Why are 318's low HP and torque?

[273]

Here's what my dyno did with your spec's Chryslerkid but look more at the Dynoed curves more than the numbers number.
(Red line) 198hp@3500rpm
(Greenline) 340FT-LB@2000rpm

 

[273]

273... Do you mind running my numbers through to give me a rough estimate?

318
600 Holley vac
Performer intake
Hedman Shorties on 2.25 duals w/ x-pipe
302 heads w/ .028" head gasket (gasket matched w/ 1.88/1.60 valves)
Comp XE268 cam

also:
2000rpm stall on 904
2.94 gears (trying hard to find 3.55 SG)

(Red Line)277hp@4500rpms
(Green Line)366FT-LB@3500rpms

 

[Palmetto]

I think I have heard of guys putting 340 heads on 318s....

 

[smokindust]

chrysler never intended the 318 to be a performance engine. thats why they designed the 340.

 

[monkey]

I am a new member to the site and I've read this thread over a few times. I have one question but first let me give you a little back ground info. I have a 73 swinger stock 318, with headers, MSD ignition, Edelbrock intake, Edlebrock 600cfm carb, and 3.55 gears, I would like to install a 262 cam, would the 302 heads be a good addition ? I have a chance to pick up a set cheap.

 

[AdamR]

302s would be a step in the right direction but nit a huge improvement. They still have small valves and the motor still lack compression even with the smaller chambers of the 302s

 

[1wild&crazyguy]

They knew he 318 base was good, stroke/rod length...but they also knew it takes air flow and a larger pump=bore/heads=340.lol..then with that came the beefier main webs and taller main caps.:happy1:

 

[273]

I am a new member to the site and I've read this thread over a few times. I have one question but first let me give you a little back ground info. I have a 73 swinger stock 318, with headers, MSD ignition, Edelbrock intake, Edlebrock 600cfm carb, and 3.55 gears, I would like to install a 262 cam, would the 302 heads be a good addition ? I have a chance to pick up a set cheap.

302 heads flow about the same as every other 273/318 heads but will bump your .5CR which might give you 5-10hp on a 300hp engine, with a thin gasket and a little milling to get 9:1CR which might get you 10-20hp but more important would allow you to go with larger cams. Not saying its not worth upgrading to 302 but not a must upgrade 262 cam, $ for $ not the most cost effective upgrade unless moving up to larger cam.

 

[goldduster360]

Smaller cylinder bore makes less power, valve shrouding does not help with smaller bore either.

318 Cylinder heads have smaller valves and intake runners which is not conducive to making big power.

All the above with shorter stroke than a 360 and you have an engine that occupies the same amount of space externally, weighs virtually the same and makes less power. 318's were built as a base engine with economy in mind. They can be built to make good power but the same cam, intake and headers will make more power in the larger engines. Bigger engines are just bigger pumps.

Just like the slant six stuff, you can increase power dramatically with the right combination of parts but the same effort applied to the larger engine is gonna make bigger power and be more tractable.

 

[benmopar318]

Mexican 318 was factory rated at 270hp
http://www.forabodiesonly.com/mopar/archive/index.php/t-14704.html

318's respond well to racing mods
this 318 with 4" bore 333 cube with 12:1 comp runs 9.1 @ 147mph in Sydney

 

[goldduster360]

Mexican 318 was factory rated at 270hp
http://www.forabodiesonly.com/mopar/archive/index.php/t-14704.html

318's respond well to racing mods
this 318 with 4" bore 333 cube with 12:1 comp runs 9.1 @ 147mph in Sydney

If a 360 were used as the foundation with the same recipe of parts that would have been an 8 second dragster.

 

[goldduster360]

Chryslerkid, Ifworking on a very similar setup, just wish i could find a sure grip for my 8.25 that was affordable... Oh well, gives me something to keep after.

