hydraulic roller cam recommedations

[J-Rod]

Howdy,

Well, after 12 years I need to freshen up the motor in our GN. I was looking over the current Hyd roller cam, and it is starting to wear on the nose of #1 intake and exhaust, so I need to come up with a new camshaft.

I haven't been keeping tabs on what curent "hot ticket" is with regard to Hyd roller cams and wanted to see what the current recommendations were in the Buick community. Most of the cams I have seen seem to be more optimzied for stock iron heads with more exhaust lobe to crutch the stock exhaust.

Are people seeing gains with the bigger exhaust on a good set of heads?

The current cam is a ATR RP309G which is an old Crane grind.
212/206 .497/.482 109 LSA

mods on the car are

109 block with billet caps and loveridge girdle
ported GN1's
BGC intake
70MM accufab TB
72# inj
Front mount IC
Precision 3500
ATR headers
Terry Houston Down pipe
TE63e turbo

 

[earlbrown]

any idea what your actual static compression is?

 

[bison]

What spring are you using? That will be the determining factor on the lobe that can be used. Fwiw your current cam shouldn't be wearing. Need to find out why. Running a larger ex lobe has more to do with the ex close timing than helping the ex flow. No positive flow can occur till the intake pressure is higher than the pressure in the cylinder. Flow won't occur till the piston is several degrees down from tdc since the ex pressure is typically quite a bit higher than manifold pressure.


BPE2013@hotmail.com

 

[J-Rod]

Thanks for the replies.

earlbrown - As for as static compression, the old combo was stock stroke with a set of JE pistons on stock rods. I don't remember exactly what static was at that time. For this round I am doing a GN1 Performance stroker kit as part of the rebuild. I need to CC the heads and look at the pistons to tell you exactly what static compression is going to be.

bison - As for the spring, I don't know specifically what spring they are, it was what ATR shipped with the cam kit. I am assuming it is probably a Crane single spring. 125# closed 325# open 1.780 - 1.800 setup height

here is the cam card.

Swapping springs is not a big deal either. I have 5 or 6 set of springs here right now, and can order whatever I need.

As for the cam, its a 15 year old combo. Its just starting to show its age. Normal wear. I'm a bit leary however that no one other than Comp does Hyd. Roller for the Buick based on all the issues Comp has been having with QC and heat treating...

What I meant on my comments was that what I see in just briefly looking over the cam combos that seem to be popular is that people are doing the same thing I see them do in the LS world. They put too much lobe on the cam, and then try to spread the LSA to make up for it which makes the car lazy. In looking back years ago people ran smaller exhaust lobes, or ran a symetric cam 212/212 218/218. Now I see exahsut biased cams. I am wondering if that has shown to make power, or if people are just trying to crutch bad cam designs.

 

[earlbrown]

Don't think of them as having a bigger exhaust lobe... think of them as having a smaller intake lobe. Send we have a manifold full of pressure you don't need to have the intake valve hanging open for a year (and killing your dynamic compression).

I have a feeling your static compression is much lower than you think it is and a huge intake lobe is not what you want. Doesn't your JE's uses a 26cc dish?

 

[BEATAV8]

I spent some time looking at this recently. Weber lists cams typically with more intake and less exhaust. FTS lists many cams with less intake and more exhaust. Opposites each other. Everybody lists cams with dual pattern. Give them a call and see what they have to say. Interesting stuff.

 

[earlbrown]

That's one of the problems with proper camshaft selection.... marketing. If you sell cams, you need to list cams that people will buy. I would estimate that 99+% of cam buyers are not qualified to pick out the ''perfect'' cam, myself included.


Years ago I immersed myself in learning everything that can be learned about camtrains... I learned a LOT, and feel as though I know much more than many many apt engine builders/hobbiests.... I also learned that I don't know shit. The nuances, tradeoffs, voodoo, etc... just never stop.


For example, the OP eluded to needing a 'big' cam to go with better flowing heads... If your heads flow more you don't need more cam (and on N/A, you don't need as much overlap).


The cool thinking about turbo engines is what a great equalizer they are. They aren't real finicky about cams, heads, etc... When can 'adjust the compression' just by turning a rod or a knob. On the upside, that lets us get away with having too big of a cam. Worst case, we can learn to live with worse gas mileage 'because it's a toy/hotrod', and if a bigass bumpstick makes it too soggy, you 'need' a higher stall converter...


