Don't understand cams

[AJ/FormS]

Nice lesson but I think I spotted a few errors of your own.

 

[Cudafever]

RE: post 36.....


aj, don't forget the time element, and lay it on top of valve lift.

Well, that's not clear is it?

When I look at overlap, I not only look at time, the time the valves are off the seat, but how FAR the valves are off the seat. If you look at the oft referred to comp drawing where they show the wider LSA having the valves off the seat longer, the valves ain't open very far. So really, when looking at overlap, you have to consider how far the valves are open, since, as a GENERAL rule, when th valve is further off the seat, it flows more.

Consider this....you have spent a long time porting your heads. And you spent a bunch of time working the seats to get low lift flow maxed out. Yes, you gave up some in the higher lifts, but damn, they flow like a striped *** ape at low lift, especially at overlap lifts. Since the air don't know what direction it's going, you can bet that the ports flow as well backwards as good as they do forward (this is critical because once the piston is on its way down, and the cylinder is gaining volume, therefore the air/fuel column is going to follow the path of least resistance), what stops your air/fuel column from going out the exhaust port during overlap? There is already a low pressure area in the header. There is virtually zero air flow moving into the cylinder at overlap, and what is moving is going to have an issue with the big *** piston in the way. So most likely, you will have some of the charge going into the exhaust, and some into the intake tract. Almost zero will make it to the chamber AT OVERLAP.

As a side bar, when you have intake reversion, you have a column of air move through the carb and it picks up fuel. Now, a little reversion shows up and the same air that just went through the carb and picked up fuel when it did, that same air turns around and goes backwards out the carb. The booster is stupid, and don't know what way the air is going, and as such, it picks up fuel AGAIN. Then the reversion changes direction, the air goes back through the carb for the THIRD time and picks up fuel AGAIN. We now have 200% more fuel in the same air. This is EXACTLY what happens at low speeds and idle.

You've got all this air moving at low engine speeds, in wrong directions, picking up more fuel, adding to a rich condition already, and now we slap a cam with a big overlap number or use a tighter LSA. You have just made the issue all the worse. So you take the big overlap/tight LSA cam out, cut way back on overlap and widen up the LSA and the engine responds so we all bless the wide LSA, market the **** out of it and get rich.

There is a flip side to this oddessy. What if you rethought your porting ideas? What if you took the time to flow your heads backwards, on both valves and learned how to do things to stop flow going the wrong way. We may lose a bit of flow all over going in the regular test direction. But we stopped flow going backwards.

So not only do we port to stop reverse flow, we port to kill low lift flow. Not to stop it, but knock it down a bit. And we now gain some in the mids and maybe a bit at high lift. Now we are getting somewhere. You can see how port flow can dictate cam timing, and the opposite is true.

Now, we decide that we not only are going to port to reduce reverse flow, and port to reduce low lift flow where reversion is at it worst, what if we play with the valve job? What if we can increase the bowl size as a percentage of valve diameter, but not use a bigger valve, which generally a big valve helps low lift flow? So now, we have the valve job helping to stop reversion.


Think about how all this affects cam timing. If the head flows more overall, you can reduce @.050 timing yet turn the same RPM. This helps with bottom and mid range power with no drop off in HP. But what if we could run a bit more @.050 and because we have reduced reversion and reverse flow, we can add a bit more @.050 to the cam, but we don't have the effects of reversion.

But we want the RPM range to not go any higher, and more duration will make it RPM higher. Now, you can move the LSA a couple of degrees tighter. You get a big boost in the middle, which helps in the gear change, and th narrower LSA will keep the engine from RPM'ing higher than we want.

The point is, it's not all about the cam. It's about what you can do to make air do what you want and then how to take advantage of it.

I think some head guys spend way too much time worrying about low lift flow and it handicaps the engines ability to use a narrower that accepted LSA, and leaving power on the table.

yellow rose, thanks, that got my mind a rolling!!!
Aj u as well. they have both been printed so i can sook up some more.

norton, them two post is only a drop in a bucket as to what a cam grinder need to know to build you the best cam for your ride and purpose.
Just like buying a Torque Converter, the more Honest you are with then about what you have and what you want, the better(in your case)"Cam" you will install, and the happier you will be with the finished product.

You don't have to understand anything they have said............but the cam company HAD DM WELL BETTER!!!!!

 

[yellow rose]

Oh brother.

