Thread: best way to get 340

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whats the best way to get the most power out of a 340 with out spendin alot of money its for a 73 duster

nothing's cheap for mopar. cheapest you can do is find 360 heads from a pre '71 motor, intake/ carb/ mild cam and a set of headders.

Go to www.summit.com

Hooker headers HOK-5901HKr
Holley HLY-O-80457S (Has Ford auto kickdown, but electric choke)
Crane cams CRN 693902
Cloyes timing set CLO-9-3103
Edelbrock intake EDL-2176 or
Weind WND-8007
Altogether will set you back about $1200

I have a good used Edlebrock 2176 you can have for $100

Originally posted by Matt167
nothing's cheap for mopar. cheapest you can do is find 360 heads from a pre '71 motor, intake/ carb/ mild cam and a set of headders.

Hold onto the 340 heads, they'll flow better than 360 heads.

Originally Posted by techinspector1

Hold onto the 340 heads, they'll flow better than 360 heads.

....They are the same.

Originally Posted by sox

....They are the same.

I yield to your superior knowledge. Just repeating what I've been told by Mopar guys....larger valves in 340 heads, etc.....

Some 340 heads are better than the common 340-360 heads, bigger valves, etc. I don't have the info right in front of me but any Mopar hop-up book will give you the straight dope.

The 360 came out in '71. 340/360 heads were open chambered and cc'd between 68-75. 68-72 most of the 340s had the 2.02 intake valves and all340/360 heads had 1.60 exhaust valves. The exhaust ports and intake ports were the same. The 360 had 1.88 intake valves....the only diff.
In pre 73 340s they had forged cranks and pistons that sat out of the hole hence the higher compression. After 72 the 340's pistons sat in the hole that lowered the compression and also used a cast crank.

What year is your 340 mopar_man?.....also check out moparts.com all the mopar info you will ever need.

The 340 had specific heads from 1968-'70. '68-'69 and some '70 used the #2531894 "X" casting (so called for the large X cast near the spark-plug holes), which was, for a long time, considered the premier SBM cylinder head... until someone actually flow-tested the 3418915 heads, marked "U", "O" or "J" in the same spark-plug area and found that with the 2.02" intake valve used in '70-'71, flows identical to the "X" head on the intake side, and even better on the exhaust.

This 915 casting is also the same as used on the Challenger T/A and 'Cuda AAR 340 Six Pack engines, though they used revised pushrod-hole locations and therefore offset intake rockers so that the "pushrod humps" could be ground out of the intake ports. This very-same casting (with standard pushrod holes) was used in 1971-'72 on every 360 built, though on the 360 application it used a 1.88" intake valve but shared the 1.60" exhaust with the 340. All '71-'72 360s were two-barrels, and were C-body and truck only in those years, though a single '71 Dart mysteriously got built with one. Regardless, the 1.88"-valved "J" heads are identical castings to the 2.02" versions, needing only the seats enlarged and the bigger valves to be "340 spec" heads.

Starting in 1972, the 340 was phased down to the 1.88" valve used in the 360, but managed to hang on to its steel crankshaft. In '73, both the 340 and the 360 went to the far-inferior 3671587 (or simply "587") casting; it was a far cry from the 915 "J". It takes a lot of porting and an intake-valve increase to 2.02" just to get this head on par with the X or J heads. The '73 340 went to an iron crank and therefore uses a 1-year-only, 340-only dampener and flywheel (or converter, if your car doesn't have the right number of pedals )

The 340 went away at the end of the '73 model year, performance small-blocks then being based on the 587-headed 4v 360. Though the casting numbers changed over the years, the 360 head didn't change much; the minor revisions to the ports did worsen it as time passed but any 360 head can be made to perform pretty well if you pay someone, or have the patience, to port them.

Then, in 1989, we got a reprieve with the introduction of the best SBM head ever put on a production engine: the 308. This is a truck-only casting, used on 1989-'91 318s and 1989-'92 360s. Though it's only a 1.88" intake valve from the factory, opening it up to a 2.02" intake allows it to surpass the vaunted X and J castings, stock-for-stock. This was the head used on the early Mopar Performance 360 Commando crate engines (before the MP Magnum crates superseded it in the mid-'90s). Tons of these heads sleep quietly in a boneyard near you; I picked up a complete '91 B250 van 360 with a lifter tick for $150 from a nearby yard. One solid J casting will set you back that much these days (I've sold bare J castings for as much as $400 per pair).