When it comes to turbo V6's I think the best plan of action if to pick out the cam you need.... Then get one 'two sizes smaller''.

 

[BEATAV8]

I learned a lot too in my adventures. Still learning! One item of interest is the negative overlap found on a typical turbo cam. Makes good sense and there's not a whole heck of a lot of discussion on it.

 

[bison]

The ATR cam is non aggressive and will easily get away with less spring than most lobes used these days. Please enlighten me on the QC issues. I've probably sold 30 cams in the last year and no issues related to heat treat. I sent back one cam in the last 2 years that was a lot lazier on the opening than I expected and they re-ground it and had it back to me within a week. There's an optimum cam timing and a more optimum lobe for just about every engine out there. For most it won't matter since they have no info on what's going on with the engine. All I'll say is spreading the lobes will help most of the time if backpressure is going to be high. If you can keep backpressure to intake close to 1:1 then you can cam more like an NA engine and get away with it. More LSA will spool slower with a given pair of lobes. The duration at .050" lift means about nothing. The faster the valves can open and close the more potential you have.


BPE2013@hotmail.com

 

[BEATAV8]

What does comp call their fast ramp lobes? Is it the XE series?

 

[J-Rod]

Earlbrown - my point was that most TR grinds in the past were what would be called a reverse split (intake biased). These days I see that they have gone the other way (exhaust biased). I also see that the cams are typically running a wider LSA. I was simply asking about what folks had discovered over the past 10-12 years that had changed. The heads haven't gotten any better.

Here is the thing. I've spent most of my time over the past 10 years in the LS world. I'll be honest, I just haven't kept up with Buick technology. What I will say about a camshaft is that you look at your valve events, and your overlap, LSA, etc.... all fall out of the bottom.

The way I see it when looking at cams, is that If its a turbo cam, its TOTALLY differnet than a N/A or even a S/C cam. Turbos are limited in exhaust duration. Let me clarify... For a STREET driven turbo car where low-end is important, the exhaust lobe is limited.

Because of the pressure in the exhaust manifold, turbo motors have a longer 'power stroke' then N/A, SC, Nitrous cars. These motor's power stroke is from 0 to 90 degrees. Turbo motors continue to push for another 45 degrees of crank rotation. Hard one to follow, but true.

Stock cams work so well with turbos becuase of the lack of overlap small lobes. Aftermarket cams are setup for N/A SC's for the most part open the exhaust inside the power stroke of a turbo motor. Average spot to open the exhaust valve is ~45 degrees BBDC @ .050 lift, which is ~ 70-80 BBDC @ .006 lift (depending on ramp-rate). So, the exhaust lobe on a turbo motor *should* be opened late to avoid bleeding off power. At roughly 60 degrees BBDC is were you can open the exhaust valve. Add this to the lack of overlap on a turbo motor, because exhaust manifold pressure is ALWAYS higher then the incoming intake charge (by 1.5-2 times depending on compressor efficiency) you can see why large cams don't work so well with these motors.


So, if you're following me, an LS street turbo motor is limited to ~ 260-270 total duration on the exhaust side. that's WITH ~40 degrees of overlap @ .006. (nominal stock overlap)

Track turbo motors use more traditional N/A grinds as they stay in the upper RPM band were overlap will actually help the turbo make power. But it KILLS the low-end.

Turbos make full boost by ~3000rpm therefore make tons of torque, so most don't notice that the N/A cam they're using is bleeding off power.

Thats not to say you can't make power with any cam, its just you won't make ideal power. I know my buddy Pete in Australia ran a turbo car with a 244/244 110 cam. The turbo calms down the overlap and makes it idle nice.

