L99 to LS3 Hollow valves? Should I do it?

[ss camaro-monte]

Like the title says. GPI is porting and CNC a pair of heads for me. Do I reuse the stock solid L99 valves or should I do hollow stem valves? I believe the weight difference is 20 grams a valve roughly.

GPI sales rep said it probably wouldn't benefit me much with my mild cam but I am thinking about the added weight to valvetrain.

Those of you who swapped cams but kept stock heads are the stock valves a problem?

Thanks,

[CamaroCracka]

Depend on how fast you want to spin it, but a lot of guys don't like the hollow stem valves because they tend to snap if the piston kisses the valve in the event of valve float. If you are concerned with valve train weight, you will want titanium retainers as well.

[morepowerjoe]

I have hollow intake valves in my l99 stock port heads. I got them because I read that they will give you like 3-400 rpm higher rev range and I wanted to rev mine as high as needed for my peak power set up. My tuner said that only use severe duty oem valves strictly for durability (but they let me bend the rules a little). My power did carry out to 6700 rpm before starting to decline. So I don't know if they were worth it or not but with your set up I would spring for a set because they aren't really that more expensive and I think it will help you get over the 6k rpm mark if you want to.

[ss camaro-monte]

https://www.motortrend.com/how-to/ti...ainers-needed/

https://www.enginelabs.com/news/stee...h-do-you-need/

Two reads on steel retainers. I called BTR last week before I made my decision and I am pretty sure GPI uses them or something similar as they already use their springs and BTR told me the same, tool Steel 90% of street rods. They told me to spend the extra money on a quality lifter GMPP or better(which basically means Johnson lifters).

I was told by GPI that the newer tool steel retainers are only about 14grams a piece and titanium was 11 grams. With my motor being so mild it would show little difference until 6500rpm or higher. Which my cam is done at already.
Plus steel retainers can last double the miles of Titanium. I won't be seeing any 7000rpm shifts is my guess.

Now the intake valves are a different story in my mind. They are 20 grams a piece lighter. I will give GPI tech team a call on Monday to see what they say. I think that might be a while the heads are off thing but I might plan to spray or boost down the road so I will see what they say. Looking at valves 108 grams is heavy compared to the LS3 but compared to some of these Manley SS race Valves they are at least 10 grams lighter.

[Prizm]

I have a 2011 camaro with the l99. Did a ss1 gpi cam kit with the dod delete. New springs, retainers, pushrods, Johnson lifters, Ketech timing chain, Longtube headers, catback exhaust, high flow cats, che trunnion bushing, and cai. I spin to 7k, is that not common? Been running that for 3 years now and the car has not missed a beat. Thought about running the ls3 valves and COMP Cams Max-Lift BSR Shaft Rocker Systems.

[zz430camaro]

Not a bad idea if you have the money to burn!

[acammer]

Originally Posted by Prizm

I have a 2011 camaro with the l99. Did a ss1 gpi cam kit with the dod delete. New springs, retainers, pushrods, Johnson lifters, Ketech timing chain, Longtube headers, catback exhaust, high flow cats, che trunnion bushing, and cai. I spin to 7k, is that not common? Been running that for 3 years now and the car has not missed a beat. Thought about running the ls3 valves and COMP Cams Max-Lift BSR Shaft Rocker Systems.

Your combination is probably right on the money shifting right around 7,000rpm. It may not even need quite that much, I'm guessing it'll peak at 6,200, but with a stock converter it'll still get pulled down quite a bit on shift recovery, so 7,000rpm is probably a good target.

That's not uncommon at all, and for that rpm range there is no need for a ligther valve or a shaft rocker. Generally speaking a spring/valve combo like yours will have good stability out to about 7200rpm. Since it's automatic, there is very little chance of any unintended RPM, and so it doesn't need much of any additional safety factor. I wouldn't change anything, other than keep the springs fresh. I don't know what you put on for mileage, but 20k is a good point to start checking springs, and then every 5k or so afterwards. When they stop giving the proper open/closed pressures then it's time for a new set. Bushed trunnions also do wear, and should be inspected whenever checking springs.

That's not to say that LS3 valves and the BSR Max Lift stuff doesn't have it's place, it certainly does. Typically, that'll be on higher RPM combinations with higher spring pressures. I've run the BSR Max Lift shaft rockers on my own car for 4 years now, and they've been great. But I've got a stick car with closer to 500lbs of open pressure, and sling it to 7800rpm routinely.