That's just bad advice. If you can't give good information then don't give any.

OP, Please ignore everything in that post.

When you select a custom grind can you will select the lobes you want based on their duration, lift and ramp velocity. They are listed in the catalogue. Some are race only and assume a short lifespan of massive abuse. Some are like factory spec and will last a million miles. there's everything in between.

You will usually pick different lobes for the intake than the exhaust as they require different function. Exhausts are subject to more heat and abuse often have slower ramp speed. Exhaust air is pushed out and intake air is pulled.

Air is much more stretchy when it's being pulled than pushed. So a faster operating intake lobe is a good choice.


For the same reason Most engines are designed with exhausts ports which don't flow as much air as the intake. Or more accurately, they prefer to make the intake flow as good as possible, and the exhaust just has to be good enough!

To help compensate for this. In a performance application the exhaust lobe often has more duration than the intake. (Meaning it's bigger)

Figuring out where the lobes will go is the next part. This includes lobe separation angle.

For a street/strip camshaft, overlap is a big consideration. Too much Overlap can makes your engine idle rough and feel soggy at low rpm.

Lots of lobe Duration is great for high rpm but makes the engine inefficient at lower rpm. Particularly idle.

Overlap increases as a cam's duration increases.

Duration is often measured as crankshaft degrees in which the valve is lifted a minimum of .050" from it's seat.

This is expressed as "degrees at 50 thou" Before this point the valve isn't really functioning in any significant way.

A cam lobe with 190 degrees duration at .050" lift is very small. Like a factory camshaft.

A camshaft with 290 degrees at .050 is very very big. Like max effort " rebuild every dozen drag strip passes" type big. Think top fuel engines.

A narrow lobe separation is considered 103-107. It makes an engine operate with higher peak torque output. (Not necessarily peak horsepower) But It takes a bit from the low end of the torque curve and adds it to the peak torque. As a result idle quality can suffer. Also chance of detonation is higher. This limits compression ratio.

A wide lobe separation does the opposite. It takes from the peak of the torque curve and adds to the areas below the peak. Idle quality is superior and chance of detonation is reduced. Meaning a higher compression ratio can be used.

Typically wide separation is favored for electronic fuel injection engines with high compression. As well as forced induction applications.

View attachment 1714987273

Dude, you wrote all that, and just screwed everyone up.

One more time for the guys on the short bus.

LSA is a FUNCTION of the other timing events.

Heads with good, or very good low lift flow will hate a tighter LSA. The opposite of that is true.

The guys at engine masters have been running tighter LSA's for awhile. Are they stupid? No. They understand that they have a narrow RPM band to deal with. They adjust the valve events according, and the LSA can be as narrow as 99 or 100*'s. Bet your *** those heads have RELATIVELY poor low lift numbers, and very good reverse flow numbers (meaning the ports flow poorly backwards).

So, before you shoot off your mouth, make sure you read what I wrote.

It's all about the valve job and the flow curve, then you set the cam events. Any other way, and you make more compromises than required. It kills me when someone has a cam, and builds an engine around it. That is perfectly *** backwards.

One more time...there is no such thing as a narrow LSA or a wide LSA. There is a correct one. And 110 is not the do all, be all, end all.

And, FIX THE TUNE UP IF YOUR JUNK WONT IDLE. That's on the tuner, unless the entire cam is wrong.

 

[RustyRatRod]

Dude, you wrote all that, and just screwed everyone up.

One more time for the guys on the short bus.

LSA is a FUNCTIONS of the other timing events.

Heads with good, or very good low lift flow will hate a tighter LSA. The opposite of that is true.

The guys at engine masters have been running tighter LSA's for awhile.are they stupid? No. They understand that they have a narrow RPM band to deal with. The adjust the valve events according, and the LSA can be as narrow as 99 or 100*'s. Bet your *** those heads have RELATIVELY poor low lift numbers, and very good reverse flow numbers (meaning the ports flow poorly backwards).

So, before you shoot off your mouth, make sure you read what I wrote.

I am just asking here so forgive my ignorance.......but since the LSA is actually a ground in and unchangeable camshaft angle, how can the LSA be a function of anything else? I would think the timing events would be a function of LSA since it is a ground in part of the camshaft. Can you elaborate on that?

 

[yellow rose]

I can tell you this. In fact, I'll tell you exactly how comp decided that 110 was the "perfect" LSA. It didn't have **** to do with anything other than cost.