So, when I look a the cams out there, my inital impresion is to much exhaust lobe, too much LSA (in plain terms). But I fully admit I might be wrong, and I am just looking for empirical evidence that says (as an example) in the same combo a 210/215 112works better, is more responsive, etc.... than a 215/210 110 (as an theoretical example)


bison - here is a thread from ls1tech on the perceived QC issues at Comp.
http://ls1tech.com/forums/generation-iii-internal-engine/1641167-whats-up-comp-cams.html

There is some debate about the root cause. Some feel it is folks going with too much lobe and too little spring. Some see the same issue with soft lobes like the XE. On of my fellow moderators has a shop that has pulled 60 defective Comp cams.

beatav8 - Comp has tons of lobe families. If you look at a 224 lobe (224 @ .050) Comp has about 50 lobes just at that duration. In the LS world it goes XE, XE-R, LSK, LSL, LSM

 

[J-Rod]

Here is what I mean

Here is my 212/206 109+5 ATR cam vs a 218/212 112 Comp
___________________________________________ 0.006 __ 0.050 __
Intake Duration - ID_______________________ 269 __ 218 __
Exhaust Duration - ED______________________ 264 __ 212 __
Lobe Center Angle - LCA (also known as LSA) 112 __ 112 __
Intake Centerline - ICL____________________ 112 __ 112 __
Intake Valve opens - IVO___________________ 22.5 __ -3 __ BTDC (- indicates ATDC)
Intake Valve closes - IVC__________________ 66.5 __ 41 __ ABDC
Exhaust Valve Opens - EVO__________________ 64 __ 38 __ BBDC
Exhaust Valve Closes - EVC_________________ 20 __ -6 __ ATDC (- indicates BTDC)
Exhaust Centerline - ECL___________________ 112 __ 112 __
Overlap____________________________________ 42.5 __ -9 __ degrees
___________________________________________ 0.006 __ 0.050 __
Intake Duration - ID_______________________ 270 __ 212 __
Exhaust Duration - ED______________________ 264 __ 206 __
Lobe Center Angle - LCA (also known as LSA) 109 __ 109 __
Intake Centerline - ICL____________________ 104 __ 104 __
Intake Valve opens - IVO___________________ 31 __ 2 __ BTDC (- indicates ATDC)
Intake Valve closes - IVC__________________ 59 __ 30 __ ABDC
Exhaust Valve Opens - EVO__________________ 66 __ 37 __ BBDC
Exhaust Valve Closes - EVC_________________ 18 __ -11 __ ATDC (- indicates BTDC)
Exhaust Centerline - ECL___________________ 114 __ 114 __
Overlap____________________________________ 49 __ -9 __ degrees
___________________________________________ 0.006 __ 0.050 __
IVO delta__________________________________ -8.5 __ -5 __
IVC delta__________________________________ 7.5 __ 11 __
EVO delta__________________________________ -2 __ 1 __
EVC delta__________________________________ 2 __ 5 __
ECL delta__________________________________ -2 __ -2 __
Overlap____________________________________ -6.5 __ 0 __

EVO on the ATR cam is at 38, EVO on the Comp is at 37, both have -9 degree overlap @ .050

Moving over to a 210/215 (the .006 are off as I didn't have the cam card for the 210/215)
Quick and Dirty Cam Calculator Spreadsheet
___________________________________________ 0.006 __ 0.050 __
Intake Duration - ID_______________________ 269 __ 210 __
Exhaust Duration - ED______________________ 264 __ 215 __
Lobe Center Angle - LCA (also known as LSA) 112 __ 112 __
Intake Centerline - ICL____________________ 112 __ 112 __
Intake Valve opens - IVO___________________ 22.5 __ -7 __ BTDC (- indicates ATDC)
Intake Valve closes - IVC__________________ 66.5 __ 37 __ ABDC
Exhaust Valve Opens - EVO__________________ 64 __ 39.5 __ BBDC
Exhaust Valve Closes - EVC_________________ 20 __ -4.5 __ ATDC (- indicates BTDC)
Exhaust Centerline - ECL___________________ 112 __ 112 __
Overlap____________________________________ 42.5 __ -11.5 __ degrees
___________________________________________ 0.006 __ 0.050 __
Intake Duration - ID_______________________ 270 __ 212 __
Exhaust Duration - ED______________________ 264 __ 206 __
Lobe Center Angle - LCA (also known as LSA) 109 __ 109 __
Intake Centerline - ICL____________________ 104 __ 104 __
Intake Valve opens - IVO___________________ 31 __ 2 __ BTDC (- indicates ATDC)
Intake Valve closes - IVC__________________ 59 __ 30 __ ABDC
Exhaust Valve Opens - EVO__________________ 66 __ 37 __ BBDC
Exhaust Valve Closes - EVC_________________ 18 __ -11 __ ATDC (- indicates BTDC)
Exhaust Centerline - ECL___________________ 114 __ 114 __
Overlap____________________________________ 49 __ -9 __ degrees
___________________________________________ 0.006 __ 0.050 __
IVO delta__________________________________ -8.5 __ -9 __
IVC delta__________________________________ 7.5 __ 7 __
EVO delta__________________________________ -2 __ 2.5 __
EVC delta__________________________________ 2 __ 6.5 __
ECL delta__________________________________ -2 __ -2 __
Overlap____________________________________ -6.5 __ -2.5 __


