Camshafts For Dummies

A primer course on all the systems and terms common to all cams

[yurbeeinwatched]

I only buy my cams based off how cool the sticker in the box is. A woodpecker smoking a cigar, an iron cross, etc. It's about the stickers.

[dontimberman]

I saw the title and thought “well if he is going to address it to me I should at least watch it.”

[robwhitez]

For the Duration of this video, you opened my lobe separation angle and lifted me to a higher place. You must be a Guru.

[Torquemonster]

Also.. something for newbies to remember.. when considering how "big" a certain camshaft is.. they're sized by their duration.. not lift. Lift is critical, but not what defines how "big" a certain camshaft is. It's more about how long you hang the valve open.. not how high you lift it... awesome video Uncle Tony. 👍

[clintonflynn]

I see " ...for dummies, " I click. Thanks, Tony, for the tutorial.

[marcoceccarelli]

Kids today have it easy everything you need to know is online. I lost my father when I was 9 years old. Everything I learned was the hard way by making mistakes. Nobody would tell you nothing everything was a secret Time Has Changed.

[manicmechanic]

My auto instructors couldn't even tell me this.

[beans]

That was a good explanation keep them coming and giving us more of those old school power adding tricks

[davidiverson]

Uncle Tony, this is the probably the most concise and straightforward cam explanation videos anyone could ask for. Thank you as always for imparting the old school know-how!

[model]

You are an excellent teacher. I've heard those specs thrown around for years and never understood exactly what they meant. And I guess I was either ashamed to admit that I didn't know, or figured I wouldn't understand it even if it was explained to me. Thanks for telling me in a way that didn't make me feel like an idiot. 👍

[raphaelhernandez]

Thanks the most someone has explained this to me. I have to watch something over and over to finally get it

[jimjungle]

The camshaft rotes at half the amount or, "speed" of the crankshaft.


Normally when referencing, "degrees" they are crankshaft degrees, not camshaft degrees.The degree wheel mounts to the crankshaft. The more aggressive, or quickly the valve opens, the heavier a valve spring usually has to be to control valve float at the same RPM and faster hydraulic lifters open valves, the heavier valve springs have to be to prevent lifter pump-up at the same RPM. There is advertised duration, 0.050" duration and there is S.A.E. duration. With hydraulic lifters S.A.E. duration is usually at 0.006" lift, opening and closing sides of the cam lobe. Some camshaft makes use a lower lift for a higher advertised duration number. Some car makers use a different opening lift with a different closing lift when computing advertised duration. Before 1964 the car industry standard for hydraulic cam lobes was to make cam lobes that had a 0.050" lift duration that was 70% of the SAE 0.006" lift. This for acceptable wear. Around 1962 the aftermarket and industry engineers were trying more aggressive cam lobes. Around 1962, Iskenderian Racing Cams promoted high performance hydraulic camshafts with more aggressive 75% cam lobes. The 0.050" duration was 75% of the SAE 0.006" duration. In 1965 Pontiac changed all of its 4 barrel and tri-power carb camshafts to75% cam lobes, with the two barrel carb engines staying with 70% cam lobes.Pontiac may have tried that with the 1964 GTO camshaft too. The 1964 GTO camshaft was the same part number for GTO engines and on paper was the same as the 1964 4 barrel automatic transmission camshaft, BUT IT HAD A DIFFERENT PART NUMBER! In 1965 Chevy had the 350 horsepower 327 and new 396 engines with 75% cam lobes. In 1966 Ford had the 390 GT and Olds had the limited W-30 camshafts, for the new 75" cam lobes. The 1967 Dodge 440 Magnum still used 70% cam lobes, but the 1968 340 went with 75% cam lobes. "Theoretical" maximum power happens with the camshaft degreed with the intake centerline at 106 degrees ATDC, REGARDLESS OF LOBE SEPARATION, but this is just theory, as is, maximum torque happens with the intake centerline at 102 degrees ATDC, regardless of lobe separation. These theories are usually very close with, "correct" sized camshafts. The closing of the valve is limited by the mechanics of the valves slamming against the valve seats. The intake valve runs, 'cold" and can take fast slamming to be noisy. The exhaust valve runs red hot and is more easily damaged and must be closed more gently. Modern computer designed hydraulic cam lobes are even more aggressive now and some are designed to prevent lifter pump up at higher RPM with less valve spring pressure, but the really aggressive camshafts make more power and their cam lobes still require the heavier valve springs.

