Detailed Cam Spec Determination ?'s
Thread Starter
Joined: Jan 2003
Posts: 2,502
Likes: 19
From: Minnesota Corn Fields
Detailed Cam Spec Determination ?'s In trying to expand on jrp's cam guide can we get some of the cam guru's to help out in explaining the finer details of cam selection. Mostly related to J-Rod's Quick and Dirty Spread Sheet.
When someone has determined what heads they're using, range of durations (RPM Range) they want to stay in and what types of lobes they want to use or can deal with, whats next?
What calculations in the spreadsheet should one be looking at to optimize the set up?
For example -> get the DCR close to 8.5 as possible
What about VE's? - which ones provide good driveability, which ones provide the power?
What about overlap? What does that affect
Can one determine if a cam will fit or not based on the spreadsheet?
or what makes one cam fit and another not fit even though the durations or lift is smaller?
Hope this will answer some questions not only that I have but others too.
When someone has determined what heads they're using, range of durations (RPM Range) they want to stay in and what types of lobes they want to use or can deal with, whats next?
What calculations in the spreadsheet should one be looking at to optimize the set up?
For example -> get the DCR close to 8.5 as possible
What about VE's? - which ones provide good driveability, which ones provide the power?
What about overlap? What does that affect
Can one determine if a cam will fit or not based on the spreadsheet?
or what makes one cam fit and another not fit even though the durations or lift is smaller?
Hope this will answer some questions not only that I have but others too.
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Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Originally Posted by No Juice
In trying to expand on jrp's cam guide can we get some of the cam guru's to help out in explaining the finer details of cam selection. Mostly related to J-Rod's Quick and Dirty Spread Sheet.
When someone has determined what heads they're using, range of durations (RPM Range) they want to stay in and what types of lobes they want to use or can deal with, whats next?
What calculations in the spreadsheet should one be looking at to optimize the set up?
For example -> get the DCR close to 8.5 as possible
What about VE's? - which ones provide good driveability, which ones provide the power?
What about overlap? What does that affect
Can one determine if a cam will fit or not based on the spreadsheet?
or what makes one cam fit and another not fit even though the durations or lift is smaller?
Hope this will answer some questions not only that I have but others too.
When someone has determined what heads they're using, range of durations (RPM Range) they want to stay in and what types of lobes they want to use or can deal with, whats next?
What calculations in the spreadsheet should one be looking at to optimize the set up?
For example -> get the DCR close to 8.5 as possible
What about VE's? - which ones provide good driveability, which ones provide the power?
What about overlap? What does that affect
Can one determine if a cam will fit or not based on the spreadsheet?
or what makes one cam fit and another not fit even though the durations or lift is smaller?
Hope this will answer some questions not only that I have but others too.
One of the best engine guys I've ever heard of heard of wants to be cremated when he dies, have his ashes mixed into 55 gallons of race gas, and run the gas thru a race engine at full grunt so he can actually see what's happening in the engine!
While he's still alive and kicking he's measuring a whole bunch of stuff going on inside race engines, and then trying to explain what he measures. He is a Phd. and works for a Cup team. Some of what he's found is surprising.My point is that a spreadsheet isn't going to do much to help you optimize a cam for a particular combination. Knowing how an engine works, what has worked or not worked in the past, and a little out of the box thinking is probably a more successful approach. Lots of testing helps too!
While I think it's neat idea to be able to spec you own cam, I'd ask a specialist before I'd spend my money. I'd do the same thing if I were sick and needed medical attention.
My $.02.
Thread Starter
Joined: Jan 2003
Posts: 2,502
Likes: 19
From: Minnesota Corn Fields
Originally Posted by Old SStroker
A very thorough knowledge of how an engine works helps a lot. No flame intended. Just because we think something should work one way doesn't mean it does.
One of the best engine guys I've ever heard of heard of wants to be cremated when he dies, have his ashes mixed into 55 gallons of race gas, and run the gas thru a race engine at full grunt so he can actually see what's happening in the engine! While he's still alive and kicking he's measuring a whole bunch of stuff going on inside race engines, and then trying to explain what he measures. He is a Phd. and works for a Cup team. Some of what he's found is surprising.
My point is that a spreadsheet isn't going to do much to help you optimize a cam for a particular combination. Knowing how an engine works, what has worked or not worked in the past, and a little out of the box thinking is probably a more successful approach. Lots of testing helps too!
While I think it's neat idea to be able to spec you own cam, I'd ask a specialist before I'd spend my money. I'd do the same thing if I were sick and needed medical attention.
My $.02.
One of the best engine guys I've ever heard of heard of wants to be cremated when he dies, have his ashes mixed into 55 gallons of race gas, and run the gas thru a race engine at full grunt so he can actually see what's happening in the engine!
