318 La with 360 heads

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I get that from 8/1 to 11/1 is only some 4 or 5% power difference. Power is measured at some peak rpm usually between 4800 and 5600 for a streeter. Ok so at the racetrack, that engine is never asked to pull in the low-rpm arena, so who cares about Scr if you just want have fun.

Ok but on the street, likely 95% of the engine's life is gonna be spent at low rpms. It behooves you to run as much compression as you can find, yes even at the expense of absolute power, so long as the cylinder pressure does not put your engine into detonation. This is to punch up the bottom end, you know, so you can spin tires with the meager stalls and gears that our cars usually come with.
In that regard, the engine I detailed will run 87E10 at WOT, without complaint.

Yur never gonna get there Normally Aspirated, with dished pistons. never.
Well maybe with 4-series gears and a 3000stall, but that don't help you to make power, it just makes a sucked out 318 spin tires .
With dished pistons and large open-chamber heads, yur looking at 8/1 at the very very best. Couple that with a small cam with an Ica of 57* and at 800 ft yur looking at a dynamic C/r of 6.7, and cylinder pressure of 126ish. Your take off will feel like a slanty.
Tire-spin? forget it.
Fuel-economy? forget it.
Passing power? forget it.
Fun times? forget it.
126psi is snailsville, my lawnmower can better that.
To make that 126psi, seem bigger than it is, yur gonna have to spin it up into the 3000s, so right away you have the additional cost of a Hi-stall. And to make a sustained spin, yur looking at 3.91s, another additional cost.
And now your 20mph 318 is down in the 12s or less.
For what reason? Because you want dished pistons? I don't understand your thinking.....
I already told you, you can run 180/185 on 87E10. with alloy heads. You need that pressure. Some guys on FABO say they are running 200psi still on pumpgas. I'm not saying that you should, but rather that 185psi is safe to run with alloy heads.
If you really want to run dished pistons with 360 heads, then you should slide a 360 under them. The factory already engineered that to work with 87E10.
Yes you can make yur 318 run with 360 heads,and dished pistons, but you are looking at a ceiling of ~150/155psi,on 89 to 91 gas, and lots of machining, or a really small cam.
 
Mopar Vinnie said:
I want dish pistons
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Why would you want dish pistons? That's like goin to a whorehouse and sayin "I'm just lookin".

You'll likely not meet your goal with a dish piston, since the compression generated will be lower.
 
AJ/FormS said:
I get that from 8/1 to 11/1 is only some 4 or 5% power difference. Power is measured at dsome peak rpm usually between 4800 and 5600 for a streeter. Ok so at the racetrack, that engine is never asked to pull in the low-rpm arena, so who cares about Scr if you just want have fun.

Ok but on the street, likely 95% of the engine's life is gonna be spent at low rpms. It behooves you to run as much compression as you can find, yes even at the expense of absolute power, so long as the cylinder pressure does not put your engine into detonation. This is to punch up the bottom end, you know, so you can spin tires with the meager stalls and gears that our cars usually come with.
In that regard, the engine I detailed will run 87E10 at WOT, without complaint.

Yur never gonna get there Normally Aspirated, with dished pistons. never.
Well maybe with 4-series gears and a 3000stall, but that don't help you to make power, it just makes a sucked out 318 spin tires .
With dishep pistons and large open-chambe heads, yur looking at 8/1 at the very very best. Couple that with a small cam with an ica of 57* and at 800 ft yur looking at a dynamic C/r of 6.7, and cylinder pressure of 126ish. Your take off will feel like a slanty.
Tire-spin? forget it.
Fuel-economy? forget it.
Passing power? forget it.
Fun times? forget it.
126psi is snailsville, my lawnmower can better that.
To make that 126psi, seem bigger than it is, yur gonna have to spin it up into the 3000s, so right away you have the additional cost of a Hi-stall. And to make a sustained spin, yur looking at 3.91s, another additional cost.
And now your 20mph 318 is down in the 12s or less.
For what reason? Because you want dished pistons? I don't understand your thinking.....
I already told you, you can run 180/185 on 87E10. with alloy heads. You need that pressure. Some guys on FABO say they are running 200psi still on pumpgas. I'm not saying that you should, but rather that 185psi is safe to run with alloy heads.
If you really want to run dished pistons with 360 heads, then you should slide a 360 under them. The factory already engineered that to work with 87E10.
Click to expand...
I wasn't thinking lol
 
