Custom cam regrind specs? - Page 2 - Mazda MX-6 Forum
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post #16 of 19 (permalink) Old 12-4-15, 9:01
 
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Quote:
Originally Posted by juanpac_tupac View Post
Does anyone have any actual experience with the lifters not performing the same with a reground cam? Colt said that it's a direct drop in so I'm just kind of curious if all of this talk about the lifters on this engine just theory or have any of you guys actually tried one out and had the lifters fail or anything of similar nature. Thanks for all the info though none the less.
The "lifters" wont perform any different with a reground cam, the problem was the rockers not clearing the valve cover with Crowers tri-flow cam, there is a chance they tested only with a 90+ car with the redesigned valve cover oil baffles. People had to hunt down the right valve cover and find HLA shims themselves.
My guess would be the tri-flow is a more aggressive profiled grind.

I am surprised they told you it's a direct drop in, no shimming the HLA's must be a very mild regrind.

The lifters (HLA's) won't know the cam has changed profile and it won't matter as long as the rockers stay in contact with the cam and clear the valve cover.

Can the HLA's make up for a lower profile on the low side of the cam?

The only thing that could collapse the lifters would be running valve springs that are to stiff for the HLA's to handle on stock or performance cam. But I figure the cam gear dowel will strip the cam gear during start up before having an HLA problem with the valve springs that stiff.

Now if when you say Lifters you mean complete rocker assembly, well they never failed from any reground cams.

As long as the lifters don't float off/ loose contact/ have a gap with the cam and the lifters don't tap the valve cover then you are good to go.
Just push on the "lifters" rockers with the valves completely shut and check for any play between the valves and HLA's. If there is you will have to shim them.

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post #17 of 19 (permalink) Old 4-5-16, 12:46
 
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Came across this in some of my car info notes. Cant remember who posted it or when:


"Whell this is the info I had gather regarding the cam specs,
Unfortunatly I pasted them in the order that interested me and not that in wich they where written,


The following was posted last to first originaly.

Other threads I found are bolow the doted line:





CROWER REGRIND

And here is the common Crower regrind: (thanks to Sick)

NOTE: CROWER MADE A MISTAKE IN THIS SHEET - READ ON!



Well this is what i took me forever to figure out, Crower's cam. Some thing just didn't line up. The original timing numbers simply don't match the duration given (every thing in this post will be at .050 lift) If you add the timing together of the original you end up with:

In: 212* not = stated 190*
EX:228* not = stated 200*

So which one is right??

To find out we have to look at Lobe Separation - remember:

{[(in. dur / 2) - dist BTDC] + [(ex. dur / 2) - dist ATDC]} / 2 = Lobe Separation

{[(190/2) - 11] + [(200/2) - 14} /2 = 85* Lobe Separation ?!?

Thats impossible when you consider that this is a regrind. So whats the problem? The timing numbers are the problem. When they wrote this the got confused with their - signs lol. Who writes - ATDC any way?? Look this is how it SHOULD be.



Now all the timing numbers line up with the duration: 180-11+21=190 and 180-14+34=200

Ok what about Lobe Separation:

{[(190/2) + 11] + [(200/2) + 14} /2 = 110* Lobe Separation

And Finally Overlap:

190 + 200
---------- - 110 = -12.5 x 2 = -25* OVERLAP
4


Conclusion:
Here I'm basicaly just putting all the numbers in one place for easy use/reference.
If you're still confused on the math, here's a great calculator with an easy-to-understand explaination of cams: Camshaft Technology and Calculations

STOCK CAM
Lobe Lift
Cam Lift (Intake): .210"
Cam Lift (Exhaust): .197" *TR-Mx6 found .230"*: https://www.mx6.com/forums/showthread...20#post1517020



Valve Lift
Intake valve lift = 0.374
Exhaust valve Lift = 0.410 *based on .230" exhaust lobe lift*
So divide one with the other and you get the ratio of the rockers at max lift.
Rocker arm ratio = 1.78

