best way to increase hp in my 318?

wanting to get close to 400 hp.

I have a bone stock ATK remanufactured 318 155 stock hp. 8.6:1 compression. I have removed all smog parts, added headers, dual exhaust, 4 barrel intake and fitech fuel injection system good for up to 400 hp. would an edelbrock top end kit get me anywhere close or is there an easier or cheaper way? im realistic and am only shooting for 400, anything over 300 would be great.

Starting with a used already running/built 400hp 360 would be simpler, easier, quicker, cheaper(?).

I know but I am past that point, I wanted a stock every day driver I thought, after everything was bought and installed, I decided I needed more power. I thought I was old enough I could do without it, I was wrong.

Easiest, bolt on a blower or turbo. With that compression ratio, no other mods may be necessary.

Otherwise, you are getting into the engine and modifying parts. Here is a recipe: https://www.hotrod.com/articles/mopp-0409-318-engine-build/

A magnum 318 would be a cam and intake swap. An LA 318 like the one you spec?

Here's one build but I don';t think the 302 heads are a solution unless that's what you already have. I'd swap magnums on before I spent a nickle on 302 heads.

im thinking with what I have done I should be close to 200 hp, how much more could I get with just the right cam? maybe some better heads?

There is a hotrod mag or some mopar mag link with an article about building a 400hp 318 with parts out of the box.

That is sometimes the disconnect between thinking you did something beneficial and actually finding the proof of it. If this 155 was discovered on a dyno, is it an actual reading or a factored reading adjusted for density altitude and dew point? Texas has a mean elevation of 1700' and nasty ass humidity. Where are you at relative to those factors?

Air flow makes power, so pumping more in with bigger heads and more cam lift and duration helps power production. Problem with your current configuration is you do not have the enough compression to utilize a big increases in air flow. Putting big heads and cam in this combo will make it lazy and less powerful than it already is.

Fine tuning of ignition curves and the carb, might get you closer to 200. If you can find the cam specs and get a cylinder pressure reading, you may be able to use that to talk to a cam company about options you might have. An RV style cam with low duration and high lift might get some extra air in without sacrificing cylinder pressure. Degreeing of the cam would be a big part of setting this up to build the most cylinder pressure.

Not sure where in Texas you are basing you humidity comment on, but Texas is a big place and yeah in Houston or eat of I 35 humidity is bad, You get out closer El Paso and not so. Or up in the panhandle.

I would dial in the timing & the carb then later some EQ mag heads & you can reuse em when you on down the line swap in a stroked 360 (408). 4" cranks are cheap now & the KB pistons ain't too bad.

That was Mopar Action. Did they use a magnum block? Either way it would be worth copying.

TC is correct with the turbo or supercharger add-on. Good HP with mileage and drivability.

- EM

found this:

https://www.hotrod.com/articles/mopp-0409-318-engine-build/

Old LA. But I was sure it was a diff article unless the article face was refreshed

Easiest?

Probably a magnum style top end and a cam in the 220’s@.050, .470-.500 lift.

It’s likely going lose some grunt in that configuration........ you could shorten the duration up a bit to get some of it back.

Something like a Comp 268H should be plenty to get you well into the 300’s with a magnum style top end.

“Cheaper”(possibly) but less powerful....... put 1.88 intake valves in the current heads along with some mild porting, Comp 268XE cam.

To get 400 HP out of that 318, you are going to have to up your compression.
Get a set of closed chamber heads(low cc),thin head gaskets, .022 range.
A good cam,480-500 range.
Performer style intake.
Headers.
A turbo or blower set up will get you there but it will be at higher price.

The usual bolt ons and spray the wee out of it.

Kevin

Yeah, I was thinking the N2O approach, too.

But it wouldn't be my pile of broken parts if I couldn't get a handle on the tune.

275-300-ish out if a 318 really isn’t that hard........ then it’s just a 100 shot.

400hp isn't that realistic. If you're going to spend that much time and money on a 318 you might as well spend a bit more and start over with a 360.

I think you could make a good case for it being cheaper to get 400 hp out of a 360 than a 318, even factoring in a core 360.

Besides, it will a lot more streetable.

Sure, a 360 is a much easier path to 400hp......... but the op did say:
“.........anything over 300 would be great.”

And that shouldn’t be that hard to get to at all.

Especially if he’s willing to buy heads.

If you went with something like the EQ heads....... and down the road you get the urge for more power, the top end could be reused on a 360 or 408.

His first opening line of the thread:
"wanting to get close to 400 hp."


300, IMO is not very close to 400.

If he can change his target, he can also change his solution, IMO.

