TexasSpeed/PRC LS3/L92 RPM questions
11-10-2009 | 08:11 PM
#1
TexasSpeed/PRC LS3/L92 RPM questions Primarily curious if the valve upgrade is worth it.. As the cam selection gets bigger, the piston to valve clearance is getting tighter, so I guess reducing weight is your primary ally.
Also, a very well spoken representative at COMP suggested their 26926-16 springs, which are about 20# stiffer seat load and roughly 60# stiffer open than the basic PRC Dual Spring package. Can anyone attest to the RPM limits or valve float using any combination of said springs or valve options?
Here's the heads I'm referring to: TSP/PRC LS3/L92
Probably get a little flame for quoting this, but that carcraft article with GM out of the box L92 heads on an LQ4 with a 228/230 @ 050 cam made peak power at 6800rpm (which is really just where they quit recording, looks like it may have gained further out). Would be nice to go 7k without valve float problems...
Here's that article for reference: CC Article
From what I've read here, the L92 heads prefer significantly more lobe split, so my cam selection will likely be a bit different, but in the same general "smallish" arena. Otherwise my build is scheduled to be from the same LQ4+L92+Carb cookbook.
Thanks in advance,
TJ
Also, a very well spoken representative at COMP suggested their 26926-16 springs, which are about 20# stiffer seat load and roughly 60# stiffer open than the basic PRC Dual Spring package. Can anyone attest to the RPM limits or valve float using any combination of said springs or valve options?
Here's the heads I'm referring to: TSP/PRC LS3/L92
Probably get a little flame for quoting this, but that carcraft article with GM out of the box L92 heads on an LQ4 with a 228/230 @ 050 cam made peak power at 6800rpm (which is really just where they quit recording, looks like it may have gained further out). Would be nice to go 7k without valve float problems...
Here's that article for reference: CC Article
From what I've read here, the L92 heads prefer significantly more lobe split, so my cam selection will likely be a bit different, but in the same general "smallish" arena. Otherwise my build is scheduled to be from the same LQ4+L92+Carb cookbook.
Thanks in advance,
TJ
11-10-2009 | 08:31 PM
#2
Valve weight is a big deal for valve train control. I had my L92 heads CNC ported by Lingenfelter, no matter who does the porting I would get the lightweight LS3 valves.
I got my LS3 valves for $175 from the dealership, although I get a small discount through work. If upgrading to lightweight valves is as expencive as buying them yourself you might want to buy the valves yourself, or ask for a your set of heavier valves also with your heads if your paying almost full price for the lightweight ones. Then sell the heavy valves to recoup some cash.
The Comp 26926 springs work very well and are designed to handle their most aggressive lobes in their catalog, LSL lobes, that are on the the new LSR cams. Make sure you get the tool steel retainers!! The tool steel retainers weigh within a gram or so of the Titanium retainers do.
The weight of the retainer is just as important as the valve, anything on the valve side of the rocker arm matters, even the weight of the valve spring. Thats why I can get away with 918s, I have a light valve, light retainer, and light springs that are meticulously setup .060" from coilbind. I also have the thick wall .105" pushrods
I personally have one of the new LSR cams, with the big split(219/235 .607/.621 113+5) on my CNC L92/LS3 heads and love it. I got mine before the 26926s were avaliable and went with the 26918s with tool steel retainers. Ive seen too many titanium retainers that have worn away over time. That Ti go somewhere, and its through your engine.
I got my LS3 valves for $175 from the dealership, although I get a small discount through work. If upgrading to lightweight valves is as expencive as buying them yourself you might want to buy the valves yourself, or ask for a your set of heavier valves also with your heads if your paying almost full price for the lightweight ones. Then sell the heavy valves to recoup some cash.
The Comp 26926 springs work very well and are designed to handle their most aggressive lobes in their catalog, LSL lobes, that are on the the new LSR cams. Make sure you get the tool steel retainers!! The tool steel retainers weigh within a gram or so of the Titanium retainers do.
The weight of the retainer is just as important as the valve, anything on the valve side of the rocker arm matters, even the weight of the valve spring. Thats why I can get away with 918s, I have a light valve, light retainer, and light springs that are meticulously setup .060" from coilbind. I also have the thick wall .105" pushrods
I personally have one of the new LSR cams, with the big split(219/235 .607/.621 113+5) on my CNC L92/LS3 heads and love it. I got mine before the 26926s were avaliable and went with the 26918s with tool steel retainers. Ive seen too many titanium retainers that have worn away over time. That Ti go somewhere, and its through your engine.
11-12-2009 | 05:53 PM
#3
How much cam are you looking to run? Like mentioned above, valve weights are a big part of valvetrain stability. If you can get me your cam specs you are running, we can get you the valve and valvespring combo with the heads that will support the cam and RPM range you will be turning the motor. Our new PRC EHT spring has been the choice on several of the LS3 motors we have run on both the engine and chassis dynos. We have run some mid .600 lift cams over 7000 RPM without a hint of valvetrain instability. I'm sure these would probably work well for your application as well. But shoot me those specs and we'll help you get everything setup properly.
Jon
Jon
