Heads/engine swap

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Sparky

Sparky

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Hey guysngals, been here forever but have not posted in a long time.
Preparing to remove the numbers motor in the fish and putting a 73 340 that has had some work done,pistons.,cam,valves?(not sure what is in there). Anyway this motor was chained down in the dart I got it from so I am thinking it is strong. What I am curious about are the heads. They are Z heads with the
casting number 3418915 under the valve cover. I have read previous threads from a few years back and I was wondering if anyone has new info on them. Seems to be the same or very similar to all the others (x, j and so on).
I have had a set of tti headers for quite a few years ready to go, looking forward to swapping , been lucky not to blow the original motor all these years. I think it should be straight forward swap but I am just wondering if there is anything else I should be aware of?...
Thanks
Sparky
 
It’s a letter head, there basically all the same.
 
Sparky said:
Hey guysngals, been here forever but have not posted in a long time.
Preparing to remove the numbers motor in the fish and putting a 73 340 that has had some work done,pistons.,cam,valves?(not sure what is in there). Anyway this motor was chained down in the dart I got it from so I am thinking it is strong. What I am curious about are the heads. They are Z heads with the
casting number 3418915 under the valve cover. I have read previous threads from a few years back and I was wondering if anyone has new info on them. Seems to be the same or very similar to all the others (x, j and so on).
I have had a set of tti headers for quite a few years ready to go, looking forward to swapping , been lucky not to blow the original motor all these years. I think it should be straight forward swap but I am just wondering if there is anything else I should be aware of?...
Thanks
Sparky
Click to expand...
As far As the engine swap goes ,should be straight forward , No changes from 68 to 73.?
 
Sparky said:
As far As the engine swap goes ,should be straight forward , No changes from 68 to 73.?
Click to expand...
While I am at it I want to prep the Koodaa for pulling the motor before I call the boys over to assist. Been a long time for me so I am wondering if there is such a thing as a list/steps to take for pulling the motor. I like to record what I am doing as well as label as I go. Want to stay organized and do it right the first time.
Thanks.
 
Sparky said:
Hey guysngals, been here forever but have not posted in a long time.
Preparing to remove the numbers motor in the fish and putting a 73 340 that has had some work done,pistons.,cam,valves?(not sure what is in there). Anyway this motor was chained down in the dart I got it from so I am thinking it is strong. What I am curious about are the heads. They are Z heads with the
casting number 3418915 under the valve cover. I have read previous threads from a few years back and I was wondering if anyone has new info on them. Seems to be the same or very similar to all the others (x, j and so on).
I have had a set of tti headers for quite a few years ready to go, looking forward to swapping , been lucky not to blow the original motor all these years. I think it should be straight forward swap but I am just wondering if there is anything else I should be aware of?...
Thanks
Sparky
Click to expand...
 
Quick question. Wondering what carb you
would run on a 340 with aprox 400 hp, air gap,headers, 650 cfm,750.? Any thoughts would be appreciated.
Thanks
.
 
Sparky said:
As far As the engine swap goes ,should be straight forward , No changes from 68 to 73.?
Click to expand...
No external changes...... EXCEPT for one BIG thing: The flexplate/torque coverter or flywheel IS neutral balanced for the '68, but is NOT neutral balanced for the 73'; the late 340's have an offset weight to provide the extra external balance needed for the cast crank in the '73. Which assumes that your motor has the later cast crank in it, and has not been rebalanced for internal balance only..... neither of which it sounds like you know for sure.

So whether you need the external balance weight on the flexplate/torque converter or flywheel is unknown. That is a big deal.

Internally, the '73 is a significantly lower compression motor than the '68. But again, it sounds like you don't really know what is in there. Hmmmmm....
 
Sparky said:
Quick question. Wondering what carb you
would run on a 340 with aprox 400 hp, air gap,headers, 650 cfm,750.? Any thoughts would be appreciated.
Thanks
.
Click to expand...
650 should be enough and could give better throttle response on the street. Lots of 750s on these engines too, but might need extra tuning for lower rpm efficiency.

There are calculators that tell you how many cfm your engine requires, and it is typically a smaller carb than you would think.
This video is in the HOW TO ARTICLES section and has some pretty good info in it. PICKING THE RIGHT CARBURETOR SIZE FOR YOUR MOTOR
 
nm9stheham said:
No external changes...... EXCEPT for one BIG thing: The flexplate/torque coverter or flywheel IS neutral balanced for the '68, but is NOT neutral balanced for the 73'; the late 340's have an offset weight to provide the extra external balance needed for the cast crank in the '73. Which assumes that your motor has the later cast crank in it, and has not been rebalanced for internal balance only..... neither of which it sounds like you know for sure.

So whether you need the external balance weight on the flexplate/torque converter or flywheel is unknown. That is a big deal.

Internally, the '73 is a significantly lower compression motor than the '68. But again, it sounds like you don't really know what is in there. Hmmmmm....
Click to expand...
 
Pulled the motor and trans from my 70 dart then sold the car as a roller, this will now go into the fish. I do know the motor has speed pro pistons as well as a cam ,valve work. Tracked down the fellow who built the motor and according to him it is pretty strong. Few years back so I do not remember all.. Will find out soon.
Thanks
 
gzig5 said:
650 should be enough and could give better throttle response on the street. Lots of 750s on these engines too, but might need extra tuning for lower rpm efficiency.

There are calculators that tell you how many cfm your engine requires, and it is typically a smaller carb than you would think.
This video is in the HOW TO ARTICLES section and has some pretty good info in it. PICKING THE RIGHT CARBURETOR SIZE FOR YOUR MOTOR
Click to expand...
Thank you,very handy. I guess this 950 cfm Holley ultra I have on my bench is a little too big huh, lol
 
If it's the SpeedPro's, then that should have fixed the later 340 lower compression situation. The situation with the crank is the same if it is the '73 cast crank; you need an external balance weight out back (and up front in the damper, like with the stock later model 340 dampers) to complete the balance.... unless it was modified/re-balanced for internal balance.
 
750DP or any TQ, I tried smaller but they sucked, especially vacuum secondary carbs. But it has a lot to do with your driving style, transmission,and rear gear. Since you already have the 950, just kidding lol.
 
nm9stheham said:
If it's the SpeedPro's, then that should have fixed the later 340 lower compression situation. The situation with the crank is the same if it is the '73 cast crank; you need an external balance weight out back (and up front in the damper, like with the stock later model 340 dampers) to complete the balance.... unless it was modified/re-balanced for internal balance.
Click to expand...
A lot of that is beyond me should be ok motor and trans from dart to cuda.
 
Sparky said:
I really wonder if it would be worth trying,literature says way too big.
Click to expand...
I would try it. You arent out anything if it doesnt. If its an early 950 hp it doesnt flow much over 850 anyway.
 
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