MOPAROFFICIAL
Oogliboogli
Open chamber 318 heads usually measure 68cc stock. 360 about 72cc, 340 x about 69-70cc
318 heads on a 360
- Thread starter texas360
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904 with revearse manual with 3:55 gears out back
im currently driving the car with a little wild 318 in it.. im just trying to get this motor built because the 318 is tired..
dartfreak75
Restore it, Dont part it!
In that case I would probably just drive the tired 318 until I could find some 360 heads.
dano
Evil Handy Man
Stock converter? If so a mild cam and your 360/318 head combo should be a fun combo.
On your 318 head, are the springs for your Comp Cam installed? That's another factor to consider, as they will need installed and set up.
dartfreak75
Restore it, Dont part it!
@67Dart273 how can you disagree with something I would do? Because I absolutely would do that!! That wasn't a recommendation I was just saying what I would do.
2800 stall
This motor is already built, cam installed? Then just run it as is. I would not tear down a freshly built motor. It will have more power than that tired 318. Try the combo as is just to see how it goes, it might surprise you, then start building the tired 318. Worst case you replace the heads later on the 360, but for now run that bastard. Save those 318 heads when you replace them for you tired teener for a later build.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Here's what I see;
The cam is a high rpm cam.
The heads are dead at 4500
The stock rebuilt bottom end is sub 8/1 Scr, the 318 heads might bring it back to 8/1. But it doesn't matter, because the XE 275H, will kill the bottom end anyway.
So what you end up with is an engine with a powerband from 3500 to 4500. But it's a cruiser so that might be Ok.
But something will have to be done with the marshmallow bottom end, and this
is a good start, but yur not gonna get away with 2.76 rear gears. Consider 3.23s as the absolute minimum
Yur not gonna like this combo much, cuz it's gonna feel as tired as your 318, until the engine gets up on the cam.
With 3.23s that will be about 34 mph.
Having said all that, the cure is a smaller fast rate-of-lift cam, with an earlier ICA. Leave the rest alone, and you will have a nice cruiser. Lessee,on an LA, Ima thinking a stock 360 2bbl cam if you already have it, Or up to a 262 if you have to buy one.
But I just gotta mention that a 318 2bbl cam would kick azz with that combo, in a cruiser.
Why am I so confident? Because I did that to a 340, back in 75 and that combo is my second most favorite cruiser combo ever! In a 360, it has just got to be even better.
I'm already running 3:55 gears with a revearse manual. I am trying to find a smaller cam kit, but I also want something big enough to give me a good lopey or choppy idle and I was told the duration @50 has to be fairly high to get that.
dartfreak75
Restore it, Dont part it!
Check this video yea it's a magnum so it's not exactly the same but he is running 12s In a truck. With a stock 360 bottom Hughes cam and 318 ported heads.
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I've run 12.6 @ 107 mph with a 360 with 318 heads and a modded 600 edelbrock carb. Granted mine are ported but the port volume is still pretty small and with a 222/234 @ 0.050 cam on a 112 lsa it seems to start making power @ 2500 rpm and mid range is great. I run a 904 with a 8 3/4 with 3.73 gears and 255 M/Ts. Strangely enough the car ran much harder when the heads had less port work and a smaller 1.84 valve and 256 @ 0.050 solid than it does now with a 11/32 1.90 and Crower 271 HDP. Chamber size is 62 cc and a performer 318 manifold.
If it were me give your heads a bowl job and mill them to 60cc to get the comp up and see how it runs.
With ported 360 heads with a 11/32 1.96 valve 60cc chamber and a 243/245 112 solid cam it ran 12.66 @ 106.7 with a weiand stealth and 800 AVS carb
Give it a go you may just be surprised by how it performs.
67Dart273
Well-Known Member
If I did that it was accidental. Did I do that? Damned if I know how. I see there was an "undo" link so I guess I did!!
dartfreak75
Restore it, Dont part it!
Haha it's all good I was just curious lol
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Partly/ mostly true; it is a combination of the late closing intake and the overlap that makes the sound.
But the late-closing intake also softens the bottom end, usually requiring a hi-stall to overcome.
And the overlap is a result of the long durations. Overlap can be exploited with headers to power up the midrange and over the top rpm. But these same headers can pull fuel charge straight across the pistons and into the headers at low rpm. And out the tailpipe the unburned gas goes. resulting in, you guessed it, terrible fuel economy at, city driving.
And the large amount of exhaust duration has to come from somewhere, so it gets stolen from the power-stroke, resulting in, you guessed it terrible fuel economy ALL the time.
Lemmee show you something;
Here is the Wallace predicting your cylinder pressure and V/P, at 500ft elevation, with that 274 cam;I upped the Scr to 8.2 to reflect the slightly smaller 318 chambers.
Here she is with the Comp
Static compression ratio of 8.2:1.
Ica of 64*, 500 ft elevation
Effective stroke is 2.79 inches.
Your dynamic compression ratio is 6.61:1 .
Your dynamic cranking pressure is 124.49 PSI.
V/P (Volume to Pressure Index) is 106
read about V/P here; V/P Index Calculation
Notice the pressure is 124.
