Which head is best..

[Jeff G 78]

Six years?

I let this one slide because it was obvious he was trying to do research an asked a follow-up question. Most noobs try to answer zombie posts.

[Fun_in_my_z]

I looked for the free head option but didnt see it???

[Jeff G 78]

^^^hee hee^^^

[colinc]

Try the link below.

http://www.geocities.com/zgarage2001/z.html

Yes I know it is 6 years old but......

I couldn't get this link to work so I thought I would add another one with similar info in case others are having the same problem:

http://datsunzgarage.com/engine/ - make sure you click through to the "head page"

Another interesting tool is attached below. This allows you to determine the compression ratio for the different L-series engine combinations.

http://www.atlanticz.ca/zclub/techtips/enginemodellingsoftware/index.html

Edited December 1, 2012 by colinc

[Careless]

On 03/06/2003 at 4:43 PM, Royce said:

Okay, I was just thinking about this more and think I am getting dizzy! Now, I am thinking that if you take a link out of the chain it would change the relationship between the cam and crank timing. Remember the crank has a small sprocket and the cam is a larger sprocket. They are syncronized so that the crank turns twice in the time the cam turns once. So I would think that removing a link in the chain (or changing the size of the either sprocket) would upset the sycronization between the two.

Does that make sense???

The crank will always turn with the same ratio in relation to cam, regardless of chain length if the sprockets remain the same size. the issue of having incorrect cam/crank geometry or relation arises from not having the same available chain slack or tension on both sides of the chain as OEM once the head is shaved- which changes the cam phasing in relation to the crank. You can try all you want to align the dots on the chain on both ends of the motor and it just won't line up. There is no in-between by tightening or loosening the chain by using a different tension, or removing/adding links- which is what creates the problem. The length difference is so small (but has a definite effect) that using a different chain length won't fix it.

the amount removed from the head is so minute that the proper tension still resides within the confines of the same belt/chain length as OEM, it's just not achievable with only a tighter factory tensioner because you'd have to put a tensioner on the opposite side to mimic the appropriate chain length on BOTH sides of the crank timing gear.

you can play with pulley/belt sizing and distance here, and see that belt length or chain length does not change speed of either pulley:

http://www.blocklayer.com/pulley-belteng.aspx

Another way of looking at it is if you were to put a tensioner on either side of the crank, you could effectively change valve timing by making them controlled by an auxiliary device, as one loosens up, the other one tightens up. This will shift the phase of the cam in relation to the crank depending on which side is commanding more chain length (than OEM) from crank to cam, but the speed remains the same. The side that has the higher increase in cam chain length will have its teeth squeezed closer together (for lack of a better way of visualising it); tighten the left side to make the chain longer = retard timing. tighten the right side = advanced timing.. Since there's only one tensioner on one side of the motor, we can't use this idea to correct the cam geometry, it only allows us to make one side longer or shorter, and doesn't allow adjustment of both sides.

essentially, it's not the speed that is altered by chain length, it's the relation between cam and crank phasing which is influenced by available chain length on either side of the two spinny bits. Tighten one, and it pulls everything closer on that side, but you have to tighten the other side to bring it back into phase.

you would need a variable cam timing device like Nissan VTC sprocket hub, but there are none that work on the L-series motors. But that's pretty much what's happening inside one of those. Tooth phase is shifting from one direction to the other to change valve timing.

Kaimeri makes a gear driven chain guide that is adjustable that corrects the geometry on both sides of the chain to account for a shorter motor and keep proper tension on both sides. You don't need to use shims in most cases if you use that product.

Edited December 23, 2016 by Careless

[Zed Head]

It took you 13 years to get your thoughts down on the screen?  I can empathize.

[Careless]

Not sure what you're trying to say... this post came up on my latest topics.

 

yet again, this forum keeps showing me old threads as active.

[Zed Head]

I was kidding.  13 years is a long time.  It's a good explanation though, of a topic that can be confusing.

[Careless]

yeah i don't know why I keep seeing decade old posts pop up on my main page like they're something everyone is discussing lately. It's not like I'm searching for them, either.

not sure if it's just my account or what, but I can't say checking the dates of the last post is my first instinct when it's in the active threads list.

Edited December 23, 2016 by Careless

[Zed Head]

@Mike

Maybe Mike knows what's up...

[Mike]

Well for sure NOW it's a recent topic.  

I think it probably popped up because I added the survey block to the main forum page.  This is the last post we had in the survey forum back then.  We've had other surveys but they weren't in a dedicated forum like this.  Anyone want to start a new survey to override this one?