65Dart270Sedan
Member
What is the biggest cam you can put in a LA 318? I saw something about you can’t put high lift cams in them without grinding down the valve stem guides. Also, what mods other than springs will need to be done?
Do you mean a "stock" 318 ? Or a 318 that has been set up for a large cam?What is the biggest cam you can put in a LA 318? I saw something about you can’t put high lift cams in them without grinding down the valve stem guides. Also, what mods other than springs will need to be done?
High lift cams mean long duration cams, which leads to very late-closing intake valves which leads to very low cylinder pressure which leads to a sluggish pig of an engine that everyone loves to hate, because it is gonna cost you a convertor and some 4series gears, and she will drink gas like a fish in a lake.Also, what mods other than springs will need to be done?
Any cam you install (unless it is real close to stock specs) should be checked for clearances.What is the biggest cam you can put in a LA 318? I saw something about you can’t put high lift cams in them without grinding down the valve stem guides. Also, what mods other than springs will need to be done?
This is generally not 100% correct since this comment ignores the lobe ground on the cam. You can have very high lifting valve with or without additional rocker ratio.High lift cams mean long duration cams, which leads to very late-closing intake valves which leads to very low cylinder pressure which leads to a sluggish pig of an engine that everyone loves to hate, because it is gonna cost you a convertor and some 4series gears, and she will drink gas like a fish in a lake.
Define should. What are the parameters that dictate a high lift cam?Let's back this up a second...........is this even an engine that SHOULD HAVE an extreme high lift cam?
This is not accurate except guide work.In other words is this a stocker with low compression pistons? IF SO you don't want to put something in there that needs guide work as it simply will not perform with stockish pistons, etc.
Has nothing to do with the cams lift.And how about the exhaust system?
Hi AJ, I think I've seen you write that you've ran the 318 cam in a 340 engine. What is the theory behind that? Thanks in advance.High lift cams mean long duration cams, which leads to very late-closing intake valves which leads to very low cylinder pressure which leads to a sluggish pig of an engine that everyone loves to hate, because it is gonna cost you a convertor and some 4series gears, and she will drink gas like a fish in a lake.
So my recommendation is that you start with available high-compression pistons, and work backwards to find a reasonable street cam, and just go have fun. I guarantee this will be better than stuffing a 292 cam into the stocker,
Wow. Thank you. Interesting read for sure!Not only the cam but the entire 318-top end, did I install. That was about 1974, and those were the parts that I had.
Plenty of cylinder pressure, and low-rpm TORQUE was the result. Which for me, made more than adequate street performance for the lightweight-A that I put it into.
The 340 cam installed at 110, has in Ica of 64*. In a 10/1 340, this will make about 163 psi and a modest V/P of 129 .
The 318 cam installed at 108 has an Ica of 48*. In a 10/1 340, this will make about 187psi and a super strong V/P of 166
That big V/P will let you run a factory stall, which is usually 1800/2000, which will stall a lil higher at the higher V/P; and very small rear gears, down to 2.76s.
whereas that V/P of 129 wants a stall in the mid to high 2000s, and at least 3.23 gears.
The small-port head 340 with the 318 cam, will power-peak at ~4200, and will want to be shifted at ~ 4600 rpm, With 2.76 gears, this will be close to 55(zero-slip) mph in First gear.
The big-port 340 with the 268 cam , will easily go to 5000, and will want to be shifted around 5500. With 3.23s this comes to ~56 mph(zero-slip) in first gear.
The difference of course is that the bigport headed 340 will make more absolute power.
The question is, which will get to 55 the quickest on street-tires, and on the street..., cuz that 318 cammed 340 is gonna spin right alongside the 340 cammed 340. If she gets ahead off the line, there's no telling which will ET lower.
In the meantime;
if you have never driven a modest-stall car with a V/P of 166;
I can tell you that a 68 Magnum 440, makes a V/P of ~167.........
And the good news is, the very high cylinder pressure is insanely responsive to the throttle, and/or you can gear it to idle down the hiway and get EFI-type mpgs.
And the bad news is, that the gasolines of today, no longer have the octane to support 187 psi with iron heads at full power.
so then, you gotta consider the alternatives;
Like alloy heads, or injection of an anti-detonant.
I wouldn't do this today, because;
1) I just ain't that poor,
2) I can't buy gas for it
3) that was a moment in history; I turned 21 that summer.
Today, at age 70, I am contemplating installing a 10/1 360 with a 360 2bbl cam, into something around 3400 pounds. The pressure may be too high for even 91 gas, but I got some ideas... I'm expecting point to point fuel-economy in the high 20's/low 30's, in overdrive.
BTW
I ran headers on that combo, as I do on almost all my combos.
Neither the 318 cam nor the 360 actually "need" headers because neither of them have much overlap. But in my experience, a 318 4bbl really wakes up with headers. The inertial tuning still works, helping to evacuate the cylinders on the exhaust stroke, which, if the rings are working, will, with the smallport topend, will yank pretty hard on the plenum.
Read about V/P here; V/P Index Calculation
Not only the cam but the entire 318-top end, did I install. That was about 1974, and those were the parts that I had.
Plenty of cylinder pressure, and low-rpm TORQUE was the result. Which for me, made more than adequate street performance for the lightweight-A that I put it into.
The 340 cam installed at 110, has in Ica of 64*. In a 10/1 340, this will make about 163 psi and a modest V/P of 129 .
