surfacing the head to increase compression
07-10-2004, 09:11 AM
#16
Race Car
My head had to be shaved .019 to make it flat again (Anderson swore it only had a few break-in laps on it...guess he should have tried putting some coolant in the engine for those laps), on top of that it looked like it wasn't the first time it had been milled. I'm not running an adjutable cam gear and AFAIK there were no problems with the belt tension. The butt dyno says there might be a little more bottom end torque but there's no high end HP at all, it just drops off at 5500 rpm. I also have euro pistons so I figure my CR is well above 11:1.
07-10-2004, 11:21 AM
#17
Burning Brakes
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I've never shaved my head that close and never shaved my armpits at all. I've gotten braver as time goes on about milling cylinder heads. I've just started the anglemilling stuff. But wouldn't do it for a street car.
07-10-2004, 11:32 AM
#18
Nordschleife Master
Originally posted by Geo
So, the belt just acts upon the cam directly, eh?
So, the belt just acts upon the cam directly, eh?
07-10-2004, 01:46 PM
#20
Race Director
Originally posted by Peckster
He must have assumed incorrectly that the cam was driven by gears from the bottom end, not a belt. Gears located in the head are obviously not going to be affected by resurfacing the head.
He must have assumed incorrectly that the cam was driven by gears from the bottom end, not a belt. Gears located in the head are obviously not going to be affected by resurfacing the head.
You don't understand what's going on here.
When you shave the head and/or the the block you affect cam timing. What happens is when you tension the belts the cam is going to turn slightly towards the side the tensioner is on. This will be a few degrees, but those few degrees can make a huge difference. So, gears located in the head obviously are going to be affected by resurfacing the head.
He was spot on.
07-10-2004, 01:49 PM
#21
Nordschleife Master
Because both sides of the pulley are lowered, I don't buy it. Even if that was a factor, there's no way 20 thou would change timing by several degrees.
Is there anyone else who is concerned about this problem? I've never heard of it.
Is there anyone else who is concerned about this problem? I've never heard of it.
07-10-2004, 01:56 PM
#22
Race Director
Originally posted by Peckster
Because both sides of the pulley are lowered, I don't buy it. Even if that was a factor, there's no way 20 thou would change timing by several degrees.
Is there anyone else who is concerned about this problem? I've never heard of it.
Because both sides of the pulley are lowered, I don't buy it. Even if that was a factor, there's no way 20 thou would change timing by several degrees.
Is there anyone else who is concerned about this problem? I've never heard of it.
Buy it or don't buy it. I don't care. It's quite correct.
07-10-2004, 01:57 PM
#23
Burning Brakes
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When you loose material at the head, the cam rocks back delaying cam timing which would actually give you less torque at the bottom and more HP at the top . Unfortunately the engine will not rev high enough to get the real gains here without bigger mods. So you are better off getting an adjustable gear and putting the cam timing at least back where it belongs. Yes I know the more compression helps all the way around but you can have more if you put the cam back where it belongs.
07-10-2004, 01:58 PM
#24
Nordschleife Master
OK, what happens when your belt stretches and you have to adjust the tensioner. Is this throwing your timing out too? How do people make adjustment for this problem? Are there adjustable gears available?
07-10-2004, 02:01 PM
#26
Burning Brakes
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Fidanza . Yes everything effects cam timing. Even belt stretch. How do you fight it with your vingence? Put a chain on it. Don't get me wrong I agree it sucks but whats a man going to do?
07-10-2004, 02:03 PM
#27
Nordschleife Master
I stand corrected, sorry about that Geo. Are there gears available to correct this problem, or do people just live with it?
Sounds like another good reason to not shave your head unless it's required.
Sounds like another good reason to not shave your head unless it's required.
07-10-2004, 02:13 PM
#29
Race Director
In addition to Fidanza adjustable cam gears, a less sexy solution is offset woodruf keys. That is what we have to use in SCCA IT since adjustable cam gears are not legal. They take more effort and it takes a lot more time to get cam timing dialed in. Much cheaper for the part. Much more expensive for the dyno time.