273 Crankshaft Quiz

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Ciguatera

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Not really a quiz, just a whole lot of questions that I'm numbering to reduce confusion. I'm confused enough for the whole forum. I have a 1965 Barracuda Formula S with the stock 273 4bbl and a 904 automatic. I've been trying to figure out what my options are in terms of engines/converters/transmissions if I decide to change anything, and it all keeps coming back to the '65 273 crank. I have several questions that I haven't been able to find answers to in other threads.

First, some basic questions:
1) This is a six bolt crank, right?
2) An automatic car crank only works with an automatic without drilling it, right?
3) Can I use a modern timing chain and harmonic balancer with this crank?

Other threads have said that the early 273 cranks use a smaller "hub", "pilot", or "register".
4) Do all these terms all mean the same thing and refer to the big hole (technical term) in the crank rear flange? What term should I use?
5) When did they switch to the larger size?
6) Would running a newer engine/crank with a larger whatever it's called prevent me from using the original 904 or the stock converter?
7) Alternatively, can I run a newer converter with the 273 crank?

Answer any questions you want, any way you want. I can use all the information I can get on this!
 
My numbers don't match yours lol, just rambling..........

1...Stick/ pilot drilling. Not sure the "track record" of 273 cranks, but you should ALWAYS check the pilot depth by measuring the gearbox shaft and same to the bell--to pilot hole bottom Generally there are two problems with Mopar cranks, and with Magnums, one more problem. A....The hole can be too shallow if it's an auto crank...B....The hole can be undersize diameter. At one time you could buy (such as Dorman) undersize pilot bushings. C...With Magnums (my former 5.9 2500pu) the pilot hole IS NOT DRILLED at all.

One solution you DON'T have available "stick it in" with an early crank is to use the later Jeep style "big" pilot bushing/ bearing which rides in the register. "I guess" you could take a late one and figure out how to turn it down to the small crank register.

2...Converter register. Never can remember they changed 68 or 69. So you'll need the small early converter for a small register shaft, or if using the early converter in a later engine, you'll need to find (used to be able to buy) or scare up a lathe and make a spacer ring between the early converter and late crank. This refers to the larger outer hole in the crank

Only way to use a newer converter/ larger snout with an early crank / small register is to have the converter "converted" to a small snout--and that could get expensive. Other than upsetting engine balance, "I guess" you could stick a later 318 crank in the 273. Even though 273's and most 318's are neutral balanced, the balance weights are DIFFERENT between the two.

3..timing/ cam drive should be no problem regardless of year, recommend use matched components and learn to check cam degree

4...So far as I know all 273's (at least pass cars) are 6 bolt cranks
 
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The crankshaft small diameter register was changed to the larger diameter in 67. Small snout converters with high stall speed are impossible to buy off the shelf but you can have one built. I ended up putting a 340 crankshaft in my 273 with the larger register diameter. I then had the transmission rebuilt and installed the proper input shaft, pump, and clutch hub for the 67 and up 904. I could now use the larger register diameter torque converter. 65'
 
The early 273 balancers are different. The timing marks are on the other side of the engine.
 
you can set crank in lathe and bore the register out to the 318/340 size easily. I've done quite a few of those. just food for thought.
 
The crankshaft small diameter register was changed to the larger diameter in 67. Small snout converters with high stall speed are impossible to buy off the shelf but you can have one built. I ended up putting a 340 crankshaft in my 273 with the larger register diameter. I then had the transmission rebuilt and installed the proper input shaft, pump, and clutch hub for the 67 and up 904. I could now use the larger register diameter torque converter. 65'


They were NOT changed in 67. Is that what you meant to say?

A 340 crank is not weighted (bob weights) the same as a 273, even though both engines "could" be neutral balanced (I did the opposite, decades ago...put a 273 crank in a 340)
 
68 my mistake! 65'
They were NOT changed in 67. Is that what you meant to say?

A 340 crank is not weighted (bob weights) the same as a 273, even though both engines "could" be neutral balanced (I did the opposite, decades ago...put a 273 crank in a 340)
 
The original 273 in 64-65 used a lot of poly 318 parts, including crank and rods, timing cover, damper, pulleys and alternator bracket (that's what the extra mounting holes are for). (Distributors are interchangeable, but 273's had a different advance curve.)