[mikethacker]

I'm a chevy guy but most everything Tony talks about is relative to all engines and he seems like a down to earth guy and seems to like to teach others. Thank you Tony

[albertgaspar]

Another benefit to roller lifters, beside reduced friction and wear at initial break-in, is that if you try a radical ramp on the lobe, it can try to push a non-roller lifter as much sideways as upwards, which causes binding inside the lobe bore. Mopar adjusted this by using "fatter" lifters and bores, meaning the diameter was wider than other engines, so a Mopar cam can get away with a faster ramp before it needs the heavier roller lifter. Other engines would use a "mushroom" lifter that had a wider foot or base on the cam lobe to have that increased diameter benefit.
The sooner you push that intake valve to full lift--assuming the valve springs can handle it--the sooner that full lift occurs during the duration the valve is open. If you ported the head to flow best at full lift, did an angle valve job that also works best at full lift, and the valve is unshrouded at full lift, this means the valve is performing longer during the duration, at the lift it was designed to work best at.
But what if the duration of time the intake is open (from its moment coming off the seat to full lift and back onto its seat again), extends into the time the exhaust valve is open? That is overlap. Too much, and you have emissions issues, low vacuum for brakes, and rough idle. But if you increase the ramp speed, ie, the intake valve pushes open to full lift sooner due to roller lifters or an increased diameter of the base of the lifter, now you can decrease the entire duration (from lifting the valve off the seat, to getting to full lift, and returning it to the seat again) but not lose (or lose much of) the amount of time the valve is at full lift. It would be as if you only had a mile of pavement to travel, and you want to spend as long as that distance at 100mph as you can. The car that accelerates to 100mph the quickest, is the one that lets you enjoy 100mph for as long as you can over that 1 mile of pavement before the car has to come to a complete stop. That's where the expense of a roller lifter setup and springs to handle its weight come in handy.
But there's a case for not designing your intake port and valve to work its best at full lift. During the duration, the valve sees full lift once, but partial lift twice--once when the valve is opening, and again when its closing. some designers like to work on mid valve lift performance for that reason.

So, now you have the basics, the terminology, and now you have some philosophy :)

[DanITGuy]

Now That's how its done! Great Video Uncle Tony!! Makes me think back to when my Uncle Bob was Explaining it to me when I was a kid! We were working on his Dual Quad Cross ram 440 and he explained why the exhaust pulse was so important for scavenging and the how the supercharging caused by the intake pulse made the Dual Quad cross ram intake so great!! Nice Job!!

[AryDontSurf]

I knew I should've kept my cam questions to myself...

[MikeBrown-iipt]

Excellent explanation! There are so many #s on cam cards that it's easy to get confused, especially for those who don't have much experience. To me, the 3 most important #s are advertised lift, 050" duration and LSA. You explained them in language that's understandable. Last summer, I was at a local car show and one of the participants was really talking up his engine. He used a term that I hadn't heard in YEARS when he said it had a 3/4 cam. Now, I know what a 3/4 cam is and, in my experience, they're not all that great. You should've seen the "deer in the headlights look" on his face when I asked him what a 3/4 cam is.

[stuborowski]

I love the old Direct Connection purple shaft cams

[davidkitting]

Very informative video. I think I used to know this stuff. Amazing how much can be forgotten. Also amazing how much knowledge is freely shared these days. Awesome!!!

I really enjoy your content and the way you explain things that are both "mandatory" and "not mandatory" and myths. I am new to your channel, but I would love for you to take a survey of which engines people want to build from scratch to stock specs, and do a series on the winner of that survey, and build it from scratch, just to stock specs to get it running on a bench. All other adjustments for various applications can be covered either by you, in a separate video, or a channel that you would recommend for that purpose. I would really love to watch that, no matter the winning engine (even though I am a Ford guy), because I love the way you explain things, and your passion for this stuff. You remind me of my engine-building teacher in college, that got down deep into this stuff, and gave physical examples of various things, to make us truly understand every nook and cranny of building an engine, including details like, heating gasoline in a beaker and putting a sample of each stage of heating into a glass tube and lighting it, to demonstrate how the different "octanes", and the way they burn. I'd like to see everything, from 'cylinder honing" to using feeler guages and that green string that you use to measure tolerances for caps and bearings, micrometers, small hole gauges, calipers, etc.., pre-oiling and preparing the engine for "first-start" and "break-in". I know that this would probably need to be a "sponsored" video, but I am just showing my interest. Regardless of whether it happens or not, I will still be watching. :)