273 & 318 Connecting rod weights

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MObarracuda

MObarracuda

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I have a 1967 273 and 1968 318 that I just disassembled. They both appeared to be stock. I put the connecting rods on the scale to see if there were any difference. I found it interesting that the assembled weigh between the 273 and 318 were almost the same and the wrist pins were sized to make up the difference in the pistons.

273 connecting rod.....723g
318 connecting rod.....726g

273 piston connecting rod and wrist pin....1576g
318 piston connecting rod and wrist pin....1572g

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Locomotion said:
Didn't later 318's go to the bigger, unbushed 360 rod?
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I was looking for the forged crank for a 340 build and found out the hard way the register for the nose of the torque converters are different sizes. The 273 has 1.55" and the 1968 changed to 1.75.
 
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MObarracuda said:
I have a 1967 273 and 1968 318 that I just disassembled. They both appeared to be stock. I put the connecting rods on the scale to see if there were any difference. I found it interesting that the assembled weigh between the 273 and 318 were almost the same and the wrist pins were sized to make up the difference in the pistons.

273 connecting rod.....723g
318 connecting rod.....726g

273 piston connecting rod and wrist pin....1576g
318 piston connecting rod and wrist pin....1572g

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Here are more photos of the specific part numbers on the 273 connecting rods

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The rods you have posted.....while different casting numbers are the same style early small rods. The later 318s got the same larger rid as the 340 and 360.
 
RustyRatRod said:
The rods you have posted.....while different casting numbers are the same style early small rods. The later 318s got the same larger rid as the 340 and 360.
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Hello RRR....thanks for adding to the post!
 
RustyRatRod said:
The rods you have posted.....while different casting numbers are the same style early small rods. The later 318s got the same larger rid as the 340 and 360.
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They happen to be the same casting number 2706782...not the best pictures. Would you say it's mutually exclusive when they stopped using the lighter connecting rods and when the compression ratio was lowered from 9.2 (per alpar) to 8.6 in the early 70's?
 
MObarracuda said:
They happen to be the same casting number 2706782...not the best pictures. Would you say it's mutually exclusive when they stopped using the lighter connecting rods and when the compression ratio was lowered from 9.2 (per alpar) to 8.6 in the early 70's?
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Ok, my old eyes thought one was different. I am not certain there was a set in stone date for going to the bigger rids.

Sorta like everybody says the 340 for 1972 had a cast crank, when clearly there were both steel and cast. I think they used parts up as needed.

I do have two nice sets of the smaller lighter rods. Mopar Performance offered them for a time in match weighted sets with good rod bolts. They are still fairly sought after in some racing circles requiring stock rods, as they are much lighter than the later 340-360 style rod.

They were proven to be just as strong, too. Although that argument will rage on forever just like everything else.
 
RustyRatRod said:
Ok, my old eyes thought one was different. I am not certain there was a set in stone date for going to the bigger rids.

Sorta like everybody says the 340 for 1972 had a cast crank, when clearly there were both steel and cast. I think they used parts up as needed.

I do have two nice sets of the smaller lighter rods. Mopar Performance offered them for a time in match weighted sets with good rod bolts. They are still fairly sought after in some racing circles requiring stock rods, as they are much lighter than the later 340-360 style rod.

They were proven to be just as strong, too. Although that argument will rage on forever just like everything else.
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What is you opinion on using the 273 rods (726g) for use in a street duty 340? Eagle makes a 605g forged connecting rod for $280 bucks for a set of 8. Do you pick the rod by the cost to recondition or buy new to better match weight of pistons and crank balancing when assembled?
 
MObarracuda said:
What is you opinion on using the 273 rods (726g) for use in a street duty 340? Eagle makes a 605g forged connecting rod for $280 bucks for a set of 8. Do you pick the rod by the cost to recondition or buy new to better match weight of pistons and crank balancing when assembled?
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I think the Eagle rods are a far better deal than reconditioning a set of the 273 rods. It didn't used to be like that. You had to run what was available and at one time, the 273 rod was the lightest rod there was next to aluminum.

At that time, aluminum rods were very exotic and expensive, so the choice was pretty clear. Nowadays, everything is available. Unless you can get the rods reconditioned for a song, the Eagle rods are the better choice.
 
4spdragtop said:
The 68 318 had pin locks (floater) and 67 273 were press fit correct?
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Now THAT I do not know. Both sets I have are floaters and came from 273s. I am not familiar with the years and breakdowns.
 
I can tell you this. Stupid as it sounds "I" would rebuild the old rods. I like original American metal and I like makin old stuff new again. JMO.
 
Thanks Rob. Im going by the pics of parts on scales. Reason I ask is im tearing a 70 318 down shortly and it has the 2406782 rods with TRW pistons. It "should" have floaters I would think which creates a dilemma for me and finding replacement pistons lol
Thanks Rob
RustyRatRod said:
Now THAT I do not know. Both sets I have are floaters and came from 273s. I am not familiar with the years and breakdowns.
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Steve, I didn't "THINK" the floating pins in the 318 went to 1970, but like I said, I am unfamiliar with when/what was used as far as rods. Also, keep in mind how Chrysler was famous for using "what they had" till "there was no more" and you can see how some overlapping occurred. So "I GUESS" you might just have either rod. Who knows? LOL
 
4spdragtop said:
Im confused lol, pic #2 shows 67 273 no clip. Pic #5 shows 68 pin and clip??
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I'm sorry...I am usually more careful and scientific. Both engines had a pair clips holding the wrist pins in. I think they were under the piston.
 
MObarracuda said:
I'm sorry...I am usually more careful and scientific. Both engines had a pair clips holding the wrist pins in. I think they were under the piston.
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Then they were both floating rod assemblies. Right?
 
No problem. Im in a similar teardown on 2 318 engines. A 1983 & a 1970. It started out as a budget build lol. Im soon learning 318's are as pricey as 273's lol.
As Rob mentioned, both are floating then?
MObarracuda said:
I'm sorry...I am usually more careful and scientific. Both engines had a pair clips holding the wrist pins in. I think they were under the piston.
Click to expand...
 
4spdragtop said:
Thanks Rob. Im going by the pics of parts on scales. Reason I ask is im tearing a 70 318 down shortly and it has the 2406782 rods with TRW pistons. It "should" have floaters I would think which creates a dilemma for me and finding replacement pistons lol
Thanks Rob
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Steve, here are your pistons if you have floating rods. They are not the cheapest, but also not the most expensive by a long shot. Will also give your teen a big compression boost.

https://www.summitracing.com/parts/uem-kb167-030
 
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