Notice the very weak VP, about what a strong slanty makes. This engine needs a hi-stall and gears to be fun
So here is the 360 2bbl cam
Static compression ratio of 8.2:1.
Ica of56*,still 500ft
Effective stroke is 2.97 inches.
Your dynamic compression ratio is 6.97:1 .
Your dynamic cranking pressure is .................. 133.78 PSI.
V/P (Volume to Pressure Index) is .................. 121VP
Here we have typical MAGNUM 5.2VP
Next, lets put a 318 cam in it, with no other changes.
Static compression ratio of 8.2:1.
Effective stroke is 3.10 inches.
Your dynamic compression ratio is 7.23:1 .
Your dynamic cranking pressure is ..........140.55 PSI.
V/P (Volume to Pressure Index) is ........... 133
Notice the pressure has risen to 140 or plus 12.9%
Notice the VP has risen to 133,which is about where the fun starts.
I would not run less than ~124VP, for me, that is already pretty sucked out.
Next lets compare the cams as to all their durations, and I'll use the advertised numbers. First the Comp274, then the Mopar 360 2bbl, and then the 318 2bbl
>276int/118comp/101pwr/286exh/110LSA/54*E-overlap/Ica of 62*
>252int/124comp/116pwr/260exh/112LSA/32*E-overlap/Ica of 56
>240int/130comp/122pwr/248exh/112LSA/20*E-overlap/Ica of 50*
Compare the power strokes; the more degrees you have in a cruiser, the higher the potential is to make good fuel economy.
Compare the Effective overlaps; the more you have, the greater the idle lope.
Compare the Ica's; The bigger the number, the later the intake closes and the lower the idle vacuum.
I like to add the compression degrees to the power degrees to come up with a number that helps tell me how suited to an application, a certain cam is. Among these from top to bottom the numbers are 219/240/252.
for your application, I know 227 is a good number, for both economy and cruiser-fun. but 227 is not on the chart.
No big deal cuz you have a 2800TC, so your bottom end can be a lil soft, cuz when you floor it, you will only be in the soft part for a second. So while I don't like 219 for your application; If you got to have idle lope, then of these three your Comp is the best choice.
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I would love to run and isky cam. Shoot I could even run a solid lift if wanted. I have the 273 rockers and pushrods. But whay about the fable comp 268 I see about 80% of you tubers use?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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why?
with 3.55s and an automatic; you will hit 44mph@5000, spinning all the way;
and 60mph at about 4000 in second gear. The 318 heads will be fine to 4000. Just put a small-port intake on it.
How much better will 360 heads be at 4000?
What good will a 68* cam be, that doesn't power peak until maybe 5000 with the 360 heads.
Ok sure, the 360 with 360 heads and a 268 cam will make quite a bit more absolute power.
But what counts is the average power, to the shutdown. Furthermore, to get that top-end power, the 268 cam gives up bottom-end power.
Street Cams are like sliding windows, about 1500 rpm wide. When you slide it up, you leave the bottom behind. The higher up you slide it, the more important the heads become, and the higher the stall-speed needs to be, to get away from the soft bottom end.
The proper way to use a 268 cam, which wants to power-peak at around 5000, is to gear the car to use second gear,to hit about your highest anticipated speed.
If that be 60mph, then you would need 4.56s, for 60=5200, now you have the potential to be quick., Now the 360 heads are a must-have. Now an overdrive transmission is a must have.Now the 2800TC is optional. Now your starter gear is 11.17 waaay killer, and street tires cannot deal with that, so you are driving on the two-barrel in first, unless you just like frying the tires.
But you could do the same thing in first gear with 2.76s and now 60=5300. But your starter gear is now a tad on the low side at 8.11, so the 2800TC is back on the table. And now, you no longer need an overdrive.
But if you work the formula backwards, you find that 60 mph requires a gear of 7.00@5000. The engine doesn't care how you get it. So in 1.45 second gear, you would need 4.83 gears. In 2.45 first gear, she would need 2.86s. So, as you can see, there is no way to satisfy the cam in either gear.
But what about at 4000? At 4000 the required gear to hit 60 is 5.11, so with 1.45 second gear, this requires a rear of, wait for it ........ 3.52.....lol. Badaboom!
Wait, you already got those. And you got the 2800TC. And the 318 heads are easily good to 4000. Soooooo, all you need is a matching intake and a 4000rpm cam.
Will it be as fast to 60mph as the 268 with 360 heads?
Since you can actually harness first gear with the smaller cam, and she hits 60 at the optimum rpm. I would almost bet money, that the smaller cam could be quicker.
But hang on, we're not done yet.
The cam does not hit peak power at a specific rpm, but rather, plateaus over a few hundred rpm. say 400. So if you had a cam that "peaks" at 4000, it will have a peak at say from 3800 to 4200. Furthermore, you can, work the heads to stretch the plateau out say another 200 to 300. So now that 4000rpm cam is actually gonna be able to be shifted at say,4500, which is about the limit of the 318 heads. So then, we could run the same percentage higher gear than 3.55s...... if you wanted to. Or you could run the next smaller cam, or you could extend the 60 mph top speed by the same percentage. Since 4500 is about 12% higher, this would be 67 mph.
