273 to 340 swap in 64 cuda auto advise needed

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guido

guido

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Ok, I need help and advise.
Found a 1974 340. What do I need to do to put it in my car. I know the passenger side motor mount is different. Here are some of my starting questions.
1. Is the 74 340 internally balanced.
2. What torque converter is needed
3. What year cast exhaust 340 manifolds will clear my borgeson steering box and steering shaft.
Anything else I should know.
Oh my 65 273 is a 4bbl and it has aftermarket AC.

20190512_110416.jpg
 
I swapped out a 65 273 for a 69 340 in my 64 Dart, I had power steering, no AC and a 833 gearbox. I could not get any iron manifolds to work mostly because of the steering and had to go with dougs headers and a uv joint from flaming river to get the steering to work.

Talk to @waggin, He did most of the work.

You will need to upgrade your radiator as the 273 rad will not be enough.

Also the hood clearance is really tight.

As for the torque converter that is more related to your CAM and gear ratios. You will need at least an 8 3/4.
 
trapster said:
I swapped out a 65 273 for a 69 340 in my 64 Dart, I had power steering, no AC and a 833 gearbox. I could not get any iron manifolds to work mostly because of the steering and had to go with dougs headers and a uv joint from flaming river to get the steering to work.

Talk to @waggin, He did most of the work.

You will need to upgrade your radiator as the 273 rad will not be enough.

Also the hood clearance is really tight.

As for the torque converter that is more related to your CAM and gear ratios. You will need at least an 8 3/4.
Click to expand...

Ty for your reply
"Waggins" inbox is full, I'm not surprised Lot of the members I've been referred to have full inboxes.
Hopefully I'll get more replies to thus thread checking Doug's headers now
 
guido said:
Ok, I need help and advise.
Found a 1974 340. What do I need to do to put it in my car. I know the passenger side motor mount is different. Here are some of my starting questions.
1. Is the 74 340 internally balanced.
2. What torque converter is needed
3. What year cast exhaust 340 manifolds will clear my borgeson steering box and steering shaft.
Anything else I should know.
Oh my 65 273 is a 4bbl and it has aftermarket AC.

View attachment 1715847657
Click to expand...
In order:
1.) There is no 1974 340. 1973 was the last model year for the 340.
Late '72 and '73 340 were externally balanced, '68 - early '72 were internally (neutral) balanced. Also, be aware that the late 340s had a unique external balance, different from both the LA 360 and the Magnum 5.9. We'll assume you have the late 340.
2.) Ideally, a custom torque convertor will be needed. The 340 came with a 727 and you have an early 904, which has a different input spline count and different "nose" diameter than later 904s. In a pinch, you can use your 273 convertor IF you use an adapter bushing in your crankshaft hub register (available from several sources, one of which is member @Charrlie_S , who makes and sells these, check for availability) and have the convertor rebalanced for your 340. As an alternative, you may be able to use the B&M flexplate 10235 instead of rebalancing the TC, but you may need to have it redrilled for the 904 TC, since it is for a 727 and not a 904. To my knowledge, nobody makes a 340 external balance flexplate for the 904.
3.) If you want manifolds, and have a Borgeson box, any of the A body 340 manifolds should fit. Early ones ('68-'71?) are slightly better flowing. This pic I stole from another thread- member @340duster340 appears to have done just that:
20211126_164503-jpg.jpg

You could also *probably* get away with Magnum manifolds, which may need a bit of clearance work. Your results may vary.
guido said:
I know the passenger side motor mount is different.
Click to expand...
Actually, both sides are different. The driver's side 273 mount can be used on the 340 by adding a ~5/8" spacer between the block boss and the mount bracket on the top rear mounting lug.
On the passenger side, two bolts will line up (and I have seen cars running just those two bolts), but a triangular piece needs to be welded on and drilled for the third mounting lug. Sorry, can't come up with a pic of that at the moment, maybe someone else has one.
Also, you will need to use the kickdown linkage from your '64, and a 340 throttle cable bracket.
You will need a different radiator, as the newer 340 has it's inlet on the opposite side.
If you're keeping your AC, you may need to source later model brackets and pullies to mount it on the 340.
The late 340s used electronic ignition- you'll need a conversion kit to run it on your '64.
 
Last edited:
guido said:
Ok, I need help and advise.
Found a 1974 340. What do I need to do to put it in my car. I know the passenger side motor mount is different. Here are some of my starting questions.
1. Is the 74 340 internally balanced.
2. What torque converter is needed
3. What year cast exhaust 340 manifolds will clear my borgeson steering box and steering shaft.
Anything else I should know.
Oh my 65 273 is a 4bbl and it has aftermarket AC.

