Big cam 346 power?
09-15-2008, 05:51 PM
#61
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Great numbers through a LS6 intake! Set up sounds similar to one I had about 4 years ago..Stock bottom end LS6 in my Z06 with TEA stg 3 6.0L heads, port matched FAST 90/90 and a T-REX Cam only 10:3:1 comp and made 480 rwhp/420 tq on pump gas in Florida heat..
12-05-2008, 11:12 PM
#63
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Here is the write up from another board. It is all explained...
We started with Prin's 167k mile shortblock. He had a TSP cam and a set of PRC 5.3 heads. We had planned on ditching the iffy cam from the start and then having his heads flowed to see if they needed any work before they went back on the rebuilt engine. We had the block honed with a torque plate, reused the stock pistons after flycutting them .100 on the intake and exhaust, added a new set of piston rings, and a set of ARP rod bolts. We had the stock crank polished and assembled the bottom end with Clevite "P" series bearings. The block also received a new set of Federal Mogul cam bearings. We reused his new timing set and oil pump he had installed with his previous heads and cam swap.
I had the heads flowed and they were pretty good at around 295cfm @ .600 and didn't stall at .650... so we didn't have to do any work on them. I did have them milled a good bit to get the DCR (Dynamic Compression Ratio) up there so that there would be some cylinder pressure with the larger cam. His stock lifters were replaced by a new set of GM LS7 lifters and we inspected/installed his stock rocker arms. The last part of the upper valvetrain is a set of .080 wall hardened pushrods.
From the start he was wanting a cam with some "thump" to it. Running a large cam really kills the DCR on these engines. After doing alot of testing with several different setups, we have found a "sweet spot" on the DCR. If you go too high, you can't put any timing in the car without detonation on pump gas and if you go too low..the car is a dog in the low rpms and has no throttle response, making for a very bad 3.42 gear'd daily driver. We try and shoot for a DCR in the mid to upper 8.x:1. The final cam specs are 242/246 .621/.614 111lsa 109icl. This uses a combination of XFI and XER lobes. If you look at the duration at .050 that I posted, the cam looks like a traditional split with 4* more duration on the exhaust. All of that changes when you look at the .200 lift duration, the cam is a 165/166 at .200 lift for only a 1* split. The .006 (advertised) duration of the cam is much lower than you'd think because of how aggressive the lobes are. That quickness off the valve seat and on the closing event keeps the cylinder from bleeding off too much pressure on the compression stroke. The Intake Valve Closing event at .050 is 50* ABDC, that's one of the variables that helps to dictate the RPM at which peak power occurs. In 90% of the applications I do cams on, I try and set this around 44-45, but the size of his cam made this impossible. It will still peak around 6300rpms due to the intake runner length of the intake and heads. Peak torque will be at 4800rpms.
We reused his LS6 intake and ported throttle body for now. I'm hoping he'll add a FAST 92mm setup in the near future, he's leaving a good 15+rwhp on the table by running the LS6 intake with this combo. We also replaced his stock fuel injectors with a set that flow 38lbs/hr, up from the 26.6 of the stockers. His exhuast is still the pace setter long tubes/offroad Y and loud mouth II cat back. I'm installing a 3in cutout in the intermediate pipe before we dyno. A cutout is a "must have" for a heads and cam setup if you aren't running true duals. The single 3in pipe going over the rear axle and into a muffler just isn't good for making power at 6300rpms.
We started with Prin's 167k mile shortblock. He had a TSP cam and a set of PRC 5.3 heads. We had planned on ditching the iffy cam from the start and then having his heads flowed to see if they needed any work before they went back on the rebuilt engine. We had the block honed with a torque plate, reused the stock pistons after flycutting them .100 on the intake and exhaust, added a new set of piston rings, and a set of ARP rod bolts. We had the stock crank polished and assembled the bottom end with Clevite "P" series bearings. The block also received a new set of Federal Mogul cam bearings. We reused his new timing set and oil pump he had installed with his previous heads and cam swap.