HFT and SFT cam cores are cast iron. They are cast with the lobes there, just in an exaggerated form. There is a reason why you don't see a lot of HFT and SFT cams with LSA's narrower that 104 or wider than about 111. You can't find the cores. You can only move the lobes so much. A core that will easily take a 110 LSA may barely take a 106 and nothing tighter. And it may not go much wider than 111 or 112 max. You do see some stuff that is over 112 but they are selected cores. My cam is on a 105. Almost went 104. If it was an automatic it may have been as tight as 102 but with the stick 105 was the best choice.

Once the cam guy decided show much actual duration you need, you can figure IVO because that starts it all. Then EVC. Now you can start to see LSA coming in. You need say, 255*'s @ .050 timing for the intake. If you open the valve at 25* btdc, then you KNOW the the closing will be 50*'s abdc. The math is 25+180+50=255 and it works the same for the exhaust. Once you have all that worked out, your LSA will just about take care of itself. You can move it a bit, but you will be be changing the other events.

It's sad to see so many getting suckered by slick marketing and mass production. There is no reason to buy an off the shelf cam and than build an engine around the cam.


EDIT: just to make sure no one comes along and twists what I say, roller cores also come with the lobes there. You can buy an UGL core. They are expensive. It stands for UnGround Lobe core. Since it is USUALLY 8260 bar stock, the heat treat is deeper and you can move the lobes a bit more. It is getting hard to find roller cores to get tighter than 106 any more.

 

[RustyRatRod]

I've never been a Comp fan. I also think that Comp caught onto some of what Harold Brookshire (RIP) was doing and that made them look at the 110* LSA as well. Harold used that a lot, so there must have been something to it........at least that's how it appears on the surface.

As for moving the LSA, I guess I was lucky. Oregon reground an early Hemi hydraulic cam for me to a small solid. It was a 114 originally and went to a 106. I've even mapped it with the degree wheel so I know it's right. It's only .435 lift, 240 @ .050 on a 106, but I will say this. The base circle of the lobes are almost dead even with the cam core. It did require custom length pushrods, of course.

Thanks for the explanation.

 

[MopaR&D]

So if I'm getting this explanation right (correct me if I'm wrong YR), essentially what he is getting at is the LSA is more of a "result" of designing a cam profile, it's not something you go into deciding on as the first factor. So once the overall duration, IVO, and EVC events are established, the LSA kind of just ends up being what it is. I'm guessing it's more applicable to off-the-shelf stuff which is why we hear about it so much.

 

[yellow rose]

I've never been a Comp fan. I also think that Comp caught onto some of what Harold Brookshire (RIP) was doing and that made them look at the 110* LSA as well. Harold used that a lot, so there must have been something to it........at least that's how it appears on the surface.

As for moving the LSA, I guess I was lucky. Oregon reground an early Hemi hydraulic cam for me to a small solid. It was a 114 originally and went to a 106. I've even mapped it with the degree wheel so I know it's right. It's only .435 lift, 240 @ .050 on a 106, but I will say this. The base circle of the lobes are almost dead even with the cam core. It did require custom length pushrods, of course.

Thanks for the explanation.

Damn, Kenny got lucky with the core. It is possible those early cores were heat treated with a different method that made the heat treat deeper (although Ken always says CI cams are floor sweepings from other casting). But that's 8*'s to close up and that's a bunch.

 

[yellow rose]

So if I'm getting this explanation right (correct me if I'm wrong YR), essentially what he is getting at is the LSA is more of a "result" of designing a cam profile, it's not something you go into deciding on as the first factor. So once the overall duration, IVO, and EVC events are established, the LSA kind of just ends up being what it is. I'm guessing it's more applicable to off-the-shelf stuff which is why we hear about it so much.

Pretty much. Once you have the basic events where you want them, you can move the LSA a bit to maybe narrow up the power curve a bit, or open it up if you are running a power glide to flatten out the torque curve.

 

[RustyRatRod]

Damn, Kenny got lucky with the core. It is possible those early cores were heat treated with a different method that made the heat treat deeper (although Ken always says CI cams are floor sweepings from other casting). But that's 8*'s to close up and that's a bunch.

That's EXACTLY what he said. He said all of the early Mopar cores and on through the muscle car years were heat treated almost to the core. He wasn't worried about it one bit.

 

[MopaR&D]

That's EXACTLY what he said. He said all of the early Mopar cores and on through the muscle car years were heat treated almost to the core. He wasn't worried about it one bit.

