Head milling question
01-12-2014, 10:19 PM
#1
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Head milling question I have a 2009 Z06 and started tracking it last year. So far I have had no problems with it but the track is where I learned about the valve issue. I'm getting ready to have that addressed. The mechanic doing the work suggests milling the heads to increase compression. I am putting on headers and will have him custom tune the engine as we'll. I am not changing the cam.
Here is my dilemma. I know very little about these things. A close friend of mine who has been racing/instructing since 1972 has cautioned me against milling the heads. He says it will add extra stress on the drivetrain and ultimately shorten the life of the engine and drivetrain. He also says that decreasing the space between valve and piston increases the risk of a catastrophic failure if the timing isn't perfect.
I'd love to get more advice on this topic. I'm convinced the valve guides need to be addressed. I'm torn about the milling issue. I want the car to be highly reliable. If milling the heads will decrease reliability then I'm going to pass I think. Thanks!
Here is my dilemma. I know very little about these things. A close friend of mine who has been racing/instructing since 1972 has cautioned me against milling the heads. He says it will add extra stress on the drivetrain and ultimately shorten the life of the engine and drivetrain. He also says that decreasing the space between valve and piston increases the risk of a catastrophic failure if the timing isn't perfect.
I'd love to get more advice on this topic. I'm convinced the valve guides need to be addressed. I'm torn about the milling issue. I want the car to be highly reliable. If milling the heads will decrease reliability then I'm going to pass I think. Thanks!
01-13-2014, 09:26 AM
#3
Out of my own curiosity...would you need to go to a shorter pushrod when milling heads like this? Seems like you would need to go to a shorter pushrod to get the correct preload on the rockers...
01-13-2014, 10:26 AM
#4
A close friend of mine who has been racing/instructing since 1972 has cautioned me against milling the heads. He says it will add extra stress on the drivetrain and ultimately shorten the life of the engine and drivetrain. He also says that decreasing the space between valve and piston increases the risk of a catastrophic failure if the timing isn't perfect.
The whole thing about reducing life by introducing extra stress is BS. Like half a point of compression is going to make that much of a difference.
Also, with a big cam that second statement might be true. But with a stock cam, you have plenty of PTV to clear. And if the *timing* is wrong like he stated, the engine would suffer a catastrophic failure no matter how much PTV clearance you have (whether stock or less).
01-13-2014, 01:45 PM
#5
The cheapest way to make power is to increase static compression. That's why it's popular - it's cheap and easy.
Racing and racing mods will always increase strain on the engine, and shorten it's life span. That's just the way it is. 6,500 rpm's lap after lap will beat on that engine pretty hard. Anybody who tells you otherwise doesn't know what he's talking about.
But, as said above, simply raising the compression a little bit isn't going to increase engine strain all that much. A little bit, but not a huge amount.
Valve springs wear out quickly. Consider them a disposable component, and replace them whenever you can. With a stock or slightly bigger cam, I like PAC beehive springs. Go about 10% higher springs rate than stock, and you'll get good control of the valves all the way to red line, without putting a big strain on components.
Racing and racing mods will always increase strain on the engine, and shorten it's life span. That's just the way it is. 6,500 rpm's lap after lap will beat on that engine pretty hard. Anybody who tells you otherwise doesn't know what he's talking about.
But, as said above, simply raising the compression a little bit isn't going to increase engine strain all that much. A little bit, but not a huge amount.
Valve springs wear out quickly. Consider them a disposable component, and replace them whenever you can. With a stock or slightly bigger cam, I like PAC beehive springs. Go about 10% higher springs rate than stock, and you'll get good control of the valves all the way to red line, without putting a big strain on components.