340 Is done for

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71Duster

71Duster

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Well the machine shop has advised me while it is rebuildable its not worth it.

Look at a .40" over bore, the caps have been bounceing off the block... also needs a serious line bore as there are some huge variations in size of the caps.

The crank is already .10' under and needs to be cut but has cracks in the radius of #2 and #4 and they cant say for sure that the cut will clean them up... and the crank would be "soft" after that anyways.

In short I need to source a good 340 short block or I want a virgin 360.
 
well, I'd say keep it..Go .040 over, that's no big deal. Get a crank..either stroke it, or get a 318 forged crank. Replace the main bolts with studs, and have the mains fixed. My guess is the crank was flexing because of the mains moving, and they moved because it wasnt done well the first time, or it had detonation problems. Mopar lower ends are fairly strong for thier design, and the caps wouldnt walk unless they were given a reason....If you are planning a good performance rebuild anyways, those operations (minus the studs) would or should be a part of it anyway. At least this block, you know what you're starting with.
If not, I'll take that usless pile of junk off your hands too...lol.
 
You seem to be butting your head against the wall with each step on this build, but as mentioned above, you might as well stay with the devil you have rather than maybe starting with someone else's devil. :)
 
Well from the looks of the crank the machine shop figures serious detonation... prior to me owning it cause it ran great once the demon was put on it.

The other thing I have been told is with the size of line bore is needed you get issues with moveing the crank "further" up? I'm jsut looking at a money perspective. I can buy a built 360 thats .30 over with diamond pistons, neutral balance and ready to roll for 3200 bucks. Just seems like the 340 will double that price tag in machine shop costs alone.

The block is numbers matching and will be tucked away in a bag with the cylinder walls greased up if I dont use it... but hey thanks for asking!
 
Not around here, but the 3200 isnt bad if it's complete. The 416 block I'm picking up today from the shop has had the following: fit Program 2 bolt caps in #1,2,3,4; align hone; bush lifter bores; square deck; torque plate hone; clearance for stroker crank. The bill is $1700 for the machine work, but this is all competition quality stuff, on new machines. Without the lifter bushing, and clearancing, it would drop to about 1200. This engine is also going to be the first use of the Mopar timing chain tensioner setup, so the chore of trying to find the shorter timing sets is over with. Good call on keeping it. It can be saved fairly easily by a good shop, and not for too much money.
 
My 340 block took 4 sleeves to make it right. An extra $400 on top of the usual machine work. Unless the block is cracked, a good machine shop can usually save it. It all depends on how much you want to spend.
 
The machine shop is the top place in the province... and lamsot out of my price range he builds nothing but race engine. Lots of Sprint car engines and Late models and jet boat engines also.

Everything is done on a cnc also they know there stuff. Its not that he said its a paper weight and junk jsut that the bang for buck in price isn't there. His opinion of a 340 is rather low too. he prefers to build 360's in that they have thicker cylinder walls.

Just such a run around as so many people give me nothing but bad news and a different idea on what to do. E-mail sent 388 Dart

I'd much rather build my 340 or run a 340 in general... I got a little flak from a few people by building the number smatching block though too.
 
Apparently you can get 360's pretty cheap and build them up to nice motors, so you might as well put the 340 aside and spend the money on something you can actually enjoy and not worry about destroying. I'd support that!

My '65 Barracuda Formula S is missing the original 273 Commando motor and although I've found a couple for sale that would be techically correct for my car, I can't see spending the money when I'd rather have a mean 340 under the hood? So I found a 1970 340 in need of rebuild and I'm gathering parts for it and will stick my money into that, to hell with the numbers matching thing.
 
Thats what I am doing jsut the 360 route. I think If I had of gone to a els sprestigious machine shop they would have built it for me with out all the worrying thoughts but whats done is done. This way if I put a rod through the block I wont feel bad. One day I'll get back to my 340. Wish I could ahve found a virgin 340 block!
 
360s are thicker? that's wrong. But, they are easy to find, cheaper, and have a longer stroke. For a street car, stroke's where it's at. As long as the work is done well, I'm sure you'll be happy.
 
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