EVO for me is one of the most critical numbers when looking at a motor. Thats just me though. Again, I'm not saying I'm right or wrong. I am just looking for input on what people have seen work. Theories are great. But practical experience is far btter which is why I am asking. Thanks again for the input.

 

[J-Rod]

earlbrown, one other thing.

The cool thinking about turbo engines is what a great equalizer they are. They aren't real finicky about cams, heads, etc... When can 'adjust the compression' just by turning a rod or a knob. On the upside, that lets us get away with having too big of a cam. Worst case, we can learn to live with worse gas mileage 'because it's a toy/hotrod', and if a bigass bumpstick makes it too soggy, you 'need' a higher stall converter...

I would have to disagree with this. I think it is a common misconception that turbo motors "don't care" about heads and cams. I would argue exactly the opposite it s true. A more efficient cylinder head will show greater gains on a turbo motor over an N/A combo. The motor is still an airpump. You can crutch it to some extent with boost (which is just a measure of backpressure). In the TR world this is like showing that an stock iron head makes 600HP at 28psi of boost while a Stage II head makes the same power at 10 psi of boost (all things being equal). The better head flows the same airflow with less backpressure as it is more efficient.

 

[Mike Licht]

Much of the change in current Turbo cam design (which is not just Buick but most applications) toward more exhaust lobe is because turbine wheels have got so much better and back pressure numbers have fallen quite a bit in the last few years. for me at least lobe separation is determined by the event timing and duration..The different turbine wheels like different exhaust opening points and different heads may want different intake opening points. We also need to look at intended RPM band and CID for duration. in those cases when needed we will move things for a customer looking for a particular result or application. IMO you are correct about EVO too it is very important and can have a dramatic impact on Turbos. advancing the exhaust side of the cam can have huge benefits in some cases too. This may determine L/S or advance / retard on a particular camshaft in the end. This may be why the numbers in terms of say overlap don't always look optimum, the gains from moving the exhaust my overshadow any losses from extra overlap. One thing I have learned about cams is they are ALWAYS a compromise in some way.

 

[bison]

Earlbrown - my point was that most TR grinds in the past were what would be called a reverse split (intake biased). These days I see that they have gone the other way (exhaust biased). I also see that the cams are typically running a wider LSA. I was simply asking about what folks had discovered over the past 10-12 years that had changed. The heads haven't gotten any better.

Here is the thing. I've spent most of my time over the past 10 years in the LS world. I'll be honest, I just haven't kept up with Buick technology. What I will say about a camshaft is that you look at your valve events, and your overlap, LSA, etc.... all fall out of the bottom.

The way I see it when looking at cams, is that If its a turbo cam, its TOTALLY differnet than a N/A or even a S/C cam. Turbos are limited in exhaust duration. Let me clarify... For a STREET driven turbo car where low-end is important, the exhaust lobe is limited.

Because of the pressure in the exhaust manifold, turbo motors have a longer 'power stroke' then N/A, SC, Nitrous cars. These motor's power stroke is from 0 to 90 degrees. Turbo motors continue to push for another 45 degrees of crank rotation. Hard one to follow, but true.