That's badass, I bet that's one reason wiping cam lobes is a lot more common now than it was "back in the day". Even if the lobe gets scuffed a bit for whatever reason the metal is still hard underneath and won't just get ground to sh*t if the very outer layer gets wiped off.

 

[318willrun]

I have two pennies to throw in.....

First let me say to the Op that nobody gets it perfect. Some think they are deep in knowledge, but really they are stuck!! Tripping over every absolute detail to the effects that nothing gets done, and many times when it is done it's major disappointment. I'm not talking about anyone in particular here, get that straight, but what I've seen over the years in this hobby. Now....

1. The purpose of the car has to be determined. Drag? Street strip? Wood hauler? casual cruiser? Gas mileage?
2. then engine components, including the cam need to be selected to fill the need of the cars intended purpose, and these selections for the engine cannot be made without considering the weight, gear, and torque converter of the car. You can make a dog or a pouncing tigre.
3. You can make a small engine a torque monster, or kill the torque of a big motor. I think a lot of in depth coverage of what goes into the cams functions has been discussed here. Do you have to have it all understood before reaching your goal for your car? absolutely not. There are many reliable cam companies that have done the homework for you, giving you general rpm ranges, and behaviors of the cams. If your happy with the results, then you made the right choice

 

[frosty_the_punk]

Pretty much. Once you have the basic events where you want them, you can move the LSA a bit to maybe narrow up the power curve a bit, or open it up if you are running a power glide to flatten out the torque curve.

just stop, no no no.

That's exactly the opposite of what they do.

You can't "just move the LSA a bit" without completely changing every single timing event and radically altering the function and design parameters of the finished camshaft.

Selecting the Duration and the LSA is a combined process. You cannot competently choose one without the other as they are mutually dependany on one another to achieve the best results.

You have it backwards. The timing events don't determine the duration and LSA.
The Duration and LSA determine the timing events.


for example. if you have two cams, 232/235 duration.

One is cut on 108.

IT has timing events like this.

INTAKE 8 BTDC 44 ABDC
EXHAUST 45.5 BBDC 9.5 ATDC

17.5 overlap degrees.

The same exact 232/235 lobes, cut on a 110 LSA make this

INTAKE 6 BTDC 46 ABDC
EXHAUST 47.5 BBDC 7.5 ATDC

13.5 Overlap degrees.

That's a huge difference in function.

Changing LSA without changing duration is a surefire way to radically change how an engine behaves. it's not "fine tuning" to change the LSA. it can be night and day.

Let me phrase it another way.

If you go to a cam manufacturer and say "I'm doing a mild 340 and I want a cam with 47.5 degrees BBDC here, 7.5 degrees ATDC there blah blah blah"

He is going to give you the biggest sigh you've ever heard in your life. I kid you not.
He's going to think you're a massive pain in the bum.

If you say "Hey, i'm looking at XE series lobes, with around 232 duration for the intake and 235 for the exhaust. Cut on a 110 degree lobe separation"

He's gonna know what you're talking about and immediately be able to determine if you're on the right track for your application or if you're way off. (he has to know what your application is)

The timing events are a bi-product of picking the lobes for intake and exhaust, then cutting them onto a specified lobe separation angle. NOT the other way around.

Essentially when they build a camshaft they are creating a stick with bumps.

You select the shape/size of the bumps.

You select where the bumps are placed.

The start and finish of the bumps are seriously just what your valve timing events end up being.

 

[frosty_the_punk]

I can tell you this. In fact, I'll tell you exactly how comp decided that 110 was the "perfect" LSA. It didn't have **** to do with anything other than cost.

HFT and SFT cam cores are cast iron. They are cast with the lobes there, just in an exaggerated form. There is a reason why you don't see a lot of HFT and SFT cams with LSA's narrower that 104 or wider than about 111. You can't find the cores. You can only move the lobes so much. A core that will easily take a 110 LSA may barely take a 106 and nothing tighter. And it may not go much wider than 111 or 112 max. You do see some stuff that is over 112 but they are selected cores. My cam is on a 105. Almost went 104. If it was an automatic it may have been as tight as 102 but with the stick 105 was the best choice.

