340 r.i.p.

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swifty

swifty

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The 72 swinger I just bought with 340 and 727 just hit a major snag. Engine did not run when bought and told it had low oil pressure. Brought it home, did compression test. 100>on 6 cylinders, 3 and 4 =0. Tore it down, hoping for a head gasket or even a cracked head. Found more pres tone in pan than oil. Oil pan had major shrapnel in it. Two broken connecting rods, huge holes in windage tray. oil pickup loose in pan. Found the pres tone leak to be coming from a crack in cylinder 4. Connecting rod 3 and 4 were broke at bottom clamp like you held a torch to them. Rod journal are welded to crank. Pulled the oil pump and found a sheared shaft and locked up pump. Cylinders look recently overhauled with traces of honing but unfortunately holes are bores to 0.060. So I have an engine with a cracked cylinder, max bore. and crank with rod journals that have bearings welded on to them.

So here is my dilemma, one reason i bought this car, always wanted a revving 340. Now I have a boat anchor and a old holley 600. So where do I go from here? I have a friend that has a 80's 318 for $100 that runs but needs to be rebuilt. I can get a junk yard 360 for about $300, no idea on condition. Or go for a rebuilt shortblock or longblock. I know nothing about magnum engines but if that is a good option, i would look into it. I am leaning toward a 360 but any advice would be appreciated. I plan on building a street driver with power brakes, power steering, factory AC. I have 3.23 gears and a 8.25" with a 727. The rest of the car is a long ways away, so there is no real hurry on engine other than knowing what i have to look forward to. I hope to post some pictures as soon as i can get my 9 year old niece to show me how. I never knew a connecting rod could stretch that far!
 
get a late 80s early 90s 360 with roller cam. still an LA motor easy to build lots of potential. I just did the same for my 72 duster. check local cl and junkyards they are cheap and a good yard will give you a warrantee on them.
 
what year 340 is it?

You could sleeve the bad holes as long as the block isn't windowed.
 
I would sleeve it but with all the heat I think everything is distorted. The rod seriously look like you held a torch to them till they melted. I forgot to mention that on every piston, the second compression ring was broke. I did not take it into the machine shop but I talked to the best machine shop guy i know and thought i would have more into machine work than a short block.
 
revving 340..looks like it was revving when it let loose. Seriously, a 360 can be built with better street manners than a 340, longer throw means more torque. Same heads mean same HP potential. Yeah, you could sleeve it for 40-90 a hole, then scrounge a steel crank (cast 340 is short run piece) damper and rods, etc.. Just get a roller 360. Youll be money ahead. You could even put the 340 pie tin on it and none would be the wiser except you.
 
I have some nasty photos of f@%^ed up connecting rods and holes in windage tray. but because i grew up on party lines i can not post them. working on it, might have to get the neighbor kids to help me. sorry.
 
I am leaning toward a 360. Just a little bummed out, I always wanted a 340. but dollar and cents wise i agree a 360 would be a better street motor. One bad thing is since the oil boom in North Dakota and American Pickers those old farmers won't let anything go for a decent price anymore.
 
Sleeve that bastard, and don't think twice. Think: ALL aluminum blocks are sleeved, and they work fine.

The heat on the rods doesn't affect the block one bit. Cranks are easy, rods are easy, etc.

OR go for a late-model roller cam 360, and have awesome midrange torque and newer parts and better heads and better accessory drive and all that shiz.

Heck, even a late-model 5.2 is a helluva a runner. If I's gonna go 318, it's GOTTA be a roller cam, though. There's no reason to settle foe a 318 with flat-tappets unless you just want a street cruiser.
 
The windage tray and leaky cylinder.
 

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connecting rods 3 and 4.
 

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Parts found in pan and broken rings.

broken oil drive shaft. What came first the shaft, the pump, the rod, what does it matter? the result is a mess!
 

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By the colour of that rod she got pretty warm, its like some thing you would see out of a drag car.Sorry to see that and it leaves a bitter taste but keep your options open as you say your in no rush.people will jump on and give you different veiws so take it on board and go from there.
 
the broken rings make me wonder if the po was spraying it? More food for thought, 318s and 340s have the same stroke and bearing size. You could sleeve the 340 and find a junkyard 318 - mid 70's and down trucks had steel cranks - for the crank and rods and re assemble a 340. It is after all what you wanted in the first place. I had a 408 stroker motor, it was a lot of fun, but it didnt rev like a 340.
 
If that crack extends down to the main webbing the block is toast. IMO just move on. It's not number matching and already whipped. I'd build a 360 before a 318. The prices are similar unless you get a 318 for free. Ppower wise the 360 is more fun on the street. There's also the option of buying another 340 and building that into what you want. They are the best sounding at 6K and higher...lol.
 
Damn. She blowed up real good! 360's a good option. Also, the For Sale pages.. see several 340 for sales here at FABO....:D

Pat
 
Daaaayyyyum bud ! LOL that is impressive !! I wouldn't think twice about tossing that block. I would start over fresh for sure. I wonder what that puppy was spinning when it let go
 
Swifty, I would take the advise these guys are giving you. I am speaking from first hand knowledge. My 69' Cuda's block was in bad shape, no where near as bad as your block. My 340 had a few minor scratches in the cylinder walls about .060 deep scratches. I ended up cleaning the motor up, Sleeving all 8 cylinders, new pistons, rods, cam, etc. except I was able to keep my crank. In the end my lower end cost around $4400 after all the machining and parts.
Here is my block before the work http://i1009.photobucket.com/albums/af213/eldaron01/DSC00730_zps475356b0.jpg
After the work: http://i1009.photobucket.com/albums/af213/eldaron01/2477_zps823f9c5b.jpg
 
i have a cast 340 crank and maybe a good steel crank cheap. but seriously i would bet the main webs are most likely cracked. that is some serious damage 250 shot for sure lol
 
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