Duration at .000''
Lobe duration (Intake): 239
Lobe duration (Exhaust): 247

Duration at .050''
Lobe duration (Intake): 197
Lobe duration (Exhaust): 208

Valve timing stock: (.000'' lift)
IN: Open BTDC 10
IN: Close ABDC 49

EX: Open BBDC 55
EX: Close ATDC 12


Overlap
@ .000 lift: 22
@ .050 lift: -18.5


CROWER

Lobe Lift
Intake : .333/1.5 = .222 Cam Lift*
Exhaust : .368/1.5 = .245 Cam Lift*
* Given numbers are divided by 1.5 b/c the sheet crower provided says: "the specs listed above are based on a rockerarm ratio of 1.5"

Valve Lift
So, thats the crower lobe lifts. Now for that cam with our 1.78 rockerarm ratio, it would look more like this.
Intake : .222 X 1.78 = .395
Exhaust : .245 X 1.78 = .436


Duration at .000''
duration (Intake): 254
duration (Exhaust): 264

Duration at .050''
duration (Intake): 190
duration (Exhaust): 200

Valve timing: (.050'' lift) - so these are the times when the cam lift =.050
IN: opening BTDC -11 (or 11 ATDC)
IN: closing. ABDC 21

EX: opening BBDC 34
EX: closing ATDC -14 (or 14 BTDC)


Overlap
@ .000 lift: 39
@ .050 lift: -25

Crower's .000 duration is pretty long yet it keeps the duration @ .050 or greater lower than stock to reduce overlap. They had to do that b/c they are trying to lift the valves much further than stock (.222, .245 vs .210, .197) and moving valves to a higher lift in a shorter time will force the valve to move much faster - that means, you guessed, it more inertia and more wear. Having more duration below .050 lift helps out - how much i don't know.

COLTCAMS - C.444.H (stage 1)
Exhaust : .368/1.78 = .207" Cam Lift
Intake : .378/1.78 = .212" Cam Lift

Valve Lift (Intake): .368"
Valve Lift (Exhaust): .378" - less than stock

Duration at .000''
In: 260
Ex: 262

Duration at .050''
In: 186
Ex: 187

COLTCAMS - C.444.H (stage 1) Overlap *Guesstamated!!*
@ .000 lift: 20.5
@ .050 lift: -16.5


COLTCAMS - C.446.H TRI FLOW
Lobe Lift
Intake : Prim .381/1.78 = .214"Cam Lift Sec .373/1.78= .210"Cam Lift
Exhaust : .387/1.78 = .217 Cam Lift

Valve Lift
(Intake): Prim .381"/Sec .373"
(Exhaust): .387" - less than stock

Duration at .000''
Prim. In: 274
Sec. In: 262
Ex: 276 .387 Lift

Duration at .050''
Prim. In: 193
Sec. In: 185
EX: 193


Duration:

Duration is critical to a turbo setup since its probably the single most important event of a turbo motor (i.e. time valve sits open and closed). Since the air is being forced instead of drawn into and out of the combustion chamber, duration will be your largest variable on how that incoming/outgoing air is managed.

Duration when using a manifold or log design on most turbo cams is usually about 6 degrees more intake duration than exhaust duration (226/220, 240/234). This is mainly because a manifold/log design will typically see higher then a 2:1 pressure ratio in the exhaust ( as high as 4:1 with some logs). By using a reverse split duration this will somewhat help prevent from getting exhaust gas reversion.

Duration when using an efficient header setup with most turbo cams will usually be (230/230, 224/224) or better known as a dual pattern cam. The thinking is with the exhaust backpressure being only 2:1 you can leave the exhaust valve open a little longer then if the exhaust backpressure was 3:1 or higher. Also some of the new turbo designs produce a much lower backpressure with the advent of better flowing turbine wheels and housings which further decrease the total amount of backpressure created by the system.

Overlap:
Overlap definition, is the time period when both the exhaust valve and the intake valve are open at the same time. The exhaust valve needs to stay open after the piston passes TDC in order to use the vacuum created of the exiting exhaust gases to maximize the amount of exhaust gas drawn out of the cylinder. The intake valve opens before TDC in order to use the vacuum created by the exiting exhaust gases to start drawing the intake charge into the cylinder.