Once the cam guy decided show much actual duration you need, you can figure IVO because that starts it all. Then EVC. Now you can start to see LSA coming in. You need say, 255*'s @ .050 timing for the intake. If you open the valve at 25* btdc, then you KNOW the the closing will be 50*'s abdc. The math is 25+180+50=255 and it works the same for the exhaust. Once you have all that worked out, your LSA will just about take care of itself. You can move it a bit, but you will be be changing the other events.

It's sad to see so many getting suckered by slick marketing and mass production. There is no reason to buy an off the shelf cam and than build an engine around the cam.


EDIT: just to make sure no one comes along and twists what I say, roller cores also come with the lobes there. You can buy an UGL core. They are expensive. It stands for UnGround Lobe core. Since it is USUALLY 8260 bar stock, the heat treat is deeper and you can move the lobes a bit more. It is getting hard to find roller cores to get tighter than 106 any more.

Again just about everything you're saying here is rubbish.

Are you talking about regrinds? yes, regrinds are limited in what LSA they can be cut on because you have to use a camshaft that's ALREADY HAD ALL THE MEAT CUT OFF IT.

If i wanted a new billet HFT camshaft with a 116 Lobe separation and .600" lift tomorrow i could get one from just about any cam manufacturer.

On the same core i could go as tight as 102 LSA

If i wanted 700" lift there may be an issue. on the other hand... maybe not of the base circle was small enough.

 

[yellow rose]

Again just about everything you're saying here is rubbish.

Are you talking about regrinds? yes, regrinds are limited in what LSA they can be cut on because you have to use a camshaft that's ALREADY HAD ALL THE MEAT CUT OFF IT.

If i wanted a new billet HFT camshaft with a 116 Lobe separation and .600" lift tomorrow i could get one from just about any cam manufacturer.

On the same core i could go as tight as 102 LSA

If i wanted 700" lift there may be an issue. on the other hand... maybe not of the base circle was small enough.

You should probably do some research, and then get some reading comprehension skills. Because you are so wrong it's silly.

I know you had the short bus education so let me say it again. If you move the LSA, you are changing the valve events. Where did I NOT say that? I'd didn't say it. You don't read.

What I said was, and I'm going to fix something I said earlier, I set the IVC point FIRST, after looking at port flow, overall induction and a few other things mentioned before.

After all the EVENTS are set, you pretty much have your LSA. Did you get that? Then I said, you can manipulate the LSA a BIT to change chacteristics. BUT, BUT, BUT, BUT you WILL alter the open and closing events when you do it.

It can't be that hard can it?

We won't even get into installed centerline because it's not my job to finish your education.


Go away now.

 

[Johnny Dart]

Yellow Rose,
Obviously you are very versed in the field of camshafts, but calling people names (short bus) which is totally unnecessary, and not helping your cause. In fact, its actually making you look like a jerk, and taking all the air out of this thread. Total buzzkill, you no what I mean ?

After the thesis on camshafts (which is great), how about suggesting a camshaft for the original poster ?
Lets turn this into something possitive.

Cheers Bud.

 

[yellow rose]

Yellow Rose,
Obviously you are very versed in the field of camshafts, but calling people names (short bus) which is totally unnecessary, and not helping your cause. In fact, its actually making you look like a jerk, and taking all the air out of this thread. Total buzzkill, you no what I mean ?

After the thesis on camshafts (which is great), how about suggesting a camshaft for the original poster ?
Lets turn this into something possitive.

Cheers Bud.

You're right. I should take the high road. But how many times should I type the same thing out and have someone say something I didn't? Repetition eats me up. I have never said to select LSA first. I even explained in very little detail how I think about cam selection, how the induction system plays a apart in it, but not mentioning weight, gearing, clutch/converter or transmission. It's all a part of the same whole cloth.

LSA is the cumulative of all the events. Then, if you have the events and you want to maybe make the power curve a bit narrower, because you have a 5 speed and your gear splits allow for an 1800 RPM drop (don't I wish!!!!) you can take that and move the LSA a bit closer together. If you move the intake lobe, you retard the intake cycle. If you move the exhaust lobe, you advance the exhaust. Maybe you move each 1 degree? IDK?
Same deal but you have the god forsaken powerglide. You may open the LSA up because with only two gears you need flatter power curve and RPM's drop some outrageous number (say 2800 RPM). But you are still moving the IVO/IVC or the EVO/EVC or both.

LSA is a tuning aid. I still say if you are moving LSA to improve idle, you missed with the original placement of the events.