Stock cams work so well with turbos becuase of the lack of overlap small lobes. Aftermarket cams are setup for N/A SC's for the most part open the exhaust inside the power stroke of a turbo motor. Average spot to open the exhaust valve is ~45 degrees BBDC @ .050 lift, which is ~ 70-80 BBDC @ .006 lift (depending on ramp-rate). So, the exhaust lobe on a turbo motor *should* be opened late to avoid bleeding off power. At roughly 60 degrees BBDC is were you can open the exhaust valve. Add this to the lack of overlap on a turbo motor, because exhaust manifold pressure is ALWAYS higher then the incoming intake charge (by 1.5-2 times depending on compressor efficiency) you can see why large cams don't work so well with these motors.


So, if you're following me, an LS street turbo motor is limited to ~ 260-270 total duration on the exhaust side. that's WITH ~40 degrees of overlap @ .006. (nominal stock overlap)

Track turbo motors use more traditional N/A grinds as they stay in the upper RPM band were overlap will actually help the turbo make power. But it KILLS the low-end.

Turbos make full boost by ~3000rpm therefore make tons of torque, so most don't notice that the N/A cam they're using is bleeding off power.

Thats not to say you can't make power with any cam, its just you won't make ideal power. I know my buddy Pete in Australia ran a turbo car with a 244/244 110 cam. The turbo calms down the overlap and makes it idle nice.

So, when I look a the cams out there, my inital impresion is to much exhaust lobe, too much LSA (in plain terms). But I fully admit I might be wrong, and I am just looking for empirical evidence that says (as an example) in the same combo a 210/215 112works better, is more responsive, etc.... than a 215/210 110 (as an theoretical example)


bison - here is a thread from ls1tech on the perceived QC issues at Comp.
http://ls1tech.com/forums/generation-iii-internal-engine/1641167-whats-up-comp-cams.html

There is some debate about the root cause. Some feel it is folks going with too much lobe and too little spring. Some see the same issue with soft lobes like the XE. On of my fellow moderators has a shop that has pulled 60 defective Comp cams.

beatav8 - Comp has tons of lobe families. If you look at a 224 lobe (224 @ .050) Comp has about 50 lobes just at that duration. In the LS world it goes XE, XE-R, LSK, LSL, LSM

That thread doesn't have any good failure analysis and some of the posts discredit the OP. Perception means just that. Internet bullshit that some people might believe. Those guys are light years behind what several others and myself have already figured out.


BPE2013@hotmail.com

 

[Mike Licht]

LOL Bison, just put it out there my friend

 

[bison]

Also the cam simulators assume symmetry and don't account for the different masters used to grind lobes when they are ground on Buick cam cores. The only one that's very close is the N master lobes. Expect to have increased advertised duration, just about hit the .050" duration and lose a few degrees duration @ .200" on anything not N master. The timing at .050" is a decent reference point if actual. EVC is just as important as EVO. Theres very little point in closing the ex valve at .050" past tdc on a turbo engine. There's a limit on how soon the exhaust can be opened with typical valvetrain components or you wind up with broken valvetrain from the pressure. Getting backpressure down and manifold pressure up and opening and closing the valves fast will make more power


BPE2013@hotmail.com

 

[turbogn_231]

Bison, please spec a cam for my future combo.

 

[J-Rod]

Bison - As with any topic you will get folks on both sides of just about any issue. I know several shops who had good realations with Comp and have moved over to other grinders related to the issues they have been having.

I know of one shop in particular who has replaced 60 comp cams. All with the same type of failure. Those were various grinds, and installed at different shops.


All that being said, I will probably end up going with a comp grind simply because no one else has a hyd. roller for a Buick that I am aware of, and even with the issues I don't want to deal with flat tappet cam issues.

 

[bison]

Bison - As with any topic you will get folks on both sides of just about any issue. I know several shops who had good realations with Comp and have moved over to other grinders related to the issues they have been having.

I know of one shop in particular who has replaced 60 comp cams. All with the same type of failure. Those were various grinds, and installed at different shops.


All that being said, I will probably end up going with a comp grind simply because no one else has a hyd. roller for a Buick that I am aware of, and even with the issues I don't want to deal with flat tappet cam issues.

Im not disagreeing. I just haven't seen legitimate evidence substantiating cam core problems. Post up the failure analysis. What I have seen on the Internet is a lot of botched installs. Inadequate spring pressures, heights not verified, etc. A cam install is not a shade tree mechanic job. I've replaced a lot of cams myself that had issues due to install error or use with incorrect valvetrain components.


BPE2013@hotmail.com