To keep the balance the same, 273's used heavy, thick-walled piston pins to keep the piston/pin weight the same as the poly 318. So using a poly 318 crank in an early 273 doesn't affect balance. Wedge 318's? I have no knowledge or any reason to doubt the comment above that their balance is different.
 
A 340 crank is not weighted (bob weights) the same as a 273, even though both engines "could" be neutral balanced (I did the opposite, decades ago...put a 273 crank in a 340)

Reason being, of course, that 340 rods and pistons are heavier than 273 (and also heavier than 318).
 
Not really a quiz, just a whole lot of questions that I'm numbering to reduce confusion. I'm confused enough for the whole forum. I have a 1965 Barracuda Formula S with the stock 273 4bbl and a 904 automatic. I've been trying to figure out what my options are in terms of engines/converters/transmissions if I decide to change anything, and it all keeps coming back to the '65 273 crank. I have several questions that I haven't been able to find answers to in other threads.

First, some basic questions:
1) This is a six bolt crank, right?
2) An automatic car crank only works with an automatic without drilling it, right?
3) Can I use a modern timing chain and harmonic balancer with this crank?

Other threads have said that the early 273 cranks use a smaller "hub", "pilot", or "register".
4) Do all these terms all mean the same thing and refer to the big hole (technical term) in the crank rear flange? What term should I use?
5) When did they switch to the larger size?
6) Would running a newer engine/crank with a larger whatever it's called prevent me from using the original 904 or the stock converter?
7) Alternatively, can I run a newer converter with the 273 crank?

Answer any questions you want, any way you want. I can use all the information I can get on this!

1) Yes
2) You have to check
3) Yes, but you need the timing mark for the 64-69 engines Early A Small Block Chrysler E-Performance Harmonic Damper [MP-IB-816-CAN] : HarmonicDampers.com by BHJ Dynamics, Performance Harmonic Dampers, Harmonic Balancers and Specialty Crankshaft Vibration Dampers
4) 64-67 cranks have a smaller crank register and use a smaller snout on the torque convertor.
5) about 1968
6) No, but use a bushing to get to the right size register, since this centers the torque convertor/transmission input shaft with the crank center line.
7) No, this puts a rearward force on the torque convertor instead of letting the flex plate locate the torque convertor front to back.
 
Thanks to everyone who replied for the great information! I still have to decide if I want to go with a new crank, but at least now I understand the pros and cons.

One more question: new Mopar Performace forged crankshafts require a Magnum rear oil seal, according to the installation instructions. Will this Magnum rear seal fit in an early 273 block?
 
They were NOT changed in 67. Is that what you meant to say?

A 340 crank is not weighted (bob weights) the same as a 273, even though both engines "could" be neutral balanced (I did the opposite, decades ago...put a 273 crank in a 340)

@67Dart273
If you don't mind, could you go through what it took to run a 273 crank in a 340? I've got a 340 block without a crank and I also have a 273 Commando short block with the crank, rod, pistons that I'm not likely to use. Was thinking that I might use the 273 crank in the 340 with some light pistons, but I really have no idea what I'd be getting myself into. We can move to PM or a new thread but I'm sure others may be interested.
 
You can get lightweight hypers for your 340, that might be close to what the 273 crank wants. But adding counterweight gets pricey in a hurry
I think the 318 crank is a better candidate.
Also, have a look at your 273 crank. Mine looks like it was barely adequate for a 2bbl-273 never mind a basic 340.
 
@67Dart273
If you don't mind, could you go through what it took to run a 273 crank in a 340? I've got a 340 block without a crank and I also have a 273 Commando short block with the crank, rod, pistons that I'm not likely to use. Was thinking that I might use the 273 crank in the 340 with some light pistons, but I really have no idea what I'd be getting myself into. We can move to PM or a new thread but I'm sure others may be interested.

you dont need to add a bunch of weight weight to a 273 crank for 340 stuff, you need to REMOVE weight from the crank throws. Lighter aftermarket 340 pistons will fit on the plenty strong 273 rods. If you can get the stock 719 g 340 pistons aftermarket to 273-4 weight (569 g) your good to go.
 
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