What crank 1970 318?

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340inabbody

340inabbody

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Anyone know if the 318 crank in 1970 was forged steel as opposed to cast? Was it shot peened? Any info and markings would be helpful!
 
Most likely cast unless it's a truck engine. Have any pics, easy to tell from the parting lines. 65'
 
Agree cast. at a glance the cast will have thin line in it forged wide and the forged crank will ring if tapped with a blunt object like a hammer handle cast will sound like "Thud". If you search the threads there are pics of the two cranks.
 
Thanks its still in the block and will be there until I can possibly get to see it out. I was on the understanding that all 1970 and earlier were
forged? Were
forged cranks even used in pre 70’s motors sb or bb? I read this somewhere but can’t find the original article.
 
More than likely in a 70 u have a cast crank. Truck engines usually had a forged crank. But not always. Plus in a 50 year old engine anything could have been replaced. Kim
 
Cast 340 and early cast 4bbl 360 were shot peened. If your looking for a 3.31 stroke forged crank beyond 340's look for a 273.
 
Early 273 pre 68 forged crankshafts have the small converter register. Just be aware of that, I believe it can be opened up to the larger diameter by a machine shop. 65'
 
340inabbody said:
Thanks its still in the block and will be there until I can possibly get to see it out. I was on the understanding that all 1970 and earlier were
forged? Were
forged cranks even used in pre 70’s motors sb or bb? I read this somewhere but can’t find the original article.
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Can you see the crank flange? If you can, you can still see tha parting line on the edge of the flange. Wide parting line=forged, thin parting line=cast.

It could be either, as there was really no rhyme or reason sometimes. If it was a manual transmission truck engine, it was more likely forged, but I've even seen some of those cast, so the only way is to verify.
 
Dartswinger70 said:
Agree cast. at a glance the cast will have thin line in it forged wide and the forged crank will ring if tapped with a blunt object like a hammer handle cast will sound like "Thud". If you search the threads there are pics of the two cranks.
Click to expand...
I've never seen a Chrysler crank that didn't ring or hear one that made a thud, cast or forged. Must have been some really spectacular steel/nodular iron poured when they cast them.
 
All '67 and earlier engines had forged cranks. 318's after 1967 it was kind of a crap shoot. Most automatics and manuals in cars came with cast cranks, but, I've seen a few forged cranks that got installed from the factory. Maybe they ran out of cast ones temporarily and used a forged crank? In trucks, most automatics came with a cast crank, and most manuals came with forged, but, then again, I've occasionally seen them both ways on seemingly original unmolested engines. Also, most automatic cranks were not machined for a pilot bushing like manual trans cranks were, but, I've pulled a few virgin automatics that received a final machining for the pilot bushing. My guess is that there could have been either be a screwup by whoever went to grab a crank off the shelf, or, that they may have run out of the correct one at the time.
 
Garrett Ellison said:
I've never seen a Chrysler crank that didn't ring or hear one that made a thud, cast or forged. Must have been some really spectacular steel/nodular iron poured when they cast them.
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It's a trained ear thing along with the marks. There are two distinct sounds maybe thud isn't accurate. But the cast is more of a "dead note' or using musical terms the forged crank will "sustain" or ring longer than a cast which wont ring long at all.

As far as being good steel ,it was .These cars are from a time when Amerca was truly great, steel and cars and parts were made here or in Canada across the great lakes from Detroit. This is one reason why I love these old cars...:)
 
Garrett Ellison said:
I've never seen a Chrysler crank that didn't ring or hear one that made a thud, cast or forged. Must have been some really spectacular steel/nodular iron poured when they cast them.
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Nodular iron is all Chrysler used for cast. Like Cleveland cranks.
 
If you go by the parts book, it will depend on year and application, but, in reality they can all be interchanged. In some applications, I see a different part number between some automatics and manuals. I don't know the reason for that. Maybe someone here knows the details as to why.
 
