317/LQ9 Stock Intake Valve Margin Question
01-06-2008, 08:32 AM
#1
317/LQ9 Stock Intake Valve Margin Question (This thread is in 2 areas of the forum because it's not totally FI related, but you guys might know more about this in here having used these heads)
I recently purchased a used set of 317/LQ9 heads to go on my 347 forged bottom end that I am planning on using to help lower the compression with my single turbo build that's in the works. My plan was a quick head swap, run better springs and new hardware on these heads and retain the stock valves (bang for the buck to lower the compression from current 10.5 to 9.5ish).
The heads arrived in good shape and came to me as described. They will need a slight milling (2-3 thousandths) on the decks and have some surface rust cleaned up.
I recently had a friend of mine examine them who is pretty knowledgeable (attended SAM in houston). He thought all of the stock exhaust valves were good (very thick margin compared to exhaust), but the intake valves were 'shot'. He thought that the margin (area around the face of the valve) was on the thin side. He was taught at SAM that anything less than .030 thickness at the edge of the valve was too little. Right now the edge is right at .030 and he's worried if I have a local shop do a valve job on the heads and clean up the valves/resurface the faces of them then they will be too thin.
So...I went and visited the local shop that will be doing the valvejob and assembly of the heads. The head porter looked over them and told me that's how they came from the factory and he didn't notice anything odd about the 'margin'.
Is this pretty standard for the intake valve margin to be thin on stock 317 heads? I'm wanting to build this thing right the first time, but I also don't want to spend a fortune. I can use the $100 that another set of intake valves would cost somewhere else in the build. Thoughts?
I recently purchased a used set of 317/LQ9 heads to go on my 347 forged bottom end that I am planning on using to help lower the compression with my single turbo build that's in the works. My plan was a quick head swap, run better springs and new hardware on these heads and retain the stock valves (bang for the buck to lower the compression from current 10.5 to 9.5ish).
The heads arrived in good shape and came to me as described. They will need a slight milling (2-3 thousandths) on the decks and have some surface rust cleaned up.
I recently had a friend of mine examine them who is pretty knowledgeable (attended SAM in houston). He thought all of the stock exhaust valves were good (very thick margin compared to exhaust), but the intake valves were 'shot'. He thought that the margin (area around the face of the valve) was on the thin side. He was taught at SAM that anything less than .030 thickness at the edge of the valve was too little. Right now the edge is right at .030 and he's worried if I have a local shop do a valve job on the heads and clean up the valves/resurface the faces of them then they will be too thin.
So...I went and visited the local shop that will be doing the valvejob and assembly of the heads. The head porter looked over them and told me that's how they came from the factory and he didn't notice anything odd about the 'margin'.
Is this pretty standard for the intake valve margin to be thin on stock 317 heads? I'm wanting to build this thing right the first time, but I also don't want to spend a fortune. I can use the $100 that another set of intake valves would cost somewhere else in the build. Thoughts?
