[Z06] GMPP stage 3 cam, will I have piston to valve clearance issues on a stock LS7?
10-15-2015, 02:43 AM
#21
Instructor
Thread Starter
I agree with having the heads checked out, that is a very important aspect, not to overlook.
Based of what you are saying here, seriously look into the BTR Stg 4 cam. Here is my idle video of this cam. I also think it is important to note that a guy by the screen name of LS7BUD is running this cam and he is a top contender for the #1 spot in the, 6 speed, n/a position running a 9.84 @ >140 mph
Based of what you are saying here, seriously look into the BTR Stg 4 cam. Here is my idle video of this cam. I also think it is important to note that a guy by the screen name of LS7BUD is running this cam and he is a top contender for the #1 spot in the, 6 speed, n/a position running a 9.84 @ >140 mph
For my understanding, could you please explain the differences between the GMPP stg 3 and the BTR stg 4 when looking at the numbers and elaborate a bit on what numbers makes what difference? I consider myself a fairly technical guy, I built a car myself at least, but I have never looked much into the world of cam shafts even though I certainly understand the basic function of one
10-16-2015, 09:32 AM
#22
It's pointless to debate whether or not 'some' engines may or many not be affected. Just have yours inspected. You should be pulling the heads to do a cam swap anyway. You can sneak one out and back in without pulling the heads, but I would not. I'd also change lifters.
You will want to have an automotive machinist or engine builder disassemble the heads. Check valve stem OD to valve guide ID clearance. Also check valve seat run out, if the guides are not worn to the point you can't fit a pilot into the guides. Once these checks are complete, you then will know if further work is required.
Camshaft theory is wildly complex. To answer your last question with any detail....it would take a thousand-word document (I have a couple that I've written over the years if you want). In a nutshell, you want to pay attention to total lift, duration at .050", and LSA (lobe separation angle). With these three data points, you can then figure out a close value of what the total valve overlap is. It will give you a rough idea of how the engine will behave. Valve overlap is the period of time in crankshaft rotational degree that both valves are open at the same time. This is when the piston is approaching TDC exh stroke, and when it starts going down the cylinder during the intake stroke. An increase in overlap will build more power at higher rpm, but will adversely affect power at low rpm.
There are some very crude rules of thumb for overlap. I have long since given up on them. But generally speaking, if you keep the .050" overlap under 15 deg, for this engine, lower rpm performance will be OK. Not great, but OK. I'd suggest you keep it under 10 deg. But....these engines with OEM cylinder head porting, need a lot more exh duration than intake. The intake flows incredibly well, but the exh does not. I'd keep exh duration at least 20 deg more than intake. If you have the heads ported, and the exhaust side worked....then you can get away with less exh duration, which will effectively reduce overlap - allowing you to run more intake duration. - It's a domino effect of sorts.
I would be more conservative with your car than a 3200 pound corvette. As vehicle weight is decreased, rolling resistance is as well. This will effectively unload the engine at low rpm cruising speeds. An unloaded engine with an aggressive camshaft will tend to behave worse than a loaded engine. That is why I gave you the camshaft recommendation earlier.
You will want to have an automotive machinist or engine builder disassemble the heads. Check valve stem OD to valve guide ID clearance. Also check valve seat run out, if the guides are not worn to the point you can't fit a pilot into the guides. Once these checks are complete, you then will know if further work is required.
Camshaft theory is wildly complex. To answer your last question with any detail....it would take a thousand-word document (I have a couple that I've written over the years if you want). In a nutshell, you want to pay attention to total lift, duration at .050", and LSA (lobe separation angle). With these three data points, you can then figure out a close value of what the total valve overlap is. It will give you a rough idea of how the engine will behave. Valve overlap is the period of time in crankshaft rotational degree that both valves are open at the same time. This is when the piston is approaching TDC exh stroke, and when it starts going down the cylinder during the intake stroke. An increase in overlap will build more power at higher rpm, but will adversely affect power at low rpm.
There are some very crude rules of thumb for overlap. I have long since given up on them. But generally speaking, if you keep the .050" overlap under 15 deg, for this engine, lower rpm performance will be OK. Not great, but OK. I'd suggest you keep it under 10 deg. But....these engines with OEM cylinder head porting, need a lot more exh duration than intake. The intake flows incredibly well, but the exh does not. I'd keep exh duration at least 20 deg more than intake. If you have the heads ported, and the exhaust side worked....then you can get away with less exh duration, which will effectively reduce overlap - allowing you to run more intake duration. - It's a domino effect of sorts.