This sequence of events above are controlled by the duration and LS (Lobe separation) of the cam. On a typical N/A motor this is essential since you have no pressure being developed on the intake side to push the charge into the combustion chamber. The problem with this event is a turbocharged motor will create a larger amount of backpressure on the exhaust side. Due to this event the above definition will not apply. Reason being is, when the intake valve opens at BTDC, the burned gasses in the chamber will exit out the intake since the pressure is lower than the exhaust. Since this is true you would not want to open the intake valve until the piston has started going down, ATDC. This will lower the combustion chamber pressure till it's below the intake manifold pressure.

To calculate the overlap of your cam simply follow these steps below:
**Example turbo cam:**

Duration @ .006 218/212
Lift .544/.544 lift
Lobe Separation (LS) 114

Add the intake and exhaust durations
Divide the results by 4
Subtract the LSA
Multiply the results by 2

Overlap is -13 Degrees of overlap


**Example N/A cam :**

Duration 236/242
Lift .568/.576
Lobe Separation (LS) 112

Add the intake and exhaust durations
Divide the results by 4
Subtract the LSA
Multiply the results by 2
Overlap is 15 degrees of overlap

Above was the process on how to calculate your cams overlap. As you can see, the overlap in the 2 cams differ greatly. Running the N/A cam example on a manifold setup would be a horribly in-efficient setup and the engine would be operating well below its potential output. While running the example turbo cam would work well even with the most in-efficient of the header systems out there. Typically a overlap spread of -8 degrees to +2 is a safe bet. Of course this will differ with whatever combination header, turbo and exhaust is used, so those #'s could be higher or lower.

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post #18 of 19 (permalink) Old 4-5-16, 12:47
 
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Lift:
How much lift should I get in my cam? Well that will depend on your heads' flow characteristics. To choose the correct turbo camshaft, you really need to know how your cylinder heads flow. Reason is if your cylinder head flows X amount of air at X amount of lift, choosing a cam that has a lift much greater then that will gain you nothing except extra heat and premature wear of the valve spring. Airflow through a head reaches a peak as the valve is opened, then starts to drop off as the valve is lifted beyond that peak. Most of this of this will hold true to definition, but with a forced induction motor, valve lift is not as critical since the incoming air is pressurized.

A good rule of thumb is to select a cam that will lift the valve 20-25% past its peak flow point.

So be the definition above if your head flows best at 0.500" of lift, use a cam that will lift the valve between 0.600" and 0.625". The reasoning behind this is, if you lift the valve only to its peak flow point, then the valve only flows best when it's wide open. The cycle is brief and would only happen once per stroke. So to benefit from you peak flow the most, you want to lift the valve past its peak. That way the valve will pass its peak flow twice in the cycle. The result is more flow during the opening and closing event of the valve. You do not want to raise the valve much past the peak flow though, or you lose total flow by going too high.
Calculating the best lift:

0.500 X 1.20 = 0.600
0.500 X 1.25 = .0625

Conclusion:
There are way too many factors to just say XX cam will make XX power with your combo. Things like "114LS is best, or 117LS, or ..etc", are just blanket statements. Backpressure, RPM range, boost level, target horsepower, A/R of turbo, turbo frame (T3, T4, T6/Thumper), head flow, cubic inches, and even location of turbo...etc. All of these factors are extremely important in determining the cam that best suits your needs. There is no rule of thumb with a turbo cam. There are too many variables and the only way to get the right cam is to take all of those your parameters into consideration, and only then can a proper cam be selected. All of the points of reference above are just to get you on your way to building the best and most powerful turbo system for you. Study your design and ask questions along the way and you will be smiling the next time your opponent lines up next to you.

ore Cam info from: Piper Cams - Technical terminology

"Cam Timing: The position of the camshaft relative to the crankshaft. This is expressed as the number of degrees that full lift occurs after top dead centre (tdc) in the case of the inlet, and before tdc for the exhaust. This figure is included in the catalogue pages, but to calculate this, take the duration figure and divide by 2. EXAMPLE: With an inlet cam of 23/76, the duration is the addition of these two numbers, plus 180, equals 270. Then divide by 2 resulting in 135. Deduct the number of degrees before tdc that the valve started to open, ie 23 degrees - the result 112. The valve is correctly timed with full lift 112 degrees after tdc.

