Check out my car and talk to me about 318/340 swap

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Heres a final model. All I changed was the head CC to 72cc360 heads, and a stock bore teener with .001" negative deck height pistons. Basically KB167s and a little deck shaving. Your still at 8.65-1 CR. Barely better than a stock teener, and this model is with better pistons.

Want to talk about port velocity. Again bigger isn't always better with a 318. A 360 has a 3.58" rod ratio. They couldent go any bigger piston diameterwise, so a 360 for lack of a better term is essentially a stroked 340. Same bore, longer stroke. And a 340 which has a 318 rod ratio is essentially a 318 with a 4.00" bore. Now theres other stuff to these engines that make them what they are, but the basics are essentially what I just said.

So this being said, you have a larger 4.00" piston surface area, and 3.58" long stroke, and this takes advantage of bigger valves, larger ports. and runners. It can pull in a larger volume of air without slowing down port velocity.

340 can do this as well because of the 4.040" piston surface area but makes due with a smaller 3.31" rod ratio.

Now the lowly 318. It has an even smaller 3.910" bore diameter, smaller than the 340, and 360, and the same shorter 3.31" rod ratio as the 340. It cannot draw near the intake volume on the down stroke as a 340 or 360. To keep port and runner velocity up, you have to make these areas a wee bit smaller. Besides ending up with a horrible compression ratio, This is the other reason why dropping 360 heads, and intake on a stock compression 318 is a horrible idea. Even if it had zero deck flat top pistons, your CR gain would be marginal over a stock 318 CR.

There is 1 exception to this rule in regards to port velocity. Turbos and supercharging. Stick them 72cc big valve 360 heads on a stock 318 with them shitty stock pistons, and put a turbo on it. The engine doesnt care how big them ports, and runners are then, because it's getting force fed, instead of relying on the intake stroke to pull in air volume.

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These models dont take into consideration any cam profiles, head work to improve flow, or valve sizes. All that plays a part in it. However onr of the biggest deals to make any internal combustion engine run well is compression. If the engine isnt built that way from the factory, it can be always corrected that way to make it run.
 
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There's more to it than the 22 cu inch difference 318s have lousy heads...low compression etc. Sorry had to chime in saying the only difference is 22 cubes is a misstatement. When talking LA 318 vs 340 stock for stock.
in first post by OP, he got j heads on the 'teen!! could even have 2.02s and 1.60s,..thank ya very much!
 
Heres a final model. All I changed was the head CC to 72cc360 heads, and a stock bore teener with .001" negative deck height pistons. Basically KB167s and a little deck shaving. Your still at 8.65-1 CR. Barely better than a stock teener, and this model is with better pistons.

Want to talk about port velocity. Again bigger isn't always better with a 318. A 360 has a 3.58" rod ratio. They couldent go any bigger piston diameterwise, so a 360 for lack of a better term is essentially a stroked 340. Same bore, longer stroke. And a 340 which has a 318 rod ratio is essentially a 318 with a 4.010" bore. Now theres other stuff to these engines that make them what they are, but the basics are essentially what I just said.

So this being said, you have a larger 4.010" piston surface area, and 3.58" long stroke, and this takes advantage of bigger valves, larger ports. and runners. It can pull in a larger volume of air without slowing down port velocity.

340 can do this as well but to a lesser extent, because of the same 4.010" piston surface area but makes due with a smaller 3.31" rod ratio.

Now the lowly 318. It has an even smaller 3.910" bore diameter, smaller than the 340, and 360, and the same shorter 3.31" rod ratio as the 340. It cannot draw near the intake volume on the down stroke as a 340 or 360. To keep port and runner velocity up, you have to make these areas a wee bit smaller. Besides ending up with a horrible compression ratio, This is the other reason why dropping 360 heads, and intake on a stock compression 318 is a horrible idea. Even if it had zero deck flat top pistons, your CR gain would be marginal over a stock 318 CR.

There is 1 exception to this rule in regards to port velocity. Turbos and supercharging. Stick them 72cc big valve 360 heads on a stock 318 with them shitty stock pistons, and put a turbo on it. The engine doesnt care how big them ports, and runners are then, because it's getting force fed, instead of relying on the intake stroke to pull in air volume.

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if you ever want any of us to value your opinions, you gona need to lern that a stock 340 bore is 4.040, not 4.010!!! and is not the same as a stock bore 4.0 360!!! these bore sizes are the fundamentals of small block mopar lore!!! and that lil bity no drawing 318 piston is only .090 smaller stock than a 360, thats bout twice the thickness of my thumb nail! a .060 over bore is only .030 smaller than you beloved 360!!
 