The 318 cam installed at 108 has an Ica of 48*. In a 10/1 340, this will make about 187psi and a super strong V/P of 166
That big V/P will let you run a factory stall, which is usually 1800/2000, which will stall a lil higher at the higher V/P; and very small rear gears, down to 2.76s.
whereas that V/P of 129 wants a stall in the mid to high 2000s, and at least 3.23 gears.
The small-port head 340 with the 318 cam, will power-peak at ~4200, and will want to be shifted at ~ 4600 rpm, With 2.76 gears, this will be close to 55(zero-slip) mph in First gear.
The big-port 340 with the 268 cam , will easily go to 5000, and will want to be shifted around 5500. With 3.23s this comes to ~56 mph(zero-slip) in first gear.
The difference of course is that the bigport headed 340 will make more absolute power.
The question is, which will get to 55 the quickest on street-tires, and on the street..., cuz that 318 cammed 340 is gonna spin right alongside the 340 cammed 340. If she gets ahead off the line, there's no telling which will ET lower.
In the meantime;
if you have never driven a modest-stall car with a V/P of 166;
I can tell you that a 68 Magnum 440, makes a V/P of ~167.........
And the good news is, the very high cylinder pressure is insanely responsive to the throttle, and/or you can gear it to idle down the hiway and get EFI-type mpgs.
And the bad news is, that the gasolines of today, no longer have the octane to support 187 psi with iron heads at full power.
so then, you gotta consider the alternatives;
Like alloy heads, or injection of an anti-detonant.
I wouldn't do this today, because;
1) I just ain't that poor,
2) I can't buy gas for it
3) that was a moment in history; I turned 21 that summer.
Today, at age 70, I am contemplating installing a 10/1 360 with a 360 2bbl cam, into something around 3400 pounds. The pressure may be too high for even 91 gas, but I got some ideas... I'm expecting point to point fuel-economy in the high 20's/low 30's, in overdrive.
BTW
I ran headers on that combo, as I do on almost all my combos.
Neither the 318 cam nor the 360 actually "need" headers because neither of them have much overlap. But in my experience, a 318 4bbl really wakes up with headers. The inertial tuning still works, helping to evacuate the cylinders on the exhaust stroke, which, if the rings are working, will, with the smallport topend, will yank pretty hard on the plenum.
Read about V/P here; V/P Index Calculation
No doubt! I always learn something from AJ. I always appreciate how thoughtful he is.Not gonna lie... all that math made me kinda happy inside
Indeed he is and on top he takes a bunch of time to run through a lot of calculations to help demonstrate to help you understand how his math is working to figure out things.No doubt! I always learn something from AJ. I always appreciate how thoughtful he is.
One downside might be if only focusing on VP index is it don't account for VE%, eg.. does compressing less fuel/air higher equal, better, worse than compressing more fuel/air lower ?
I'm just trying giving the OP a counter to AJ, I do believe AJ gives valuable info, but seems super focus on VP which I do believe is important but I find something missing from it, most have put a cam in a low cr engine with factory stall and highway gears at some point and probably found it overall better, 318willrun has basically centered his builds/channel around doing that.
Here's a dyno of a low cr 360 and xe250h and xe268h both pick up low rpm tq over stock and there's ton more examples out there.
I just feel something is being left out of his equation.
Pointing out the possible down sides is fine but saying it basically can't work when there's obvious examples of it working is too much.
I'm just trying giving the OP a counter to AJ, I do believe AJ gives valuable info, but seems super focus on VP which I do believe is important but I find something missing from it, most have put a cam in a low cr engine with factory stall and highway gears at some point and probably found it overall better, 318willrun has basically centered his builds/channel around doing that.
Here's a dyno of a low cr 360 and xe250h and xe268h both pick up low rpm tq over stock and there's ton more examples out there.
I just feel something is being left out of his equation.
Pointing out the possible down sides is fine but saying it basically can't work when there's obvious examples of it working is too much.
Whats V/P?The 340 cam installed at 110, has in Ica of 64*. In a 10/1 340, this will make about 163 psi and a modest V/P of 129 .
The 318 cam installed at 108 has an Ica of 48*. In a 10/1 340, this will make about 187psi and a super strong V/P of 166
Have to disagree with this statement. A local guy had no problems running 240 psi in 87 pump fuel. Granted he was not the ordinary guy on a forum but a well accomplished tuner who pushed the boundaries of combustion but still he would often state that people run too high an octane fuel for the cylinder pressure they run. There's more to detonation than just octane numbers.And the bad news is, that the gasolines of today, no longer have the octane to support 187 psi with iron heads at full power.
I keep forgetting all the abbreviations. It’s always short hand with his response. It’s Ok if you can remember them.Whats V/P?
Have to disagree with this statement. A local guy had no problems running 240 psi in 87 pump fuel. Granted he was not the ordinary guy on a forum but a well accomplished tuner who pushed the boundaries of combustion but still he would often state that people run too high an octane fuel for the cylinder pressure they run. There's more to detonation than just octane numbers.
I'm just trying giving the OP a counter to AJ, I do believe AJ gives valuable info, but seems super focus on VP which I do believe is important but I find something missing from it, most have put a cam in a low cr engine with factory stall and highway gears at some point and probably found it overall better, 318willrun has basically centered his builds/channel around doing that.
Here's a dyno of a low cr 360 and xe250h and xe268h both pick up low rpm tq over stock and there's ton more examples out there.
I just feel something is being left out of his equation.
Pointing out the possible down sides is fine but saying it basically can't work when there's obvious examples of it working is too much.