Im I the middle of my build and the short block is done. I'm doing a 408 with ls3 heads and trying to get a little more compression. I have wiseco -3 pistons with the valve reliefs and had the heads were 68.5cc and milled 30 thous ( 65cc ) and using .041 gaskets, I've clayed the valve reliefs and rotated the engine twice over. Removed the head and found that the exhaust valve didn't even touch the clay and the intake valve just barley touched the clay. I by no means a pro and learning as I go along ( google is my best friend ) I put the clay a little higher than the piston top. With me already removing 30 thous off the head already, should I just use a .027 head gasket ? I have a friend that told me to remove another 30 thous off the head. I think I remember someone about killing the ls3 head chamber by removing to much. So looking for some advise on this, and no the block was not decked live and learn and im not willing to strip down the block, well not yet, SO WHAT DO YOU THINK ? thanks guys

 

What kind of compression are you shooting for? You're already over 12 with the current setup.

 

Even with such a large amost of ptv clearance ? from what I've read it seems that anyone running a some what of a large cam they are close to the piston. Like I said, learning as I'm going along.

 

You have valve reliefs, doubt you'll have much PTV issues. Again, the thing here is knowing what compression ratio you are shooting for. Without that, noone can answer the question whether or not you should "remove another 30 thous off the head." and that includes your friend.

 

I'm looking for around 12.1

 

You are at 12.1 now. That's assuming your pistons are .005 above deck.

Russ Kemp

 

stock deck and just in the hole a hair,if im between 11.7 and 12, i would be happy.

 

Then you're done, I don't see the need to mill anymore if that's the target CR.

What was the reasoning for your friend saying you need to mill another .030 if you've already achieved your goal?

 

Most likey becouse of the ptv clearance was so much even with valve reliefs. I've tried the compression calculater and its from 11.1 to 12 bepending on which one I use, so ill be happy with that, thank you for the responces

 

Hey redtan, do have your car put away for the winter ? I have family in ashby mass, thanks for the help

 

That's a silly way of doing it, "hey you have plenty of PTV clearance so mill the heads some more". You should be setting up the CR based on what your target is, not how much PTV clearance you have. Depending on the cam and how big the valve pockets are, you can probably mill the heads to 50cc yielding 13s CR before getting into PTV issues. But that's not an ideal setup on pump gas.

It's not perse, I still use it here and there when it's nice out. Just during the winter it sits alot more than the summer.

 

This is why i ask questions,so i can understand and learn from you guys

 

You did use light valve springs when checking?

 

Yes, I was checking push rod length and had the checker springs in. I got stuck on the ptv clearance to much and lost my thought about compression. I'm glad I have a lot of room with ptv. I'm back on track and playing with valve height now