View attachment 1715847657
Click to expand...
If you internally balance that 340 (with either a forged crank or MalloryMetal) you can use the 273 balancer along with all the other 273 parts (brackets, pulleys, timing cover, water pump, etc) to convert the 340 over to fit your car without having to reinvent the wheel. That would help with the torque converter too. Just get the crank bushing reducer for your converter button. Your aftermarket A/C should fit fine depending on what you use for an intake/carb(s) setup. Same with hood clearance. You'd want to rebuild the 904 to beef it up a bit to handle the extra horsepower, along with a better rear axle assembly and better than stock brakes. Engine mounts and exhaust have already been mentioned.
 
cudamark said:
If you internally balance that 340 (with either a forged crank or MalloryMetal) you can use the 273 balancer along with all the other 273 parts (brackets, pulleys, timing cover, water pump, etc) to convert the 340 over to fit your car without having to reinvent the wheel. That would help with the torque converter too. Just get the crank bushing reducer for your converter button. Your aftermarket A/C should fit fine depending on what you use for an intake/carb(s) setup. Same with hood clearance. You'd want to rebuild the 904 to beef it up a bit to handle the extra horsepower, along with a better rear axle assembly and better than stock brakes. Engine mounts and exhaust have already been mentioned.
Click to expand...
It's a 1971 340 so it's internally balanced
 
Professor Fate said:
In order:
1.) There is no 1974 340. 1973 was the last model year for the 340.
Late '72 and '73 340 were externally balanced, '68 - early '72 were internally (neutral) balanced. Also, be aware that the late 340s had a unique external balance, different from both the LA 360 and the Magnum 5.9. We'll assume you have the late 340.
2.) Ideally, a custom torque convertor will be needed. The 340 came with a 727 and you have an early 904, which has a different input spline count and different "nose" diameter than later 904s. In a pinch, you can use your 273 convertor IF you use an adapter bushing in your crankshaft hub register (available from several sources, one of which is member @Charrlie_S , who makes and sells these, check for availability) and have the convertor rebalanced for your 340. As an alternative, you may be able to use the B&M flexplate 10235 instead of rebalancing the TC, but you may need to have it redrilled for the 904 TC, since it is for a 727 and not a 904. To my knowledge, nobody makes a 340 external balance flexplate for the 904.
3.) If you want manifolds, and have a Borgeson box, any of the A body 340 manifolds should fit. Early ones ('68-'71?) are slightly better flowing. This pic I stole from another thread- member @340duster340 appears to have done just that:
View attachment 1715847803
You could also *probably* get away with Magnum manifolds, which may need a bit of clearance work. Your results may vary.

Actually, both sides are different. The driver's side 273 mount can be used on the 340 by adding a ~5/8" spacer between the block boss and the mount bracket on the top rear mounting lug.
On the passenger side, two bolts will line up (and I have seen cars running just those two bolts), but a triangular piece needs to be welded on and drilled for the third mounting lug. Sorry, can't come up with a pic of that at the moment, maybe someone else has one.
Also, you will need to use the kickdown linkage from your '64, and a 340 throttle cable bracket.
You will need a different radiator, as the newer 340 has it's inlet on the opposite side.
If you're keeping your AC, you may need to source later model brackets and pullies to mount it on the 340.
The late 340s used electronic ignition- you'll need a conversion kit to run it on your '64.
Click to expand...

motor mount blueprint

16519AA1-EF65-4E6E-9D10-4609803744FE.png
 
Yes I did , not on an engine stand yet just on a floor dolly,
Spun over easy oil looked new
But the outside looks 50 years old.
Let's hope all looks good inside,
Supposed to be low miles well see
 
guido said:
Yes I did , not on an engine stand yet just on a floor dolly,
Spun over easy oil looked new
Shoveling flippin snow
But the outside looks 50 years old.
Let's hope all looks good inside,
Supposed to be low miles well see
Click to expand...
 
The 273 intake and exhaust manifolds will bolt on to the 340, but, the flow is not the greatest, and sometimes it's hard to keep exhaust manifold gaskets from blowing out.
 
In dead from shoveling snow for 7 hours, so if I'm scatter-brained im sorry. I keep hearing there.are early model 340 driverside manifolds that will fit on my 64 cuda with power steering. I have a picture of one installed but no definite year or p/n.yet I hate to be buying 340 manifolds willy nilly. I'm afraid I'd end up with a collection. I am convinced someone here knows
It may just take a while. I can't be the 1st one to do this
I didn't know the 273 intake will bolt up. It's good to know. It will simplify linkages if I go that way.
I do have to say though there are a lot of great people here on this site
 
guido said:
In dead from shoveling snow for 7 hours, so if I'm scatter-brained im sorry. I keep hearing there.are early model 340 driverside manifolds that will fit on my 64 cuda with power steering. I have a picture of one installed but no definite year or p/n.yet I hate to be buying 340 manifolds willy nilly. I'm afraid I'd end up with a collection. I am convinced someone here knows
It may just take a while. I can't be the 1st one to do this
I didn't know the 273 intake will bolt up. It's good to know. It will simplify linkages if I go that way.
I do have to say though there are a lot of great people here on this site
Click to expand...
If your 273 is a '64-'65 model, the intake will NOT bolt up to the 340. Besides the port mismatch, the intake bolt angle is different on the early 273 than on '66 and later smallblocks.
Since your 340 is a '71, that simplifies things quite a bit from my earlier post. The 273 torque convertor should bolt up with just the crank adapter bushing.
Did your 340 come with an intake or exhaust manifolds? The fit of the 340 exhaust manifolds is the same, early or late- as long as they are A BODY manifolds. Anything else is at your own risk. Just like the pic in my previous post, 340duster340 has early 340 manifolds fitted with the Borgeson box. Drop him a PM if you need particulars. MUCH better breathing than the 273 exhausts.
 
