In the market for a Camshaft
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Joined: Jul 2001
Posts: 151
Re: In the market for a Camshaft
The 847 cam is way to much for the stock heads. There are Big Blocks and even the LS1's not running cams as big as this. It will be a low vacuum motor, and needs a set of heads, intake and T Body and exhaust to compliment it.
I dont understand the Big Cam Big Injector theory here, but driveability has got to be important.
The Cams inthe 210-220 in, 215-225ex range are very good cams, and very driveable.
I dont understand the Big Cam Big Injector theory here, but driveability has got to be important.
The Cams inthe 210-220 in, 215-225ex range are very good cams, and very driveable.
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Re: In the market for a Camshaft
As do others who have posted here, I see too many "big" cams in the context of mismatched components. Some of the ideas about what constitutes a big cam have gone out of date when applied to a properly tuned EFI setup. The whole issue of getting a good vacuum signal to the carb boosters obviously no longer applies. So, some of the issues with respect to stalling, very poor throttle response, etc. have been ameliorated. If you have ever driven an "overcammed" carb car, you will know exactly how un-fun that can be.
Nonetheless, or perhaps even more than in the past, you see lots of grossly mismatched parts. A cam that is "too big" for the rest of the intake tract will make your car slower than a cam which is optimally sized, iow a smaller cam. Period. And, of course, the issues of the compatibility and longevity of the supporting components hasn't changed. So, a bigger cam will need better (= more expensive) valvetrain parts to have reasonable longevity. And at some point, even with premium parts there are going to be problems. I agree with the poster who said that an LT1 with stock or near stock heads should not have a cam bigger than 210-220 @ 0.050" intake duration. The upper end of the range is good for a stroker, the lower for a 350. Lift is another factor to consider. While I suppose it is possible, in theory, to open a valve "too fast" and consequently lose power this does not occur in practical terms. So, cams with high valve acceleration generally work well. A good way to help achieve this is with higher ratio rockers. Total lift needs to be limited to preserve spring life. There is point in having "wasted" lift.
Where does that leave this discussion? I'd listen to Bret on this one. In fact, shell out a few bucks and have him pick/design it for you ALONG WITH SELECTING THE RIGHT SUPPORTING PARTS. Can't emphasize the latter strongly enough. Without the right pushrods, srpings, lifters, etc. the whold thing can fall apart. You can waste money on stuff you don't need, or worse yet get stuff that doesn't work right. This isn't "rocket sicence" but there are number of subtleties involved that as well as a big role for experience.
Rich
Nonetheless, or perhaps even more than in the past, you see lots of grossly mismatched parts. A cam that is "too big" for the rest of the intake tract will make your car slower than a cam which is optimally sized, iow a smaller cam. Period. And, of course, the issues of the compatibility and longevity of the supporting components hasn't changed. So, a bigger cam will need better (= more expensive) valvetrain parts to have reasonable longevity. And at some point, even with premium parts there are going to be problems. I agree with the poster who said that an LT1 with stock or near stock heads should not have a cam bigger than 210-220 @ 0.050" intake duration. The upper end of the range is good for a stroker, the lower for a 350. Lift is another factor to consider. While I suppose it is possible, in theory, to open a valve "too fast" and consequently lose power this does not occur in practical terms. So, cams with high valve acceleration generally work well. A good way to help achieve this is with higher ratio rockers. Total lift needs to be limited to preserve spring life. There is point in having "wasted" lift.
Where does that leave this discussion? I'd listen to Bret on this one. In fact, shell out a few bucks and have him pick/design it for you ALONG WITH SELECTING THE RIGHT SUPPORTING PARTS. Can't emphasize the latter strongly enough. Without the right pushrods, srpings, lifters, etc. the whold thing can fall apart. You can waste money on stuff you don't need, or worse yet get stuff that doesn't work right. This isn't "rocket sicence" but there are number of subtleties involved that as well as a big role for experience.
Rich
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Joined: Oct 2002
Posts: 6,518
Re: In the market for a Camshaft
Originally Posted by rskrause
ameliorated
ameliorate \uh-MEEL-yuh-rayt\, transitive verb:
To make better; to improve.
intransitive verb:
To grow better.
BTW Cam wise.... the timing events can be manipulated to make up for lost TQ in some areas.... it's all a tug o war though. You get something in one place and give it up in another.
Bret
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Joined: Dec 1969
Posts: 10,745
From: Buffalo, New York
Re: In the market for a Camshaft
Originally Posted by SStrokerAce
I actually opened up the dictionary for that one..... THANKS
ameliorate \uh-MEEL-yuh-rayt\, transitive verb:
To make better; to improve.
intransitive verb:
To grow better.