There used to be Trak-Lok diffs from jeeps all over evil bay for cheap. I scored a near zero mileage take-off from an offroad shop for $180.00 about 5 yrs ago. I still run it in my 3:55 geared 8-1/4 and it works great.

 

[moparmat2000]

saying 318s have small bores and cant be hotrodded is bogus. the LS guys run smaller bores in those new LS327s and make big power. biggies are cam and compression, good flowing cylinder heads or lack of. this may be the rodney dangerfield of mopar V8s because it was a rather pedestrian engine and used in everything. it doesnt mean it wont respond to a good cam, higher compression, and some better breathing like headers, and a good intake. all engines respond to these basic principals. the way most folks think of these engines as boat anchors just means you can get em super cheap to even free. i am all about fast n cheap if you can.

look at it this way, the 340 X castings are good castings for their time of course. they are better than a stock pre magnum 318 casting. but these were designed back in the day when sunoco 260 was .35 cents a gallon. volumetric effiency wasnt a word in mopars vocabulary back then. yes you can get a set of 65 to 67 273 closed chamber head castings, port the snot out of them, and add bigger valves, but then you got a whole lot of money and time in an old set of castings which if they crack, or get damaged if you grenade an engine will probably not be easily or cheaply replaced. a stock magnum casting will outflow a stock 340 X casting any day of the week. this is a proven fact, plus 1.6 ratio rockers and 62CC chambers are stock. this and the fact that they are a bolt on swap to the older LA engines made me a believer in them except for the cracking problems.

check out my newest thread on mopar magnum heads titled magnum heads redux. there is now an aftermarket supplier for these heads available with both intake manifold bolt patterns, $399 per head machined with hardened seats and silicon bronse guides installed Enginequest A&A specialty midwest has corrected the cracking problems associated with these heads by beefing up the castings where they crack on the stock magnum heads, revising the water passages, and flowing the runners & ports better than stock. these are being used in dirt track and paved circle track competition. they have 62CC chambers, and with some KB flattopps can yield 9.8 to 1 compression which is plenty of pop for pump gas. they also use 1.6 ratio rockers. a set of engine quest magnum heads are on my list for my 74 318 rebuild. i will gladly work overtime and pay the $399 each for em. i feel they are well worth the money

popular hot rodding did an article on this setup as a bolt together with no gee whiz machining a mopar 318 with flat tops, the right cam and some EngineQuest magnums, and a holley 750 made 402 HP 341 ft lbs of torque, at 6200 RPM. id say thats not so rodney dangerfield these are very respectable numbers for a bolt together setup with no porting on a pretty much stock cast crank refreshed 318 with no laughing gas either. they did this as a what if that anybody with basic engine rebuilding skills and basic machine shop work could duplicate in their garage.

now think how much more you could get out of it by beefing up the bottom end, adding a hughes stroker kit to make it into a 390, and porting the snot out of em. is 500HP on motor w no juice a feasable number with the last combo i mentioned? maybe someone will try it and find out. i will build my bolt together "boat anchor" 402HP 318 in my basic garage and have fun with it. maybe get another "cheap free boat anchor 318" that someones giving away to make my future 390 bottom end for a later hotter swap.

every cloud has a silver lining ! EngineQuest magnums make this one brighter

matt

 

[gtmopar]

Well said Matt I agree with you 100 percent. I have built 318's that have run high 11's low 12's in a convertible 4 speed car with 3.91 gears. The only reason I only ran twice was because I got kicked off the track because I refused to cage my convertible show car. I used a forged factory 340 bottom end because I already had it. Balanced it to near perfect, took 318 heads had 2.02 1.60's put in, boosted compression, wish I would have ran a little more aggressive cam but live and learn. I think most guys get a little offended because they went out and spent 2 grand on a running 340 ( which is a sweet motor ) and could have gotten a 318 cheap or free and would have been able to put that into a 390 stroker rotating assembly. Look we are all here to accomplish the same thing so people that get pissy can go elsewhere. I'm building a D1 pro charged 318 stroker right now that I'm hoping to get 750+ hp out of. If you think that's far fetched look at mopar muscle mag and look up pro charged 318 and see they got 667 hp out of a virtually mild 318. Yea I know blowers are expensive but if a little 318 can handle that then I'm in!

