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?
318 cam
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Do you mean a "stock" 318 ? Or a 318 that has been set up for a large cam?
Here ya go. Here's 7 pages of threads with "318 cam" in the title. There is no good answer to your question but a lot of information about it.
Search results for query: 318 cam
Search results for query: 318 cam
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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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,
.750 lift without hitting the piston. lol
Any cam you install (unless it is real close to stock specs) should be checked for clearances.
Some have reported a tic over .500 lift with no issues with retainer to guide clearance. Others have said they've had contact with as little as .450 lift. So it's best to check. IMO, any type of performance build "SHOULD" have some type of positive valve seal on it, which requires cutting down the valve guide anyway. On my slant 6 head I have built, I machined the guides to accept positive valve seals and I have over .750" between the top of the guides and the retainers. Better safe than sorry.
Also, you don't "grind" the guides. Lets use the correct terminology here, since you are wanting to learn. They are cut with a special cutter. There are several different sizes. Which valve spring you choose needs to be a deciding factor based on the ID of the valve spring. This is an example of the type of tool that I use for the job. It will cut the OD of the valve guide, cut the top down and also will enlarge the spring seat all at the same time. Although it will also cut the spring seat deeper, at NO time whatsoever do I recommend THAT. There are different tools that will do the same job(s) but this is similar to the style that I use. I don't think the one in this picture will cut the top of the guide down, but mine does.
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.
You should pay attention to it though, it’s your fair warning.
Even though it assumes a lot, a real lot! It also ignores and assumes a lot in your behalf. Then again, maybe you want to go there?
Rustyratrod has posted up the tool needed. You can use this in a hand drill or better yet a drill press. Pay big attention to the angle of the bit as it contacts the bottom. Take off only as much as needed to create a smooth even surface as the drill bit is in the guide as straight as you can get it. You’ll be fine.
67Dart273
Well-Known Member
Let's back this up a second...........is this even an engine that SHOULD HAVE an extreme high lift cam? 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. And how about the exhaust system?
Define should. What are the parameters that dictate a high lift cam?
This is not accurate except guide work.
Has nothing to do with the cams lift.
Norm.P
Well-Known Member
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.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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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
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
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Norm.P
Well-Known Member
Wow. Thank you. Interesting read for sure!
Norm.P
Well-Known Member
No doubt! I always learn something from AJ. I always appreciate how thoughtful he is.
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.
That and other things is why you say I bust AJ’s balls on the assumptions. There are a bunch of holes I can shoot fish in a barrel with.
Overall, AJ is fine and his post above isn’t worth loading the gun over. Some of the engine build has to be on the builder/car owner to consider and work out. AJ wasn’t asked to build an engine for him. He was just pointing something out. Everything can and should be adjusted for “YOUR” build and what you’re looking to achieve.
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.
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.
He constant focus on the issue is to max out the available octane available to return the mist power for a given cam and compression combo. This can be a problem since he swears by the self claimed fact of being able to run 87 octane on 11-1+ engines and small cams.
This may it be a good combo for the available octane in the region as well as elevation. Also a side note of, the pump says 87-89-91-93…. What it will test out to is another issue. This is why I pull his chain among other things.
I’ve stated this before and did receive some pushback though the key is where the pushback is in a certain build of an engine. The constant use of a calculator IMO leads people blindly down a path that veers off the road their use to traveling and others a stray.
Your above video as an example is perfect and a prime example. To push it a step further, let’s pretend the combo with the smaller cam is specked out as a perfect build. AJ loves to come back and state such things as, “Your really loosing out on power with the bigger cam plus your making enough power to completely blow the tires off and waste time spinning them going nowhere fast.
This is only true when you’re at wide open throttle which is an assumption on his behalf that you have no right foot control and did nothing for tires or suspension. The engine side of it is very small potatoes and the increase in compression is very small to make up what the calculators will show as a loss. A loss you’ll never feel and be hard pressed to see at the drag strip. Also when you do, you’ll probably want to chop off your hand for following a fools advice by tearing down your engine to fix a problem which really doesn’t exist.
Technically- yea, he’s right. Will you ever feel 10ft lbs in a 360 producing 400 ft lbs? If you do, register your *** with the earthquake people for their early warning system substitute in case the machine should loose power, your *** will be a OUTSTANDING substitute. But according to AJ, you’re an idiot for a few things and it starts with assembling a bad combo.
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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 keep forgetting all the abbreviations. It’s always short hand with his response. It’s Ok if you can remember them.
On this and most forums, the way I see it, I’m most likely dealing with people that are average tuners and that would be at best at times considering the questions being asked. Above average guys already know. With that said, my answers given are thoughts on the simple KISS method rather than possibly get the guy into trouble.
I’d rather suggest something easier or less powerful than run on the edge of their knowledge or push the power potential and have them upset when things don’t go well or run right. In the end, it’s more helpful to the new guy or novice and sometimes, even the intermediate gearhead.
This isn’t meant to be rude, insulting or diminish the person’s intelligence but just to help a guy out so they can enjoy the ride and get motoring on down the road. That’s where they’ll be happiest.
It beats throwing a wrench and pinging while they drive.
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