For instance, in 1966 a 273 balancer (all transmissions) part# 2658458 is the same as a 318 poly with a manual transmission. The 318 with and automatic is part# 2658459. All these cranks are forged. In 1968 all the 273, 318, and 340 engines use the same 2658458 balancer that the earlier 273 and manual trans 318 use. In '68 the 273 and 318 cars used a cast crank, but, the 340 crank is forged. I have no idea why a 318 poly with a manual trans would be different. It's internally balanced like all the others and the balancers look the same physically. I have seen a few varieties of the outer ring of some stock balancers. Some have flat front and back surfaces and some have a concave curved surface on one side.
 
In 1970. the balancer changed part number because they moved the timing slot to the driver's side. The new part# is 2951673 and is listed for all 318's (cast crank) and 340's (forged cranks) regardless of transmission. They still swap back and forth with the earlier balancer if you remark the timing slot depending on which timing cover and indicator you use. In '72 they changed the balancer once again by going to an even bolt pattern for the pulley instead of the early one with one bolt offset. Simply slot that one hole with a file and they will swap with the early balancers too along with the other caveats I mentioned. Mopar even made replacement crank pulleys with the slotted holes later on so they would fit both applications.
 
Vibration dampers will be different depending on application. There are a few factors that determine what damper is on the engine. The amount of inertia required is determined by the torsional amplitude requirement/specification. The frequency is determined by the spring rate of the crankshaft, rotating and reciprocating masses and cylinder pressure. The damper should be tuned to attenuate the resonant frequency of the crankshaft system. A undertuned damper can push the torsionals to the higher RPM range. A overturned damper will push the torsionals to the lower RPM range. Automatic and manual transmissions can use different dampers based on the above factors. Most people have no idea what that resonant frequency is once they build an engine with various components. That's why an ATI or Fluid damper should be used. These type dampers operate over a larger RPM range and are not tuned to a specific frequency. 65'
 
I'm still trying to figure out what makes a '66 318 automatic different than a '68 318 automatic, especially when all transmissions use the same balancer some years. It must be something real subtle that they decided didn't make enough difference to continue making different ones for different applications.
 
cudamark said:
I'm still trying to figure out what makes a '66 318 automatic different than a '68 318 automatic, especially when all transmissions use the same balancer some years. It must be something real subtle that they decided didn't make enough difference to continue making different ones for different applications.
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Most of the 318s (maybe all???) in 1966 were poly 318s, not LAs
 
Yup, there were some early '67's with poly 318's too. That still doesn't explain why the poly automatic would have a different balancer than all the other small blocks when the poly manual's are the same.
 
Dartswinger70 said:
It's a trained ear thing along with the marks. There are two distinct sounds maybe thud isn't accurate. But the cast is more of a "dead note' or using musical terms the forged crank will "sustain" or ring longer than a cast which wont ring long at all.

As far as being good steel ,it was .These cars are from a time when Amerca was truly great, steel and cars and parts were made here or in Canada across the great lakes from Detroit. This is one reason why I love these old cars...:)
Click to expand...

no steel or cast iron is as good as the steel milled or cast iron that is cast today, especially if it is manufactured in North America, Europe or japan. There is only one company that makes and mills steel from raw materials in the United States, United States steel. Every other company mills steel from scrap in the states. And quality steel scrap is as pure as you can get.
 
Plymouth 65 said:
Vibration dampers will be different depending on application. There are a few factors that determine what damper is on the engine. The amount of inertia required is determined by the torsional amplitude requirement/specification. The frequency is determined by the spring rate of the crankshaft, rotating and reciprocating masses and cylinder pressure. The damper should be tuned to attenuate the resonant frequency of the crankshaft system. A undertuned damper can push the torsionals to the higher RPM range. A overturned damper will push the torsionals to the lower RPM range. Automatic and manual transmissions can use different dampers based on the above factors. Most people have no idea what that resonant frequency is once they build an engine with various components. That's why an ATI or Fluid damper should be used. These type dampers operate over a larger RPM range and are not tuned to a specific frequency. 65'
Click to expand...
. Interesting subject… what I would like to know is how is that resonant frequency determined and measured and how do you design a harmonic balancer to absorb that frequency.
 
The crankshaft and components are modeled as a spring mass system. The engine cylinder pressure is then used as the forcing function to excite the model. Based on the firing frequency of the particle engine i.e. 4, 6, 8 cyl. the torsional analysis can determine the order and amplitude of the system's resonance. 65'
 
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