Editing Z31/camspecs (section)

== XenonZcar.com - Z31 Camshaft Specifications and Upgrade Information ==

===  Nissan VG30/33 camshaft information. ===

Understanding cam specs and their affects will help you select the best cam for your specific engine. The four important camshaft specs to understand are duration, centerline, separation and lift.

=== DURATION ===

Duration refers to how long a valve is opened in relation to crankshaft rotation. This open valve time period is expressed in degrees of crankshaft rotation. So, a cam specification of 220 degrees duration simply means the cam holds the valve open for 220 degrees of crankshaft rotation.

As strange as this may sounds, more duration can be helpful in high RPM engines but not low RPM engines. The extra degrees of open valve time in high RPM engines gives the air flow a little more time to get into (or out of) the cylinder in spite of the piston's stroke. However, at lower RPMs, more duration can cause less power because the valves will be open at the wrong time in relation to the piston's stroke up or down in the cylinder.

In order to measure a camshaft's duration, you must use a degree wheel in conjunction with a predetermined lift point. The most common duration references are advertised duration measured at 0.050-inch lift. While the advertised numbers are supposed to be measured at 0.020-inch lift, some cam grinders measure farther down the lobe to make their camshaft look more radical than it really is. Because of this confusion, most engine builders use the 0.050-inch duration figure,

=== CENTERLINE ===

The cam's centerline specification is used to tie the valve timing to the crankshaft's rotation. This spec is expressed as the number of degrees the crankshaft must rotate from top dead center until the cam has rotated to the peak (or centerline) of the lobe.

The centerline spec and the duration spec can be used to calculate when the valves open and close in relation to the crankshaft's rotation. When the valves open (or close) relative to the crankshaft's rotation is known as valve events or valve timing. Some cam manufacturers will provide valve event information and others only provide duration and centerline information.

Understanding the effects of valve events or valve timing is the real secret to understanding engine performance. For the engine to run at its peak performance, the valves must open and close at the correct time in relation to the piston's position and the crankshaft's speed.

==== FINDING INTAKE LOBE CENTER ====

Remove ALL lash. With your dial indicator on the retainer or follower, rotate the engine in the direction it would normally turn, and come up to .050 inches of lift. Write down that figure from the degree wheel. This is your opening figure. This is when the intake opens BEFORE Top Dead Center. Example would be 10 degrees on the degree wheel BTDC.

Now go over the top on the lobe until your indicator is .050 inches off the Base Circle. Now you should be where the intake closes AFTER Bottom Dead Center. Keep in mind to continue turning the engine in the same direction it runs and DO NOT BACK UP. Example would be 39 degrees on the degree wheel ABDC.

You can now calculate your duration. The valve opens at 10 degrees, plus it closes 39 degrees, plus 180 degrees (the distance in degrees between TDC and BDC). Your duration at .050 inches of lift would be 229 degrees.

+10° Opening Before Top Dead Center (BTDC)

+39° Closing After Bottom Dead Center (ABDC)

+180° Distance from Top Dead Center (TDC) to Bottom Dead Center (BDC)

= 229° Total duration @ .050 inches of lift

You can now calculate your lobe centerline. Divide your total duration by 2 and subtract your intake-opening figure. This would normally be the smaller number of the two figures.

229° / 2 = 114.5°

114.5° - 10° = 104.5°

104.5° would be your lobe centerline.

'''Please Note:''' If you have a low overlap cam, the intake opening may be AFTER TDC, if so, you will have to SUBTRACT that figure from the closing number and add 180. This will be the duration at .050 inches of lift.

-10° Opening After Top Dead Center (ATDC)

+39° Closing After Bottom Dead Center (ABDC)

+ 180° Distance from Top Dead Center (TDC) to Bottom Dead Center (BDC)

= 209° Total duration @ .050 inches of lift

You can now calculate your lobe centerline. Divide your total duration by 2 and add your intake opening figure. This would normally be the smaller number of the two figures.

