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L92 heads
- Thread starter rocket69GTP
- Start date
mill them to keep the stock compression ratio. solid valves will be better than the hollow for boost, but it's nothing you need to worry about until you are making some serious serious steam. if you cam the car, be aware of the piston to valve clearance since the l92/ls3 heads use a larger intake valve, plus the heads being milled
Yes, the clearance for the pushrods is what I am most worried about since I will be changing out to the Lunati lifters but I will contact them about specifications for the nominal preload but I am pretty sure that I will need a pushrod length checker. I can always do the the math but most just do not know until they are putting everything back together. Stock compression right now is 10.4:1 and the GXP runs 10.8:1 and they are running these combo builds with little to no issue with the motor. I would like to have the head work taken care of in advance that way when it is time for FI, I won't have to worry about them again. For now, this is going along with the cam I will be putting in and this is definitely the hardest part is determining the specs for this and staying with a stock converter.
Yeah, dual valve springs, hardened pushrods, retainers, etc. is being swapped out. Just don't see the point of AFM in these cars and I shouldn't see more than a 1-2 mpg reduction.
I know from the GTO LS3 top swaps, running unmilled LS3/L76 heads on the LS2 block will reduce the compression from 10.9:1 to ~10.4:1. Milling them .030" will bring it back to 10.9:1 but the PTV clearance is reduced. So if your G8 already has 10.4:1 compression, get the heads milled .030" to bump it up to stock LS2 compression.
If you're going FI route, don't mill them as you reduce the deck strength if you do.
If you're going FI route, don't mill them as you reduce the deck strength if you do.
^^^I thought about this as soon as I seen your post but I could always put the stock L76 heads back on with all of the hardware when I am ready to go that route so I can get the deck strength back...
The only thing I would have to worry about is pushrod length unless there is anything else that would be affected by this.
The only thing I would have to worry about is pushrod length unless there is anything else that would be affected by this.
Received this email from Patrick G and didn't realize the PTV clearance would get so close
from milling that it would limit you on cam aggressiveness. This same guy took cathedral style heads, had them ported (along with a few other bolt ons) and made over 500 to the wheels on stock cubes. Most guys with L92's have a hard time getting there.
I've taken stock bottom ends over 7000 rpm. I would caution you on milling heads if you want to run a cam of any decent size though. With an unmilled head, you can only run a 231 @ .050" cam on a 112 intake centerline before you get tighter than .080" piston to valve clearance. If you mill .030", you can only run a 219 @ .050" cam on a 112 intake centerline before you get tighter than .080" P to V clearance. You will make more power with a bigger cam and lower compression.
from milling that it would limit you on cam aggressiveness. This same guy took cathedral style heads, had them ported (along with a few other bolt ons) and made over 500 to the wheels on stock cubes. Most guys with L92's have a hard time getting there.
I've taken stock bottom ends over 7000 rpm. I would caution you on milling heads if you want to run a cam of any decent size though. With an unmilled head, you can only run a 231 @ .050" cam on a 112 intake centerline before you get tighter than .080" piston to valve clearance. If you mill .030", you can only run a 219 @ .050" cam on a 112 intake centerline before you get tighter than .080" P to V clearance. You will make more power with a bigger cam and lower compression.