Valve Timing: The opening and closing position of inlet and exhaust valves relative to the crankshaft as figures before and after TDC and BDC

Lobe Angle: The angle between the inlet and exhaust lobe, measure in degrees.

Ramp: The ramp is the part of the profile that takes up the valve clearance and slack in the valve train gradually, before the valve is actually lifted from the seat. It also rests the valve gently back to the seat after the closing flank. Mechanical profiles use a much larger ramp than hydraulic ones, as the hydraulic cam follower should be in contact with the lobe at all times. The height of the ramp dictates what measurement the valve clearances should be set to.

Flank: This is the part of the profile between the ramp and nose. It is the most important part of the whole design. The flank controls the velocity and acceleration of the valve train. The acceleration / deceleration rate must be within the working limits of the valve spring, too much and valve float with occur. Generally high acceleration & velocity figures are beneficial to engine performance.

Nose radius: The larger the nose radius the better. Our profiles are designed to utilise the biggest nose radius possible to keep the stresses to a minimum.



Dwell: As the valve reaches full lift it will stop moving for a few degrees before starting to drop back towards the seat, this period is known as the dwell. When checking the cam timing using the full lift figure method the mid-point of the dwell should be taken as exact full lift.
Rocker Ratio:The ratio between valve motion vs cam follower motion. Push rod engines typically use a ratio of between 1.1:1 & 2.0:1. Over head cam, direct operating engines obviously have no rocker ratio as the cam follower motion is exactly the same as the valve motion.

Overall height: The measurement from the nose of the lobe to the bottom of the base circle, in a straight line through the centre of the lobe.

Base circle diameter: The measurement across the lobe, calculated by measuring the overall height and subtracting the cam lift."
- http://www.pipercams.co.uk/NewPiperW...CamFrames.html



Applying the Formulae


Remember, the only good way to judge a cam's duration or timing is at .050 lift - b/c thats where it really starts to matter the rest is ramp-up.

So, now that we understand the guidelines, lets look at a couple examples of the math in action:

STOCK CAM
Cam Lift (Intake): .210"
Cam Lift (Exhaust): .197" *TR-Mx6 found .230"*: https://www.mx6.com/forums/showthread...20#post1517020

*based on .230" exhaust cam lift*
Intake valve lift = 0.374
Exhaust valve Lift = 0.410

So divide one with the other and you get the ratio of the rockers at max lift.
Rocker arm ratio = 1.78

Duration at .050''
Lobe duration (Intake): 197
Lobe duration (Exhaust): 208

Duration at .000''
Lobe duration (Intake): 239
Lobe duration (Exhaust): 247

Valve timing stock: (.000'' lift)

IN: Open BTDC 10
IN: Close ABDC 49

EX: Open BBDC 55
EX: Close ATDC 12

Source:
Camshaft Calculations - Lobe Center / Duration
"Your F2 has an Overlap of 22.00 degrees and has in Intake Duration of 239.00 degrees. The Exhaust Duration is 247.00 degrees. The Inlet Cam has an Installed Centerline of 109.50 degrees ATDC. The exhaust cam has an Installed Centerline of 111.50 degrees BTDC" - Crower Cams (thanks to Sick)

Ok, good stuff. Now lets start crunching numbers with the right formula(s).

To make sure that the number are right we will calculate in to ways.

#1 Obvious, look at the pic method.


comes out to 22* overlap at .000 lift.

#2

to find duration at .000 lift - In= 10+180+49= 239* Ex= 55+180+12= 247*

instead of gust guessing the lobe seperation we'll find the real thing.

