ae13291

iTrader: (8)

hey guys i just ordered a custom cam, the employee also asked what is the grind # for the cam, i had no idea because i was never told anything about a grind #?? does that mean like 113LSA+4 or something?? and then he emailed me later asking I need to know what centerline this cam was specced for? so what would i say for that? this is going to be a cam only car and im not touching the heads, how can i get the correct grind #, please if somebody can help me out, they wont start the grinding till every info has been provided. thanks guys

Sid447

http://www.compcams.com/DefaultWide.asp

stevied916

iTrader: (30)

why doesn't he just degree it?

Old SStroker

You are finding the basic reasons that you should use a professional cam guy to spec you cam. Even that is a crap shoot.

Grind # may refer to one of the company's "shelf" cams. If you made up the cam, he wants the lobe numbers you want used (there are many), and where you want the intake centerline (ICL) to be. You need that to degree in you cam properly.

If you don't know the answers to this, you should not be ordering anything other than a "shelf" cam. An even bigger problem is how do you know what you are specing is correct for your engine/car/personal desires?

Cancel your order and find a good cam person...or just a cam person.

Good luck...you'll need it.


Jon

ae13291

iTrader: (8)

i got the cam specs from PAT G as you can see its a pretty odd duration and lift combo. but i mean he never gave me a grind # or centerline. the emplyee at thunder racing said they are going to get a hold of Pat to get his recommendations but i just want to know whats goin on you know. the cam was specced out about 1 year ago.

ae13291

iTrader: (8)

cool il ask to see if he would, so by degreeing you mean he would get all the correct #'s right?

02*C5

iTrader: (1)

When it comes to performance parts, 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. 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. So, bigger numbers are not always better when it comes to engine performance parts.
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. If your cam manufacturer doesn't provide valve event information, a software program such as Cam Shop can calculate this info for you.
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.
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. This is where the Cam Shop software can make your decisions easier because the software does all of the calculations for you and you don't have to guess at these confusing relationships.
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.

Get Pat to email you the cam spec card. 99% of the info will be on there that you need. Usually the grind# like stated before is for off the shelf cams.

ae13291

iTrader: (8)

^^^thanks alot for the post very usefull. so the centerline has to do with advancing or retarding the timing of when the valves open correct? i know the car is going to be NA so i know i dont need to advance it any more, and im going to use pump gas so i think through timing the spark i would be able to get a good amount of advance? cant i just keep the centerline neutral so things dont get more complicated? anyways i already pm'd Pat hopefully he will help me with the correct #'s

02*C5

iTrader: (1)

yes

A good tuner will take care of this. If you can get between 36* and 38* of total timing @ 2500 to 2800 rpm your in the money. This will depend on your fuel and compression ratio also.

ae13291

iTrader: (8)

thanks for the help, let me see what happens, im not sure what i need to do with the centerline for the cam.

stevied916

iTrader: (30)

you cant change the icl...it's what the cam is ground on. the difference between the lsa and icl is the advance or retard which is ground into the cam. The only thing you can change is the advance/retard of the cam as it's installed by a adjustable timing set. If he degrees it the icl should be obvious. The actual would be something like 113.23 if the icl is 113.

PREDATOR-Z

It actualy is a 224/230 .609, .604 113+4 LSA

It will come ground as 226/232

It is a XFI Comp Cam lobes:

Here are the specs to give to your shop:

Intake lobe # 3015R
Exhaust lobe # 3036R
113 LSA (lobe separation angle)
109 ICL (intake centerline)

That is all the info you need to get this cam as Pat G speced it. (highlight)

Interspy24

iTrader: (4)

Quick question - what is the power difference between this cam on xer lobes and xfi lobes? Thanks in advance.

PREDATOR-Z

That is difficult to say, it would depend on overall combo.

Interspy24

iTrader: (4)

Combo #1: 243 heads and intake manifold, intake, longtubes, tune, etc..

Combo #2: ported 243 heads and ported fast, intake, longtubes, tune, etc..

Btw, can both the xer and xfi be used with pac beehives or are are dual springs recommended? Seems that while the xfi lobes have larger lifts, they are actually easier on the springs. Seems people have used pac/918 beehives with good luck, just wanting your opinion. Thanks in advance.

02*C5

iTrader: (1)

Use dual springs it is a relatively cheap investment on securing the future of you valve train and your engine. Comp 921s are great to have a little on the expensive side but bets springs i have ever used.

ae13291

iTrader: (8)

thanks for responding in this thread, i have heard lots of great things about you. i got the email from Pat this morning and called Gene at thunder racing right away, Pat emailed me

"The cam is 113LSA with 2 degrees of advance ground in. Lining up the dots will put you at 111 intake centerline".

so i guess that sounds right, i put the order in already.


PREDATOR-Z- so by the +4 runnnig on 109ICL the only differance would have been a more advanced cam right? meaning valves will open up earlier. im sure the +2 will suite my needs. thanks again for replying in the thread, i really appreciate your help. thanks for everybody else who responded back in this thread.

PREDATOR-Z

+4 would indeed open the intake 2* earlier and close it earlier for a 42 IVC.
Basicaly bring the powerband down ~100 rpm or so earlier. There would be very little difference between the +2 and +4.