I agree with everything except that an equally built 360 would make a different hp eg. 400hp.
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My attempt at an equivalent 360, to what I described as the path forward to a 350hp 318 has already been done.
It made 419tq/420hp.

That build in a 318 isn’t going to make 420hp.

If you think it would, then we’ll agree to disagree.
 
RustyRatRod said:
Maybe not for you, not for me, not for a lot of people, but for someone asking if 360 heads will work on a 318 it might not be as easy. Think through someone's perspective other than your own sometimes.
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Why would I think through someone else’s perspective on something like an engine build combo?
The OP is here asking questions and opinions on what it would take to build a 350hp Street/strip 318...... so I offered mine.

I’m sure there are other ways to go about it.
You don’t like mine? Offer an alternative.
 
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PRH said:
Why would I think through someone else’s perspective on something like an engine build combo?
The OP is here asking questions and opinions on what it would take to build a 350hp Street/strip 318...... so I offered mine.

I’m sure there are other ways to go about it.
You don’t like mine? Offer an alternative.
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Ok. Nevermind.
 
Frankly, after rereading it, I don’t see how anyone could have a problem with what was outlined in my first post.
 
I always chuckle at these 'big chamber heads on small bore'' threads. You can make power with bigger valves and ports but at the expense of a bigger open chamber and a loss of compression. You can put bigger valves and enlarge the chambers of a 318 head to almost equal the 360 head or you can mill the large chambers off to 318 size. Lots of material. Probably .060 or more) If I was to just "swap heads" on a 318 to gain horsepower, I would go 920's, 302's or Magnum if I wanted to loose the open chambers and increase compression. Aluminum's to increase flow If porting wasn't happening. There is no perfect answer, no magic bullet!
 
Using KB167 pistons, it only requires the heads be as small as 64cc to get to 9.5:1.
With nailhead valves it usually doesn’t take too milling to get a 360 head down to that 64cc area.
 
PRH said:
My attempt at an equivalent 360, to what I described as the path forward to a 350hp 318 has already been done.
It made 419tq/420hp.

That build in a 318 isn’t going to make 420hp.

If you think it would, then we’ll agree to disagree.
Click to expand...

Displacement builds torque not HP, if you look at similar NA HP engines of different displacements and even brands the general specs are usually very similar eg. a 550 hp street/strip 302 vs 340 vs 400 M vs 440 vs 454 etc.. they will be in the ballpark of cam size and head flow. Just the powerbands and torque will very greatly depending on size.

A 318 may or may not make the same but it's not gonna be 70 hp difference.
 
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IN 1978 Mopar produced a 318hp . Now I'm not sure what the specs were but AIR it was 360heads and 360hp cam /intake/carb . A racer friend had one in his Aspen (L/SA , I think ) ran 12.04 . A real slug out of the hole but 12.04 is gettin' it on for a 318 .
 
