1st 340 build

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drtybttr

drtybttr

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Greeting everyone. I have acquired a bare 340 block pretty recently. I have never assembled a short block before so I need some help. I have been doing some research on cranks and I noticed that there seems to be a difference in early year and later 340 cranks. Is it just the material? Or are they balanced different? From what I have seen the early units were forged. I am on a very limited budget and am really trying to avoid machine costs. So can I just get a remaned crank from autozone or somewhere. I looked and they are only 200 bucks. Any rotating assembly thoughts would be helpful.
 
do you have pistons and rods? a stroker kit might be more what your looking for depending on your use getting crank from autozone is gonna be a cast crank you want a steel one. if you engine is gonna see lots of rpms in my opinion. for about 1500 you can get it all crank rods pistons rings bearings, everything for your shortblock. with crank choices you can get one with the same main journal size. good luck
 
drtybttr said:
I am on a very limited budget and am really trying to avoid machine costs.
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Then Superbee's idea isn't very practical. My advice would be to find someone who is building a stroker and buy their stock bottom end. Earlier cranks are forged and internally balanced, later cranks are cast and require a special harmonic balancer and weighted converter. Both cranks are fine for a street car, but would need to be checked out by a machine shop before installing.
 
I have used a few cranks from autozone and advance auto................. Do not buy. They are junk. They take your old junk one in as a core. If it spun a rod bearing to where it is not serviceable, they will re-weld the journal up, and then re-cut it. It will not hold up , they are junk. They are the real term of a boat anchor.lol
 
Get hold of a 340 forged steel crank .. on e-bay time and time again (internal balance deal) .. get the rods, pistons, pins, bearings, rings, locks for the full floater pistons.. drop off at machine shop for internal balance.
 
Another alternative would be a '64 to '66 polysphere crank or a 273 crank. Also, the '67 318 also had a steel crank, jus not as good as a real steel 340 crank. (at some point in 67 they started to use the cast cranks). 340 has the same stroke as a 318 so I assume that autozone crank would be a cast 318 crank for that price. I seriously doubt you could buy a real 340 steel crank for $200. If you could, we all would have them.
 
Just get a scat or eagle forged crank. Now it the time to order through summit using a code to save some money (15%)
 
omahamoparguy said:
Another alternative would be a '64 to '66 polysphere crank or a 273 crank. Also, the '67 318 also had a steel crank, jus not as good as a real steel 340 crank. (at some point in 67 they started to use the cast cranks). 340 has the same stroke as a 318 so I assume that autozone crank would be a cast 318 crank for that price. I seriously doubt you could buy a real 340 steel crank for $200. If you could, we all would have them.
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200 is exactly what I paid for one on e-bay. It was ground 20/20. When my assy. went out for balance, they took metal out after they spun the bob weights.



There out there.. jus gotta keep looking.
 
drtybttr said:
Greeting everyone. I have acquired a bare 340 block pretty recently. I have never assembled a short block before so I need some help. I have been doing some research on cranks and I noticed that there seems to be a difference in early year and later 340 cranks. Is it just the material? Or are they balanced different? From what I have seen the early units were forged. I am on a very limited budget and am really trying to avoid machine costs. So can I just get a remaned crank from autozone or somewhere. I looked and they are only 200 bucks. Any rotating assembly thoughts would be helpful.
Click to expand...

All 68-72 340 crankshafts were steel. Only the one year, 1973 was cast. You will hear people say the 318 steel cranks ain't the same yap yap yap.....but they are STEEL just like the early 340 cranks are ummm uhhh errr....STEEL. yeah, they might be a tad different, but completely interchangeable. with a good quality balance job and correct assembly, that 318 crankshaft will spin snot buckets of RPM, just like a 340 one will. You'll never know the difference. Likewise, if you're gonna build an engine 500 or less HP, a cast crank properly prepped will be all you'll ever need. I do agree though to stay away from big box auto parts stores. They suck when it comes to engine parts like cranks. There's nothing wrong with welding up a crank for repair. It's HOW it's done, and those mass produced "reman" crank shops ain't the place to get it done. Since all these cast steel cranks and such hit the market, the 340 stuff ain't the holy grail it once was. If somebody wants more than a couple hun for a good turnable 340 steel crank, they are stupid. Plain and simple.
 