Just like installing the cam 4,5 or 6 *'s ahead of LSA. If you have to move a cam THAT far, you probably have the wrong cam. And you would make more power, have a better idle, more power after peak...all the important stuff no one talks about.

I'm sure someone will come along a poo poo this. I learn new things every day. Post it up. Just do do the if we have 2 cams, both with 280 lobes etc. that becomes a dick comparison as RRR likes to point out.


EDIT: somewhere in this tread I did make a suggestion to the OP. It's in there somewhere.

The short of it was don't use the cam he posted and call a cam grinder and get a custom cam.

 

[RustyRatRod]

With the cost of custom camshafts through the floor, there's really no reason not to go custom on just about everything.

 

[moper]

YR likes to pick fights. Very little of the level of detail he gets into is at all relevant on a 100% street engine where the budget is tight and the power levels are lower than 1.1hp/inch. Nobody building a street cruiser is spending to maximize high lift flow and reduce low lift. NOBODY. Very few are buying custom camshafts of any type. I'd bet less than 15% of buyers will on a street car.
I am not debating right or wrong. I'm saying the OP is looking for a "Cessna" answer and some here are pushing the "Blue Angels" to puff themselves up. There is very, very little relevence here to the original question. There is only weak ***** contest BS.

 

[frosty_the_punk]

Lmao this is actually gotten hilarious.

Lobe separation is literally THE reference so that the cam grinder knows where the lobes need to be cut onto the camshaft.

Camshaft manufacturers machine lobes. not valve events.

You can't look in a catalogue and find a LOBE with a IVO event because that lobe hasn't been placed anywhere yet.

Yes, You can use the valve events (IVO, IVC etc) to measure a camshaft.

But that is not how they are "specified" when customizing the camshaft to work appropriately with a given application.

Ordinarily (see below) A cam manufacturer doesn't need to look at the IVO IVC EVO EVC separately . Valve events are MOSTLY (see below) useful for checking a cam's specification. but they aren't where you MOSTLY (see below) START when you're figuring out what kind of cam you need for your application.

For example, no cam grinder is going to ever say "Oh a towing motor/street-strip/performance street camshaft is going to need an IVO spec of exactly XX and an exhaust EVC of exactly XX degrees. Now we'll just figure out how to make that with the tools we have available because any other IVO than XX degrees just won't do at all!"

The reason for this is that They can get a very clear understanding of the RPM range and torque curve a camshaft will be suited for by looking at 2 things.

Duration.
Lobe separation.

trying to "tune" an existing profile by narrowing or closing the lobe separation in some kind of attempt to get a different valve event is bizarre as it affects ALL valve events and dramatically changes the torque curve.

a 2 or 3 degree change in lobe separation, with no other changes. on a racing engine could add or subtract 500 usable RPM of the engine's usable power in a racing application because it affects EVERY valve event.

I will conceed one thing though (this is the below part, yay!). When someone is trying to build a MAX EFFORT racing engine, they will try to gain every last iota of potential out of a camshaft without running into problems with detonation.

This is really only done when you are trying to UGRADE from an existing camshaft to a newer improved spec.

That's when you start looking VERY carefully at timing events themselves. that's when you start to push the limits by examing and designing a camshaft with a specified IVC in particular.

But for your average joe that is using pump fuel, building an engine that gets driven to the shops from time to time etc. etc. isn't trying to squeeze every last little poofteenth of horsepower out of a competitive racecar. No, just no.

Duration, Lobe separation.

Valve events are a measuring tool.

 

[RustyRatRod]

YR likes to pick fights. Very little of the level of detail he gets into is at all relevant on a 100% street engine where the budget is tight and the power levels are lower than 1.1hp/inch. Nobody building a street cruiser is spending to maximize high lift flow and reduce low lift. NOBODY. Very few are buying custom camshafts of any type. I'd bet less than 15% of buyers will on a street car.
I am not debating right or wrong. I'm saying the OP is looking for a "Cessna" answer and some here are pushing the "Blue Angels" to puff themselves up. There is very, very little relevence here to the original question. There is only weak ***** contest BS.

I think 75 bucks to grind a cam is Cessna territory.

 

[yellow rose]

Lmao this is actually gotten hilarious.

Lobe separation is literally THE reference so that the cam grinder knows where the lobes need to be cut onto the camshaft.

Camshaft manufacturers machine lobes. not valve events.