209° / 2 = 104.5°

104.5° + 10° = 114.5°

114.5° would be your lobe centerline.

==== FINDING EXHAUST LOBE CENTER ====

Once again remove ALL lash. With your dial indicator on the retainer or follower, rotate the engine in the direction it would normally turn, and come up to .050 inches of lift. Write down that figure from the degree wheel. This is your opening figure. This is when the exhaust opens BEFORE Bottom Dead Center. Example would be 44 degrees on the degree wheel BBDC.

Now go over the top on the lobe until your indicator is .050 inches off the Base Circle. Now you should be where the exhaust closes AFTER Top Dead Center. Keep in mind to continue turning the engine in the same direction it runs and DO NOT BACK UP. Example would be 8 degrees on the degree wheel ATDC.

You can now calculate your duration. The valve opens at 44 degrees, plus it closes 8 degrees, plus 180 degrees (the distance in degrees between TDC and BDC). Your duration at .050 inches of lift would be 232 degrees.

+ 44° Opening Before Bottom Dead Center (BBDC)

+ 8° Closing After Top Dead Center (ATDC)

+ 180° Distance from Top Dead Center (TDC) to Bottom Dead Center (BDC)

= 232° Total duration @ .050 inches of lift

You can now calculate your lobe centerline. Divide your total duration by 2 and subtract your exhaust closing figure. This would normally be the smaller number of the two figures.

232° / 2 = 116°

116° - 8° = 108°

108° would be your lobe centerline.

'''Please Note: '''If you have a low overlap cam, the exhaust closing may be BEFORE TDC, if so, you will have to SUBTRACT that figure from the closing number and add 180. This will be the duration at .050 inches of lift.

+ 26° Opening Before Bottom Dead Center (BBDC)

- 10° Closing Before Bottom Dead Center (BTDC)

+ 180° Distance from Top Dead Center (TDC) to Bottom Dead Center (BDC)

= 196° Total duration @ .050 inches of lift

You can now calculate your lobe centerline. Divide your total duration by 2 and add your exhaust closing figure. This would normally be the smaller number of the two figures.

196° / 2 = 98°

98° + 10° = 108°

108° would be your lobe centerline.

=== SEPARATION ===

Separation refers to the spacing between the intake lobe and exhaust lobe on the cam shaft. This spacing (or separation) is expressed in degrees on the cam, not on the crankshaft. So, a 108 lobe separation means the intake and exhaust lobes are 108 degrees apart from each other on the cam shaft.

This spec by itself really doesn't mean anything. If you hear someone else is using a cam with 108 separation, don't think that you should use cams that only have 108 separation!

Separation, just like centerline, is another way to tie the duration to the crankshaft rotation and end up with valve events. This spec is a little more complicated though, because it is in cam shaft degrees and the crankshaft rotates two degrees for each one degree of cam rotation. Also, if the cam has been installed either advanced or retarded, the valve events will be different.

=== LIFT ===

The final cam spec to understand is lift. While duration refers to how long the valve is opened, cam lift is used to determine how wide the valve is opened.

If the valves are not opened wide enough, they will cause a restriction for the air trying to enter or exit the cylinder. However, opening the valve past a certain point will not increase the flow to (or from) the cylinder. A good way to demonstrate this is with the garden hose in your back yard. When you first start to turn the water on, the flow increases but after a turn or so, opening the valve more has no effect on how fast the water comes out of the hose.

=== VG30E(T) Camshaft Specs ===

Manufacturer, type, duration (Int/Exh), cam lift (in inches), other info.

