CAM Selection???
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
Posts: 4,983
Likes: 13
From: Texas
Bigger isn't always better.
Just because you make a big peak number doesn't always mean you are going to be faster.
If all you look at is peak HP, and you ignore the area under the curve, you'll miss the most important part.
This thread over on the GTO site is a prime example...
http://www.ls1gto.com/forums/showthread.php?t=20945
Look guys I have driven some 346s with some fairly large cams. There are certainly tradeoffs. Some folks don't mind drivability issues. Some folks can't stand them. There are some fairly simple formulas that have been posted which would help you determine what the duration requirements for your motor are based on cylinder head flow. You can prop your valve open longer to try to squeeze out more power up top. The net result is you may (or you may not). You might get some upper end gain. On the other hand you may kill all the bottom end in your car that won't be resolved until you dump in a big converter (if its an auto), and a set of gears (no matter what). The other net result of thinking that you simply just go bigger is that you end up slowing down airspeed (think velocity there).
Am I saying everyone needs a 220/220 cam? No. What I'm saying is that combination is where it is at. But basing your cam selection simply on LSA is probably the worst mistake a I see folks make along with thinking that just adding more lobe is the cheap and easy way to make power....
In closing here is a comment on a Futral cam...
Just because you make a big peak number doesn't always mean you are going to be faster.
If all you look at is peak HP, and you ignore the area under the curve, you'll miss the most important part.
This thread over on the GTO site is a prime example...
http://www.ls1gto.com/forums/showthread.php?t=20945
Big camshafts do not guaranty big numbers, on the dyno nor on the track.
If it takes a G5-X3 to make 440+ RWHP then something is wrong with the package. That much camshaft is good for over 500 RWHP in a good engine combination. Note the word "combination"...
I'm not a fan of all this internet hype about "cam only" or whatever type of catagory that some people need to make a name for themselves. Next it'll be the "Highest horsepower, torrid red, M6 with ROH wheels GTO in the world" BFD. Make the most power with the least amount of BS and run it. That's impressive.
When you can create an efficient, well thought out combination that runs extremely good, well that is much more of an achievement than some contrived internet catagory winner.
Besides...
Why go to that type of extreme camshaft if a small cam with the proper peripherals make for a better combination? There are plenty of examples of F-body, C5 and lately some GTO combinations with small streetable camshafts making between 400 and 430+ RWHP. All without all the BS required to get a camshaft with high 230/low 240 duration figures.
If it takes a G5-X3 to make 440+ RWHP then something is wrong with the package. That much camshaft is good for over 500 RWHP in a good engine combination. Note the word "combination"...
I'm not a fan of all this internet hype about "cam only" or whatever type of catagory that some people need to make a name for themselves. Next it'll be the "Highest horsepower, torrid red, M6 with ROH wheels GTO in the world" BFD. Make the most power with the least amount of BS and run it. That's impressive.
When you can create an efficient, well thought out combination that runs extremely good, well that is much more of an achievement than some contrived internet catagory winner.
Besides...
Why go to that type of extreme camshaft if a small cam with the proper peripherals make for a better combination? There are plenty of examples of F-body, C5 and lately some GTO combinations with small streetable camshafts making between 400 and 430+ RWHP. All without all the BS required to get a camshaft with high 230/low 240 duration figures.
Thunder Racing got the TREX cam on a Trans Am to run 10.433 @ 130, w/ stock cylinder and pistons. Thats impressive. Not everyone has two grand to drop on an AFR head, thats why they do cams only. Me being one of them. After rent, bills, child support, insurance, car payment I'm 2800 in the hole already. If money was no object I would be driving a Ferrari.
So they put that cam in and did nothing else??? Do you believe in the tooth fairy too?
That car is far from "stock" and just a "cam only" bolt in deal. If you read carefully into this package, it's obviously not a "stock" TransAm. It's a great advertising tool and while impressive, it's not a street GTO combination.
Let's throw out headers, exhaust and intake mods since both the street cars and race cars will use these mods. Start with the big differences. Camshafts and the peripherals required to run the cam of choice.
The T-Rex cam has been checked on a CamPro and it has 243.5* duration on the intake and 249.5* on the exhaust at .050" tappet lift. It also has .610" lift on intake and .614" on the exhaust. With a 110* lobe separation do you think it is just a bolt in? It sure ain't clearing stock pistons! You are certainly not going to use stock valvetrain pieces, are you? It's not a "bolt-in and go" as you are assuming.
With specs like this, there must be a professional tune put on it. Figure $500 for any tuning system (HPTuners, LS1Edit), dyno time and then flycutting the pistons to clear it. Now add in a spring kit to handle the profile, titanium retainers and hardened push rods. Now add in the labor. Also bear in mind the yearly spring replacement because those lobes sure aren't going to give great valve spring life. Especially at the 7000+ rpm level this camshaft has to run in.
Then there's the power band of 3500-7000+ rpm. Figure 3.91 gears and a great clutch and/or convertor for the A4 cars. My Precision Industries converter with all the bells and whistles was close to $1200 and that's not including a shift kit and cooler and my first cam is not as big as the T-Rex.
All this contributes to not really being a "street car" anymore.
I can drop in a small street-friendly cam, out of the box AFR 205 heads and still drive this two ton GTO anywhere in the world and not have any issues. Valvetrain, tuning or drivability.
If you think a "cam only" deal like the T-Rex is a money saver, you have a false sense of economics. Racing cams belong in race cars. Just the maintainance involved to keep these HP levels there should tell you this.
Sorry but I live in the real world.
