340 cam, converter

71_Duster

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Car is pretty much a Frankenstein. Originally 71 318 duster. Was my brother’s since late 70’s and swapped in a 340 from a 68 barracuda. Rear from a 73, A body(3:55 posi). I believe it has a 904 3spd transmission. A friend of his back in the day out a high lift cam 850 carb which made no sense. As I grew up learning about cars in general I’ve done some work to it in time. As he’s getting older, I want to build a solid street able motor. The 68 340 ran just fine before engine was removed. Plan on taking heads(x heads) and inspecting. It does not have the hardened seats and have read that people still run unleaded gas and not worry. Then again if I’m going to replace seats with hardened and springs/retainers and possible guides if needed might as well just get an aftermarket? Any recommendations on brands? If able to stay with stock seats, obviously I’d change springs and check guides. Can anyone recommend a cam with either stock X head or cam/head combo. Has an edelbrock rpm intake manifold and I believe last 650 Holley carb which replaced the 850 which it used to have. Is there a cheap alternative to the 904 that would fit stock location and transfer of parts or just build the 904? Any recommendation for converter? I know 727 are hard to come by. Would a 46re from a 2wd ram fit in stock location of 71 duster? Any help on recommendation for replacement parts such as head gaskets, head bolts. Cam springs. As for lifters are hydraulic flat tappets better than solid lifters? I’ve been reading lately as of brand new cam/ lifter failures from cheap material regardless where it’s bought.
 

ch1ll

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Thats alot of what’s and if’s. Dig deep to decide what you expect performance wise what you want with how you intend to use it. Then follow a proven combination of parts that others have used.
 

krazykuda

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Car is pretty much a Frankenstein. Originally 71 318 duster. Was my brother’s since late 70’s and swapped in a 340 from a 68 barracuda. Rear from a 73, A body(3:55 posi). I believe it has a 904 3spd transmission. A friend of his back in the day out a high lift cam 850 carb which made no sense. As I grew up learning about cars in general I’ve done some work to it in time. As he’s getting older, I want to build a solid street able motor. The 68 340 ran just fine before engine was removed. Plan on taking heads(x heads) and inspecting. It does not have the hardened seats and have read that people still run unleaded gas and not worry. Then again if I’m going to replace seats with hardened and springs/retainers and possible guides if needed might as well just get an aftermarket? Any recommendations on brands? If able to stay with stock seats, obviously I’d change springs and check guides. Can anyone recommend a cam with either stock X head or cam/head combo. Has an edelbrock rpm intake manifold and I believe last 650 Holley carb which replaced the 850 which it used to have. Is there a cheap alternative to the 904 that would fit stock location and transfer of parts or just build the 904? Any recommendation for converter? I know 727 are hard to come by. Would a 46re from a 2wd ram fit in stock location of 71 duster? Any help on recommendation for replacement parts such as head gaskets, head bolts. Cam springs. As for lifters are hydraulic flat tappets better than solid lifters? I’ve been reading lately as of brand new cam/ lifter failures from cheap material regardless where it’s bought.


First, welcome to FABO...
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Welcome to FABO.gif


for cam, you need to decide on what you are going to do with the car and then that will determine what size cam to choose... The cam will determine what size/rate springs will be needed...

Solid lifters will have to be adjusted periodically, hydraulics don't...

We worked with Oregon cams to make a reproduction 68 340 4 speed cam which is one step above the stock 340 automatic cam which would be a good choice for a street/strip engine:

Reproduction 340-4 Speed Cam


I ran an engine without hardened exhaust seats and the valves beat the **** out of seats and sunk the valves within 10,000 miles without lead or lead substitute in the gas... --->>> I recommend having hardened seats installed on the exhaust valves.... Replace the guides if they are worn...

Small block 727's aren't hard to come by, keep an eye out for one or place a wanted ad on here and wait for replies.... 360's have a different balance than the 318/340 make sure to get the proper balanced torque converter for your application...
 

71_Duster

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Thats alot of what’s and if’s. Dig deep to decide what you expect performance wise what you want with how you intend to use it. Then follow a proven combination of parts that others have used.
Just a street
 

71_Duster

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Def a street vehicle with a great improvement on the powerband. Was reading and looking at 2200-2500 powerband. Was quoted $700 for a refresh on X heads. Was debating if I’m going to end up paying that much to just get aftermarket, but not sure if overkill and what brands work well with 340’s. I am looking for reliability since I’m building it for him just want a healthy 340 with good power.
 

BrianT

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A mild cam would be fine for the street. There are numerous vendors who produce modern designs to work with today's gasoline. I would have the heads inspected before sinking any money into them. You can stick a lot of money into an old head (surface, guides, seats, springs, valve(s), etc). By the time you get the bill for them, you'll realize that you could have sold the stock X heads to someone building a period correct engine, and used the money towards a good set of aftermarket heads. A rebuilt 904 will handle almost any power level you throw at it if built using the right parts.

A good cam/spring combo and the right convertor will wake that old 340 up. Good luck!
 

mad dog

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just a thought.. you might want to check out Rustyratrod guide to hot rod bliss... to me he is spot on.
 

PG Duster

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I changed my 904 to a 727 in my 1974 Duster, you will need to get your drive shaft modified to fit the 727, the 904 trans cross member will fit. I had a new drive shaft built.

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5BD67FB2-3B68-4301-89D1-55880C0C89D8.jpeg
 

furrystump

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Welcome aboard! Keep the 904, weighs less, less parasitic loss and will live behind a “street” 340 easily. Search 904 compared to 727. or how strong is a 904? A couple of pretty cheap upgrades and a good valve body and the 904 will be fine and a bit safer than a 727. You should really determine if the performance goals will continue to go up or it is, “put it in and drive it until it needs to be rebuilt” I think the cost to rebuild a set of cast iron heads is just not really wise. Save up, and go aluminum. Sell the X’s to a resto guy or class racer. Let them sink the money into a 50 year old, so-so casting. At an ABSOLUTE minimum, it’s 35+ lbs off the nose. The LAST thing you choose is your converter.
 

71_Duster

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Welcome aboard! Keep the 904, weighs less, less parasitic loss and will live behind a “street” 340 easily. Search 904 compared to 727. or how strong is a 904? A couple of pretty cheap upgrades and a good valve body and the 904 will be fine and a bit safer than a 727. You should really determine if the performance goals will continue to go up or it is, “put it in and drive it until it needs to be rebuilt” I think the cost to rebuild a set of cast iron heads is just not really wise. Save up, and go aluminum. Sell the X’s to a resto guy or class racer. Let them sink the money into a 50 year old, so-so casting. At an ABSOLUTE minimum, it’s 35+ lbs off the nose. The LAST thing you choose is your converter.


Thank you for response. I’ve been researching and read about the lunati voodoo 60402 with comp 901 springs. I’ve also read not a good cam if you plan on running brakes with a booster. Not much info about aftermarket heads considering trickflow are a bit better than the edelbrock and don’t really want to get in the expense of indy heads. Unless there’s a cheaper alternative upgrade from stock x heads. This def won’t be a racer, just nice cruiser to enjoy, at the most want a little power to merge on highways etc. Has 3:55 gears. Wouldn’t mind mimicking someone else’s 340 build that’s not fairly expensive but delivers reliability and a bit performance. The original cam/converter were all off and it ran terribly. Just want to make sure I don’t spend on things that are unnecessary since it’s a gift for my brother and I have my family to look after. Thank you all for replies.
 
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