F54/P79 Swap Project

[Mark Maras]

1 hour ago, grannyknot said:

While there are so many good minds talking about this subject I would like to ask a question about a timing fact/myth I've heard many times. 

Starting with a new chain, by deliberately advancing the cam gear to #2 or #3 you can gain more low down torque. True or false?

 

 True. Back in the day we used offset keys to retard the cam timing and improve top end performance in drag racing engines. Years ago when replacing a timing belt on a Camry, I was sure I installed it correctly until I fired it up and drove it. Rushed job due to miserable weather and working outside. The cam timing ended up retarded by one tooth. The poor little 4 cylinder would struggle with low end performance BUT when it reached 4000 RPMs the power came on like gangbusters. It acted like the 12A in our RX7. It just wanted and loved more revs. I drove it for a few days until the weather improved and I could redo it. I was a bit disappointed after the repair. It was a lot of fun driving it with the cam retarded.

[240260280]

Nope. Distance and tension are not the same. When you take up the slack by rotation change of the sprocket, there is less chain under tension between the sprocket and the crank on the drivers side, so there is more chain under slack on the passenger side. . It is a bit confusing as there are many teeth grabbing the chain at the same time and it is continuous.  An easier way is to  think of the chain as a string tied to a fixed crank. When you go from 1 to 3, you are pulling tighter on that string so the excess string falls behind the puller on the slack side. 

For an observer working from the top of the engine like @siteunseen did, moving the sprocket from 1 to 3 while keeping the crank at TDC, it appears that the chain is getting tighter but this illusion is because they can not observe the resultant extra slack hidden inside the timing cover area.  For an observer like @Captain Obvious with the timing cover exposed, they can see they are making more slack and the tensioner is protruding more to correct it.

See it is special relativity and is dependent on the viewer ?

Edited September 15, 2019 by 240260280

[siteunseen]

Another true or false question.

Can a timing chain be too tight and cause HP drain?

I can't remember if I got the chain on then tightened the guides as far out as they would go.  I do remember a rubber like washer that went between the plunger and the housing.  It was a ZX timing kit with an extra adjustment or two, IIRC the guides were hard to line up to the 2.4 block. 

[Zed Head]

The tension on the chain comes from the tensioner spring, when nothing is moving.  It's not much, I think it's mainly to keep things tight until oil pressure takes over.  The straight side tension during operation comes from the crankshaft gear pulling it tight.  Slack side tension comes from oil pressure in the tensioner.

Rotate the camshaft forward or the crankshaft backward and you'll see the slop appear on the straight side.  Chain tension on the loose side will push the tensioner back in its hole and the slop will end up on the straight side.  That's how you can end up with confusing cam timing marks.

That's my understanding.

Kameari makes a pretty cool adjustable tensioner.  https://www.thezstore.com/page/TZS/PROD/10-5452

 

[240260280]

You can see the evolution of the tensioner position on Nissan engines. Thanks to @Carl Beck here: http://zhome.com/History/LSeries/LSeriesR1.htm

The inspection plate on the top seems like the tensioner was going to be placed behind it but it was later moved lower.

 

 

[madkaw]

9 hours ago, Captain Obvious said:

@madkaw, another question... What is "a bunch"?

Did you advance it to bring it back to stock timing, or did you go beyond that and advance the timing past the original stock settings?

I was running 8 degrees in advance and wouldn’t have minded some more . Running the ISKY 290 duration put the power band up pretty high. About 4K+ is where she started to really “ come on the cam “! 

 

[siteunseen]

5 minutes ago, madkaw said:

I was running 8 degrees in advance and wouldn’t have minded some more . Running the ISKY 290 duration put the power band up pretty high. About 4K+ is where she started to really “ come on the cam “! 

 

Doesn't each hole on the cam sprocket increase advance by 8 degrees?

[madkaw]

1 minute ago, siteunseen said:

Doesn't each hole on the cam sprocket increase advance by 8 degrees?

No - I believe it’s 4 . I was running an adjustable anyway . 

[madkaw]

10 hours ago, grannyknot said:

While there are so many good minds talking about this subject I would like to ask a question about a timing fact/myth I've heard many times. 

Starting with a new chain, by deliberately advancing the cam gear to #2 or #3 you can gain more low down torque. True or false?

Bruce, this is one of those great lines that should be permanently fixed to bottom of each post regardless of whether you are right or wrong

I would say true. Closing the intake valve earlier will get some low end grunt . 

[Captain Obvious]

10 hours ago, 240260280 said:

For an observer working from the top of the engine like @siteunseen did, moving the sprocket from 1 to 3 while keeping the crank at TDC, it appears that the chain is getting tighter but this illusion is because they can not observe the resultant extra slack hidden inside the timing cover area.  For an observer like @Captain Obvious with the timing cover exposed, they can see they are making more slack and the tensioner is protruding more to correct it.

See it is special relativity and is dependent on the viewer ?

I disagree completely. I do not believe it depends on the perspective of the viewer. I say that the tension on the chain is independent on which cam index hole 1-3 is used.

Would you believe me if I took some pics? I'll put the gear in position 1 and take a pic of the tensioner. Then I'll move the gear to position 3 and take another pic of the tensioner. My belief is that the tensioner will look identical in both those pics. I say the plunger will be the same distance out regardless of what hole the cam gear is in..

If I show you, would you believe it then? What say ye?  Haha!!   @240260280   I challenge thee to a geek-off.    

[Captain Obvious]

2 hours ago, siteunseen said:

Doesn't each hole on the cam sprocket increase advance by 8 degrees?

Nope. What he said. It's four (crank) degrees per position change:

[siteunseen]

21 minutes ago, Captain Obvious said:

Would you believe me if I took some pics? I'll put the gear in position 1 and take a pic of the tensioner. Then I'll move the gear to position 3 and take another pic of the tensioner. My belief is that the tensioner will look identical in both those pics. I say the plunger will be the same distance out regardless of what hole the cam gear is in..

Finally! 

1 zip tie.