Merc 2.0 V6 crack in exhaust chest

[looperdude]

Hello everyone. I’ve got an ‘87 XR2 that has cracks in the exhaust chest. Is this something that needs to be welded? Will these cracks spread? I have attached a picture of my block. Thanks for looking.

[FORBESAUTO]

Nah, most every one I’ve seen has em. Let it be and run it

[looperdude]

The crack extends down to the cast iron sleeve that partially makes up the exhaust outlet...will that be ok?

[FORBESAUTO]

My ole eyes can’t tell, it looks to be extending from divider down exhaust pocket,which is common. If It goes all the way to cylinder sleeve then ya got issues

[looperdude]

Here is a better picture

[looperdude]

You can see where is stops, maybe a 1/4 in from where the liner starts.

[FORBESAUTO]

Yeah, you good, as long as it ain’t making that turn which would mean its deeper and you ‘bout to break in half

[Jay Smith]

Every V-6 Mercury that I’ve ever built has those don’t fret run it ...

Jay

[looperdude]

Ok thanks guys. Separate question; I want to do a little bit of massaging on this motor. Its on a 1400 lb. bass rig. I dont want to turn it over 7000 or so, pump gas 93 octane only. With that being said, what kind of cuts do i need to make in the exhaust chest? Ive already cleaned up the rodslots and am planning on d-porting the pistons, and cutting the heads. Any guidance would be greatly appreciated. Thanks yall.

[FORBESAUTO]

:d

[looperdude]

Ive got a good understanding of two stroke design and fundamentals, and am a machinist by trade, just looking for a little guidance and a few extra ponies. But if you REALLY think I’m opening a can of worms, I will leave it be��

[FORBESAUTO]

Didn’t mean it in that way, I cut on about all of em I build. Meant lots of controversy on what works and what don’t. Most are gonna tell ya, you need to leave it tight to make torque. I run some aggressively cut chest on a Tr 20 bass boat that will skull drag a stock 200 out the hole an take off with props my stock 200 wouldn’t even think about. The key is making everything work together. Hog out a chest and not change anything else and yeah it’ll kill it. Most important is good smooth flow, If your not gonna turn it hard, don’t change your pocket lengths much, don’t change upper section of pocket any, smooth out lower part some use 30 degree angle on lower section of pocket. Either mill out ant trails or at least widen them, I wouldn’t go any deeper in this deal. And smooth/flatten out floor between cylinder sleeve and holding pocket. Got some pics of different styles in my engine building pics folder

[FORBESAUTO]

I’ve got one in the shop that T-Rex done that would prob work good for what you looking to do. When I get home I’ll get some pics of it for ya. It’ll be dirty because it hasn’t been cleaned but it make sense of what I’m saying

[looperdude]

Ok ok I understand. Ive grasped that fact, cant have a 240 hp chest with intake and transfers that will only support, say, 200hp. With the heads, whats the minimum safe chamber volume i can run on pump gas? I want this engine to live haha.

[Capt.Insane-o]

You've got a sh*t ton of porting and compression before even thinking of getting to 240 hp.