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saltydog251
12-04-2001, 01:46 PM
how can I identify a 340 crank if it is out of the engine?

gthomas
12-04-2001, 06:24 PM
This is a tough one that isn't even covered in the 1972 Factory Manual. I know the good 340 cranks were forged and I think the last years were cast. I doubt if any of the 273/318 crankshafts were forged, but I could be wrong. None of the 340 cranks will have the off-center weight that the 360 has. In my manual for 1972 Chryslers, there is a section "Crankshaft Identification" that unfortunately only references the size of the "undersized journal" and the "Identification Stamp". Sorry I couldn't be much help.

Fast_Eddie
12-05-2001, 06:12 PM
All '68-'72 340 crankshafts were forged steel. They carry a forging number of 2532457 or 2843868.

The '73 340 crank is cast, but is also shot peened for extra strength and carries a casting number of 3462387.

The 340 forged crank will have a 3/8' to 1/2" wide forging flash that runs the full length of each throw.

The 340 cast crank will have a 1/4" wide casting flash on each throw.

Hope this helps.

saltydog251
12-05-2001, 06:35 PM
Thanks Fast Eddie, And if its a 318 crank the it will be cast. Is that right?

Fast_Eddie
12-05-2001, 10:33 PM
To the best of my knowledge, they never made a 318 with a forged crank from the factory, but that doesn't mean someone hasn't done it on their own because they have the same stroke, same main and rod journal diameters too (same across 273, 318 amd 340 engines). They also use the same size flywheel and balancing technique (Neutral).

'67-'73 318 cast cranks used "light duty" rods and have casting numbers 2658278 and 2658393.

'74-86 318 cast cranks used "heavy duty" rods and have the same casting numbers as above and two additional castings, 3462387 and 2658391.

As with all cast cranks, the casting flash will be about 1/4" wide.

Note that the 3462387 casting number is the same as the '73 340 cast crank casting number and is a shot-peened cast crank.

Also, 2128278 and 2658393 were also used in '68-'69 273 engines.

Just keep in mind that manual tranny cranks have pilot bushing bores of 15/16", the auto tranny pikot bores are considerably smaller. So if you end up getting one from a junkyard or other source (eBay, etc.) and your car is a 4-speed and the crank is an auto setup, you'll have to have it machined to accept the manual tranny pilot bushing.

And always, make sure you use the correct damper for the crank in question.

badcaruda
12-07-2001, 01:28 AM
The 273 also had a forged crank 64-66. this was supposed to be "weaker" than the 340 but I doubt that is true. balancing a 273 crank with 340 rods and pistons may be costly having to add heavy metal to the counter balancers. The heaver rotating assembily of the 340 may stress the lighter 273 crank and cause bad vibrations so find the numbers and be sure before assembly.

six pack
12-07-2001, 09:28 PM
The 318-3 engine actually had the strongest factory forged crank of all mopar small blocks. But this motor was for use in large trucks.
I think the cranks were the same between the early 318 and 340's. I know the balancers are the same in the same years of 68-71.

Larry S.
12-07-2001, 09:54 PM
Some 318's definately came with forged cranks. When I spun a couple of rod bearings in the 340 I used to have I found a replacement forged crank in a 318 at the salvage yard. The casting numbers were different on the rods though, so I had to track down a couple of 340 rods. I had everything rebalanced before putting the 340 back together, and the shop had to do very little to the crank to balance it to my 340 rods & pistons.

Fast_Eddie
12-08-2001, 09:07 AM
Good info to know.

My source doesn't mention anything about truck motors, or 318's with forged cranks.

Charrlie_S
12-08-2001, 09:50 AM
All 273 cranks were forged. 318 cranks up to 1971 were forged, I don't know about the later 318 cranks.


See post below

Charrlie_S
12-08-2001, 11:26 AM
Addition to previous post.
As best I can determine from the 1989 mopar engine book, all 318 cranks were forged. The 318-3 truck crank was also hardened.

See Post Below

Fast_Eddie
12-08-2001, 07:31 PM
Charlie,

That is incorrect. Not all 318 cranks are forged at all, and hardening is something they do via "shot peening" to a "cast" crank, not a forged crank. Trust me, a forged crank is plenty hard enough for most of us. ;)

I have no less than 3 rotting, 318 cast crank, carcasses sitting in a junk pile in my backyard if you'd like to come over sometime and check them out. :D

I actually have a 71 forged 340 crank about to join them and keep them company (imagine the stories they'll tell each other). :D

According to both Mopar Small Blocks (HP Books) and an old Chrysler publication I have (not sure, cover is riped off, could be an early version of Mopar Small Block Hop-up), the above info came directly from those publications AND from my 20 year experience in owning many Mopars.

Neither publication lists any 318 ever having a forged crank, and none I have owned ever have either. I think some of you are mistaking some of the shot peened cast cranks as forgings.

If you have different concrete information, please post your source and/or experience.

Not all 273's were forged either, that is incorrect info. The later 273's (68-69) shared the same cast crank as the 318 castings.

64-67 273 were forged, light duty rod, cranks.
68-69 273 were cast, light duty rod, cranks.

I can verify this myself as I have had both forged and cast crank 273's throughout my "mopar-dom". :)

For the 318's:
67-73 318 were cast, light duty rod, cranks.
72-86 318 were cast, heavy duty rod, cranks.