The big difference, that I know of, between the 318 and 340 forged cranks is that the 340 is balanced for HD rods while the 318 is balanced for lighter duty rods. The 360 ran HD rods that are interchangable with the 340.

If the piston is not going to be an OEM replacement, it would seem that re-balancing the crank is going to be a good idea. Doing this will let you use whatever piston/rod combination you want.

StrokerScamp makes a good point about the cast crank for a less than 500 HP motor. A good, straight, used one would be best as the metal has been through many heat and cool cycles which improves the temper of the metal.

Here's another point worth considering. The cast crank weighs less than the forged crank. That means if all else is equal, a cast crank should be quicker to accelerate than a forged crank because there is less mass to move.
 
has block been to machine shop yet to see if it is a good one, if you buy a used crank you will have to get it checked (probably machined) i would still look at new cranks from summit and see if they have a stroker kit cheap enough for your buget
 
Just my opinion, but if you only have a block, you will be spending on parts and machining. If you dont want to spend on that, you have to buy a running engine and pay at that point... You need a 340 or 318 crank of some type, I'd get whatever rods to match the crank, and then buy KB hyper pistons. The block will need to be bored and honed if it hasnt benn, plus degreasing, etc.
You cannot cheap out by buying only a block. You'd be better to trade the block for a running 360. JMO...
 
340 cost a lot more to build and are hard to find. 318 and 360 easier to find but why build a 318 when you can build a 360 for the same money as a 318 but make more power with a 360
 
1970Duster said:
340 cost a lot more to build and are hard to find. 318 and 360 easier to find but why build a 318 when you can build a 360 for the same money as a 318 but make more power with a 360
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This isn't really inaccurate.

340's don't really cost any more to build than 318's or 360's, as long as you're talking about similar builds component-wise. The only extra cost is finding/buying a 340, which can be a big cost. If you already have one, then the rebuild price is pretty much the same.

Machining costs will be the same for any small block. Reconditioning the crank and rods is the same (or the same cost as a 318 if you buy new parts). Only real difference is the pistons. Usually I would say the 340 pistons would set you back a little more. But a quick check at Summit says that 318 pistons, KB 167's, cost 319.99. KB 243's, 340 pistons, cost 255. Go figure. So the pistons don't have to cost more. A 340 timing set, gaskets, bearings, oil pump, etc are all the same as a 318. Head gasket may be different depending on the bore, but it shouldn't be that different $ wise. Comparing complete rebuild kits, they're the same. I see Summit doesn't have a cast piston kit for the 340's, but they're out there (or you can sub in the KB hypereutectics). And the forged piston complete rebuild kit for a 340 is priced the same as a 318.

As far as rotating assemblies go, you would probably be better off buying a complete rotating assembly since you don't have anything right now. Buying used parts that need to be reconditioned might actually cost more money than some of the new set ups if you're not careful, depending on your local machine shop and how much you pay for the used parts. For example, if you pay a couple hundred bucks for a forged crank core, and another $100 or so to have it reconditioned, and you could have bought a brand new cast crankshaft.

Depending on your goals for the engine, a cast crankshaft can be more than sufficient, and quite a bit cheaper. If you're shooting for 500 hp stay away from cast, but for a stock to moderately built engine they're fine.
 
Not to highjack this thread, but I want to pull my running when parked cast crank 340 down and at least freshen the bearings before I put it in the Duster. I picked up an aftermarket steel flywheel for it and have the diagram for drilling it from the DC chassis book. How different, if any, is the counterweight balance of a steel 318 crank from a steel 340 crank, and would be worth the additional time and trouble to use the one I have from my '67 Coronet?
 