And the last line of the first post says anything over 300 is fine.

I would have no trouble hopping up a 318 and landing somewhere between 300 and 400hp, and not building a whole new motor to get there.

As always the intended application should dictate the path you take to 400 hp especially when you limit your displacement to 318.

Lightweight racecar only? W2's or better, big cam and set the shift light at 7200.

Not so lightweight street/strip car and street manners don't concern you? See above.

Daily driver heavy gotta get to work dependable? Budget type aluminum heads well prepped, factory type roller should easily get you 1hp per cubic inch without destroying street manners and then depending on how adventurous you are, a single turbo to easily surpass your goal or spray it.

My vote would be turbo if for no other reason than it doesn't need to be WFO to enjoy its benefits.

Kevin

if the guy wants to get that juice from a 318 let it be!!!! even more is it posible!!!! he has his reasons to work on his 318!!!!

shame the article about 318 400hp WITH PARTS OUT OF THE BOX is not anymore on line!

Copying from the HotRod Article:

Why build a 318? Some may argue there is never a reason to build the Mopar 318. When the time comes to rebuild a small-block, the 318 should always be cast aside in favor of a 360. We won’t argue. A 360–built properly–will always have a torque advantage over a 318.

Does this sound familiar around here ?, lets continue:

However, 318 cores are free for the asking, and that offers some economic incentive. But the real motive usually isn’t a matter of cost. The bottom line is like it or not, 318s are being rebuilt by enthusiasts every day. Some guys have a certain sentimental attachment to these cute little engines. sometimes it’s just the desire to retain the car’s original powerplant. And some guys dig the idea of blowing doors in with just a 318. Count us in that last group. We were intrigued with working out a combo that shows how to really make one run. Our goals were straightforward:



-The engine would be based on a regular 318.
-The engine must run on 91-octane pump gas or less.
-The camshaft must be daily-driver streetable, at least in a hot-rod sense.
-The build will not include any exotic, rare, unusual, or excessively expensive parts.
-The parts will be bolted on out of the box with no custom tricks, massaging, or porting.
-The final output would break the 400hp barrier.

and goes on... to THE BUILD.

I think the mopar mag article was built with diff parts

I guess I should have noted that this is a daily driver and yes I would love to have 400 hp but I know with the compression ratio that would be difficult. So anything 300 hp or over would be absolutely fine with me

Also I already have new long 318 block with 0 miles. I usually do go with 360 mainly for the torque. I’m just trying to make do with what I have.

I'm just noticing 3 members including me posted the hotrod mag link LOL.

there is a fact, Pistons must be replaced to reach close as posible zero deck

The 155 hp is factory rating which is typically a little low. My engine will now breathe a lot better with all of the emission restrictions removed, headers added and free flow exhaust. Also with fuel injection you can get the fuel ratio better which helps also. So assuming I’m somewhere near 200 hp is not implausible.

Some are paying too much attention to the 400 hp and not the thread title. Best way to increase hp in my 318

A relevant question is what year motor do you have, different years have different compression ratios and technicals.
Is it a later model 318 roller cam motor?

Alright, so you may already be near 200 but have not confirmed that. I'm not so sure that mopars have emissions hardware that really impede airflow, but if you have changed the intake and added a 4bbl, headers and duals, then yes, you have probably improved pumping capability.

Still recommend trying to find the cam specs, determine what casting heads you have, and taking a cylinder pressure reading. Knowing actual cylinder pressure is much more helpful than a published compression ratio. The factories have demonstrated a wide variance in actual ratios compared to advertised ratios. Knowing the year of the engine, as pointed out above, may help with this. All of these thing can help determine if a cam change or head change is going to be a negative or positive impact on cylinder pressure and power output.

If you don't mind throwing money at it, then you can just start changing things and backpedaling into the corrections to fix what you just changed. I'd recommend against this approach.

30 years ago I re-ringed a previous stock rebuilt 318.
675 heads with some clean up, 340 cam, std performer intake, headers...... dynoed it with a few different carbs........ best result was mid-290’s hp.
I’d have to see if I could find the sheets, but I think that was a 650dp on a 1” spacer and 40dg timing.
That thing really liked timing.

Better heads and cam would easily be worth another 25hp+, and then you’re solidly into the 300’s.

A few years later I was building 318 oval track motors.
596 heads, block decked/heads milled for 10:1cr, solid cam, roller rockers, stock 360 2bbl intake and a 500/2bbl Holley......... they were well into the 350hp range.
Multiple track and series championships with those.

