PTV clearance for my setup?
Thread Starter
Joined: Jan 2008
Posts: 3,428
Likes: 4
From: Beaufort, SC
PTV clearance for my setup? Just wanted to get some info on whether or not I'll have to flycut my pistons for this setup. I don't think I will have to, but knowing before hand is always better than guessing and hoping.
Here is the setup:
- Thunder Racing's 230/236 .591 .601 112+4 LSA utilizing XER lobes
- Double valve springs
- Hardened 7.400 PR's
- Stock 1.7 roller rockers with Comp Cams Trunions
I have 04' LS6 243 heads with the sodium valves that I'll be sending to TEA for their STG 2 CNC program (http://totalengineairflow.com/products/gmhead/gmls6/). I will most likely be using the stock sodium filled 1.55 exhaust valve instead of the 1.575 valve included in their program, due to better flow numbers. I am wanting the heads milled down to about 61cc to bump the compression to 11:1.1-11:2.1. Also, I plan to use stock GM MLS gaskets. I see a lot of part numbers for these gaskets and would like to know which one exactly to get and how thin it is. Here is the one I have found from WS6store, http://www.ws6project.com/user_stor/...oducts_id=1618.
I plan to get LS7 lifters, ARP head bolts, LS2 lifter guide trays. As far as the LS7 lifters go, I think I've read somewhere that they change the length of the pushrod? I have 7.400s right now. I am going to measure everything and check but I just wanted to see if someone had info on if the LS7 lifters change the length etc.
Thanks for any info.
Here is the setup:
- Thunder Racing's 230/236 .591 .601 112+4 LSA utilizing XER lobes
- Double valve springs
- Hardened 7.400 PR's
- Stock 1.7 roller rockers with Comp Cams Trunions
I have 04' LS6 243 heads with the sodium valves that I'll be sending to TEA for their STG 2 CNC program (http://totalengineairflow.com/products/gmhead/gmls6/). I will most likely be using the stock sodium filled 1.55 exhaust valve instead of the 1.575 valve included in their program, due to better flow numbers. I am wanting the heads milled down to about 61cc to bump the compression to 11:1.1-11:2.1. Also, I plan to use stock GM MLS gaskets. I see a lot of part numbers for these gaskets and would like to know which one exactly to get and how thin it is. Here is the one I have found from WS6store, http://www.ws6project.com/user_stor/...oducts_id=1618.
I plan to get LS7 lifters, ARP head bolts, LS2 lifter guide trays. As far as the LS7 lifters go, I think I've read somewhere that they change the length of the pushrod? I have 7.400s right now. I am going to measure everything and check but I just wanted to see if someone had info on if the LS7 lifters change the length etc.
Thanks for any info.
My guess is that you wont have to fly cut.. but of course its only a guess. With LS6 heads and ls7 lifters i used 7.425 pushrods but if you're milling them down and depending on the thickness of the head gaskets then it might be 7.4 Both will just need to be double checked when doing the mods really. My intake side of the cam is pretty close to yours and I didn't have to fly cut.
When those heads come back throw some model clay on the piston and measure it. Very easy you only need to tighten 4 head bolts down. You dont even need to torque them down just tighten them pretty good. Think your good with anything over .1 mils of clearance but you can verify what some of the more experienced guys say. I am right in the middle of doing this now. Some people say its not 100 percent accurate because the clay can distort but if you are carefull you can get close enough to know if your going to need to take more precise measurements. The other way is to install the head and get the cylinder you are measuring at TDC and use a checker spring and push the valve all the way down until it lightly touches the top of the piston. You will get a 100 percent accurate measurement of how much space you have before things may go south real fast. Its nothing too hard its just time consuming but its alot easier than tearing everything down again if a valve happens to kiss a piston.
Thread Starter
Joined: Jan 2008
Posts: 3,428
Likes: 4
From: Beaufort, SC
My guess is that you wont have to fly cut.. but of course its only a guess. With LS6 heads and ls7 lifters i used 7.425 pushrods but if you're milling them down and depending on the thickness of the head gaskets then it might be 7.4 Both will just need to be double checked when doing the mods really. My intake side of the cam is pretty close to yours and I didn't have to fly cut.
When those heads come back throw some model clay on the piston and measure it. Very easy you only need to tighten 4 head bolts down. You dont even need to torque them down just tighten them pretty good. Think your good with anything over .1 mils of clearance but you can verify what some of the more experienced guys say. I am right in the middle of doing this now. Some people say its not 100 percent accurate because the clay can distort but if you are carefull you can get close enough to know if your going to need to take more precise measurements. The other way is to install the head and get the cylinder you are measuring at TDC and use a checker spring and push the valve all the way down until it lightly touches the top of the piston. You will get a 100 percent accurate measurement of how much space you have before things may go south real fast. Its nothing too hard its just time consuming but its alot easier than tearing everything down again if a valve happens to kiss a piston.
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
You will have to measure pushrod length after the engine is assembled. There is no correct guessing. Measure for PTV also. Can't really guess on that either. When your motor is done and you go to turn the key, you want to KNOW its right, not hope it is.
Thread Starter
Joined: Jan 2008
Posts: 3,428
Likes: 4
From: Beaufort, SC