A couple of caveats:

1. There are later 318 heads with an X or J cast into them, which I've only found on trucks. These are not the good 340/360 heads. Check the numbers, but unless the X or J is over 1" tall, keep looking.

2. The current rage among head shops is to try and sell you the "swirl port" 302 cylinder heads. First off, they're not swirl port, they're swirl chamber. Second, they're 318 heads, originally equipped with a 1.78"/1.50" valve combo. Yes, they will garner you nearly a point of compression due to their heart-shaped, closed combustion chambers... but opened up to 2.02"/1.60" valve and fully ported (and I mean, like $1200 worth of work here), they flow less than a stock 2.02" X/J/308 head. Oh, and the upsized valves destroy the swirl effect--this straight from a Chrysler engineer (not me) While compression is nice, it's fairly useless when there's nothing to compress: horsepower is all about airflow. So why the big push? Virtually every non-cop 318 from 1985-1989 (except '89 trucks) had these heads--there are a million out there. So, the shops push the compression aspect and folks eat it up. Magazines further embellish the myth, because these shops pay to advertise with them (the real money in magazines). Unless you're building a stump-pulling, trailer-towing truck motor, don't fall for it. If you don't believe me, then look under the hood of any '80s Mopar cop car with a 318: they all had later ("945"-casting) 360 heads, as well as 360 intake manifolds and carbs.

3. The Edelbrock Performer intake, while lighter, makes less power than any factory SBM iron four-barrel intake. It has smaller ports, so you'll feel an improvement off-idle in the seat of your pants, but in the middle and on the top end, you'll lose. The lighter weight doesn't account for the HP loss. I've seen the dyno runs and flow-tested them; numbers don't lie. Also, avoid the '70s-era Streetmaster and SP2P intakes like the plague; you can clog the ports with two fingers. Both were designed with towing and fuel mileage in mind and have no place on a performance engine.

That's all I can think of at the moment... I'm pooped. Anyone got a beer?

Originally Posted by Call_me_Doc

The 340 had specific heads from 1968-'70. '68-'69 and some '70 used the #2531894 "X" casting (so called for the large X cast near the spark-plug holes), which was, for a long time, considered the premier SBM cylinder head... until someone actually flow-tested the 3418915 heads, marked "U", "O" or "J" in the same spark-plug area and found that with the 2.02" intake valve used in '70-'71, flows identical to the "X" head on the intake side, and even better on the exhaust.

This 915 casting is also the same as used on the Challenger T/A and 'Cuda AAR 340 Six Pack engines, though they used revised pushrod-hole locations and therefore offset intake rockers so that the "pushrod humps" could be ground out of the intake ports. This very-same casting (with standard pushrod holes) was used in 1971-'72 on every 360 built, though on the 360 application it used a 1.88" intake valve but shared the 1.60" exhaust with the 340. All '71-'72 360s were two-barrels, and were C-body and truck only in those years, though a single '71 Dart mysteriously got built with one. Regardless, the 1.88"-valved "J" heads are identical castings to the 2.02" versions, needing only the seats enlarged and the bigger valves to be "340 spec" heads.

Starting in 1972, the 340 was phased down to the 1.88" valve used in the 360, but managed to hang on to its steel crankshaft. In '73, both the 340 and the 360 went to the far-inferior 3671587 (or simply "587") casting; it was a far cry from the 915 "J". It takes a lot of porting and an intake-valve increase to 2.02" just to get this head on par with the X or J heads. The '73 340 went to an iron crank and therefore uses a 1-year-only, 340-only dampener and flywheel (or converter, if your car doesn't have the right number of pedals )

The 340 went away at the end of the '73 model year, performance small-blocks then being based on the 587-headed 4v 360. Though the casting numbers changed over the years, the 360 head didn't change much; the minor revisions to the ports did worsen it as time passed but any 360 head can be made to perform pretty well if you pay someone, or have the patience, to port them.

Then, in 1989, we got a reprieve with the introduction of the best SBM head ever put on a production engine: the 308. This is a truck-only casting, used on 1989-'91 318s and 1989-'92 360s. Though it's only a 1.88" intake valve from the factory, opening it up to a 2.02" intake allows it to surpass the vaunted X and J castings, stock-for-stock. This was the head used on the early Mopar Performance 360 Commando crate engines (before the MP Magnum crates superseded it in the mid-'90s). Tons of these heads sleep quietly in a boneyard near you; I picked up a complete '91 B250 van 360 with a lifter tick for $150 from a nearby yard. One solid J casting will set you back that much these days (I've sold bare J castings for as much as $400 per pair).