I would be more conservative with your car than a 3200 pound corvette. As vehicle weight is decreased, rolling resistance is as well. This will effectively unload the engine at low rpm cruising speeds. An unloaded engine with an aggressive camshaft will tend to behave worse than a loaded engine. That is why I gave you the camshaft recommendation earlier.
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Is2scooby (10-16-2015)
10-16-2015, 01:54 PM
#23
Premium Supporting Vendor
HOLY Schnikes talk about a split duration!!!! and that LSA!!! hope you dont need vacuum or plan on any power adders. Those HP/TQ numbers have to be at the crank. I personally dont think you will have a ptv issue, but if you are unsure always measure
https://sdparts.com/details/gm-perfo...arts/k88958723
Specifically released as a cam upgrade for the LS7 engine, these cams will work with all LS style engines --- nasty sound and big torque. Also includes 12499225 LS7 lifters.
Advertised Duration (I/E) 294/335
Durartion @ 0.050 233/276
LSA 107
Lift (w/1.8) 0.630/0.630
LS7 engine-dyno results with "Stage 3" cam show;
600hp @ 6800rpm
526ft-lbs @ 4900rpm over 450ft-lbs from 3200 to 6800rpms
https://sdparts.com/details/gm-perfo...arts/k88958723
Specifically released as a cam upgrade for the LS7 engine, these cams will work with all LS style engines --- nasty sound and big torque. Also includes 12499225 LS7 lifters.
Advertised Duration (I/E) 294/335
Durartion @ 0.050 233/276
LSA 107
Lift (w/1.8) 0.630/0.630
LS7 engine-dyno results with "Stage 3" cam show;
600hp @ 6800rpm
526ft-lbs @ 4900rpm over 450ft-lbs from 3200 to 6800rpms
I've driven a car with this cam on the street. No vacuum issues.
The PtoV will technically clear, but it is way too close in our opinion.
The K501 cam will make more power and have FAR better drivability than the GM Stage 3. Also it has plenty of PtoV.
10-16-2015, 04:34 PM
#24
Team Owner
Reminds me of this one a friend built. I tuned and helped with it. GM crate LS6. 228/228 cam. Made great power, and was scary as hell to drive.
10-16-2015, 10:09 PM
#25
Melting Slicks
What a beautiful car!
I would pull the heads and send them to either American Heritage or WCCH.
I would install a Katech K501 camshaft as Jason recommended. Lots of great results from folks using this cam.
Be careful with your dual springs and Ti retainers. Lots of failures out their. Remember, a broken spring and a dropped valve in a cast piston motor can ruin your day. A set of PSI Endurance Beehive springs (1511 or 1515) would be a much better choice. The 1511 spring is shorter and will work with your LS1 titanium retainers (there are no LS7 1.959" height titanium retainers). You can use your OEM steel retainers with the taller 1515 spring and only give up a few grams while gaining some additional height and spring pressure.
There are some great dual springs available also. However, as you increase seat pressure you can overwhelm OEM LS7 lifters and rockers.
Best of luck!
I would pull the heads and send them to either American Heritage or WCCH.
I would install a Katech K501 camshaft as Jason recommended. Lots of great results from folks using this cam.
Be careful with your dual springs and Ti retainers. Lots of failures out their. Remember, a broken spring and a dropped valve in a cast piston motor can ruin your day. A set of PSI Endurance Beehive springs (1511 or 1515) would be a much better choice. The 1511 spring is shorter and will work with your LS1 titanium retainers (there are no LS7 1.959" height titanium retainers). You can use your OEM steel retainers with the taller 1515 spring and only give up a few grams while gaining some additional height and spring pressure.
There are some great dual springs available also. However, as you increase seat pressure you can overwhelm OEM LS7 lifters and rockers.
Best of luck!
10-16-2015, 10:46 PM
#26
Yeah, essentially, 335 out of 360 degrees, this cam has an exhaust valve off the seat, which means it will make GREAT power up top but it will not make any cylinder pressure until it reaches a very high engine speed.
The forever open valve will keep bleeding the pressure off!
Then there is the 40.5 degrees of overlap @ .050"
The forever open valve will keep bleeding the pressure off!
Then there is the 40.5 degrees of overlap @ .050"
10-18-2015, 10:17 PM
#27
Safety Car
The beauty of having it in your hands is you can try it. It will still cost you consumables and gaskets and a Heck of a Lot of tuning time, but worst that will happen is that you pull it out and put something else in.
However, I am in the camp that your car (Factory 5?) has enough HP already given the chassis. That is a good looking car and vary trick, but my Race Car often ran in the same Race Heat with Factory Five Racing and they really don't look good after a major shunt or off. There is not a lot of steel up front other than the engine and it is pretty easy to shed a lot of that steel if you hit something hard.