==== OE cams: ===

{| class="wikitable"
|-
| '''Manufacturer'''
| '''Duration Intake'''
| '''Duration Exhaust'''
| '''Cam lift Intake Lobe Inches'''
| '''Cam lift Exhaust Lobe Inches'''
| '''Intake Centerline'''
| '''Exhaust Centerline'''
|-
| Stock "early" US 7/83 to 7/87 Z31
| 252 or 193 @ 0.050
| 252 or 193 @ 0.050
| .393"
| .393"
| 106
| 116
|-
|-
| Stock "late" US Z31 08/87+
| 248 or 189 @ 0.050
| 248 or 192 @ 0.050
| .393"
| .393"
| 114
| 114
|-
| J-spec Z31 cams
| 252 or 193 @ 50 thousands
| 252or 193 @ 0.050
| .393"
| .393"
|-
| European Z31 Cams
| 264
| 262
| .393"
| .393"
|-
| NISMO Z31 Cams
| 264
| 262
| .393"
| .393"
|-
| USDM VG30 "Truck" cams (D21, WD21 and J30)
| 248 or 189 @ 0.050
| 248 or 192 @ 0.050
| .393"
| .393"
|-
| USDM VG33 Cams (all)
| 240
| 244
| .366"
| .366"
|}

==== Colt Cams: ====

{| class="wikitable"
|-
| Manufacturer
| Duration Intake
| Duration Exhaust
| Cam lift Intake Lobe Inches
| Cam lift Exhaust Lobe Inches
|-
| [http://allthingsz.com/store/images/VG30Ecams.png Colt Cam Na/turbo Grind (Stage 1)]
| 256 or 202 @ 0.050
| 256 or 202 @ 0.050
| .420"
| .420"
|-
| [http://allthingsz.com/store/images/VG30Ecams.png Colt Cam Na (Stage 2)]
| 262 or 210 @ 0.050
| 262 or 210 @ 0.050
| .428"
| .428"
|-
| [http://allthingsz.com/store/images/VG30Ecams.png Colt Cam Turbo (Stage 2)]
| 262 or 210 @ 0.050
| 256 or 202 @ 0.050
| .428"
| .420"
|}

==== Schneider Racing Cams: ====

Inknown Number @ 0.050 Advertised @ 0.006

* Non-turbo grind 256/256 .420"/.420" CLSA 110
* Non-turbo grind 262/262 .420"/.420" CLSA 110
* Non-turbo grind 270/270 .440"/.440" CLSA 110
* Non-turbo grind 280/280 .450"/.450" CLSA 110
* Turbo grind 262/256 .420"/.420" CLSA 114
* Turbo grind 270/262 .440"/.420" CLSA 114
* Turbo grind 280/270 .450"/.440" CLSA 114
* Turbo "race only" grind 284/274 .450"/.440" CLSA 114

==== Motorsport Auto: ====

Inknown Number @ 0.050 Advertised @ 0.006

* Stage 1 Turbo 262/256 .420"/.420" $169.95 Exchange only
* Stage 2 Turbo 270/262 .420"/.420" $169.95 Exchange only
* Stage 1 Non-Turbo 260/260 .420"/.420" $169.95 Exchange only
* Stage 2 Non-Turbo 270/270 .427"/.427" $169.95 Exchange only
* Stage 3 Non-Turbo 280/280 .435"/.435" $169.95 Exchange only

==== Iskendarian Cams: ====

Inknown Number @ 0.050

* Turbo and non 262/258 .450"/.450" About $200 Exchange only

==== PAECO: ====

Inknown Number @ 0.050

* DSV-5800 Street 280/280 Turbo .328"/.328" $230 Each - $250/Core
* DSV-6200 Strt/Strp 288/288 Turbo and non .360"/.360" $230 Each - $250/Core
* DSV-6800 RACE 302/302 Turbo and non .373"/.373" $230 Each - $250/Core

==== Jim Wolf Technology: ====

Inknown Number @ 0.050

* Stage 1 Turbo (S1) 260/260 .440" About $450
* Stage 2 Turbo (S2) 266/266 .473" About $450

==== Other Custom grinds used by Z31 owners: ====

Inknown Number @ 0.050
Tempestas custom turbo grind 270/270 .480"/.480"