340 block value?

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Idaho

Idaho

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In my research for building a 5.9 into a 408 stroker, I read that the 340 is a preferred production engine for a stroker build due to its large bore and thick walls that can take a .040 overbore to make a 418 stroker.

This reference (How to Build Big-Inch Mopar Small Blocks) suggests that although its common to bore 0.030 over, the 5.9 should really only be bored to .020 over to avoid thin walls and distortion. Seems a little silly all the stroker kits advertised are at .030 over.

I happen to have a 340 from a 73 Duster, uncertain miles, but running when pulled. I don't plan to use it as I have a lot of parts for the 5.9 already that don't transfer over. So I'm curious regarding its value. I may consider having it tanked and magnafluxed if there's enough value there. I'm assuming the rest of the engine has no real value given that the 73 340 used a cast crank (shot peened IIRC).

A quick check on EBAY turned up a single very rusty 340 block for $900. Course he might be dreaming.
 
Check craigslist....probably wont find many 340s for sale....but plenty of 360s .....just bought a complete 72 360 engine 100 bucks...and a complete 904 attached to it....for another 100 bucks...

I have an early 360 71-74....that is overboarded .070......i just tried to bore an 77 360 .060 and it hit water......no guarantee

For thicker walls...i would use a 71-74 360 before I spend hundreds of dollars on a rusty 340 block....JMO....and experience
 
The real value for a 340 is from the resto crowd. The best block is the first 1 out of the mould. On the starter side there will be the block is the casting number followed by 340-1. The dash number can be up to 11. The last number is what time it came out of the mould. Kim
 
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Idaho said:
In my research for building a 5.9 into a 408 stroker, I read that the 340 is a preferred production engine for a stroker build due to its large bore and thick walls that can take a .040 overbore to make a 418 stroker.

This reference (How to Build Big-Inch Mopar Small Blocks) suggests that although its common to bore 0.030 over, the 5.9 should really only be bored to .020 over to avoid thin walls and distortion. Seems a little silly all the stroker kits advertised are at .030 over.

I happen to have a 340 from a 73 Duster, uncertain miles, but running when pulled. I don't plan to use it as I have a lot of parts for the 5.9 already that don't transfer over. So I'm curious regarding its value. I may consider having it tanked and magnafluxed if there's enough value there. I'm assuming the rest of the engine has no real value given that the 73 340 used a cast crank (shot peened IIRC).

A quick check on EBAY turned up a single very rusty 340 block for $900. Course he might be dreaming.
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Most of that is old wives tails. Most of the LA engines will take a .060” overbore, 360’s included. I’ve heard of 318’s going .090” over. Like everything else made back then there were tolerances so on any LA block it’s good practice to have a sonic check done if you’re going much past .030”, core shift happens and there are blocks that won’t go .060”. The ‘68 340 in my Duster is .060” over and works great.

As for the 5.9’s, I wouldn’t be surprised if they were a little more “economic” with their wall thickness. But probably more consistent too. I have heard the .020” over limit before, but I don’t have one so I never bothered to investigate further.

The 340 blocks do get a little more money, just a nostalgia thing mostly. I’ve seen them go for a few hundred bucks all the way up to a thousand. Depends on condition and the current bore diameter. I assume some of the earlier ones go for more because there are probably folks out there looking for date code or even matching number blocks for some of the more valuable 340 cars.


oldkimmer said:
The real value for a 340 is from the resto crowd. The best block is the first 1 out of the mould. On the starter side there will be the block is the casting number followed by 340-1. The last number is what time it came out of the mould. Kim
Click to expand...

Funny, I’d heard to look for early castings but not “1”. Reason being it usually took a couple modifications to the mold for them to get things sorted out. So like a “3” would be great. Obviously by the higher numbers the mold might be getting used up and those wouldn’t be great either.
 
I’m going by what oldmanmopar posted earlier in a thread. I also messaged him as I have a 340-1. I do know that in the 60s that the 318 HD truck engines were 318-3. Kim
 
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One Million Dollars.jpg
 
$400 + or - seems to be a range where you can get a decent 340 block out in this neck of the woods. Lots of rust can be a problem; I sure would not pay much for one with the lifter bores rusted badly.
 
I think a fair price for an empty 340 block with it's main caps is $300-400 for one that hasn't been cut yet. I happened to get a stock bore 72 340 block for $100 but it is a bit rusty and the caps are probably not from that block so I offered accordingly. Good crank adds value but an aftermarket or used crank isn't that expensive and a lot of guys are going to stroke it anyway. Restoration guys will pay extra for a complete motor with the right date codes for their applications.
 
72bluNblu said:
Most of that is old wives tails. Most of the LA engines will take a .060” overbore, 360’s included. I’ve heard of 318’s going .090” over. Like everything else made back then there were tolerances so on any LA block it’s good practice to have a sonic check done if you’re going much past .030”, core shift happens and there are blocks that won’t go .060”. The ‘68 340 in my Duster is .060” over and works great.

As for the 5.9’s, I wouldn’t be surprised if they were a little more “economic” with their wall thickness. But probably more consistent too. I have heard the .020” over limit before, but I don’t have one so I never bothered to investigate further.