However, I am in the camp that your car (Factory 5?) has enough HP already given the chassis. That is a good looking car and vary trick, but my Race Car often ran in the same Race Heat with Factory Five Racing and they really don't look good after a major shunt or off. There is not a lot of steel up front other than the engine and it is pretty easy to shed a lot of that steel if you hit something hard.
10-19-2015, 07:36 AM
#28
Instructor
Thread Starter
It's pointless to debate whether or not 'some' engines may or many not be affected. Just have yours inspected. You should be pulling the heads to do a cam swap anyway. You can sneak one out and back in without pulling the heads, but I would not. I'd also change lifters.
You will want to have an automotive machinist or engine builder disassemble the heads. Check valve stem OD to valve guide ID clearance. Also check valve seat run out, if the guides are not worn to the point you can't fit a pilot into the guides. Once these checks are complete, you then will know if further work is required.
Camshaft theory is wildly complex. To answer your last question with any detail....it would take a thousand-word document (I have a couple that I've written over the years if you want). In a nutshell, you want to pay attention to total lift, duration at .050", and LSA (lobe separation angle). With these three data points, you can then figure out a close value of what the total valve overlap is. It will give you a rough idea of how the engine will behave. Valve overlap is the period of time in crankshaft rotational degree that both valves are open at the same time. This is when the piston is approaching TDC exh stroke, and when it starts going down the cylinder during the intake stroke. An increase in overlap will build more power at higher rpm, but will adversely affect power at low rpm.
There are some very crude rules of thumb for overlap. I have long since given up on them. But generally speaking, if you keep the .050" overlap under 15 deg, for this engine, lower rpm performance will be OK. Not great, but OK. I'd suggest you keep it under 10 deg. But....these engines with OEM cylinder head porting, need a lot more exh duration than intake. The intake flows incredibly well, but the exh does not. I'd keep exh duration at least 20 deg more than intake. If you have the heads ported, and the exhaust side worked....then you can get away with less exh duration, which will effectively reduce overlap - allowing you to run more intake duration. - It's a domino effect of sorts.
I would be more conservative with your car than a 3200 pound corvette. As vehicle weight is decreased, rolling resistance is as well. This will effectively unload the engine at low rpm cruising speeds. An unloaded engine with an aggressive camshaft will tend to behave worse than a loaded engine. That is why I gave you the camshaft recommendation earlier.
You will want to have an automotive machinist or engine builder disassemble the heads. Check valve stem OD to valve guide ID clearance. Also check valve seat run out, if the guides are not worn to the point you can't fit a pilot into the guides. Once these checks are complete, you then will know if further work is required.
Camshaft theory is wildly complex. To answer your last question with any detail....it would take a thousand-word document (I have a couple that I've written over the years if you want). In a nutshell, you want to pay attention to total lift, duration at .050", and LSA (lobe separation angle). With these three data points, you can then figure out a close value of what the total valve overlap is. It will give you a rough idea of how the engine will behave. Valve overlap is the period of time in crankshaft rotational degree that both valves are open at the same time. This is when the piston is approaching TDC exh stroke, and when it starts going down the cylinder during the intake stroke. An increase in overlap will build more power at higher rpm, but will adversely affect power at low rpm.
There are some very crude rules of thumb for overlap. I have long since given up on them. But generally speaking, if you keep the .050" overlap under 15 deg, for this engine, lower rpm performance will be OK. Not great, but OK. I'd suggest you keep it under 10 deg. But....these engines with OEM cylinder head porting, need a lot more exh duration than intake. The intake flows incredibly well, but the exh does not. I'd keep exh duration at least 20 deg more than intake. If you have the heads ported, and the exhaust side worked....then you can get away with less exh duration, which will effectively reduce overlap - allowing you to run more intake duration. - It's a domino effect of sorts.
I would be more conservative with your car than a 3200 pound corvette. As vehicle weight is decreased, rolling resistance is as well. This will effectively unload the engine at low rpm cruising speeds. An unloaded engine with an aggressive camshaft will tend to behave worse than a loaded engine. That is why I gave you the camshaft recommendation earlier.
10-19-2015, 08:15 AM
#29
Instructor
Thread Starter
What a beautiful car!
I would pull the heads and send them to either American Heritage or WCCH.
I would install a Katech K501 camshaft as Jason recommended. Lots of great results from folks using this cam.
