interesting engine question....

[uiuc240]

Some say that when adding a thicker head gasket, or milling the head, you need to mess with timing to compensate for the change in height.

I disagree. Seems to me, the chain is a preset lenght, and the sprockets are a set ratio. Given this circumstance, as long as the chain will "stretch" the extra .3mm (from .9mm to 1.2mm for a thicker head gasket for example), you shouldn't have to F with the timing at all. The only reason would be if you had to add or remove a link (like if you milled it a TON).

Agree? Disagree?

Eric

[Foxcolt]

Don't think you need to mess with it when installing a bigger head gasket. However when doing major mods, stroker kit etc etc it's a must.

[uiuc240]

well, see it's interesting you should say that because some very reliable sources (SRFiveTen on FA, for example) would say that any change in the total height requires timing correction. I think that's BS unless the change is significant enough to warrant clearance problems (or removing a link in the chain).

Eric

[HippoSleek]

I can't imaine the margin of error in creating a timing chain that will last for 200,000 mi. is .3 mm. Hence, a tensioner. My opinion would be that the tensioner would just be a bit less firm.

[$100,000 in education and I can't figure out how to say that the tensioner wouldn't tension as much, hence allowing more length in a coherent manner]

[uiuc240]

Originally posted by HippoSleek
My opinion would be that the tensioner would just be a bit less firm.

[$100,000 in education and I can't figure out how to say that the tensioner wouldn't tension as much, hence allowing more length in a coherent manner]

You're exactly right. That's what I'm saying too. It'll just adjust itselft and move on.

You meant to say "The tensioner would simply adjust to account for the added/decreased length from crank to cam." :o :D

Eric

[AKADriver]

Timing will be thrown off (retarded). Not by too much, though.

The problem is, I can't explain it in words. If you all were sitting here with me, I could explain it with hand gestures and doodles on the backs of envelopes though :p

[AKADriver]

Okay, I drew this real quick in ms paint:

http://mywebpages.comcast.net/akadriver1/images/timing.gif

Timing chains are the same length in both cases; the tensioner is taking up the slack on the milled engine (right). The chain length between the marks on both gears is the same. See that angle? That's cam timing retard. Obviously this example is exaggerated for clarity - you won't see 30 degrees of retard like that - but 1 or 2 isn't out of the question.

[DamnedButDetermined]

I am with aka!

[tnord]

depending on the ECU.........i know you have the SR, but for OBDII people i think that it wouldn't even matter, and maybe not even do you any good. OBDII systems would adjust the timing to compensate for the increase in compression. then again, i suppose you could manually adjust the timing yourself with the distributor cap. then again, i don't really know what i'm talking about.

[uiuc240]

Originally posted by AKADriver
Okay, I drew this real quick in ms paint:

Timing chains are the same length in both cases; the tensioner is taking up the slack on the milled engine (right). The chain length between the marks on both gears is the same. See that angle? That's cam timing retard. Obviously this example is exaggerated for clarity - you won't see 30 degrees of retard like that - but 1 or 2 isn't out of the question.

Dude, you rock. I want to change my vote! I'm glad we cleared that up. Makes sense to me now!

:)

Eric

[240 2NR]

I agree with AKA, but how much does that tiny amout really effect timing. Considering most cam gears allow for several degrees of adjustment, will a mm really alter that much? Maybe when every adjustment is critical, but on s street car, I doubt it.

[mrdirty]

Will it change timing? Yes, but by how much?

Ok, take the increase in gasket height multiply it by two.
Divide this length by the length of the mean radius of the sprocket (@ cam), and multiply by 360 degrees...

[HippoSleek]

Okay, do we know if there is a single tensioner or is it a dual system - b/c now I can't help but think that a single tenioner is nothing but a bad idea. :confused:

[uiuc240]

Originally posted by HippoSleek
Okay, do we know if there is a single tensioner or is it a dual system - b/c now I can't help but think that a single tenioner is nothing but a bad idea. :confused:

Well, it only has one pressure point...but I think it rides on a channel on the other side. But would that matter? I think to do what you're saying, you'd have to have two ACTIVE tensioners...which these Nissan motors do not have. I'd be surprised to see a single-chain/belt motor with dual tensioners, actually.

Eric