mudpup226
Member
Have a chance to buy a 73 340 is a good motor to start with put in a318 dart swinger . Where the heads any good for this year and such thanks for your replies. Kyle
340
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bobs340dartsport
Well-Known Member
a 1973 340 came with 1.88 valve "J" heads, heads would work pretty good on a 318 as is.
for the 340: You should upgrade to 2.02" valve "J" heads or maybe have those heads reworked for the larger valves.
If you are doing a lot of street driving with the car, you should have hardened exhaust seats installed in them so they will live with modern lead free fuels.
Bob
for the 340: You should upgrade to 2.02" valve "J" heads or maybe have those heads reworked for the larger valves.
If you are doing a lot of street driving with the car, you should have hardened exhaust seats installed in them so they will live with modern lead free fuels.
Bob
GTXperience
Orig Stealth Mod
Depending on its intended use, consider that '73 is the cast crank year. I believe I heard that some early '73s still had a steel crank but am not 100% sure. Good luck.
perfacar
Well-Known Member
hi, look and see if it has 587 casting heads. if it does, install sst 1.88 valves.
this head will flow quite well with a 1.88 valve. it has higher port flow velocity,
less shrouding around the intake valve also, over a 2.02 valve!!! i've seen 2.02 put in these heads and lose velocity and flow in the midlift range. which is where the valve spends more time at, opening and closing. i've tested this on a flow bench. you can use regular seats with same face angles and keep the seats from pounding out. make then little wider.
this head will flow quite well with a 1.88 valve. it has higher port flow velocity,
less shrouding around the intake valve also, over a 2.02 valve!!! i've seen 2.02 put in these heads and lose velocity and flow in the midlift range. which is where the valve spends more time at, opening and closing. i've tested this on a flow bench. you can use regular seats with same face angles and keep the seats from pounding out. make then little wider.
DERICKS
Well-Known Member
The 73 340 is a great starting point for to throw in a DArt or any car for that matter. Dont let it get away cast crank and small valves aside they are not making em anymore and you can always upgrade it.
bobs340dartsport
Well-Known Member
all 1973 340's were cast crank external balance engines, early 1972 340's came with steel cranks.
Do not worry about this, you can build a very good street performance or street/strip engine out of a cast crank 340.
Rebuild the short block, upgrade the heads to 2.02 intake valves with 1.6 exhaust valves with hardened seats (I am not sure if the '73 "J" heads are hardened). install your preferred induction system, cam, exhaust and hang on!!
Before you invest much into this engine, verify it is stock bore, boring 340's beyond .030 can be risky business. You will need to sonic check a 340 block to verify it can be bored to a diameter over 4.070" bore. If the engine is already .030 over with lotsa of miles then there might not be enough material left in the block to bore it .060 over.
Bob
Do not worry about this, you can build a very good street performance or street/strip engine out of a cast crank 340.
Rebuild the short block, upgrade the heads to 2.02 intake valves with 1.6 exhaust valves with hardened seats (I am not sure if the '73 "J" heads are hardened). install your preferred induction system, cam, exhaust and hang on!!
Before you invest much into this engine, verify it is stock bore, boring 340's beyond .030 can be risky business. You will need to sonic check a 340 block to verify it can be bored to a diameter over 4.070" bore. If the engine is already .030 over with lotsa of miles then there might not be enough material left in the block to bore it .060 over.
Bob
perfacar
Well-Known Member
hi, the 340 already has 1.6 exhaust valves from the factory!! for most use ,hardened seats are not required!! if you're going to use it in a truck, then ,yes. the 340 block will take a .040 over bore easily, most will also go .060 without any problems. the 1.88 valve will provide more port velocity for street performance, which gives better throttle response.
DERICKS
Well-Known Member
Mines .040 over right now witha sleeve in one cylinder and did check ok out to .060. I agree that all blocks should be sonic tested for wall thickness to be safe.
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