BTW Cam wise.... the timing events can be manipulated to make up for lost TQ in some areas.... it's all a tug o war though. You get something in one place and give it up in another.
Bret
ameliorate \uh-MEEL-yuh-rayt\, transitive verb:
To make better; to improve.
intransitive verb:
To grow better.
BTW Cam wise.... the timing events can be manipulated to make up for lost TQ in some areas.... it's all a tug o war though. You get something in one place and give it up in another.
Bret
Rich
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Joined: Oct 2002
Posts: 6,518
Re: In the market for a Camshaft
Thread Starter
Registered User
Joined: Sep 2003
Posts: 5,907
From: The Wild West
Re: In the market for a Camshaft
I agree with what I understood from your post, lol. Now what does TINSTAAFL mean? Ah-ha the economic theory of oppurtunity cost.
I am definately considering going the extra mile and getting a cam from Bret. We have been talking back and forth between emails for quite some time. The main reason I made this thread was to get a range for a cam to talk to Bret about making. I knew a bit about the size of the cam compared to drivibility, power, torque, etc. But I didnt know what to ask from Bret, its like having the biggest all-you-can eat buffett right in front of you, but not fully knowing wether to start with salad or steak. I have no gauge to go on what to ask for. All I can say is "smaller than a 847, but bigger than cc305, but drivable, but powerful." I just want to learn a bit more so I can zero in on extactly what I want. If I know that a GM 846 has good manners with a A4, and someone can plop a dyno sheet in here and see how high it pulls, I could say, drives like GM 846 but pulls 200rpm higher that touches 350rwhp. I definately am not doing something like a GM 847 on stock heads. Now the thing is I dont care much what it makes on a dyno, I care how it performs. I am sure Bret could make me a cam that peaked with great HP numbers, but what I want (I think) is something that has lots of area under its TQ/HP curves for great real world performance and fun driving. If it hits 350rwhp on the rollers great, if it doesnt and I run 11.8 with stock heads, who cares? Trick is something I can drive on a daily basis and that wont annoy me or my G/F when we are in it. The one thread was awesome where JonA put up dyno sheets and everything looked about what I am looking for, the only thing he was missing was a 1/4 mile time to see how the cam was used in real life. Also, watching his racing video's I couldnt really get a grasp for how it would be drivibilty wise, but it did sound nice and mean. So there you have it, everyone knows what I am thinking. I will be doing a 2800/3000rpm stall somewhere, which I already told Bret. I will probably leave stock 3.23's in for now. Hopefully when I get to Dragway 42, I can listen and possbily drive a LE2 package to give Bret a better description of what I'd like.
-Dustin-
I am definately considering going the extra mile and getting a cam from Bret. We have been talking back and forth between emails for quite some time. The main reason I made this thread was to get a range for a cam to talk to Bret about making. I knew a bit about the size of the cam compared to drivibility, power, torque, etc. But I didnt know what to ask from Bret, its like having the biggest all-you-can eat buffett right in front of you, but not fully knowing wether to start with salad or steak. I have no gauge to go on what to ask for. All I can say is "smaller than a 847, but bigger than cc305, but drivable, but powerful." I just want to learn a bit more so I can zero in on extactly what I want. If I know that a GM 846 has good manners with a A4, and someone can plop a dyno sheet in here and see how high it pulls, I could say, drives like GM 846 but pulls 200rpm higher that touches 350rwhp. I definately am not doing something like a GM 847 on stock heads. Now the thing is I dont care much what it makes on a dyno, I care how it performs. I am sure Bret could make me a cam that peaked with great HP numbers, but what I want (I think) is something that has lots of area under its TQ/HP curves for great real world performance and fun driving. If it hits 350rwhp on the rollers great, if it doesnt and I run 11.8 with stock heads, who cares? Trick is something I can drive on a daily basis and that wont annoy me or my G/F when we are in it. The one thread was awesome where JonA put up dyno sheets and everything looked about what I am looking for, the only thing he was missing was a 1/4 mile time to see how the cam was used in real life. Also, watching his racing video's I couldnt really get a grasp for how it would be drivibilty wise, but it did sound nice and mean. So there you have it, everyone knows what I am thinking. I will be doing a 2800/3000rpm stall somewhere, which I already told Bret. I will probably leave stock 3.23's in for now. Hopefully when I get to Dragway 42, I can listen and possbily drive a LE2 package to give Bret a better description of what I'd like.
-Dustin-
Last edited by Bersaglieri; Apr 22, 2005 at 12:03 PM.
