Advice on stroker build with cracked cylinder

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moparodbuster

moparodbuster

moparodbuster
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My stock stroke 340 engine has a crack in 1 cylinder. I want to sleeve that cylinder and rebuild as a .040 over 500+ HP stroker but looking for advice first to see if It would be ok or if I would need an unsleeved block?
I would feel safer going 60 over with an uncracked block than running a sleeved 500+hp block with the 2"+ crack in my block (see pic). The guys at Dandy Engines here are famous for their aluminum 1000+HP gm and fords but have no experience with iron mopar 340's here in Australia so I'm falling back on the experience of the guys back home who've been there, done that and hoping for some solid advice. It'll cost me a LOT to ship a used 340 over so just wondering how much a cracked block will take trying to squeeze the piss out of it with stroked crank, 11:1, expensive ported eddy heads, .600ish list cam etc. Im I asking for trouble or...? They mentioned a greater tendency for core shift having a cracked block with this build.

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The crack should be a warning to you. 340 blocks do not like .040 over bores even before you try to get big hp/ stroker numbers out of it. Since you are already going to stroke, don't waste it on a 340 block. Save it and get a good 360 block. Thicker walls and dirt cheap.
 
moparodbuster said:
My stock stroke 340 engine has a crack in 1 cylinder. I want to sleeve that cylinder and rebuild as a .040 over 500+ HP stroker but looking for advice first to see if It would be ok or if I would need an unsleeved block?
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My stock stroke 340 is .040 over and runs great. Sonic check is the only way to know how thick the cylinder walls are. Personally I would run an old 340 block with a sleeve over a later year 360 block.
 
Hogwash, you can run a 340 that is 40 over.
I recently bought a 40 over 418 shortblock with 2 bolt pro gram caps. Plan to make decent steam with it
Every block is different. Cant throw out a blanket statement. Heck some might be thin at 20 over.
Regards the OP, i would sleeve it and run it.
 
stixx said:
Member RAMM has a thread going this very moment where he bores a 340 .100. I always was under the impression
that he knows what he's doing... stock stroke btw.
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I would feel safer going 60 over than running a sleeved 500+hp block with the 2"+ crack in my block (see pic). The guys at Dandy Engines are famous for their aluminum 1000+HP gm and fords but have no experience with iron mopar 340's here in Australia so I'm falling back on the experience of the guys back home who've been there, done that hoping for some solid advice.
B3422w5 said:
Hogwash, you can run a 340 that is 40 over.
I recently bought a 40 over 418 shortblock with 2 bolt pro gram caps. Plan to make decent steam with it
Every block is different. Cant throw out a blanket statement. Heck some might be thin at 20 over.
Regards the OP, i would sleeve it and run it.
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The 40 over isn't my worry, spending big $ building a race motor with a crack in it is.
 
Sleeving (IF done properly) will not make the block weaker... as many have said.
 
moparodbuster said:
I would feel safer going 60 over than running a sleeved 500+hp block with the 2"+ crack in my block (see pic). The guys at Dandy Engines are famous for their aluminum 1000+HP gm and fords but have no experience with iron mopar 340's here in Australia so I'm falling back on the experience of the guys back home who've been there, done that hoping for some solid advice.

The 40 over isn't my worry, spending big $ building a race motor with a crack in it is.
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Too bad your wayyyyyyyyyyyy over there in Aussie,I've got a '73 30 over 340 block been maggged and sonic checked came out perfect shipping probably too much.
 
stixx said:
Member RAMM has a thread going this very moment where he bores a 340 .100. I always was under the impression
that he knows what he's doing... stock stroke btw.
Click to expand...

Stixx, I am working on a 340 that is .060" over for a final bore size of 4.100" . Somedays even I think I know what I'm doing-lol . The last part of your statement is way more important than you know. J.Rob
 
The Melling sleeves catalog says this: "A long crack or large chunk missing will reduce the press because the damage will open under stress. Increase or decrease the amount of press according to what will seal the damage. Pressure testing is recommended." (The term 'press' in this context means the amount of interference fit.) So this seems like a common situation. The sleeve itself contains the cylinder pressure and the good ones are made from a high quality ductile iron material; the residual block material is there to hold it in place. If the rest of the block in that bore is good and not cracked to up near the deck or the bottom of the bore, then the sleeve should be secure.

Bursting pressure of a .093" sleeve should be well over 2000 psi. So it will contain your cylinder pressures just fine. (And you can get .125" thick walled ones for more strength.) That is as strong or stronger than plain cast iron bores once the core shifts are considered. I can't address the side thrust on the sleeve in computed numbers, but all sleeves have to support thrust forces by themselves so it indeed does look to be OK, even with the crack. Being made of ductile iron achieves this.

The area with the crack may not create any interference pressure to hold the sleeve, as it will spread. So it all has to be held by the top and bottom areas; wet-liner sleeved blocks work that way so it seems OK. Plus, I have to wonder how many bores have holes once bored for a sleeve anyway, and how many develop unseen cracks in the remaining cylinder wall material with the interference fit process.

I would try to stop drill the ends of those cracks to prevent the crack from spread up and down; perhaps some of the machinists will comment. My instinct would be to seal that crack while installing the sleeve to try to keep coolant from creeping around in between the sleeve and block. That could create corrosion and some future issues. It may be that the compounds used for sleeve retention do this.

