Why Degree A Cam Shaft?

[Immortality]

You missed my point. You're talking about making clearance for a valve to stop interference. That is different to setting correct PTV clearance.

Not at all. Piston to valve clearance changes depending on the cam specs.

You are talking about changing cam timing to achieve some set clearance as the valve chases the piston down the bore. Changing cam timing to achieve some magical PTV clearance..... If you have a really big cam without fly cutting the piston you would have to retard the cam timing a huge amount to achieve that on the intake but what about the exhaust? Nope, I think I'll degree that cam as per the cam card and just make sure the PTV clearance is acceptable (but then again, on the 304 you need a huge cam before PTV clearance becomes an issue so I'm not bothered).

 

[Deuce]

A shop that does these types of cam swaps regularly will know what cams will fit without valve to piston clearance issues or cams that will need to be checked and possibly have pistons fly cut to suit. Knowledge that comes with experience....

Fixed

 

[EYY]

Also a vernier cam gear is the only way to go. Those 2 deg chain sets are crap.

Can’t be bothered trading the whole thread, but did read that you didn’t even know adjustable chain sets were available till a few posts ago, and now they’re crap?

As for looking to cam manufacturers for an explanation for why their cams need decreeing for ‘standard’ engines...

Quite often vehicle manufacturers will fit alternate timing gear sets to a model to adjust power characteristics. E.g. advanced timing in some applications to give better torque in larger vehicles etc. I know that there were a number of different timing gear sets for the Holden V8’s from factory which influenced power delivery.

It becomes incredibly important to degree your cams where you’re using longer duration cams with higher lift. If you’re too far out, pistons may meet and greet the valves. Not typically an issue with most street engines, but that extra 4 degrees of advance over what the cam manufacturer prescribes could make for catastrophic failure where things are already a little too close for comfort.

Just because you can just throw a cam in and have it run ok, doesn’t mean you should. You’re leaving power, reliability and driveability on the table if you do. Not sure where tuning comes into it, but tune alterations won’t make up for performance losses due to a poorly built engine or half hearted cam Swap.

 

[shane_3800]

Not at all. Piston to valve clearance changes depending on the cam specs.

You are talking about changing cam timing to achieve some set clearance as the valve chases the piston down the bore. Changing cam timing to achieve some magical PTV clearance..... If you have a really big cam without fly cutting the piston you would have to retard the cam timing a huge amount to achieve that on the intake but what about the exhaust? Nope, I think I'll degree that cam as per the cam card and just make sure the PTV clearance is acceptable (but then again, on the 304 you need a huge cam before PTV clearance becomes an issue so I'm not bothered).

It's not a magical figure for PTV clearance. You want the intake valve as close as you can get it and in valve relief pistons you want about 50thou for air flow.

The limiting factor for getting good pressure recovery is intake valve to piston clearance. If you let the piston travel too far down before you crack the intake valve open you loose port energy and power.
Pro stock engines have the valves making marks in the carbon. It's one of the most critical aspects of the engine where a cam card states zero should be is irrelevant.

 

[shane_3800]

Can’t be bothered trading the whole thread, but did read that you didn’t even know adjustable chain sets were available till a few posts ago, and now they’re crap?

As for looking to cam manufacturers for an explanation for why their cams need decreeing for ‘standard’ engines...

Quite often vehicle manufacturers will fit alternate timing gear sets to a model to adjust power characteristics. E.g. advanced timing in some applications to give better torque in larger vehicles etc. I know that there were a number of different timing gear sets for the Holden V8’s from factory which influenced power delivery.

It becomes incredibly important to degree your cams where you’re using longer duration cams with higher lift. If you’re too far out, pistons may meet and greet the valves. Not typically an issue with most street engines, but that extra 4 degrees of advance over what the cam manufacturer prescribes could make for catastrophic failure where things are already a little too close for comfort.