Registered User
Joined: Oct 2002
Posts: 2,931
From: Upstate NY
Re: In the market for a Camshaft
Originally Posted by rskrause
Cam design is an exercise in compromise. That's why I always found those Comp Cams ads "Comp, not compromise" to be ironic. In the words of Robert Heinlein "TINSTAAFL". Nowhere in the world of automobiles is that more true than in cam design.
Rich
Rich
Totally agree with you on cam design. A lot of tweaking goes on to get the "best" cam for a given application.
Thread Starter
Registered User
Joined: Sep 2003
Posts: 5,907
From: The Wild West
Re: In the market for a Camshaft
I'll probably be going with Bret for the cam. Head work will come down the line. Right now I am working on getting a stall, the rest (CAI/Exhaust) is done. I dont want a 306 or 847, too much for my lil A4.
PS The wheels are working great, thanks again.
-Dustin-
PS The wheels are working great, thanks again.
-Dustin-
Registered User
Joined: Sep 2004
Posts: 1,152
From: Wyoming
Re: In the market for a Camshaft
Originally Posted by rskrause
As do others who have posted here, I see too many "big" cams in the context of mismatched components. Some of the ideas about what constitutes a big cam have gone out of date when applied to a properly tuned EFI setup. The whole issue of getting a good vacuum signal to the carb boosters obviously no longer applies. So, some of the issues with respect to stalling, very poor throttle response, etc. have been ameliorated. If you have ever driven an "overcammed" carb car, you will know exactly how un-fun that can be.
Nonetheless, or perhaps even more than in the past, you see lots of grossly mismatched parts. A cam that is "too big" for the rest of the intake tract will make your car slower than a cam which is optimally sized, iow a smaller cam. Period. And, of course, the issues of the compatibility and longevity of the supporting components hasn't changed. So, a bigger cam will need better (= more expensive) valvetrain parts to have reasonable longevity. And at some point, even with premium parts there are going to be problems. I agree with the poster who said that an LT1 with stock or near stock heads should not have a cam bigger than 210-220 @ 0.050" intake duration. The upper end of the range is good for a stroker, the lower for a 350. Lift is another factor to consider. While I suppose it is possible, in theory, to open a valve "too fast" and consequently lose power this does not occur in practical terms. So, cams with high valve acceleration generally work well. A good way to help achieve this is with higher ratio rockers. Total lift needs to be limited to preserve spring life. There is point in having "wasted" lift.
Where does that leave this discussion? I'd listen to Bret on this one. In fact, shell out a few bucks and have him pick/design it for you ALONG WITH SELECTING THE RIGHT SUPPORTING PARTS. Can't emphasize the latter strongly enough. Without the right pushrods, srpings, lifters, etc. the whold thing can fall apart. You can waste money on stuff you don't need, or worse yet get stuff that doesn't work right. This isn't "rocket sicence" but there are number of subtleties involved that as well as a big role for experience.
Rich
Nonetheless, or perhaps even more than in the past, you see lots of grossly mismatched parts. A cam that is "too big" for the rest of the intake tract will make your car slower than a cam which is optimally sized, iow a smaller cam. Period. And, of course, the issues of the compatibility and longevity of the supporting components hasn't changed. So, a bigger cam will need better (= more expensive) valvetrain parts to have reasonable longevity. And at some point, even with premium parts there are going to be problems. I agree with the poster who said that an LT1 with stock or near stock heads should not have a cam bigger than 210-220 @ 0.050" intake duration. The upper end of the range is good for a stroker, the lower for a 350. Lift is another factor to consider. While I suppose it is possible, in theory, to open a valve "too fast" and consequently lose power this does not occur in practical terms. So, cams with high valve acceleration generally work well. A good way to help achieve this is with higher ratio rockers. Total lift needs to be limited to preserve spring life. There is point in having "wasted" lift.
Where does that leave this discussion? I'd listen to Bret on this one. In fact, shell out a few bucks and have him pick/design it for you ALONG WITH SELECTING THE RIGHT SUPPORTING PARTS. Can't emphasize the latter strongly enough. Without the right pushrods, srpings, lifters, etc. the whold thing can fall apart. You can waste money on stuff you don't need, or worse yet get stuff that doesn't work right. This isn't "rocket sicence" but there are number of subtleties involved that as well as a big role for experience.
Rich
Dustin, i would listen to Rich and have Bret get you a custom cam or maybe even talk to Joe O. I am a good example of a cam that is to big for my car. I will be getting a stall convertor sometime but my car as of now is a total dog and it sucks. It is only about .8 sec faster that before the heads cam, but then again i have no traction.
GET DRS and a STALL first. Or go the cam first and have a car that you no longer like driving.
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