Again, no listing or experience of any 318 being a forged crank spec.

I have had 3 different pre-70 318 cars, not a single one had a forged crank, all cast, period, AND 2 out of the 3 were factory 4-bbl cars. I have also had 4 different post-70 318 cars, again, not a forged crank in the bunch AND 3 of those 4 cars were 4-bbl cars as well.

I also had a 76 Power Wagon (with a 318), again, this was a cast crank, no forging there either.

For the 340's:
68-72 340 were forged, heavy duty rod, cranks.
73 340 were cast, shot peened, heavy duty rod, cranks.

I can verify this as I am currently restoring a numbers correct 71 Demon 340, and I also rebuilt a 72 Duster 340 motor as well long ago.

For the 360's:
71-86 360 were cast, heavy duty rod, cranks.
74-75 4-bbl 360 were cast, shot peened, heavy duty rod, cranks.

I have no experience with this motor, so I can only print what I have in front of me. :(

This is all noted, verifiable specifications in two different publications, backed by my own experience with the mopar small blocks.

If someone had a 318 with a forged crank, chances are it was popped in by an owner, dealer, or speed shop during a rebuild or hop up.

Charrlie_S
12-08-2001, 08:37 PM
Fasteddie

Since my last post, I have found additional info. It looks you are correct and I am wrong. According to the Mopar Engine Book 9th Edition part # P5249704 Chapter 3, "A" engine, pg 51.

64-66 273 auto 2463551 forged
64-66 273 man 2268119 forged
67 273&318 2268119 forged
68-71 273&318 2843699 cast
72-74 318 3898267 cast
74-89 318 3751831 cast
80-89 318-4bbl 4227880 cast
68-71 340 2843868 forged
72-73 340 3751162 cast
71-73 360 3418995 cast
74-80 360 3751160 cast

The numbers posted are not casting numbers, the are Service Part Numbers.
I posted the complete list to eliminate any confusion my previous posts may have caused. My apoligies, it has been a few years, and brain fade set in. I am just getting back into Hot Rods, after a 15 year layoff, and have been plying with the slant six.

six pack
12-09-2001, 10:45 PM
Originally posted by Fast_Eddie


Neither publication lists any 318 ever having a forged crank, and none I have owned ever have either. I think some of you are mistaking some of the shot peened cast cranks as forgings.

I have had 3 different pre-70 318 cars, not a single one had a forged crank, all cast, period, AND 2 out of the 3 were factory 4-bbl cars. I have also had 4 different post-70 318 cars, again, not a forged crank in the bunch AND 3 of those 4 cars were 4-bbl cars as well.



318-3 was definitely a forged crank.

Fast_Eddie, From my long experience with Chrysler the first year an LA 318 had a factory 4bbl was 1978.

Good informative post guys!! Keep it up:)

George G. Leverette
12-09-2001, 11:28 PM
This is a quote from the Mopar small block engine manual "The 1968-72, 340 engine used a different crankshaft than the 318, although both were forged. The 318-3 truck crankshaft was a forged and hardened crankshaft". The chart also depicts the 1967 273 and 318 as having forged crankshafts. Hope this helps.

Fast_Eddie
12-10-2001, 08:10 AM
Originally posted by six pack


318-3 was definitely a forged crank.

Fast_Eddie, From my long experience with Chrysler the first year an LA 318 had a factory 4bbl was 1978.

Good informative post guys!! Keep it up:)

I think we're pretty much proving in this thread just how crappy Chrysler was at keeping track of things back in those days. :D

John Kunkel
12-13-2001, 03:32 PM
All '68-'72 340 crankshafts were forged steel.

Not all '72 340 cranks were forged, after April 11, 1972 they started using cast cranks in the 340.

tim
12-24-2001, 10:47 AM
Hi everyone, well this post started out very good but as ones reads the more confused one gets,lol. I have 73 # matching 340 in my barracuda with a cast crank. Recently I brought home a 71 demon 340 4 spd with a supposedly forged crank, this motor had a forged dampner on it. Well it started making some noise so I took it apart and I beleive it is a cast crank as the forging mark is very very small. Since then I have scrounged up 3 other cranks , one has a tag from alberta machine shop saying 72 340 cast crank, but the forging mark is very wide? the other one has also the wide forging marks, and also has the pilot bushing for 4 spd. and the third I have a complete marine engine , 71 340 bored .40 over with the crank having the very wide casting mark also.This engine is in very good condition (so far), so I am probraly going to use it for the demon.I will go get some # off these cranks and post today, while I wait for Santa,lol.Have a very merry xmas everyone. Tim

jkailholz@aol.com
12-30-2001, 01:59 PM
Didn't the 318 poly have a forged crank? And aren't they a drop in the LA blocks? I'm sure that the early 273's had a forged crank since I've pulled several out.

hotglass
01-06-2002, 01:39 PM
Wow, good info.
The early 273s were forged, I have one from a 66 Formula S.

The 318-3 truck engines were forged as well but are hard to find, so most folks aren't aware of this. I think the "hardened" refers to a cast crank used in later dates that were shot peened.

The 340 had cast for at least half of 72 and all of 73. The dampeners for these are very specific as well. I think the 73 was externally balanced like the 360 engine for the year.