 

[frosty_the_punk]

A 318 can make as much power as a 340 or 360, everything else being equal. it just will just do it at a higher RPM and with less torque.

 

[moparmat2000]

A 318 can make as much power as a 340 or 360, everything else being equal. it just will just do it at a higher RPM and with less torque.

have you checked out the engine quest magnum heads?

 

[frosty_the_punk]

My brother in law is building a 318 for his dad using those heads. they're impressive for the price.

 

[moparmat2000]

My brother in law is building a 318 for his dad using those heads. they're impressive for the price.

yep i want a set of em. did you check out the popular hotrodding article linked at engine quest about their 402HP magnum headed 318?

matt

 

[273]

A 318 can make as much power as a 340 or 360, everything else being equal. it just will just do it at a higher RPM and with less torque.

Just got too add a little more gear to equal torque to the tires out.

 

[swingn71]

I used to run a 73 dart sport , back when I was 18 , It was a 318 bored out 30 tho over with 340 heads /manifold 67 cuda rear end . nothing else . and it was doing mid 10,s in a quarter mile . Sold it when my first son was born . . 30 years later just bought a 71 Dart , 318 ---30 tho over and am starting again . Wish I had never gotten rid of the 73 . Before that I had a 1970 Valient duster(Plain Jane ). Nothing special .

 

[69 Cuda 440]

1968,

No need for a High Performance 318 Commando.

The 340/275 HP was the 'ticket', and Mopar labeled the 318/230 HP as the durable,
low-performance, efficient running, no problem, low-rev 'Work-Horse' engine.

Even the NHRA re-rated the 318/230 2-Barrel to 195 HP, and then even lower to
185 HP.

* 9.2-1 Compression Ratio {Advertised}
* Pistons down in the Cylinder
* Small-Port/Small-Valve Cylinder Heads {Open-Chamber Design}
* Hydraulic Camshaft {.373"/.400" Lift ~ 240*/248* Duration ~ 24* Overlap}
* Valve-Springs {88 lbs. Valve-Closed / 184 lbs. Valve-Open}
* Short-Runner Intake Manifold
* Carter BBD {285 CFM Carburetor}
* Restrictive Exhaust Manifolds

The engine just won't rev.

230 HP @ 4400 RPM
340 Ft/Lbs. of Torque @ 2400 RPM

Designed to run all day at 2400 RPM's, which was it's best operating level.

Performance-Wise, the Chevrolet 327/210 HP {2-Barrel} will run circles around the 318 {2-Barrel}.

 

[YY1]

...but the 318 will circle the 307 all day, as well.

 

[69 Cuda 440]

...but the 318 will circle the 307 all day, as well.

That Sir,,,,,,,,,,,Is a Given..... '318 Mopar' devours '307 Chevy'

318 "Mr. Torque".....340 Ft./Lbs. of Torque @ 2400 RPM's.

Check out the 1968 Commando 318' thread,,,,,,,,,

I'll post results from January 1968 tests at Irwindale Raceway.

 

[YY1]

I'd be interested to see a 318 built as close as possible to one of the 4 barrel 327 specs...and see if that 9 inch displacement advantage made that much of a difference.

 

[69 Cuda 440]

I'd be interested to see a 318 built as close as possible to one of the 4 barrel 327 specs...and see if that 9 inch displacement advantage made that much of a difference.

You would need 10.0-1 Compression-Ratio Pistons, a 4-Barrel
Medium-Riser Dual-Plane Intake and a Carter AVS {625 CFM}.

And an improved Exhaust Pipe System.

Not sure if that gets you to 250+ Horsepower.