’s more about how much meat is removed from the lower pocket when laying it downward resulting in a shorter distance from port in sleeve to the next cylinder and ultimately to the end of the tuner, the longer the distance, the better low end, shorter the distance the better upper rpm. When ya go moving a lot of meat, ya gotta be careful to maintain some type of pocket to hold some of the fuel charge that escapes before the closing of the exhaust port, so shape is very important. As far as how much to remove from chest volume all depends on porting and how well the engine is gonna be able to breathe. You always hear you don’t want to cut too much out or it’ll kill the bottom end, that’s true on a stock 150, but to tight will also kill the bottom end on a highly modified motor also. The trick is you don’t want any back pressure, regardless of what people say. They think back pressure is needed for bottom end, in reality it’s just enough flow to prevent back pressure is where the power is made, more flow than what is needed to to prevent back pressure is what kills ya. So how much ya take out and where ya take it out all depends on the rest of the equation.

[Gmcviper]

I think I understand what you're saying, if the exhaust is flowing too much it will pull the intake charge right out of the exhaust. And if you don't have enough flow the exhaust will stay in the cylinder.

So I'll probly need to do more to the front half to make up for all I took out off the chest. I have 5 petal I cleaned up casting lines on the cages and trimmed screws. Took the flashing out of the rod slots and plan on cutting pistons. What do you think?

[Merc 2.5]

U should really try sum of Carson stuffer b4 u go cutting front , does exact same thang but REVERSIBLE , also add intake spacer and all will help with bottom -mid range and run like scalded dog up top , combo usually makes mean lake mota