{[(in. dur / 2) - dist BTDC] + [(ex. dur / 2) - dist ATDC]} / 2 = Lobe Separation

{[(239/2) - 10] + [(247/2) - 12} /2 = 110.5* Lobe Separation

ok, now we can find overlap:

239 + 247
---------- - 110.5 = 11 x 2 = 22 of overlap at .000 of lift
4

Now remember that we are supposed to look at cam specs at .050 lift? But we don't have timing numbers for that lift so we need to do it with some math...

Ok so now that we know the math method works, we can find out what our overlap at .050 is. Using:

Duration at .050''
Lobe duration (Intake): 197
Lobe duration (Exhaust): 208

197+208
--------- - 110.5 = -9.25 x 2 = -18.5 overlap at .050 of lift
4

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post #19 of 19 (permalink) Old 4-5-16, 12:48
 
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----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

(The following info was something I found looking for the rocker ratio's)



f2t head info, missing parts...
I need the real thing. Haynes and the online car(all data i believe) thing are messing with numbers or something. I need real numbers for a modified rebuild. If ANY of this is wrong or if any of you are actually going to check stuff in your manuals PLZ tell me. I'll give ya good karma lol . Oh i could mesure all i need with my own head in my hands but i probably won't get it back before monday because i'm having a night time rush, i can't sleep worth [shizzle], get up way too late and have to go straight to school, and the guy who has my head is closed at 10:20 at night.

Valve clearance - self adjusting(hla's if correctly understand)
Valve face angle - 45degrees (online mitchell says 35?!?!)
Valve seat angle - same thing (online say 15??
Valve stem diameter:
Intake - 0.2744 to 0.2750in
Service Limit - None specified
Exhaust - 0.2742 to 0.2748in
Limit - none again?!?!?!obviously this can't be
Valve seat width - 0.047 to 0.063
Valve seat sinking - Can someone explain plz?In the head i assume?
Standard - 1.949in
Limit - 2.008in that would be .08mm farther in the head if this is head sink
Valve stem to guide clearance IN & EX:
St - 0.0010 to 0.0024in
Lt - 0.0079in

Valve spring angle limit - 0.067in Hell of a twisted spring to me! (1.7mm)
Spring free length:
Intake
Standard - 1.949in
Limit - 1.902in
Exhaust - 1.984in
Limit - 1.937in
Valve guide projection - 0.780in

Now this is what i need, preferably in lbs and mm's(ya ok that's mixing it up):
-Coil to coil gap size
-Open valve spring tension @ height
-Closed valve spring tension @ height
-Spring retainer diameter
-Spring retainer dish depth if any(i don't recall them to be dished
-Spring keeper's width,height,angle and # of notches
-Valve stem seal's inner and outer diameter, height (same as guide projection?)
- valve guide diameter
- maximum rocker arm lift

That's it. You probably can all se where I am going with this. If not. Who cares. And if so and you disagree well i don't care.

Ok new numbers in -

My old springs show very minimal sign of wear.

Pressure to coil bind - 180lbs
Closed valve pressure @ mm's
Intake- 45.5-51.5lbs @ 41mm
Exhaust - 54-61 @ 41mm

Inner diameter - Intake = 26.6mm
Exhaust = 24.46mm
Outer Diameter - Intake = 33.4
- Exhaust = 34.00

I didn't find open valve pressure.

------------------------------------------------------------------------------------------------------------------

Stock cam lift #'s/rocker ratio/valve lift
I've seen lots of ppl with regrinded cams around here and I don't believe anyone ever posted stock cam #'s and I don't think the manual has them, well I don't know because I don't have one so...

Intake lobe lift = .210
Exhaust lobe lift = .230

+/- 0.001in. These measures were taken on a used cam and the average of all lobes were taken. None of them differed more than 0.001.

Intake valve lift = 0.374
Exhaust valve Lift = 0.410

So divide one with the other and you get the ratio of the rockers at max lift.
Rocker arm ratio = 1.78

So here it is. You can compare your custom grinds to these and re-calculate valve lift for your engines and then calculate piston to valve clearance without taking appart your engines."

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