Would having your head and block decked throw off the timing belt

[dsmtalontsi95]

Would having your head and block decked throw off the timing belt if it's not compensated. I had my block and head decked when it was being built and when we put the timing belt on it didn't line up perfectly. I have skunk adjustable cam gears and the indicators aren't perfectly lined up. We couldn't get it any closer, we would be a tooth off (we tried 3 different ways). Let me know your input.

 

[300dollarGSX]

It shouldn't be a full tooth off, but yes, it will change the timing geometry. I had both my head and block decked/surfaced as well. In fact, the head is slightly beyond the service limit if I remember correctly. I wasn't a fully tooth off, though. I used aftermarket cams (Comp 101200's), so I degreed them and used adjustable cam gears. The metal headgaskets are also thicker than stock and can compensate for the material lost if it wasn't too much.

 

[crimsondragon]

If it has come to the point where you're throwing your timing off because you decked and milled the block and head, I'd worry about the valves hitting the pistons even if it was timed correctly. Regardless, that's what the automatic hydraulic tensioner is for.

 

[dsmtalontsi95]

It shouldn't be a full tooth off, but yes, it will change the timing geometry. I had both my head and block decked/surfaced as well. In fact, the head is slightly beyond the service limit if I remember correctly. I wasn't a fully tooth off, though. I used aftermarket cams (Comp 101200's), so I degreed them and used adjustable cam gears. The metal headgaskets are also thicker than stock and can compensate for the material lost if it wasn't too much.

I worded that part wrong, I'm not a full tooth off. How much did it cost to get the cams dialed in?

 

[300dollarGSX]

No money, just time. I'm sure there are plenty of people you could pay to check it for you, but it's not too difficult to do yourself. All you need is a degree wheel, a dial indicator with stand, a pointer of some sort (even a bent metal clothes hanger can work), a couple of solid/adjustable lifters, and the spec cards that come with your cams (if you're using aftermarket cams, if not the service manual should have the specs you need or they may be posted somewhere). I made my adjustable lifters by disassembling two of my old lifters and putting a small bolt and a nut inside the hollow end. The bottom of the top half of the lifter rests on the top of the nut. The bolt sits inside the lower half of the lifter and points upward. I adjust the height by simply tightening or loosening the nut. None of that may have made any sense, so I will find them when I get home and take some pictures. If I remember correctly, there was a thread somebody made about degreeing cams that included another way to make some solid lifters using shims. I'll probably post pics of my lifters in there as well.

Here's the link to the degreeing thread:
Cam degree-in degreeing-in degreeing

If it has come to the point where you're throwing your timing off because you decked and milled the block and head, I'd worry about the valves hitting the pistons even if it was timed correctly. Regardless, that's what the automatic hydraulic tensioner is for.

Any amount of surfacing, decking, or milling will change the valvetrain geometry. Other than to prevent weakening of the head or block (or cutting into a water passage, etc), I'm sure the service limit's are to show how much material can be removed without changing the timing too much. The automatic tensioner isn't going to bring the timing back into spec, it can simply take up extra slack in the timing belt. The cams will still be indexed differently in relation to the crankshaft unless they are corrected somehow (thicker head gasket, adjustable cam gears, ...). The fact remains that after this type of machine work, the crankshaft and camshafts are physically closer together unless something is used to space them back apart. You are correct, though, piston to valve clearance is already at a premium and this will increase the "window of opportunity" for contact.