While he's still alive and kicking he's measuring a whole bunch of stuff going on inside race engines, and then trying to explain what he measures. He is a Phd. and works for a Cup team. Some of what he's found is surprising.My point is that a spreadsheet isn't going to do much to help you optimize a cam for a particular combination. Knowing how an engine works, what has worked or not worked in the past, and a little out of the box thinking is probably a more successful approach. Lots of testing helps too!
While I think it's neat idea to be able to spec you own cam, I'd ask a specialist before I'd spend my money. I'd do the same thing if I were sick and needed medical attention.
My $.02.
If you have two cams (that have been known to work) to throw into the spreadsheet, how do you tell if one is better for you than the other(based on your desired result)?
TECH Fanatic
Joined: Jun 2002
Posts: 1,979
Likes: 3
From: Upstate NY
Originally Posted by No Juice
Good point, maybe I should have added this instead:
If you have two cams (that have been known to work) to throw into the spreadsheet, how do you tell if one is better for you than the other(based on your desired result)?
If you have two cams (that have been known to work) to throw into the spreadsheet, how do you tell if one is better for you than the other(based on your desired result)?
Engines don't read spreadsheets.
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Thread Starter
Joined: Jan 2003
Posts: 2,502
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From: Minnesota Corn Fields
Well I want to know why this cam: 220/224 557/575 112 will fit and is the largest cam that will fit without flycutting per a certain vendor
and this cam will NOT fit: 224/228 578/578 112 per the same vendor
Both cams are sold by this vendor. However this is all the information I have on these two cams. I don't know what types of lobes they are.
I want a cam that will be a fun on the street cam only and then work well with a good set of heads.
and this cam will NOT fit: 224/228 578/578 112 per the same vendor
Both cams are sold by this vendor. However this is all the information I have on these two cams. I don't know what types of lobes they are.
I want a cam that will be a fun on the street cam only and then work well with a good set of heads.
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Originally Posted by No Juice
Well I want to know why this cam: 220/224 557/575 112 will fit and is the largest cam that will fit without flycutting per a certain vendor
and this cam will NOT fit: 224/228 578/578 112 per the same vendor
Both cams are sold by this vendor. However this is all the information I have on these two cams. I don't know what types of lobes they are.
I want a cam that will be a fun on the street cam only and then work well with a good set of heads.
and this cam will NOT fit: 224/228 578/578 112 per the same vendor
Both cams are sold by this vendor. However this is all the information I have on these two cams. I don't know what types of lobes they are.
I want a cam that will be a fun on the street cam only and then work well with a good set of heads.
Those cams are both really small for not fitting so i'm guessing you have a big valve in there and a lot of milling on the heads.
Bret
Originally Posted by SStrokerAce
What you want to look at is the IVO and EVC points, that's why it will not fit. Those two points are what determines piston to valve clearance.
Those cams are both really small for not fitting so i'm guessing you have a big valve in there and a lot of milling on the heads.
Bret
Those cams are both really small for not fitting so i'm guessing you have a big valve in there and a lot of milling on the heads.
Bret
Maybe you can help all of us out by telling us what you are trying to do with your car? It seems this post is more about you choosing between two cams so you can find whats right for you.
rick
You have already received a lot of good advice. There are a lot of questions on this forum where members ask questions like the one you asked and ones like " what length pushrod will I need with such and such combination" The main reason those questions cannot be anwsered is because of all the unknown variables with a particular engine. That is the reason experienced folks are always saying that "you have to measure and check everything all the time" Were those cams both used in the exact same engine in determining that one cleared and the other did not? Like was mentioned those are small cams so one would think that other factors not being considered are the culprits. Thanks.
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Joined: Mar 2004
Posts: 14,620
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From: BFE
While spreadsheet design is not 100% accurate as to how a cam will perform in the motor, it is a pretty close picture.
As mentionned above, experience and motor dynamics understanding play the major role.
Still understanding how VEs work will give a good image of the power range of said cam.
We are now going on our 10th year dealing with LS motors and one can see how cam theologies are evolving. Just in the recent months, we are starting to see members paying interest to VE's, SCR and DCR instead of just "this is the biggest I can fit, so it will make more power".
Missmatched parts are the biggest dissapointment in actual modding. So the trick is to match parts properly and not just shove the biggest part in there a expect ultimate power.
As mentionned above, experience and motor dynamics understanding play the major role.
Still understanding how VEs work will give a good image of the power range of said cam.
We are now going on our 10th year dealing with LS motors and one can see how cam theologies are evolving. Just in the recent months, we are starting to see members paying interest to VE's, SCR and DCR instead of just "this is the biggest I can fit, so it will make more power".
Missmatched parts are the biggest dissapointment in actual modding. So the trick is to match parts properly and not just shove the biggest part in there a expect ultimate power.