You can't look in a catalogue and find a LOBE with a IVO event because that lobe hasn't been placed anywhere yet.

Yes, You can use the valve events (IVO, IVC etc) to measure a camshaft.

But that is not how they are "specified" when customizing the camshaft to work appropriately with a given application.

Ordinarily (see below) A cam manufacturer doesn't need to look at the IVO IVC EVO EVC separately . Valve events are MOSTLY (see below) useful for checking a cam's specification. but they aren't where you MOSTLY (see below) START when you're figuring out what kind of cam you need for your application.

For example, no cam grinder is going to ever say "Oh a towing motor/street-strip/performance street camshaft is going to need an IVO spec of exactly XX and an exhaust EVC of exactly XX degrees. Now we'll just figure out how to make that with the tools we have available because any other IVO than XX degrees just won't do at all!"

The reason for this is that They can get a very clear understanding of the RPM range and torque curve a camshaft will be suited for by looking at 2 things.

Duration.
Lobe separation.

trying to "tune" an existing profile by narrowing or closing the lobe separation in some kind of attempt to get a different valve event is bizarre as it affects ALL valve events and dramatically changes the torque curve.

a 2 or 3 degree change in lobe separation, with no other changes. on a racing engine could add or subtract 500 usable RPM of the engine's usable power in a racing application because it affects EVERY valve event.

I will conceed one thing though (this is the below part, yay!). When someone is trying to build a MAX EFFORT racing engine, they will try to gain every last iota of potential out of a camshaft without running into problems with detonation.

This is really only done when you are trying to UGRADE from an existing camshaft to a newer improved spec.

That's when you start looking VERY carefully at timing events themselves. that's when you start to push the limits by examing and designing a camshaft with a specified IVC in particular.

But for your average joe that is using pump fuel, building an engine that gets driven to the shops from time to time etc. etc. isn't trying to squeeze every last little poofteenth of horsepower out of a competitive racecar. No, just no.

Duration, Lobe separation.

Valve events are a measuring tool.

100% horseshit.


I don't know who you deal with, but I know I discuss the events long before LSA ever comes up.

So I stand by what I write. You don't open the LSA to fix a bullshit idle issue from using the wrong cam to start with.

Harold Brookshire and I stopped doing business together over two issues. He never wanted to use enough lift on Chrysler cams.

And his die hard love for installing the cam 6* ahead of LSA. Wasted a whole day on the dyno testing his cam and it ran better 1* retarded. So I sent it back and wanted a refund. He kept the cam and my money.

Who argues the events aren't what matters? Someone talking out his ***.

 

[yellow rose]

YR likes to pick fights. Very little of the level of detail he gets into is at all relevant on a 100% street engine where the budget is tight and the power levels are lower than 1.1hp/inch. Nobody building a street cruiser is spending to maximize high lift flow and reduce low lift. NOBODY. Very few are buying custom camshafts of any type. I'd bet less than 15% of buyers will on a street car.
I am not debating right or wrong. I'm saying the OP is looking for a "Cessna" answer and some here are pushing the "Blue Angels" to puff themselves up. There is very, very little relevence here to the original question. There is only weak ***** contest BS.

I'm not picking a fight. It's called point it out facts. Do you have a problem with facts?

You have no idea what a machine shop does. I know when I did a valve job and I was selling the cam, I did a valve job to reduce reversion and reduce low lift flow. I didn't ask the customer if I could do it. I did it. I don't ask the customer. If you think you are smart enough, then you should do your valve job and do your own ****.

The last thing I want the customer to do is help me. Just pay money and shut up. If you don't like it, there's other shops out there.


If you knew how many custom cams I sold compared to shelf junk since 1999, you'd realize how stupid your statement is.

 

[Cudafever]

the name of this thread is
Don't understand cams!
my self, i think it has been way informing and have enjoyed it ALL!

 

[Cudafever]

I think that a cam company has to talk, to you, at your level. Anyone who has read this thread with any diligence can understand Duration, Lift and Lobe Separation. He will listen to what you have to say, then recamend a cam in XXXduration and *** lift(knowing what head you're using now) With a Lobe Seperation of *** and recommend you advance(or retard) it a couple of degrees to help the tall gears or low gears, Convert EXC.
Now if you have heads, that were ported and you know the flow ### for intake and exhaust. He may NOT go into more details but he will be thinking more of the intake/exhaust open and closed events.
Even though both of you are on opposite side of the fence......You both could be correct.