318 cam

[Hysteric]

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.

Nothing wrong with abbreviations. I just don't know what it means so as to understand what the poster is trying to get across.

How low can we set the bar......

 

[rumblefish360]

Nothing wrong with abbreviations. I just don't know what it means so as to understand what the poster is trying to get across.

How low can we set the bar....

Same boat

No TQ tested, QJ was subbed out.

 

[273]

Nothing wrong with abbreviations. I just don't know what it means so as to understand what the poster is trying to get across.

How low can we set the bar......

"The V/P Index is a mathematically-derived figure, the product of the corrected volume and cranking pressure."

Cam Timing vs. Compression Analysis

 

[273]

What's up with the large TQ and HP dip between 3100 and 3500 RPM in the green curve @ 12.58 in that vid?

Not to sure but the swap from stock intake & Q jet to airgap & demon straighten it out, probably able to tune the demon better.

 

[Hysteric]

Not to sure but the swap from stock intake & Q jet to airgap & demon straighten it out, probably able to tune the demon better.

I would argue that the dip is because they don't tune anything out they just bolt stuff on and off and then make proclamations about performance.

 

[Dale Davies]

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?

What exactly do you mean by "how big a cam?" You can put a long duration cam in, but you will loose bottom end torque and gain high RPM power. For that the rest needs to be up to the forces the RPM generate. Rod bolts and valve springs come to mind just off the top. A high lift lobe also accelerates the valvetrain to higher velocities, requireing stiffer springs. The other issue is retainer to valve seal clearance and then coil bind. If measuring the retainer to seal shows that the new lift will cause interference, the guide needs to be machined as Rusty states.
An engine is a compendium of compromises, and the weakest link will fail. Putting a "big" cam in an engine with factory shortblock and valves is a disaster waiting for the time and place to happen.
There is a fellow races a 1941 International at Bonneville with a 16V92 on the frame behind the cab. His tow vehicle is a '70's vintage Chev 3/4 ton truck. Well it appears to be that. Has a 5 ton frame, 6V92 with twin turbos mounted on the manifolds to fit under the hood, and 8 spd transmission (Fuller I think) and SQHD axles. You would not want to install either engine with a stock frame as you would probably make a pretzel out of them. The old weakest link story.

 

[Dale Davies]

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.

Considering the OEM cams and rockers were doing good if they got to 0.400" lift, much over an "RV" cam with 0.425" lift should be verified.

 

[Dale Davies]

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

Look up a video or two by GT 350 Garage that discusses tuning to run 12:1 on pump fuel. DV also did a video on running up to 17:1 possibly on 87 fuel using water injection. Run a bit lean and advanced timing by say 2° and water to about half what the fuel going in is. The water cools and slows the combustion so the ignition needs a bit of advance. In the phase change from water to steam absorbs huge amounts of heat and the water expands by 1600× in the change to steam.
Watch the two and make a plan.

 

[Dale Davies]

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

Obviously you do not speak of an emisions era 318 cam. The OEMs shortchanged the bread and butter engines by 0.020" to 0.050"intake valve lift as compared to pre emisions and the 350/360 CID engines.

 

[Dale Davies]

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.

Those Comp Cams both have more lift than the OEM. The XE250H is more intended for trucks and/or fuel economy. The XE268H is a mild performance cam kind of a step over an "RV" cam. Both respectable for their intended purpose.

 

[Dale Davies]

Not gonna lie... all that math made me kinda happy inside

If that got you wet, then try High Performance Camshafts and Valvetrains by Billy Godbold. I'm thinking that will require me to read a couple of more times.

 

[toolmanmike]

Those Comp Cams both have more lift than the OEM. The XE250H is more intended for trucks and/or fuel economy. The XE268H is a mild performance cam kind of a step over an "RV" cam. Both respectable for their intended purpose.

@RustyRatRod what was that Comp Cam you always liked. I can't find it in my notes.