Just because you can just throw a cam in and have it run ok, doesn’t mean you should. You’re leaving power, reliability and driveability on the table if you do. Not sure where tuning comes into it, but tune alterations won’t make up for performance losses due to a poorly built engine or half hearted cam Swap.

You make some good points. But degreeing a cam won't stop a piston hitting a valve you have to check that physically.

Also when did I say I never knew cam gears could be adjustable?
I've known about them before I was even a mechanic lol. Like I saud already the first system was eccentric dowls used in NASCAR back in the late 60's early 70's.

 

[Immortality]

It's not a magical figure for PTV clearance. You want the intake valve as close as you can get it and in valve relief pistons you want about 50thou for air flow.

The limiting factor for getting good pressure recovery is intake valve to piston clearance. If you let the piston travel too far down before you crack the intake valve open you loose port energy and power.
Pro stock engines have the valves making marks in the carbon. It's one of the most critical aspects of the engine where a cam card states zero should be is irrelevant.

Once again you are on about high end motors not a street Commodore with a cam swap/tune.

Lets remind ourselves exactly what you said....

Yea but if you're an engine shop these things don't take very long as they have guys that do different things.
It all depends on how much work is going to be done. For a street car with a cam a lot of the things you mentioned aren't worth dooing. Like degreeing a cam like who does that on a cam swap and tune for a street car?

As has been said OP needs to get the break down of the invoice.

Even cams like the one mentioned in the video I posted will have the intake valve opening before the piston reaches TDC and with the 15° valve angle on the LS heads PTV clearance will be reasonably tight.

 

[shane_3800]

Once again you are on about high end motors not a street Commodore with a cam swap/tune.

Lets remind ourselves exactly what you said....



Even cams like the one mentioned in the video I posted will have the intake valve opening before the piston reaches TDC and with the 15° valve angle on the LS heads PTV clearance will be reasonably tight.

And I still agree with my comment.
If it's a street car and degreeing the cam changes horse power by 4hp is that really a gain that will be felt on the street....... The answer is NO.
If you watched that video on changing cam timing you would see how minimal the changes are in the curve it only really starts making a difference noticeably above 5500rpm so not street car territory.
Your whole argument is that it destroys low end power which it clearly doesn't. Much more low end is lost with incorect exhaust and using short runner intakes or by just selecting to much cam to start with.

So again degreeing a cam on a stage 2 cam swap in a street car is utter wank factor and just showing the internet you're "real
" engine builder.

 

[Immortality]

The problem with your comment is that the engine builder isn't some guy who builds engines on the web, no this guy does it for a living and been doing it for a lot longer than you.

Guess he knows more than you!

 

[shane_3800]

The problem with your comment is that the engine builder isn't some guy who builds engines on the web, no this guy does it for a living and been doing it for a lot longer than you.

Guess he knows more than you!

But I'm not saying he is wrong. There is no problem in someone degreeing a cam infact I encourage it for people building engines as it helps peopel get their heads around the concept.
But for street cars most shops just do the spin trick throw the cam in set it dot to dot on the cam stock cam gears tune it and send it.

My whole point is it's an unnecessary step in some cases and lots of shops don't bother with it (you would be surprised at who dont do it).
Also there is an increasing amount of people that don't know what they're doing that watch YT videos on how to degree cams then do it and make out like they're experts to people because they show them they're doing a process that they don't totally understand.

I'm willing to teach people my knowledge and I can show people how to degree cams but I also would need to explain why it's not need in every case and ways you can make do without a cam wheel ect.

I bet I could degree a cam in without a cam wheel or dial gague. I just thought how to do this is because I was taught ingenuity. Some people get stuck in this mantra that if Kieth Dorton degrees every cam in then every good engine builder must do or he's not a good engine builder.
This is the problem today too much armchair experts.

 

[Immortality]

LOL. When we started this discussion you didn't even seem to know about the adjustable timing sets for the LS. I think you're making this **** up as you go.