Be careful with your dual springs and Ti retainers. Lots of failures out their. Remember, a broken spring and a dropped valve in a cast piston motor can ruin your day. A set of PSI Endurance Beehive springs (1511 or 1515) would be a much better choice. The 1511 spring is shorter and will work with your LS1 titanium retainers (there are no LS7 1.959" height titanium retainers). You can use your OEM steel retainers with the taller 1515 spring and only give up a few grams while gaining some additional height and spring pressure.
There are some great dual springs available also. However, as you increase seat pressure you can overwhelm OEM LS7 lifters and rockers.
Best of luck!
I would pull the heads and send them to either American Heritage or WCCH.
I would install a Katech K501 camshaft as Jason recommended. Lots of great results from folks using this cam.
Be careful with your dual springs and Ti retainers. Lots of failures out their. Remember, a broken spring and a dropped valve in a cast piston motor can ruin your day. A set of PSI Endurance Beehive springs (1511 or 1515) would be a much better choice. The 1511 spring is shorter and will work with your LS1 titanium retainers (there are no LS7 1.959" height titanium retainers). You can use your OEM steel retainers with the taller 1515 spring and only give up a few grams while gaining some additional height and spring pressure.
There are some great dual springs available also. However, as you increase seat pressure you can overwhelm OEM LS7 lifters and rockers.
Best of luck!
And yes, the K501 seems to be a very good cam from what I’ve heard.I bought the springs and retainers as a kit from Texas Speed some 6 or 7 years ago, to be honest I do not really remember what they are, I’ll have to get them back out and have a look.
10-19-2015, 08:32 AM
#30
Instructor
Thread Starter
The beauty of having it in your hands is you can try it. It will still cost you consumables and gaskets and a Heck of a Lot of tuning time, but worst that will happen is that you pull it out and put something else in.
However, I am in the camp that your car (Factory 5?) has enough HP already given the chassis. That is a good looking car and vary trick, but my Race Car often ran in the same Race Heat with Factory Five Racing and they really don't look good after a major shunt or off. There is not a lot of steel up front other than the engine and it is pretty easy to shed a lot of that steel if you hit something hard.
However, I am in the camp that your car (Factory 5?) has enough HP already given the chassis. That is a good looking car and vary trick, but my Race Car often ran in the same Race Heat with Factory Five Racing and they really don't look good after a major shunt or off. There is not a lot of steel up front other than the engine and it is pretty easy to shed a lot of that steel if you hit something hard.
My car is not a FFR, the chassis is custom built in Sweden to use the front and rear parts from a Corvette C4, my car uses parts from a 1992 ZR1 with a Dana44 axle and I’m using the calipers from the C6 Z06 up front and I have GAZ coil overs all around. It’s actually pretty competent when it comes to road/track performance. But still, I do not think I would like to hit something solid with it, but even worse if I were to be hit by an SUV or something from the side, it would probably run right thru and/or over me
I have attached a few early pictures from the build.
10-19-2015, 10:56 AM
#31
Melting Slicks
Nice build 
10-21-2015, 04:05 PM
#33
Supporting Vendor
Member Since: Sep 2013
Location: Harbor City California
Posts: 2,817
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Very nice build and nice shop.
Just FYI, to date we have shipped our heads to 5 country's in Europe. We ship worldwide, Europe, UAE, Asia, South America, ect...
HP@americanheritageperformance.com
310-326-2399
http://www.americanheritageperformance.com/
Just FYI, to date we have shipped our heads to 5 country's in Europe. We ship worldwide, Europe, UAE, Asia, South America, ect...
HP@americanheritageperformance.com
310-326-2399
http://www.americanheritageperformance.com/
10-23-2015, 03:51 AM
#34
Instructor
Thread Starter
Very nice build and nice shop.
Just FYI, to date we have shipped our heads to 5 country's in Europe. We ship worldwide, Europe, UAE, Asia, South America, ect...
HP@americanheritageperformance.com
310-326-2399
http://www.americanheritageperformance.com/
Just FYI, to date we have shipped our heads to 5 country's in Europe. We ship worldwide, Europe, UAE, Asia, South America, ect...
HP@americanheritageperformance.com
310-326-2399
http://www.americanheritageperformance.com/
The plan is early spring btw
10-25-2015, 11:56 PM
#35
Intake flow of these heads is what makes them so special. 12 deg valve angle, port size and shape, size of int valve... The exhaust just needs a little love is all.
10-27-2015, 03:08 PM
#36
11-10-2016, 10:01 AM
#37
Instructor
Thread Starter
A year later I thought I’d bring life to this thread again
I have now pulled the heads to have the guides replaced etc. It will be done by a local workshop who has done about 35 pairs of LS7 heads by now. I was talking to AHP but we came to the conclusion that it was just not feasible money wise to send them back and forth.
