340 Parts Interchangeability??

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cosgig

cosgig

MoBro Inc.
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Howdy all, I have a couple questions about the interchangeability of parts from one 340 to another. Heres the details...

I have a 1969 340 block and crank that was given to me by my engine builder a couple years ago. It was sent in about 10 years ago and never picked up. It has been hot tanked but thats about it. I also have a 1973 340 motor complete but is locked up and needs to be dis-assembled and gone through. My question is this...

Can I use all of the interior parts from the 73 on the 69 motor, parts such as the main caps, rods and any other parts that the 69 is missing, which is pretty much everything. I know the 69 has a forged crank and the 73 is cast, and that's where my question originates. I would of course have it align bored and completely gone through, but I just am not sure the parts are interchangeable. Any 340 guru's out there know for sure??

Thanks for any input received!! Geof
 
you can take the internals and use them all in the 69 340.

but if you use the 69 steel crank, you must also use the steel crank harmonic balancer.
 
Yup plus if you swap main caps from one block to another, the one you use will need to be line bored or honed.
 
The balancer is not a problem, except that I don't have one. What I am trying to do is use the 69 motor and a 904 trans in one of my early A's, and I know that the cast crank 340 motor was coupled to a 727, which is a tight fit in the early A's.

I guess that begs another question...is the 340 cast crank motor also balanced at the converter?? The flex plate looks to be standard issue, but I gave the trans and converter to my brother to use in his race car. I'm sure he's not using the converter, but I don't want it anyway as I don't want to use a 727.

Thanks for the replies guys!! Geof
 
Hi Cosgig,

I recommend you go to your nearest Chrysler dealer and purchase the Mopar Engine Modification handbook. It will answer a lot of your questions and satisfy for yourself what is right. Later on, consider one for chassis performance book too.

During your teardown of the 340 cast crank motor, I would check for crank alignment and straightness to avoid frustration and $ later. Remove the caps and crank, clean the bearings if they look okay, remove the rear main seal and trash. Add well, oiled upper bearing shells at #1 and #5 journals. install crank. Add #1 and #5 caps and torque to spec. Check #3 journal with dial indicator. Turn crank over with torque wrench. The ideal reading should .0015-.002, .004 max. Check with dial indicator at #1 and #5 journals. Dial indicator reading should be no more than .003". P87, paragraph 3, engine modification book.


Next, add all bearing shells plus crank and retorque caps to spec again. Turn the crank over with torque wrench. After breaking bearing friction, crank should turn over 360 degrees with index finger and less than 15 ft-lbs of torque. 73 crank then should be okay for reuse elsewhere.

P 101, in 1972 all the "LA" engine dampers were changed. The newer dampers have a revised fan drive pulley bolt pattern.
Tom Oliver
 
If you use the cast crank you will need the correct balancer and flex plate/convertor. They are external balanced and if you just throw some parts together you are almost garenteed to have a vibration.
 
Use the 69 crank, align, summit or what ever balancer. Question is what rods and pistons are you using?
 
Get yourself an SFI balancer, because they don't come apart (at least I've never seen that happen, regular ones seen it happen to many times to count). I'd also recommend an SFI flexplate/flywheel. Rather do it once then over again.
 
Hey everyone, I want to use the 69 block and steel crank, the main caps from the cast crank motor, the rods from the cast crank motor, and buy new pistons. The 69 block is already .030 over so I would need to have it cut and fit with new pistons anyway, but I thought I could use the rods and caps from the 73. I have a couple balancers around from other motors.

What I am not sure of is whether the cast crank 340 motor is also balanced at the converter. I know it is at the balancer, and I think I just read here somewhere that there is currently no way to use a 904 with a cast crank 340. According to what I read, B&M doesn't make an offset balanced flexplate for a cast crank 340 to mate to a 904, and the 360 one won't work. There is also no offset balanced torque converter being produced for the cast crank 340 to 904, and only a mention of a weight kit available once upon a time in the old Direct Connection catalog.

The only reason I would even bring up the above point is that the cast crank motor I have is standard bore and low miles. and that was going to be my project motor until this little prediciment came up. And with the 69 block and crank I was looking to use parts from both motors and achieve a zero balance motor that I could just hook to a 904 and go!! Does that make sence?? Geof
 
Geof, the '73, 340 is an external balanced engine while the 69, 340 is an internal balanced engine. IF you use the '73 cast crank, you will have to do 1 of the following.

1. Re-use the harmonic balancer up front and the torque converter from the 904 to re bolt up to the 904 without issue. External balance.

2. With use of the cast crank from the '73, purchase a neutral balancer for up front and likewise for the converter made to go to a 904. Internal balance the assembly.

Are you looking for new main caps rather than re-use the old ones. I found a set for sale.
There the 4 bolt ductile caps from MP.
http://marketplaceadvisor.channelad...ail.aspx?sid=1&sfid=92390&c=411768&i=26152726
 
He want to put a steel crank and a generic balancer in a 73 block. Should not be a problem if the caps plasti-gauge. Pistons and rods should be the same, every forged 340 was neutral balanced. Crank to rods and pistons, balancer was a neutral balance (same as a 318 balancer) and the convertor was neutral. Theory behind that was all those "0"s put together would still add up to "0". So get a forged crank 273/318-3/340 balancer, and a neutral convertor and youll be set.
 
1970Duster said:
Get yourself an SFI balancer, because they don't come apart (at least I've never seen that happen, regular ones seen it happen to many times to count). I'd also recommend an SFI flexplate/flywheel. Rather do it once then over again.
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