Here is the specs I have for my 340 if this will help you.
.30 over bore (4.070) using forged alum Ross racing pistons.
Eagle forged crank and forged H-beam rods with their ESP armor.
Full grove bearings from federal.
Total seal gapless piston rings.
Stud girdle from Hughes (which is so close to the crank it acts like a crank scraper).
SFI balancer, SFI flexplate, high volume water pump. Standard volume oil pimp.
Milodon's new road race oil pan. Dougs headers.
Crane roller cam, Hughes roller lifters, comp pro magnum roller rockers.
Edelbrock alum airgap intake, X heads with Ferrea stainless steel (2.02, 1.60) valves.
Holley electric fuel pump. Be cool ( cross flow) radiator with duel electric fans and I'm using Evan's coolant (same stuff they use in NASCAR, I recommend it if you get your block hot tanked).
All this stuff if bolted together using the strongest arp bolts that will bolt to the motor.
Hope this helps you some.
 
twofosho said:
Not to highjack this thread, but I want to pull my running when parked cast crank 340 down and at least freshen the bearings before I put it in the Duster. I picked up an aftermarket steel flywheel for it and have the diagram for drilling it from the DC chassis book. How different, if any, is the counterweight balance of a steel 318 crank from a steel 340 crank, and would be worth the additional time and trouble to use the one I have from my '67 Coronet?
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the balance between the 1967 318 forged crank and the forged 340 crank wil be the same,,but i believe the 67 318 forged crank is the same as the 1965/66 273 hi po forged crank,,if so the torque converter register hole may be smaller, then the later small blocks,,but im not sure when they changed the size of the converter hole,,,

ide be intrested in finding a complete 1967 318 forged crank engine, as a replacement if i end up needing a momtor for my street rod,,
 
superbee79 said:
why does everyone on this site want you to build a 360?
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I dont care what is ultimately built...lol Starting with a bare 340 block will more expensive than a running 360 by a long shot. JMO. This is why I only have 2 340s but 4 360s. I can buy (2) 360 running cores for the price of (1) non-running complete 340.
 
The only difference in cost between a 340 /360 is piston price.
When comparing KB hypers 'for instance' there is a $40'ish dollar diff, woopity doo...

what costs even more then a 340/360 in the performance piston depot is a 318.

all parts cost the same after pistons, so you'd be no further ahead or less spent if you had a 360 block instead.

build the 340, just grab a 318 cast crank/rods and buy some KB243 pistons, balnace it all, and put it together.
truck 318's in the '70s had shot peened/blasted cranks, '387' was the number, look for one of those, they are actually quite common...I have a couple std
 
or just buy a stroker kit for the 340 and some rhs heads or rebuilt iron, there guys on here still making 425+hp and around 500ftlbs of torque w/ bowl blended stock heads.fwiw
 
StrokerScamp said:
All 68-72 340 crankshafts were steel. Only the one year, 1973 was cast. You will hear people say the 318 steel cranks ain't the same yap yap yap.....but they are STEEL just like the early 340 cranks are ummm uhhh errr....STEEL. yeah, they might be a tad different, but completely interchangeable. with a good quality balance job and correct assembly, that 318 crankshaft will spin snot buckets of RPM, just like a 340 one will. You'll never know the difference. Likewise, if you're gonna build an engine 500 or less HP, a cast crank properly prepped will be all you'll ever need. I do agree though to stay away from big box auto parts stores. They suck when it comes to engine parts like cranks. There's nothing wrong with welding up a crank for repair. It's HOW it's done, and those mass produced "reman" crank shops ain't the place to get it done. Since all these cast steel cranks and such hit the market, the 340 stuff ain't the holy grail it once was. If somebody wants more than a couple hun for a good turnable 340 steel crank, they are stupid. Plain and simple.
Click to expand...



http://www.hamtramck-historical.com/images/TSBs/1972/09-07-72C page1.jpg
 
Just understand the difference between neutral balance and weighted so you order the right last 2 components after balance.
 
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