PTV Question Milled 317s
10-13-2013, 10:07 PM
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PTV Question Milled 317s I conducted a lot of research on here and attempted to measure the PTV on my build. The clay method of measuring PTV does not seem difficult, I am just a little surprised by the result so I am asking if anyone thinks that this make any sense.
I have a set of 317 heads that were sent to Patriot a few years ago for a stage 3 CNC to use on a HC LQ4. The shop building my motor thought I was using 241's so to keep the desired CR we ended up milling the 317's to 62cc, somewhere around 050. The LQ4 has a monster cam and valve reliefs so PTV was never a concern. OK with the back story out of the way, I want to put these heads on a gen iv 5.3 with boost so PTV is my main concern. I put a set of dummy springs on the 317s bolted them up to a stock gen iv 5.3 with a 228/571 cam and LS9 gaskets then tried the clay PTV measurement. The results were so small I couldn't even take a measurement. Am I doing something wrong or is this a result anyone has seen before? After doing some research on here I expected the PTV to be tight but the valve almost touches the pistons. I am doing something wrong? I also have a set of 243s that I hand ported the rocker studs out of, am I better of using these regardless? I have read a lot about using milled 317s on boosted applications and have gotten mixed answers. The posts I have read usually address the fact that the 317s create a lower CR, but in my case the CR will stay the same. I guess the question is if the PTV is sufficient does the gain in flow of the ported 317s make up for the fact that they are milled so much for a boosted application? This is my 1st turbo build so I apologize if the alcohol driven long winded post is an easy answer for an experienced hand. I have research this issue extensively before I decided to post. Thank you in advance for any help.
Stock gen iv 5.3 30k, T76 turbo, 228/571 cam, with ARP head studs and rod bolts on E85, desired RWHP is 700 through a DR6060 and Dana 60. 01 F-Body
I have a set of 317 heads that were sent to Patriot a few years ago for a stage 3 CNC to use on a HC LQ4. The shop building my motor thought I was using 241's so to keep the desired CR we ended up milling the 317's to 62cc, somewhere around 050. The LQ4 has a monster cam and valve reliefs so PTV was never a concern. OK with the back story out of the way, I want to put these heads on a gen iv 5.3 with boost so PTV is my main concern. I put a set of dummy springs on the 317s bolted them up to a stock gen iv 5.3 with a 228/571 cam and LS9 gaskets then tried the clay PTV measurement. The results were so small I couldn't even take a measurement. Am I doing something wrong or is this a result anyone has seen before? After doing some research on here I expected the PTV to be tight but the valve almost touches the pistons. I am doing something wrong? I also have a set of 243s that I hand ported the rocker studs out of, am I better of using these regardless? I have read a lot about using milled 317s on boosted applications and have gotten mixed answers. The posts I have read usually address the fact that the 317s create a lower CR, but in my case the CR will stay the same. I guess the question is if the PTV is sufficient does the gain in flow of the ported 317s make up for the fact that they are milled so much for a boosted application? This is my 1st turbo build so I apologize if the alcohol driven long winded post is an easy answer for an experienced hand. I have research this issue extensively before I decided to post. Thank you in advance for any help.
Stock gen iv 5.3 30k, T76 turbo, 228/571 cam, with ARP head studs and rod bolts on E85, desired RWHP is 700 through a DR6060 and Dana 60. 01 F-Body
06-16-2015, 08:34 PM
#4
1) You revived a thread that's almost two years old. Kudos for doing your research to find the answer, but asking the OP in a thread this old almost never works. This is because of...
2) The guy that posted this thread hasn't been active on here in over a year. You can tell by clicking on the screen name, selecting "view profile", and it will bring you to a profile page with recent activity at the top. There's a slim chance that he may get an email saying someone responded to a thread he may not even remember making.
To help answer your question, .050" is kind of a lot to mill off. Like the OP in this thread, you're going to almost certainly run into PTV issues, but may also run into slight to severe alignment issues with the intake manifold. The general concensus here is that .030" is about the most you want to mill before you start to run into problems.