Professor Fate said:
If your 273 is a '64-'65 model, the intake will NOT bolt up to the 340. Besides the port mismatch, the intake bolt angle is different on the early 273 than on '66 and later smallblocks.
Since your 340 is a '71, that simplifies things quite a bit from my earlier post. The 273 torque convertor should bolt up with just the crank adapter bushing.
Did your 340 come with an intake or exhaust manifolds? The fit of the 340 exhaust manifolds is the same, early or late- as long as they are A BODY manifolds. Anything else is at your own risk. Just like the pic in my previous post, 340duster340 has early 340 manifolds fitted with the Borgeson box. Drop him a PM if you need particulars. MUCH better breathing than the 273 exhausts.
Click to expand...
 
Here are some pics of the 71 340
Pretty sure this was in a 71charger with a standard transmission, no exhaust manifolds

662919791.jpg


662919872.jpg


662919844.jpg
 
The diagram in post #7 is not correct for a 64-66 273 bracket. It's in the Mopar Performance manual since forever, but it's wrong. That's a 67-up bracket. For 64-6 bracket, just fab a triangle that matches the opposite side and weld it and you'll be good to go. Pic:

20200816_172540.jpg


Driver's side bracket, you can fab a spacer, or just use a few washers. Viz:

20200223_232128.jpg


If you use the 71 340 water pump, pulleys and brackets, you'll have to move your lower radiator hose opening to the opposite side, and you won't have room for a clutch fan. Or - just use the 273 timing cover, pulleys and water pump and keep your original radiator and you'll have room for a clutch type fan. The original 273 water pump used a smaller pipe for the crossover hose, but modern replacements are machined for the larger 340 style hose, with a spacer to use for the smaller 273 hose.

20180403_100857.jpg


20180403_100935.jpg


As for exhaust, I've run 340 manifolds in the past, both early and late. Late (i.e., 71-73) center dump fits quite well on the passenger side, early barely clears on that side (and may not on some, given dimensional vagaries back in the day). Driver's side interfered in my car with the steering joint. Doesn't in every one. I fixed mine by using a manual steering gear box, power steering column, and an adapter to mate the two. That moved the joint out of the way. Since you are running a Borgeson box, you may not have any clearance problems, don't know, never tried that. Routing the exhaust downwind of the driver's side manifold is another issue. In my 4-speed car, the only way I saw was to run the pipe between the torsion bar and the frame. Others (perhaps with automatic trans) have successfully tried a different route.

I have TTI headers now, but I can tell you that installing them is a huge job, given the various things that have to be moved out of the way (like fuel and brake lines, wiring, etc) and clutch linkage clearance issues. Can all be fixed, but they are not a straight bolt in. Also not cheap, but I sold my early hi-po 340 exhaust manifolds for enough money to pay for the TTI's. Your 71 manifolds probably aren't worth as much, but could still defray much of the cost of a set of headers, TTI or Doug's.
 
Last edited:
I found this LH drivers side manifold on ebay
Anyone know if this will fit my 64 cuda

Screenshot_20220108-114440_eBay.jpg
 
Your 340 appears to still have it's factory TQ 4bbl. intake manifold, that's a very good manifold, and the only appreciable thing you would gain with a different manifold is lighter weight. Having the 4bbl. throttle bracket is another bonus, and for the transmission kickdown you should be able to make the one from your 273 work.
 
You should be able to make a few extra bucks selling that idle solenoid and bracket too.
 
OK it's been a while since I replied on this post. The day before I got the rebuilt '71 340 motor from the shop. My wife and I got t-boned by a girl on a cell phone who ran a stop sign while we were stopped dead in traffic. 23K worth of damage to my car. The body work is now 40% done so I started installing the 340 before they finish the car.
I am going to use the stock 273 logs for ease of installation for now. Motor mounts were purchased form Norm's speed shop. I went with an Edelbrock aluminum intake, and Edelbrock AWS carb.
After removing the radiator, it was a tiny Nothern radiator for a mustang mickey moused in. I am considering a 3 row champion CC1635. need to check the dimensions for fit up before buying. The radiator cap on the northern radiator slightly hit the hood when closed. I am going to start another post for recommendations on a radiator.
 
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