 

[273]

Those Comp Cams both have more lift than the OEM. The XE250H is more intended for trucks and/or fuel economy. The XE268H is a mild performance cam kind of a step over an "RV" cam. Both respectable for their intended purpose.

Yes but I bet AJ VP index calculations on these cams would come out as losses to VP.
Which he states will give loss to low rpm tq which that video shows opposite.

 

[rumblefish360]

Yes but I bet AJ VP index calculations on these cams would come out as losses to VP.
Which he states will give loss to low rpm tq which that video shows opposite.

This is the problem with AJ and why I seemingly bust his balls.
He runs things through calculators.
I keep writing that the calculators aren’t the end all be all because the math says so so it must be true. I get push back from several members on this but yet again, and thank you very much! (Takes a bow.) I’m proven right again.

What AJ thinks the calf’s are showing is a 50/50 true and false issue. You did loose some dynamic cranking pressure but he failed to take into account the extra air and fuel that is making more power. This is a fail. Most everyone praises AJ for his wizardry and thanks him for having them loose power or stopping them form even trying a cam swap.

To “Make the most” from a change, other things must be change to go along with it. (Welcome to engine development.) I don’t see a need to adjust the compression that scant amount to recap what you lost in the dynamic cranking compression. It’s ridiculous to take off a set of heads, mill them the amount needed to recapture the pressure and put it all back together.

But according to AJ, you’re a looser if you don’t.

Do what you will…….
Think what ya want……

 

[rumblefish360]

@RustyRatRod what was that Comp Cam you always liked. I can't find it in my notes.

*I Think* it’s the XE268.

 

[273]

What generally I see when looking at dyno'd cam shootouts, most street type cams will make about the same to greater low rpm tq than a stock non performance cam.

 

[273]

If you look at these similar built 496 with 8.5 vs 10.1 there's about an average 5% tq difference across there similar tq & hp curves.

 

[toolmanmike]

*I Think* it’s the XE268.

No that wasn't it. They may not grind it any more.

 

[toolmanmike]

*I Think* it’s the XE268.

265deh is what it was.

 

[AJ/FormS]

I speak from nearly 50 years of slapping SBMs together; some winners and some losers. The Wallace merely predicts what I have already experienced, so that I don't do it again;
because, you know,
doing the same thing over and over, is the definition of being crazy.

 

[rumblefish360]

because, you know,
doing the same thing over and over, is the definition of being crazy.

Not exactly, doing the same thing over and over again expecting a different outcome to the one before (and presumably a disappointing outcome) is a sign of insanity.

Doing the same thing over and over again is a sign of you like what you did so much you want to do it again.
AKA - You built an engine that pleases you that you do it again for the next car.

You say Wallace “merely predicts” but yet you out it forth as an oncoming fact.

My 40 years of experience says you can’t always believe in calculators. But they are helpful you know how to read into them.

 

[273]

I speak from nearly 50 years of slapping SBMs together; some winners and some losers.

Which I find you do have valuable experience and info to pass on.

In the end off the day we should be trying to figure out what would make the OP's happy not us,

eg.. there was one guy with a 2bbl 273 car he put a tunnel ram and a solid 280 cam rest stock and was super happy with it, he eventually added headers gears etc.. now most of us would think that's a terrible idea and for most it probably is but him it was great.

 

[RustyRatRod]

Considering the OEM cams and rockers were doing good if they got to 0.400" lift, much over an "RV" cam with 0.425" lift should be verified.

I absolutely agree!

 

[RustyRatRod]

265deh is what it was.

They will still grind the DEH cams, but you have to call and request it. You won't find them listed anywhere anymore. Kinda dumb because they were a good line.

 

[Hysteric]

They will still grind the DEH cams, but you have to call and request it. You won't find them listed anywhere anymore. Kinda dumb because they were a good line.

I'm pretty sure UDHarold designed those.