AJ/FormS said:
In my crystal ball I see 10.7 Scr and an Ica of 57* @800 ft.
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To make 10.7Scr requires a maximum total chamber size of 662.3cc/10.7less 1=68.2cc on a 3.94 bore. Very doable with a closed chamber alloy head.
You can get the 57* ICA on a multitude of cams. This is a very common area for mid-performance cams.
For instance; a 260 advertised. in at 107.
On a hydro, that could be 216 to 212 @.050 That'll make a stout 318@180psi; not 350 hp but in a streeter who cares, cuz with 2.76s she will only hit 3450@60mph with 10% slip and 80" tires (25.5s) .. 3.23s would get you 4100. The power peak with a 260 hydro cam might not come around until 4800. So with these kinds of street gears, absolute power means about nothing. That mythical 350 hp is waaaay outta sight, so you might as well built for mega-torque at where you need it; from 3450 with 2.76s, to 4100 with 3.23s.
To take advantage of a 4800 power peak, outshifting at 5200 with good heads, will require 4.10s for 60=~5180. How many streeters would be willing to run 4.10s full-time without an overdrive.
IMO, a 318 owner will be waaay happier having a tire frier in first gear, that pulls stoutly to 60mph in second, irregardless of it's absolute power rating.
A solid lifter cam , for the same [email protected] hydro rating x1.5=.012 valve opening, might be over one cam size bigger than the hydro, so say [email protected]. And that is a funtastic street cam. It will push the power peak up about 300rpm so say 5100, and now those 3.23s are looking mighty fine.
That 180/185 psi is now cooking the tires from a stop all thru first gear, and probably lighting them up at will to deep into the 30s mph. Sixty mph in Second gear with 3.23s is gonna get you about 4400 rpm , a lil short of the proposed 5200 shift rpm, leaving you with some dynomite passing gear power to 5000=~75 mph.
I mean, IMO, in a 2-gear streeter, peak-power should not be the target. Having the right midrange power for every occasion is gonna make a happy driver. You can only ever hit the power-peak once in any zero to sixty speed contest, and that will be in first gear with both tires blazing; and you don;t need 350 hp to do that. Heck, you don't need even 300. There was never a 3.23 equipped 340 that couldn't do that. Heck, even a 230 rwhp 5.2 magnum can do that. So you might as well say ~270crank hp. Any old 318LA with compression can get there, without even breathing hard. That's only ~.85 hp per cube.
Think about this, those early 340s spun both E70-14s to well past 60 mph. I never had one that couldn't. Even the last one I had that already burned a lotta oil, still spun 2 gears.

Anyway,to re-iterate what I would do;
flat-tops at +009 deck, .039 FelPros, small closed chamber alloys, targeting about 10.7 Scr for a 57*(@.012 valve open) Ica with a fast-ramp, tight-lash, solid lifter cam; then all the usual bolt-ons.
That's what I would build. And I would run it with 3.23s, and I would try the stock TC whatever it mightabin. I like me an 850 Carter rated TQ spreadbore for this combo. Why? For the visceral roar when the secondaries announce their arrival to the party.

Like I said; If I was building a 318, which at age 67, I can't see me doing, that's what I would do.
Except;
I would aim for more pressure, and
I would run ~4.10s with an overdrive,lol., and
Probably a manual trans.
And no skinny donuts in the back, cuz spinning ain't winning,lol.
 
Displacement builds torque not HP
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I disagree with the notion that it “only” builds tq.
What I usually see, especially as the hp/ci goes up, is that when you start higher(more tq), you end higher(more hp).

My experience is that builds of equivalent effort, based around the same overall “theme”, will often end up making similar hp/ci.

Your saying that if I take the top end and camshaft off/out of a 560hp 416 and put it on/in a 323, it’s going to make the same power.
And my position is that those same parts that made 1.34hp/ci on the 416 are nowhere near exotic enough to make 1.73hp/ci on a 323.
 
one only has to line up the three factory smallblocks, to witness what is spoken of.
Put the same middle of the road top end and cam on/in each,equalizing the cylinder pressure, and see what happens.
The horsepower follows the torque until she runs outta air. It cannot be any other way; they are inseparable due to the equation that forever links them. You can't have more of one, at a particular rpm, without also having more of the other.