I never said It was my beloved 360. Merely pointing out some differences. BTW You got some thick assed thumb nails if they are .045" thick lol. And yes so it is 4.040", i fixed it for ya. Anyhow, the fact still remains that sticking big chamber heads on a stock 318 short block which has a shitty TDC to begin with, is going to make it a gutless pig.
 
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but if its built to have 10-1 static and 8.5-1 dynamic and build a bout 175 psi with j heads shaved bout .060 and a good intake that works with a good cam,set of dougs headers...itll run great!
 
Very true, but we dont even know what the OPs 318 has in it piston wise. He says a Kia can out run it. That's pretty bad. I am assuming at this point it's a sucky compression stock 318 bottom end with the J heads on it, making it pretty gutless.
 
very posibile,..or maybe the kia doing better than we thunk????

2019 Kia Soul 0-60 Times
Trim 0-60 times, 1/4 mile
Base 4dr Hatchback 130 Hp, 118 Lb-Ft., N/A, 2884lbs Weight, 24 City / 30 Hwy mpg, 4-wheel disc, front-wheel, 6-spd man transmission 8.5 sec, 16.6 @ 85
 
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very posibile,..or maybe the kia doing better than we thunk????

2019 Kia Soul 0-60 Times
Trim 0-60 times, 1/4 mile
Base 4dr Hatchback 130 Hp, 118 Lb-Ft., N/A, 2884lbs Weight, 24 City / 30 Hwy mpg, 4-wheel disc, front-wheel, 6-spd man transmission 8.5 sec, 16.6 @ 85
Thats slow. Clock that ***** with a sun dial.
 
I understand the whole “if it ain’t broke don’t fix it” mindset. I do. The car is a really fun cruiser, but the 318 is REALLY slow. Like…the Kia Soul I drive to work every day will run off and leave it easy.
Something wrong with your 318.
 
very posibile,..or maybe the kia doing better than we thunk????

2019 Kia Soul 0-60 Times
Trim 0-60 times, 1/4 mile
Base 4dr Hatchback 130 Hp, 118 Lb-Ft., N/A, 2884lbs Weight, 24 City / 30 Hwy mpg, 4-wheel disc, front-wheel, 6-spd man transmission 8.5 sec, 16.6 @ 85
My 100% bone stock 318 2bbl in a b-body with 2.94 gears ran 15.9's.
 
Now that I am done at work today and have time to reply, heres for all you smart guys on here talking about running 360 heads on a teener. That performance gain is all in your mind. Heres 3 models for you to look at. Standard bore 318, stock rod ratio, pistons TDC .080" in the hole, and I will give it 5cc valve reliefs from a quickee rebuild. .038" compressed height felpro permatorque headgasket with a 4.03" diameter. Real common autopart store stuff. And the 72CC 360 heads. The first model shows 7.46-1 compression with them 72cc 360 heads on a stock 318 with stock pistons. Hardly an effing hot rod

Second model I changed nothing on the equation but stuck 60cc heads on it. CR jumps to 8.34-1. Better yes, but about a stock 318 running on rat piss.

The 3rd and final model I changed the heads to 62cc, and put the piston at near zero deck height with 5cc valve reliefs. This is typical of the KB167, and some decking. That shows 9.66-1 compression. A nice pump gas hot 318.

In closing are ya gonna get there with a low compression 318 short block and 360 heads. Hardly. You may get closer with zero deck flat tops and them 360 heads, but not on a stock low compression 318 your not. The numbers dont lie

LOL, I don't play with "computer" power. Your problem is: 1 not all 318's are the same; 2 Your cc are off, have you cc'd the heads you are talking about? I used Justin's numbers 68 cc for 675 casting number 318 heads, I trust his are right. Virgin stock closed chamber 273 heads measure about 65 cc, so not sure where you find 60 cc 318 heads. I personally have cc'd J heads, virgin untouched stock, and the largest chamber measures about 73cc. The example I gave was a J head milled 020 cc'd to about 69 cc. That leaves 1 cc larger chamber that a stock 318 chamber. Why mill heads? Because after time and thermal cycles they are not flat anymore. My machine shop charges one price up to .020, so that is what I do. So, your big compression difference is nonexistent. If you read my post the first time. The rest is what combination you use to make it work. There are more ways to mess that up than I care to think about, let alone gears and torque convertors. Airflow is what makes power, I use the best heads I can. No matter what size engine I am building.
 
Very true, but we dont even know what the OPs 318 has in it piston wise. He says a Kia can out run it. That's pretty bad. I am assuming at this point it's a sucky compression stock 318 bottom end with the J heads on it, making it pretty gutless.
Bingo! this is what I say all the time. Guys that say 318s run just as well as a 340 never finish the sentence which would be something like "...after you convert it with 340 style internals and or stroker kits"
 
You can build a /6 to run with a 340 but, the 340 is the most respected and generally the most desired small block v-8 mopar of that (maybe any) era. Even brand Xer's are somewhat envious of 340 mopars.
 