A couple of caveats:

1. There are later 318 heads with an X or J cast into them, which I've only found on trucks. These are not the good 340/360 heads. Check the numbers, but unless the X or J is over 1" tall, keep looking.

2. The current rage among head shops is to try and sell you the "swirl port" 302 cylinder heads. First off, they're not swirl port, they're swirl chamber. Second, they're 318 heads, originally equipped with a 1.78"/1.50" valve combo. Yes, they will garner you nearly a point of compression due to their heart-shaped, closed combustion chambers... but opened up to 2.02"/1.60" valve and fully ported (and I mean, like $1200 worth of work here), they flow less than a stock 2.02" X/J/308 head. Oh, and the upsized valves destroy the swirl effect--this straight from a Chrysler engineer (not me) While compression is nice, it's fairly useless when there's nothing to compress: horsepower is all about airflow. So why the big push? Virtually every non-cop 318 from 1985-1989 (except '89 trucks) had these heads--there are a million out there. So, the shops push the compression aspect and folks eat it up. Magazines further embellish the myth, because these shops pay to advertise with them (the real money in magazines). Unless you're building a stump-pulling, trailer-towing truck motor, don't fall for it. If you don't believe me, then look under the hood of any '80s Mopar cop car with a 318: they all had later ("945"-casting) 360 heads, as well as 360 intake manifolds and carbs.

3. The Edelbrock Performer intake, while lighter, makes less power than any factory SBM iron four-barrel intake. It has smaller ports, so you'll feel an improvement off-idle in the seat of your pants, but in the middle and on the top end, you'll lose. The lighter weight doesn't account for the HP loss. I've seen the dyno runs and flow-tested them; numbers don't lie. Also, avoid the '70s-era Streetmaster and SP2P intakes like the plague; you can clog the ports with two fingers. Both were designed with towing and fuel mileage in mind and have no place on a performance engine.

That's all I can think of at the moment... I'm pooped. Anyone got a beer?

now thats what im talking about , you know your stuff about small block mopars

is this the stock motor for that car , because i dont think it is 340 was only offered to the cuda in 73 , if im wrong let me know , now with that 340 i would stroke it 416 stroker , cost about $1500 or the kit , and then edelbrock heads 557 purple shaft cam , 850 hp holley ,,,,, http://www.hughesengines.com/ best place for the killer parts and some serios hp for the small block guys , or just nos would be a nice way to have some fun , and another thing if the 340 is a cast crank , just find a 318 steel crank , same crank , 509 purple shaft is a killer cam and flow out your j heads with flat tops would be a killer set with a victor intake

Not a big fan of steel cranks, I've had 'em break too many times. Two Fords, one Dodge, one IHC. Cast would have pounded out too, but wouldn't have snapped and taken out the block at the same time. I still use 'em if the engine has one, but I won't go out of my way to get one.
A 340 can be made to use a 360 crank, 372 cubes fairly inexpensively.

ive never seen a steel crank break before , man you must be pushing over 600 ponys , those bottom ends are good for 600 hp max

It's not a question of power, it's just time. A very slight looseness of bearings that would never hurt a cast crank will shatter a steel one. In the case of the 318 truck engine, the oil pressure dropped, and before I could react, the crank broke in two places and wiped out everything but the exhaust manifolds! (It was flat out at the time.) Block, heads, even the 340 hirise intake, all smashed to hell and gone.

Hard to beat the cubes...Getting a .030 over 360 to a 426 is impressive!
No replacement for cubic displacement they always say

At any rate 2500 bucks is not a bad deal...Then you need some oval port aluminum W2 racing heads a Air Gap intake, Demon carb...It gets expensive quick....

But for about $10,000 you will definately have a motor that will run with anything out there....600 hp without nitrous easy...In a lightweight small block that is amazing....Bang for the buck it is hard to beat...

...Mind you it is tough to get a car that can handle that kind of power down the track or street without mini tubs, tying in the frame rails and a roll cage...

putting too much motor in a Car means mini tubs and a roll cage at the local track...Once you go faster than 11.5....And with a small block Stroker kit you can top that in your sleep.