But one thing is true and proven, more displacement .........by stroke moves the torque curve down, and perhaps that is what is meant when using the phrase " displacement builds torque". It's not very meaningful or accurate to say that unless you also have a context, like more displacement at the same bore. Taking that 4.04ish bore from 340 to 367 to 379 to 408/416, you can clearly see the progression of low-rpm torque production.
If you have a tow truck you wouldn't consider a 340. By the same thinking, does an early-A need a 408? What's the right size for a 3400pound car?
A lot of it will depend on the combo and the application.
At 5000 ft, you will need the bigger displacement, ie longer stroke, to be able to process enough oxygen. At 500 ft, the 340 ,ie 3.315 stroke might be adequate. It's always about getting the air(oxygen) in at a suitable rpm, for the application.
I know you gearheads and builders know this; this post is for the OP.

in a nominal 4.04" bore, a 4" stroke is over 20% more displacement than a 3.31 stroker. At 4 inhales per revolution,and at low-rpm, that 416incher is theoretically able to inhale nearly 1.8 more, 340-sized cylinders worth of air on every ONE revolution compared to a 340. That's a really, really........... really, big deal,If you need it.
To process the same amount of air, the smaller stroked engines will have to rev higher; that's just the way it is.
And that leads to hi-stalls and race gearing. Or supercharging.
And that's AJs 2cents
 
PRH said:
I disagree with the notion that it “only” builds tq.
What I usually see, especially as the hp/ci goes up, is that when you start higher(more tq), you end higher(more hp).

My experience is that builds of equivalent effort, based around the same overall “theme”, will often end up making similar hp/ci.

Your saying that if I take the top end and camshaft off/out of a 560hp 416 and put it on/in a 323, it’s going to make the same power.
And my position is that those same parts that made 1.34hp/ci on the 416 are nowhere near exotic enough to make 1.73hp/ci on a 323.
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What I mean say your looking to build 500 hp street/strip engine your probably gonna use or port some heads that flow 300 ish cfm and add a 245 ish cam with enough lift to use most of the 300 ish cfm and have a cr around 10-11 to 1 with appropriate intake/exhaust. No matter what displacement, obviously the fine details will very but that's the ballpark I don't care if were talking 273 or 440.

477 hp 318 nothing to crazy here.
https://www.hotrod.com/articles/0901phr-mopar-318-magnum-engine/
 
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What I mean say your looking to build 500 hp street/strip engine your probably gonna use or port some heads that flow 300 ish cfm and add a 245 ish cam with enough lift to use most of the 300 ish cfm and have a cr around 10-11 to 1 with appropriate intake/exhaust.
No matter what displacement, obviously the fine details will very but that's the ballpark I don't care if were talking 273 or 440.
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So..... you are saying the top end off the 560hp 416 will make 1.73hp/ci on 323 cubes.

In my actual experience...... where extremely similar motors were built(other than displacement) and dyno tested, the bigger motors made noticeably more power.

Since that’s how it usually plays out for me....... I’m just going to keep doing what I’m doing.
 
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273 said:
477 hp 318 nothing to crazy here.
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Hang on friend;
This is waaaaaaaay beyond the OP.
And certainly not something to put thousands of miles a year on. That engine is, IMO, nothing but bragging rights.

"The brain of the engine was a COMP solid flat-tappet camshaft with 247/247 degrees of duration at .050-inch lift. A mix of Harland Sharp and Crane rocker arms (1.7 intake and 1.6 exhaust, respectively) brought the lift to an impressive .622/.597 inches. The R/T Magnum heads were designed as basically an upgrade to the later-style Magnum heads, and the nonadjustable pedestal mount rockers wouldn't cut it with an aggressive solid lifter cam. A Crane rocker stud adapter kit was used that also incorporates a set of built-in pushrod guideplates. The kit goes a long way toward improving the valvetrain on the R/T heads, but with the 5/16-18 threaded holes that the studs live in, there is not a whole lot of stability there. Being a machinist, Adney solved this dilemma by making his own stud girdle."
 
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