F54/P79 Swap Project

[siteunseen]

Wait until about 7p.m.  That's when things start getting fuzzy.

When I did #3 it was just about impossible to get the sprocket on the cam. Everything was new.

[Captain Obvious]

11 hours ago, 240260280 said:

You can adjust the slack side guide inward at the top to take up all the chain slack so that the tensioner goes back.

I completely forgot about that. I had talked about it before, but by this time, my brain was full.

So I slotted mine some and it's almost back to where it should be. I'm confident with a new set of non-worn guides, I'll be able to make that work fine. Thanks for the reminder!!  

[Captain Obvious]

7 hours ago, siteunseen said:

When I did #3 it was just about impossible to get the sprocket on the cam.

So now I'm not sure if your kidding or not... You do know that the timing hole you use has absolutely no effect on how tight the chain is, right?  Haha!!

[Captain Obvious]

Oh, and I'm not worried about the valve timing. I've got a lathe and I've already verified that I can set-up to bore the locating pin hole:

I didn't cut any metal yet, but if I need to, I can adapt to the offset bushings.

[madkaw]

Don’t worry about chain slack, go for the CR you want . Move the guide to take up slack. Advance cam timing a bunch and roll with it!

I have .050+ off my e88 , no shims . 

Plug in 39cc chamber numbers for the MN47! I got my fingers crossed for my engine .

[Zed Head]

Generally, as I understand things, advancing cam timing moves the power band to lower RPM.  A bit ironical because it means that as the engine gets more miles it makes more power at higher RPM.  Where it should spend less time due to wear and age.  Might be why Nissan added the two extra holes.

I'd think that you'd want to degree the cam to perfection, to where the cam builder has designed it.  Low RPM grunt can feel like more power.  Might also be more detonation prone though..  You need to build a dyno.

[siteunseen]

7 hours ago, Captain Obvious said:

So now I'm not sure if your kidding or not... You do know that the timing hole you use has absolutely no effect on how tight the chain is, right?  Haha!!

The book I have says use the higher numbers for chain stretch. Try it and see, all you'll loose is a zip tie.

[Av8ferg]

The book I have says use the higher numbers for chain stretch. Try it and see, all you'll loose is a zip tie.

Interesting. When I moved my sprocket from 3 back to 1 is when I noticed I could hear chain slap on the cover as the motor decelerated from a rev up. I think moving the sprocket only tightens or loosens the right right (upward side when running) of the chain and pushes the slack to the tensioner side where it is supposed to taken up by the tensioner. The tensioner can only take up so much.
This is my guess. Someone feel free to shoot my theory down, I’m still on my first cup of coffee this AM ️


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[240260280]

@siteunseen @Captain Obvious

I believe both of you to be correct. 

Adjusting the Cam Sprocket makes the chain feel tighter and more difficult to install on the Cam nose; so it seems like taking up the slack when doing the operation. It however, puts more chain on the slack side of the assembly.  Moving the chain guide inward takes up the slack by making the chain run along a longer path.

btw when moving the cam spocket, it is ok to turn the cam a degree or so as needed to help get the sprocket back on the cam nose.

Edited September 14, 2019 by 240260280

[Captain Obvious]

Actually I am completely confident that I am 100% right and 0% wrong. Changing the cam gear to a different index hole has absolutely nothing to do with chain tension. It changes relative teeth position, but not chain tension.

This is what the different index holes do... They change the relative position of the gear teeth to the hole. (Which changes the relative position of the teeth to the cam lobes.) But it does nothing to the overall tension on the chain. Remember this pic?  :

The reason they say you can use a different hole to account for chain stretch is ONLY to bring the valve timing back into spec. It won't tighten up the chain any... That's the tensioner's job.

[Captain Obvious]

Here's another way to think about it... Within a small amount of manufacturing tolerance, the centerline axis of the cam gear must always be on the same axis as the camshaft. It if weren't, the gear would wobble eccentric and make the chain tighter in one spot and looser in another.

If changing to a different indexing hole is expected to have an effect on the chain tension, then what happens when you rotate the cam 180 degrees? Does it get extra loose?  

[240260280]

There is less chain under tension on the tight side and more on the slack when you take up the slack (as mentioned above). You can tighten by one whole link if you want to push to more easily understand what I mean and why @siteunseen found moving the sprocket to seem like it tightened and took up slack. Don't think of it as quantized to number of links.

Edited September 15, 2019 by 240260280