That car is far from "stock" and just a "cam only" bolt in deal. If you read carefully into this package, it's obviously not a "stock" TransAm. It's a great advertising tool and while impressive, it's not a street GTO combination.
Let's throw out headers, exhaust and intake mods since both the street cars and race cars will use these mods. Start with the big differences. Camshafts and the peripherals required to run the cam of choice.
The T-Rex cam has been checked on a CamPro and it has 243.5* duration on the intake and 249.5* on the exhaust at .050" tappet lift. It also has .610" lift on intake and .614" on the exhaust. With a 110* lobe separation do you think it is just a bolt in? It sure ain't clearing stock pistons! You are certainly not going to use stock valvetrain pieces, are you? It's not a "bolt-in and go" as you are assuming.
With specs like this, there must be a professional tune put on it. Figure $500 for any tuning system (HPTuners, LS1Edit), dyno time and then flycutting the pistons to clear it. Now add in a spring kit to handle the profile, titanium retainers and hardened push rods. Now add in the labor. Also bear in mind the yearly spring replacement because those lobes sure aren't going to give great valve spring life. Especially at the 7000+ rpm level this camshaft has to run in.
Then there's the power band of 3500-7000+ rpm. Figure 3.91 gears and a great clutch and/or convertor for the A4 cars. My Precision Industries converter with all the bells and whistles was close to $1200 and that's not including a shift kit and cooler and my first cam is not as big as the T-Rex.
All this contributes to not really being a "street car" anymore.
I can drop in a small street-friendly cam, out of the box AFR 205 heads and still drive this two ton GTO anywhere in the world and not have any issues. Valvetrain, tuning or drivability.
If you think a "cam only" deal like the T-Rex is a money saver, you have a false sense of economics. Racing cams belong in race cars. Just the maintainance involved to keep these HP levels there should tell you this.
Sorry but I live in the real world.
Look guys I have driven some 346s with some fairly large cams. There are certainly tradeoffs. Some folks don't mind drivability issues. Some folks can't stand them. There are some fairly simple formulas that have been posted which would help you determine what the duration requirements for your motor are based on cylinder head flow. You can prop your valve open longer to try to squeeze out more power up top. The net result is you may (or you may not). You might get some upper end gain. On the other hand you may kill all the bottom end in your car that won't be resolved until you dump in a big converter (if its an auto), and a set of gears (no matter what). The other net result of thinking that you simply just go bigger is that you end up slowing down airspeed (think velocity there).
Am I saying everyone needs a 220/220 cam? No. What I'm saying is that combination is where it is at. But basing your cam selection simply on LSA is probably the worst mistake a I see folks make along with thinking that just adding more lobe is the cheap and easy way to make power....
In closing here is a comment on a Futral cam...
His OTS F12 is priced at $400 as shown on Allan's site. To get a comparable spring package to the AFR heads, on your stock heads, you'd be looking at the Comp 26921 kit at $560 (FMS pricing). That puts the "net" difference between stock heads and and AFR at a $1640 difference. While it is quite a bit more, it's surely not the $2200 for the cost of the heads alone.
Then there's the performance differences between the two heads. It's been tested time and time gain that the ported OEM heads can be worth about 35-40 RWHP over a stock head, let alone a better head like the AFR 205. Is the extra power worth the $1640? If not, then let's get a set of Precision or ET Performance heads in the mix. They'll add some bucks to the project but they are a lot better than stock.
That extra money/work is a personal choice but a lot of people think it's worth the extra bucks. It all boils down to the whole cost, not just the price of one item. That's why good shops offer a lot of "choices" in their packages.
What would be fun to see is what you can do with the stock heads, LT headers and the FMS F12 cam in your car. It'll be a real test of whether or not the extra money for a good cylinder head is a value per HP or not. Maybe after the cam swap, you can add a ported head package to the mix?
I also like how you're thinking and who you are talking to. Allan's stuff is good quality with no Mexican or overseas grinds. He uses Cam Motion, made in the USA so the parts are top shelf! You'll just need to get the rest of the parts to make the cam work to its potential.
It'll be fun once you've done this swap, I'll let Anthony (Bone) borrow one of my medium grinds, a 229*-230* profile, and see what he gains over his "baby" camshaft. I'm thinking he'll top the 475-480 mark and still not even be close to size of a T-Rex, LG G5X3 or the HPE S-Cam... In a GTO no less...
Then there's the performance differences between the two heads. It's been tested time and time gain that the ported OEM heads can be worth about 35-40 RWHP over a stock head, let alone a better head like the AFR 205. Is the extra power worth the $1640? If not, then let's get a set of Precision or ET Performance heads in the mix. They'll add some bucks to the project but they are a lot better than stock.
That extra money/work is a personal choice but a lot of people think it's worth the extra bucks. It all boils down to the whole cost, not just the price of one item. That's why good shops offer a lot of "choices" in their packages.
What would be fun to see is what you can do with the stock heads, LT headers and the FMS F12 cam in your car. It'll be a real test of whether or not the extra money for a good cylinder head is a value per HP or not. Maybe after the cam swap, you can add a ported head package to the mix?
I also like how you're thinking and who you are talking to. Allan's stuff is good quality with no Mexican or overseas grinds. He uses Cam Motion, made in the USA so the parts are top shelf! You'll just need to get the rest of the parts to make the cam work to its potential.
It'll be fun once you've done this swap, I'll let Anthony (Bone) borrow one of my medium grinds, a 229*-230* profile, and see what he gains over his "baby" camshaft. I'm thinking he'll top the 475-480 mark and still not even be close to size of a T-Rex, LG G5X3 or the HPE S-Cam... In a GTO no less...