The 340 blocks do get a little more money, just a nostalgia thing mostly. I’ve seen them go for a few hundred bucks all the way up to a thousand. Depends on condition and the current bore diameter. I assume some of the earlier ones go for more because there are probably folks out there looking for date code or even matching number blocks for some of the more valuable 340 cars.




Funny, I’d heard to look for early castings but not “1”. Reason being it usually took a couple modifications to the mold for them to get things sorted out. So like a “3” would be great. Obviously by the higher numbers the mold might be getting used up and those wouldn’t be great either.
Click to expand...

I read several years ago that the number after the dash was the number of core boxes replaced in the mold before the pour. A 360-4 would mean that four core boxes were replaced.
 
If I had it to go all over again, I'd start with a LA roller block 360 or 5.9. Cheaper and more common.
 
About 400 bucks.
Early 340 exhaust manifolds can fetch a little higher than a 340 block, always been that way.
You can only get about 100-150 bucks for a 340 crank anymore.... because the after market pops them out so cheap.

400 is still up there considering 360s go for 200 -250 all day
 
I have a 360 date coded 4-70
No nothing after the 360?? New mold?
No core shift maybe? idk
I punched it .070

7E9CCF93-E314-44B7-865D-62D569B0580F.jpeg
 
12swinger said:
I have a 360 date coded 4-70
No nothing after the 360?? New mold?
No core shift maybe? idk
I punched it .070

View attachment 1715461133
Click to expand...
I checked mymopar.com and they only show LA 360 from 71-74 casting # 3418496, 75-78 casting #3870230 and 75-93 casting # 4179930. What is your casting number?
 
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krazykuda said:
The early 360's used the 340 bore cores and had thicker walls...
Click to expand...

I have always understood this as well.
If your running a max effort motor I think wall thickness is more important than a few extra cubes.

I happen to have a 71 360 but not sure I want to part with it cheap. For $200 its worth having it sit around in case I need it someday.
 
Just some interesting info, when I built my stroker we sonic tested several 360 blocks and one 340. I had 3 72 360 blocks and 1 73 and all were different thickness. 2 of the 72 blocks were .135 or less on the trust side but the last one was over .200!, and the 73 360 was around .185. After seeing this we tested a std. bore 68 340 and believe it or not the thrust side was about .140. Like most things mopar I don't believe there is a any consistency to what years/ci blocks are thicker.
 
lead69 said:
Just some interesting info, when I built my stroker we sonic tested several 360 blocks and one 340. I had 3 72 360 blocks and 1 73 and all were different thickness. 2 of the 72 blocks were .135 or less on the trust side but the last one was over .200!, and the 73 360 was around .185. After seeing this we tested a std. bore 68 340 and believe it or not the thrust side was about .140. Like most things mopar I don't believe there is a any consistency to what years/ci blocks are thicker.
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This is exactly what I've found.

If you don't sonic test EVERY block, you have no idea what you have.

Casting dates and all the other myths palmed off as truth are just plain lies or at best, repeated lies.

Sonic test and verify everything.
 
yellow rose said:
This is exactly what I've found.

If you don't sonic test EVERY block, you have no idea what you have.

Casting dates and all the other myths palmed off as truth are just plain lies or at best, repeated lies.

Sonic test and verify everything.
Click to expand...
It sure makes total sense, especially if you're investing money to build from a platform that's 40-50 years old.
 
Idaho said:
In my research for building a 5.9 into a 408 stroker, I read that the 340 is a preferred production engine for a stroker build due to its large bore and thick walls that can take a .040 overbore to make a 418 stroker.

This reference (How to Build Big-Inch Mopar Small Blocks) suggests that although its common to bore 0.030 over, the 5.9 should really only be bored to .020 over to avoid thin walls and distortion. Seems a little silly all the stroker kits advertised are at .030 over.

I happen to have a 340 from a 73 Duster, uncertain miles, but running when pulled. I don't plan to use it as I have a lot of parts for the 5.9 already that don't transfer over. So I'm curious regarding its value. I may consider having it tanked and magnafluxed if there's enough value there. I'm assuming the rest of the engine has no real value given that the 73 340 used a cast crank (shot peened IIRC).

A quick check on EBAY turned up a single very rusty 340 block for $900. Course he might be dreaming.
Click to expand...
yellow rose said:
This is exactly what I've found.

If you don't sonic test EVERY block, you have no idea what you have.

Casting dates and all the other myths palmed off as truth are just plain lies or at best, repeated lies.

Sonic test and verify everything.
Click to expand...

BAMM & BINGO! What YR said!

Let me tell ya something Idaho, any block you get, no matter the miles, year, CID, when you go to build your engine and even more so a stroker, sonic check your block so you KNOW the state of the block. If you don’t, I suggest a sonic check of your head instead.:D

FWIW, around here, 340 blocks = $700.

The larger bore is most desirable since it has a direct impact on HP. The added CID you get is peanuts.
Also the fact that the 340 block is a ‘73 means nothing. The block is worth something to the one who has to have it. Even more so if it fits there date code. But it is only worth what someone is willing to pay for it. Find a sucker. The crank, not so much. Even a forged crank.
 
That’s why I located this early 360 block as I wanted a 4.100 bore, same as the last engine in the car.
We sonic tested it, and decided 4.070 is safe. I just thought it was cool no -anything after the size. Obviously an early early casting.
 
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