To the OP. If I were in your position I'd drive the car with the 318 while accumulating the parts to build the 340. I'd put a set of light weight flat top pistons in it, Ross makes some nice ones. A small cam, and a RPM Airgap manifold with a 750 DP.

Years ago I rebuilt the 340 I had in my 72 Duster, used a set of the heavy OEM 68-70 pistons, IIRC a MP 280/474 hydraulic, a 650DP the original 340 intake and manifolds. The car had 3.55 gears and ran very well. It was a hoot to drive.
 
How far in the hole were those 273 pistons at TDC? I am betting they were much much closer to the top of the deck than your run "o" the mill 318. I have 2 of these 318s the 77 one the piston TDC was .080" in the hole the 74 was .100" in the hole at TDC. If his teener pistons TDC at around that, with 72cc 360 heads, your really dropping that CR. Mid 7s on CR.

You would be surprised how much it can change by just changing the head cc. Do you have any numbers to share on that 273? What was the piston depth in the holes at TDC, what were the CCs of the heads you used?

273 2 barrel pistons are only .020 to .040 in the hole. My 273 had 10.5 TRW forged pistons. I only brought it up when talking about port and valve size. You guys are missing my point completely. You don't know the size chambers you are talking about, and you are fixated on compression. If you are building from scratch that is all and well and good, but that is not what we are talking about here. You must match your combination. How do Magnum heads work so well on a 318 with their air flow about the same as 360 heads? Think it through.
 
Bingo! this is what I say all the time. Guys that say 318s run just as well as a 340 never finish the sentence which would be something like "...after you convert it with 340 style internals and or stroker kits"

Why not copy a 340? A 318 is just a few less cu in without the 340 premium price. If you add all the good parts, not much difference... Not interested in strokers and all the money that go with them.
 
You can build a /6 to run with a 340 but, the 340 is the most respected and generally the most desired small block v-8 mopar of that (maybe any) era. Even brand Xer's are somewhat envious of 340 mopars.

Ok, I have two YT video recommendations for ya first "Bud Lindemans" test drive 69 Dart 340..watch all the way through till they run the 4 speed car,

second and not so entertaining... any video of Uncle Tony running that Plan Z "porta potty" slant Dart down the track...then come back and tell us which one you'd want to have/drive...
 
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Stock teener pistons TDC at .080" to .100" below the deck. Thats a serious loss in compression. This is compounded with heads designed for a bigger bore engine along with the associated valves for a bigger engine. To make a teener run, you need pistons that change direction at the deck, or a couple thousandths below the deck not 80 to 100 thousandths below. The valves , ports, and runners need to be sized for the bore it's got. The whole throw bigger at it does not apply. Putting 340/360 top end on a stockerish 318 bottom end, actually hurts it, not helps it. It slows down port velocity. Bigger valve J heads on a low compression 318 makes it perform worse than if the stockers were left on it. Most engines (street engines) live at off idle to 5,000 rpm max. Rev it higher?? Ok how much higher to get the power back? Will that require better rods, better crank? Etc?

this is my experience, my post is on page one. now it ran like a scalded dog up to a 100 mph with 4.56 gears in the eighth mile but it layed over to the quarter mile stripe. oh yes it ran high 13's with a loose convertor till I broke the trans tail housing and then went back to low 14's with the stock convertor. NOT ENOUGH COMPRESSION.

Have you actually tried what you say can not work? I have run a 273 with 72 340 J heads. Best it ever ran, and that is with a 3.665 bore and 67 cu in smaller. No valve notches in the block. No port velocity problems. Not sluggish. Not torque limited. What compression loss? 675 heads are about 68 cc per chamber and a .020 milled J head is about 69 cc, at .040 you are about 65 cc. Bore is the smallest adder there is. I used to put 360 heads on 318's all the time. Never a complaint, never a dog. Do you know how to tune an engine and set up a transmission? I would never run a stock 360 cam in anything. Would a low compression 318 beat a 10.5:1 340 with X heads, no, but it will beat the snot out of a 318 2 barrel.

this is not my experience. a motor needs compression,
 
Why not copy a 340? A 318 is just a few less cu in without the 340 premium price. If you add all the good parts, not much difference... Not interested in strokers, going fast and the HP that go with them.

Fixed. :rofl:
 
a couple of questions to the op, have you had the car/engine set up properly, ie carb, timing etc to get the best from it? second have you ran it side by side with the kia or at least timed both to confirm what you say that the kia is faster?
 
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