Cam Timing Guru: Advanced vs Retarded?

Post by **cn90** » 10 Dec 2012, 11:36

Hi guys,

Just curious what you guys do for your cam timing:

* Your year/model: _____

* Intake Cam: advanced vs retarded: how many degrees?

* Exhaust Cam: advanced vs retarded: how many degrees?

This is the thread that I am referring to:

Check your cam timing
https://www.matthewsvolvosite.com/forums ... =5&t=22124

Photo:

Post by **Ozark Lee** » 10 Dec 2012, 16:21

Matt tried to salvage as much as he could from the Quick Brick Motorsports website after they went Tango Uniform.

I've always just centered the bolts in the slots and gone on with life but it is an interesting topic.

https://www.matthewsvolvosite.com/adjust ... iming-tool

...Lee

Post by **jimmy57** » 10 Dec 2012, 17:43

I advanced intake cam only on my two 95 960's (one deceased, one sold now). The low end torque gain was very noticeable and MPG was improved 1 MPG. high RPM power suffered but I never had an issue with that given the daily usable power was so much better.
The intake cam was rotated about 1/3 the slot distance and bolts retorqued.

Post by **cn90** » 10 Dec 2012, 19:03

Thanks Lee and jimmy,

I also read IPD cam adjustment. See the pdf.

Yes, I read the whole thread by QBM with interest. QBM said this:

In general, advancing the camshafts improves low-end power and response. Likewise, retarding the camshafts generally improves top-end power and response. Not all engines are the same however. You should experiment with advancing or retarding to see what works best for your particular setup.

So, for the sake of experiment, I set BOTH cam sprockets to full retard condition, i.e., when the bolts are loose, I turned BOTH cam sprockets Clockwise until they stop. Then tighten the bolts.
This is full retard position.

Low-end torque is decent (BTW, I have brand-new spark plugs, cap/rotor/, Bougicrod, part of Stage zero process!).
High-end torque is very good.

So I am tempted to leave it alone the way it is (Also I am "lazy" and don't want to remove the hydraulic tensioner and re-compress the thing to bring the cam back to neutral position!).

This is my current cam setup, note that BOTH sprockets are in retarded position.

: VolvoTB10.JPG (115.92 KiB) Viewed 6826 times

Post by **erikv11** » 10 Dec 2012, 20:06

Read the pdf from IPD. Cam timing (pun intended

!!) is usually adjusted on an assembled vehicle, without touching the tensioner. You actually don't rotate the sprockets either - you just pull the cap and the CPS, and rotate the cams while the sprockets remain still.

Post by **cn90** » 10 Dec 2012, 20:22

Yes,

I understand that part but the IPD instruction is for people with cam in neutral position and they need to tweak thing a bit here and there, in that case, no need to remove the TB.

In my case, the sprockets are fully retarded, so to set it back to neutral, I think the TB needs to come off because it is about 1 tooth that needs to be adjusted. I may be wrong but this is what I understand.

With the sprocket boltss loose, you can see it rotates (because of the oval slot for the bolt) a full 2 teeth.

Post by **jimmy57** » 10 Dec 2012, 21:26

You do know that centered is not neutral, it is just centered. The bolt holes drilled on end of cam for gears are randomly placed.
The gears are fitted at factory and belt is fitted with cams locked and as long as the bolts aren't touching the ends of the slots when the belt is tensioned that is where the bolts end up. There IS NO referencing of the bolt to the mid range of the slots as the random location of the three tapped holes is random. The size of the size of slots on gears is wide enough to accommodate all placements of the three holes on cams. The last thing done is the scribing of the marks on gears after setup is completed.

Post by **erikv11** » 10 Dec 2012, 22:13

Hmmm interesting. Here's some food for thought:

42 teeth per cam gear (did I count right?)
so (360 degrees) / (42 teeth) = 8.57 degrees per tooth.

The amount of adjustment on the cam slots is 15 degrees, ±7.5 if the bolts were in the center when it left the factory (I know, that is arbitrary and maybe they weren't). So if you now rotated the cams so both sprockets went all the way the other direction, you should be moving them exactly 1.75 teeth, yes! But back to the middle would be just under one tooth (7/8 of a tooth).

So in the picture up there of your engine, I can see the cams are not yet in the timing position (they are a little cockeyed) - is the crank not on the mark even though the sprockets are? In that case, when you do put the crank on the mark, how far off are the cam marks? If the crank is in fact on the mark, then how far off are the cam marks when the triangles are in the home position?

In other words, how many teeth is it off right now, just by observation? Would adjusting the cams back make it better, or worse?

Post by **cn90** » 11 Dec 2012, 01:38

erikv11,

You are correct, about 8.57 degrees/tooth.

Actually this is it:
The Cam timing marks are on (it depends on the angle of the camera)
The Crank mark is on.

I did all these cam adjustments AFTER the cam seals were replaced, but BEFORE the TB was installed.

Car runs just fine, so I am planning on leaving it alone.

Post by **jimmy57** » 11 Dec 2012, 05:28

Were the cams locked when you did this?