And Melling lists some high performance sleeves that can be considerably overbored in the future.
https://www.melling.com/wp-content/uploads/2018/06/Melling-2018-Cylinder-Sleeve-Catalog.pdf

BTW, I would have the block examined thoroughly before moving ahead.

All in all, I would do it and not be worried. I have done a few unconventional mods to heads and blocks in the past and they all worked out. Sleeving is well known process so seems like a pretty good bet here.
 
You can always sonic check the block. If there is enough minimal wall thickness to build at that oversize you are all set of that is your preference. If there is not enough then you can pursue the sleeve. A good shop should give you an honest opinion on your block given the crack and your intended plans? What are they telling you is the best course of action given the blocks current condition? Sounds like they build high horsepower engines. They are likely to have seen cracks before.
 
The crack you've pictured is not an integrity concern. Ones by head bolt holes or near the base of the cylinder can be an issue. Use something "meaty"
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stixx said:
Sleeving (IF done properly) will not make the block weaker... as many have said.
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^^^^^^^^^^This is correct. Done PROPERLY the sleeved cylinder will probably have the most integrity of all the cylinders. Sleeving is a simple process but requires precision and a machinist that can hit their marks dead on. For example you just don't bore a hole and slam a sleeve in. You determine with a sonic check if the major and minor thrusts will favour a slight offset. Then you setup the cylinder and bore the hole (leaving a step at the bottom) while also leaving .002"-.003" interference-based on measuring the sleeve first. The boring tip will leave a chamfer at the step so before breaking setup I have to change tips to a counterbore style that will square up that chamfer at the step. Then I measure the length of the cylinder (usually 6") and install the sleeve in the lathe and part off the excess from the non-chamfered side of the sleeve leaving me about .125" that will protrude from the deck after install. Then the sleeve gets cleaned and tossed in the freezer for a few hours or overnight. Then the cylinder gets thoroughly cleaned and dried. When the time is right, I get my sleeve driver (which is a 2" thick disc of aluminum with a 1" bolt through it), BFH (2lb sledge), PPE (gloves, glasses, ear defenders) sitting on the deck of the block. Then I smear Permatex green sleeve retainer stuff all over the crack. Then I don all my PPE, walk to the freezer (about 40' away) run back to the boring mill and beat the sleeve until I feel it bottom. With any luck at this point the sleeve will protrude about .100-.125" and I proceed with the same counterbore cutter to machine the excess off as close to the deck as I dare. If the block is not getting decked then I finish with a nice sharp large file. The sleeve is then bored to within .005" of final size and the block then moves to the CK-10 for honing. When all is said and done if I did the job right you cannot tell where the sleeve is. I am sure I am forgetting some of the steps but it is simple but not easy to execute at least based on some of the sleeve jobs I have seen. I charge by the hour and the last sleeve I did two weeks ago (BBC 468 lots of nitrous) cost $600+ sleeve. If you are worried about the job have the shop pressure test it afterwards--I only do that if I have any doubt if I "got" all of the crack.

Sorry for the wall of text--to make a long story longer--have it sleeved it will be fine. J.Rob
 
mderoy340 said:
My stock stroke 340 is .040 over and runs great. Sonic check is the only way to know how thick the cylinder walls are. Personally I would run an old 340 block with a sleeve over a later year 360 block.
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In order to convolute this thread further we could discuss the rod to stroke ratios and how that impacts cylinder side loading. Just another reason why I prefer stock or short strokes. LOL J.Rob
 
Being that he's .040 I'd rather choose something that gives a little more than a .073 wall thickness (using the Melling CSL 160) as the book suggest. Sure I agree about the retention of the parent material, but pick something with more than .073 end result.
 
Max1196 said:
Being that he's .040 I'd rather choose something that gives a little more than a .073 wall thickness (using the Melling CSL 160) as the book suggest. Sure I agree about the retention of the parent material, but pick something with more than .073 end result.
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Agreed but anything over 1/16" and no gaping holes behind it , I'm good. J.Rob
 
RAMM said:
In order to convolute this thread further we could discuss the rod to stroke ratios and how that impacts cylinder side loading. Just another reason why I prefer stock or short strokes. LOL J.Rob
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Actually, I have been looking at that and would like to delve more into this. But, resolve the sleeve question 1st....
And thanks for the long explanation of your sleeving process; that kind of detailed description is quite appreciated.
 
moparodbuster said:
The sleeve is not my worry, the crack's compromise to the integrity of the block is.
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Ok then throw it in the ditch and move on. You asked for opinions. You were given opinions. Yet you still argue. That's the end of it for me.
 
moparodbuster said:
The sleeve is not my worry, the crack's compromise to the integrity of the block is.
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'Stop drill' the ends of the crack. Once stopped, I can't see how it can effect anything else. And if you bore for a sleeve, the remaining wall integrity is not anything you can count on anyway. Take a bore that has a walled thinned to .150" or less due to core shift, bore for a .093" sleeve, and you have <.060" wall remaining. Not much strength left there anyway. So the crack issue goes away IMHO, as long as you stop it form extending into the upper and lower ends of the bore. The orientation of the crack is good in that regard, since it leaves the vertical strength of the other parts of the bore intact.
 
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RustyRatRod said:
Ok then throw it in the ditch and move on. You asked for opinions. You were given opinions. Yet you still argue. That's the end of it for me.
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RustyRatRod said:
Ok then throw it in the ditch and move on. You asked for opinions. You were given opinions. Yet you still argue. That's the end of it for me.
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Thanks for your opinion buddy!
 
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