Ok soooooo what cam is gonna power-peak in the ballpark?
That would be the 318 2bbl cam. But If you have to buy a cam, Then I would not use the Mopar OEM cam, because it has notoriously long clearance ramps that are designed to outlast the engine,lol. as are most oem cams. including the 360 2bbl cam.
So then, you could up-cam one or two sizes, with a fast-rate-of-lift- design, and not sacrifice bottom end torque. Or you could keep it the same which would pump up your cylinder pressure, making the potential for better fuel economy. Or do some combination.
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i was going to private message you,but box is full. my ultimate goal for the 360 is to be at around 300-350 hp to the ground... i want something that is stronger and pulls harder than the 318... car weighs like 3600 lbs with me in it...
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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4bbl 360s were born at 240RWHP, back in 71, with nothing but a 340 cam, and an advertised compression ratio of 8.0
After headers, and a timing adjustment, she'll be chasing 300.
But just remember, this horsepower does not arrive until 5000rpm,44 mph with 3.55s, in first gear. But to reap it, you gotta get there first! So if the combo is a slug below 3500/31 mph, where say 95% of your driving will be done, then do you still want 300plus horsepower? Well, with a 2800TC, she won't be that much of a slug off the line,lol. But the point remains, that the power does not show up until ~44mph.
What you really want is torque lots and lots of torque. With a normally aspirated engine, there are about two ways to get it;
1) cubes, and 2) cylinder pressure.
Cylinder pressure is a balance of Static compression ratio, and Intake closing angle, against the ability of your gas to resist detonation.
What that means is; A) if your engine has a low Scr, then it needs an early closing Intake, to make pressure. The more pressure she makes, the more torque she will make, until the engine hits the detonation wall. But B), if the engine is a hi-Compression unit, then the Intake has to close a lil later, to prevent detonation from too much pressure.
The definition of horsepower is;
Torque x rpm/5250= hp
So, to make lots of hp, you just need to create lots of torque, hi up in the rpm band. And the cam unlocks this by moving the hp up or down the powerband.
Like this; say you had an engine that made 300ftlbs of torque at 5250 rpm; then
300x5250/5250=300hp. Say you then changed the cam and moved the 300ftlbs up the powerband to 5450;about one camsize, then
300x5450/5250= 311 hp.
That is how you make hp. Of course the rest of the engine has to support the new rpm, to achieve that.
But, with no other changes, that bigger cam is gonna cost you about 6 or more psi cylinder pressure on the bottom, which could represent 6 or more hp off the bottom, depending on your stall-rpm. If your pressure is already very low, then this sucks, and costs you the next bigger TC to overcome. The loss is still there, you just never feel it anymore.
After headers, and a timing adjustment, she'll be chasing 300.
But just remember, this horsepower does not arrive until 5000rpm,44 mph with 3.55s, in first gear. But to reap it, you gotta get there first! So if the combo is a slug below 3500/31 mph, where say 95% of your driving will be done, then do you still want 300plus horsepower? Well, with a 2800TC, she won't be that much of a slug off the line,lol. But the point remains, that the power does not show up until ~44mph.
What you really want is torque lots and lots of torque. With a normally aspirated engine, there are about two ways to get it;
1) cubes, and 2) cylinder pressure.
Cylinder pressure is a balance of Static compression ratio, and Intake closing angle, against the ability of your gas to resist detonation.
What that means is; A) if your engine has a low Scr, then it needs an early closing Intake, to make pressure. The more pressure she makes, the more torque she will make, until the engine hits the detonation wall. But B), if the engine is a hi-Compression unit, then the Intake has to close a lil later, to prevent detonation from too much pressure.
The definition of horsepower is;
Torque x rpm/5250= hp
So, to make lots of hp, you just need to create lots of torque, hi up in the rpm band. And the cam unlocks this by moving the hp up or down the powerband.
Like this; say you had an engine that made 300ftlbs of torque at 5250 rpm; then
300x5250/5250=300hp. Say you then changed the cam and moved the 300ftlbs up the powerband to 5450;about one camsize, then
300x5450/5250= 311 hp.
That is how you make hp. Of course the rest of the engine has to support the new rpm, to achieve that.
But, with no other changes, that bigger cam is gonna cost you about 6 or more psi cylinder pressure on the bottom, which could represent 6 or more hp off the bottom, depending on your stall-rpm. If your pressure is already very low, then this sucks, and costs you the next bigger TC to overcome. The loss is still there, you just never feel it anymore.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The truth is that you can bolt all the 318 top end stuff onto your 360, including the cam; and the 360 will feel NOTHING like the 318 you just robbed.. No contest. For best results install a free-flowing dual exhaust or Big single. Headers on 318 heads with a 318 cam, IDK . I doubt you'll notice much, other than the racket,lol..
Already have long tubes and 2.5" with flows on the 318 in the car.
I have put the 302 heads on a few 360s. 2 were in A bodies. Totally stock 360. Both cars picked up about .5 in the quarter mile at the street drags. Kim
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U Betch ya. On stock 360s. KimWait...... You put smaller heads on an big engine and ran faster
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