This was the California emission variety. I did install 4 barrel aluminum intake with fitech fuel injection. I will look on the block and get the date I think it is a mid 80’s though

My recipe for the Waygun's tired 80,000 mile original 318 3 on da tree in the spring
Hone,re ring and reseal.
Using original pistons.
Summit K6900 cam,Cloyes Timing set,bumped up 4 degrees.
Eddy Perfromer spreadbore intake with 800CFM Thermoquad,Hedman Hedders
"Worked" 596 360 heads.
Hayes HD Street clutch set.
I already have dual exhaust,recurved distributor,and said mentioned Thermoquad (but on a 71 340 iron intake) exhaling through factory logs.

Not sure how much I will gain till I put the car on the Dyno.
Heavy wagon so torque is what I am after.
If I gain a few ponies that is also a plus
I am stoked and curious on how it will work.

Dizuster and his buddy ran a 70 Dart right out of high school. Bone stock 318 short block, stock LA style 360 heads, stock 4 barrel intake, T quad, headers with 2 1/2" exh. It had a Mopar performace .484 cam, (yes I know to big). Stock converter, 245 street tires (non sticky) 4.10 gear. would run 14.0@100 with no tire spin. Not a world beater. But cheap and it worked.
Doug

Since OP has zeroed in on a few concerns, such as using what he has, a 318, and the cost savings there of, in lieu of various other suggestions, true costs usually take into account final market value when completed, and eventually offered for sale, or parted, so, how much demand/market is out there for 300-400hp used 318's?

The engine is a 1984 so should be in the 8.6:1 ratio. I have called atk and gave them the serial number and a tech is supposed to call me back tomorrow to verify. I will also do a compression check when I get everything wired back up.

How to get 400hp out of your 318 in three easy steps:

1) Add enough nitrous to get you to 400hp
2) Run it until it blows up
3) Replace 318 with a built 360...

Replace 318 with a built 360... Not!

- EM

The hotrod article for 400hp 318 is "junkyard jewel". Here is the link... https://www.hotrod.com/articles/318-small-block-build/

Block is less important. Head casting numbers, which are under the valve covers, are more important. It was in the mid 80s when high swirl heads were being released, but they still had open chambers (less than ideal squish and compression). It wasn't until the 90s that the small chamber, high swirl and tumble Magnum heads came out.

Hopefully ATK can give you the scoop on heads and cam.




This would be link number 4 to this article that was first posted in reply #3.

302 heads, mid 85 release, where small chamber, high swirl and tumble LA heads

That's also around the time roller cams were coming from the factory. Moparmad might luck out and have all of the good stuff, or he might have just missed it and got traditional LA stuff.

I confirmed it is 302 heads and they shoot for 9:1 CR. But they allow 3/10ths either way. Could be from 8.7:1 all the way to 9.3:1.

Casting date on block is 11/24/84

302 heads, without some “work” done to them aren’t an easy path to 300hp+.

Even with some cost effective work(subjectively speaking), they’re not great.

IMO, better off selling them to someone who really wants a set and replacing them with something more hp friendly.

Alternatively, you throw some parts at it...... it makes what it makes, and you live with it and you start saving for that 360.

302 heads are fine for a mild build. Put a 340 cam in it, a 4bbl intake on it and a 318 with 302 heads can run nice. Is it even close to 300hp? Probably not, it is worth spending any more money than free on 302 heads for HP builds? Nope.

Now if they had made 308 heads with a closed chamber then we'd be talking.

Use magnum, heads if you are going with a stock type casting for a HP build.

if you up the valves on those heads to 1.88 and 1.60 and do some port work ,they will make over 300 horses ,and more with assistance(turbo,supercharger).

TC...actually my link is a different article than posted in reply #3. Completely different test with additional information.

and this is without get new pistons closer to deck...

and composite headgaskets ?

I’m surprised nobody asked what read gears you are running. I know that wasn’t in your question but it has everything to do with the answer. Start with 3.23SG bare minimum. Doesn’t matter go much HP you make if you don’t have the gears.

So it is. My bad.

No, Nacho, you still change to KB167 pistons to get the compression up and use .027 head gaskets. The only way to get more CR and use your stock pistons are to deck the block/heads/ and then the intake...way more expensive than just getting the pistons. You can get heads that have the smallest combustion chamber you can find, about 62CC.

True Big Bad Bee, but then you need to ask what transmission is being used. My 318 (original engine) ebody I am building will have close to the "junkyard jewel" setup, but I will be using a strengthened 42RH trans, for the OD gear and the 2.74 first gear. I am planning on a 3.55 rear gear, that will give me the 10:1 spread that is recommended. You take the gear ratio and multiply it by the 1st gear in the trans. You want close to a 10:1.