I had the heads flowed and they were pretty good at around 295cfm @ .600 and didn't stall at .650... so we didn't have to do any work on them. I did have them milled a good bit to get the DCR (Dynamic Compression Ratio) up there so that there would be some cylinder pressure with the larger cam. His stock lifters were replaced by a new set of GM LS7 lifters and we inspected/installed his stock rocker arms. The last part of the upper valvetrain is a set of .080 wall hardened pushrods.
From the start he was wanting a cam with some "thump" to it. Running a large cam really kills the DCR on these engines. After doing alot of testing with several different setups, we have found a "sweet spot" on the DCR. If you go too high, you can't put any timing in the car without detonation on pump gas and if you go too low..the car is a dog in the low rpms and has no throttle response, making for a very bad 3.42 gear'd daily driver. We try and shoot for a DCR in the mid to upper 8.x:1. The final cam specs are 242/246 .621/.614 111lsa 109icl. This uses a combination of XFI and XER lobes. If you look at the duration at .050 that I posted, the cam looks like a traditional split with 4* more duration on the exhaust. All of that changes when you look at the .200 lift duration, the cam is a 165/166 at .200 lift for only a 1* split. The .006 (advertised) duration of the cam is much lower than you'd think because of how aggressive the lobes are. That quickness off the valve seat and on the closing event keeps the cylinder from bleeding off too much pressure on the compression stroke. The Intake Valve Closing event at .050 is 50* ABDC, that's one of the variables that helps to dictate the RPM at which peak power occurs. In 90% of the applications I do cams on, I try and set this around 44-45, but the size of his cam made this impossible. It will still peak around 6300rpms due to the intake runner length of the intake and heads. Peak torque will be at 4800rpms.
We reused his LS6 intake and ported throttle body for now. I'm hoping he'll add a FAST 92mm setup in the near future, he's leaving a good 15+rwhp on the table by running the LS6 intake with this combo. We also replaced his stock fuel injectors with a set that flow 38lbs/hr, up from the 26.6 of the stockers. His exhuast is still the pace setter long tubes/offroad Y and loud mouth II cat back. I'm installing a 3in cutout in the intermediate pipe before we dyno. A cutout is a "must have" for a heads and cam setup if you aren't running true duals. The single 3in pipe going over the rear axle and into a muffler just isn't good for making power at 6300rpms.
12-06-2008, 12:37 AM
#64
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I dunno about 475-500, but why not? If through a 10 bolt and T56 and lightweight drivetrain, and that kind of compression ration 475+ shouldnt be a huge problem, but the intake will choke you and you wont see 475 with it, I think...
12-08-2008, 01:01 PM
#65
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It probably isn't going to make much more power through the LS6. Get the FAST, and then you will see more power and will utilize the rest of the band to 7k.
12-08-2008, 01:24 PM
#66
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I am putting a huge cam in my 346. It is a 242/246 .621/.614 111LSA 109ICL.
The heads are 2.5 5.3 prc heads that are going to be milled .040. The SCR is going to be around 12.2:1 and the DCR will be 8.8:1. The bottom end will be completely freshened as well.
What type of power should this put down?
The heads are 2.5 5.3 prc heads that are going to be milled .040. The SCR is going to be around 12.2:1 and the DCR will be 8.8:1. The bottom end will be completely freshened as well.
What type of power should this put down?
12-08-2008, 07:36 PM
#68
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Haha! Thanks a lot man!
I think those numbers are pretty good considering the ls6 intake.
But, we are now going back to the drawing board. This setup was a beast, but I think I made a big mistake by not getting new pistions. Either I have a problem with a pistion or there is a issue with the rings. We shall see. I am in the process of building a forged 348!
I think those numbers are pretty good considering the ls6 intake.
But, we are now going back to the drawing board. This setup was a beast, but I think I made a big mistake by not getting new pistions. Either I have a problem with a pistion or there is a issue with the rings. We shall see. I am in the process of building a forged 348!