My engine has less than 4k miles on it now, I understand that you often reuse the stock TI intake valves but if the exhaust valves are in good condition would I be fine using them as well or should you always use new LS7 stock or hollow SS valves?
I have also looked into what springs and retainers I got there back in 2007. They are PRC's Double Gold springs, part number 199-spkit. Included in the package are steel spring seats, titanium retainers and viton valve seals, supposedly good up to .660 lift. Would there be any major drawbacks in using those springs compared to for example PSI 1511 beehives that where mentioned earlier here?
I have decided to try out the GM stage 3 cam as I already have it and I'll make sure to have a good tuner at hand. If it’s too much to live with I’ll swap it out for something else later on.
As this is my first cam swap in a push rod V8 I need to know what else I should consider changing. What about push rods, rocker arms, lifters, trunnions, etc etc?
I have now pulled the heads to have the guides replaced etc. It will be done by a local workshop who has done about 35 pairs of LS7 heads by now. I was talking to AHP but we came to the conclusion that it was just not feasible money wise to send them back and forth.
My engine has less than 4k miles on it now, I understand that you often reuse the stock TI intake valves but if the exhaust valves are in good condition would I be fine using them as well or should you always use new LS7 stock or hollow SS valves?
I have also looked into what springs and retainers I got there back in 2007. They are PRC's Double Gold springs, part number 199-spkit. Included in the package are steel spring seats, titanium retainers and viton valve seals, supposedly good up to .660 lift. Would there be any major drawbacks in using those springs compared to for example PSI 1511 beehives that where mentioned earlier here?
I have decided to try out the GM stage 3 cam as I already have it and I'll make sure to have a good tuner at hand. If it’s too much to live with I’ll swap it out for something else later on.
As this is my first cam swap in a push rod V8 I need to know what else I should consider changing. What about push rods, rocker arms, lifters, trunnions, etc etc?
11-10-2016, 12:09 PM
#38
Le Mans Master
My first comment - for goodness sake, get all those bolts off the top of the engine! You've got a veritable domino effect waiting to happen, best case scenario you knock a fastener down into a part of the engine bay where it can't be easily retrieved, worst case scenario one falls down into an oil gallery..
That said, with 4,000 miles in total on the engine, and if the exhaust valves are the newer model (which I believe that change occurred somewhere around the 2008 time frame), and the exhaust valve guides in the heads you just pulled we're not out of spec, then it's pretty safe to reuse them. If any of those conditions are not met then my recommendation would be to replace with brand new GM exhaust valves, or the Ferrea hollow stem. In consideration of the larger cam, maybe go ahead and swap them with the Ferrea.
That said, with 4,000 miles in total on the engine, and if the exhaust valves are the newer model (which I believe that change occurred somewhere around the 2008 time frame), and the exhaust valve guides in the heads you just pulled we're not out of spec, then it's pretty safe to reuse them. If any of those conditions are not met then my recommendation would be to replace with brand new GM exhaust valves, or the Ferrea hollow stem. In consideration of the larger cam, maybe go ahead and swap them with the Ferrea.
Last edited by Dan_the_C5_Man; 11-10-2016 at 06:21 PM.
11-10-2016, 03:31 PM
#39
Drifting
11-10-2016, 03:57 PM
#40
Instructor
Thread Starter
My first comment - for goodness sake, get all those bolts off the top of the engine! You've got a veritable domino effect waiting to happen, best case scenario you knock a fastester down into a part of the engine bay where it can't easily be retrieved, worst case scenario one falls down into an oil gallery..
That said, with 4,000 miles in total on the engine, and if the exhaust valves are the newer model (which I believe that change occurred somewhere around the 2008 time frame), and the exhaust valve guides in the heads you just pulled we're not out of spec, then it's pretty safe to reuse them. If any of those conditions are not met then my recommendation would be to replace with brand new GM exhaust valves, or the Ferrea hollow stem. In consideration of the larger cam, maybe go ahead and swap them with the Ferrea.
That said, with 4,000 miles in total on the engine, and if the exhaust valves are the newer model (which I believe that change occurred somewhere around the 2008 time frame), and the exhaust valve guides in the heads you just pulled we're not out of spec, then it's pretty safe to reuse them. If any of those conditions are not met then my recommendation would be to replace with brand new GM exhaust valves, or the Ferrea hollow stem. In consideration of the larger cam, maybe go ahead and swap them with the Ferrea.
Does anybody know exactly what changed with the exhaust valves at that time? Is there a way to tell which I have got? My engine was bought in late 2008 but I do not know when it was manufactured.
I asked Jason @ Katech about this and he said he didn't know but according to their experience it had nothing with durability issues to do.