Amazon: Cam Gear Nut loose and Gear Moves

[gothamus]

Recently I noticed some increased engine sounds that I initially thought was a valve clearance issue. After being away, starting the car and taking off from idle, the sound was clearly defined to my ear and I suspected the cam gear, having read articles about this another time.

Removing the timing gear casing it was confirmed. The cam nut was backed off the gear about 2 turns. The cam gear was in the correct position. Then, as I was rotating the crank in order to verify the timing gear marks correct alignment, the cam gear suddenly moved forward about 5mm. As I continued to turn the crank it moved forward another 5mm, both in what appeared one motion. As the markers came into alignment the gear slipped back into place and correctly aligned.

One observation that may or not be typical condition of the engine rotation. In the rotation of the crank, after the point where I think the engine reached tdc, the crank turns much easier. As after the pressure on 2 chambers causes resistance, then some weight falling and free gaseous flow speeds the revolution. It is at this point I observed the cam gear move forward.

Details- I have an aluminum cam gear. B20e engine

(1) Should I just put that nut back on (with Loctite green and 75-85 lbs) and carry on, relieved to have caught the problem before catastrophe?

(2) What does anyone make of the gear moving forward at 2 points in the turn and then back into place a little later?

(3) Does the nut exist to counter gear movement that is expected like this? I will probably be checking it again in about 200 miles in order to ease my active mind.

*For an earlier post with relevant information that may assist others:
https://www.volvoforums.org.uk/showthread.php?t=250654
A helpful article from Ron (thanks):
http://www.sw-em.com/Timing%20Gear%20Notes.htm

[arcturus]

First of all how was the nut allowed to move loose in the first place.There should be a fairly thick washer between the nut and gear and it should be tabbed over.This should prevent the nut from rotating loose. The oil pump gear mesh with cam shaft should prevent the whole cam from lateral movement. The nut also has one flat face (highlighted in white) which should but flat to washer. The cam nut needs about 100p.lb torque tightening.The photo of gears shows the nut curved back face. Looks like sloppy assembly but this is only my opinion without a fuller exam

[mocambique-amazone]

1: 75-85 lbs is waaaay to much, maximum 60lbs!!! Loctite green isn't good enough, use Loctite red instaed. Loctite 262
2: should be as is on your car. Result of non even drag of the cam and the slant cut gears
3:the nut should fix the gear to the camshaft, nothing else. There should be no movement of any direction between the gear and the cam

clean the thread and the nut and fix it with Loctite 262 and maximum 60lbs. Let it sit for 24h to give the Loctite a chance to do the job.
If you want to remove the nut later you have to add heat, around 250°C, to destroy the red Loctite.

Good luck Gothamus, Kay

I saw a few cracked of threads of the cam by tightened with 100lbs!!!!

[arcturus]

OK Kay. Official numbers

Whoops, just dawned on me, yours is a B18 /20. My advice was for B16

B18720 Second one is B18

[Ron Kwas]

Richard;

I have observed that the threads of replacement Cams are cut very loosely, and this can contribute to the Camnut loosening...we had terrible noises shortly after first Start of a newly reworked engine (that will sink ones throat into ones pants in short order...!), which turned out to be due to the Camnut having loosened and intermittently bapping into the Timing Cover...better that then something more serious...(good thing we took off the Timing Cover before pulling engine again) to correct, we drilled and safety wired Camnut after retorquing to spec. Once Nut is loose Cam can move...no surprise there!...verify nose of Cam has everything including thrustwasher correctly installed...be certain you don't push Cam into engine beyond its normal position while securing hardware at nose is off allowing this...this risks pushing freezeplug out the back of block creating a huge oil-leak from rear Cam Bearing, in-turn necessitating engine removal for access to replace and correct.

After assuring all is correct at nose of Cam, I'd torque Nut back on, and secure it with either a new locking tab plate and thread locking compound or safety wire.

...and now you know what a Camnut bapping the inside of Timing Cover sounds like...!

Good Hunting!

[gothamus]

Washer? What washer!? Haha! I believe you but I didn't have one on the old b20 or this new b20. There are several steps in building where this washer would have gone on it if I had it (timing gear parts bagged together when dismantling, new gear replacement kit, removal of gear from new used engine...). My picture from removing the timing cover from the old engine shows that nut straight on the gear. Hard to be 100% from image. But I pulled out the old cam, gear, spacer and nut then reassembled as I could then compared to image. If the washer is thin and no rim can be viewed looking straight on, then I don't have 100% sure.

Is it a b16 part not on the b20? Or maybe previous rebuilders of my engines did away with washer.

This be a mighty concern and I am digging through my drawers still. Too much stuff!

I like Ron's hole in cam with wire or circlip. Is this difficult to drill with a hand tool and with cam in engine? I suppose I need the stout drill and not my little portable job.

I don't know where I read green loctite. Glad I don't need to buy another color in the loctite rainbow.

[gothamus]

I've been fixated on the cam nut washer. I don't think they went on the b20 engines. I have at least verified installation without from a number of places. The manuals make no mention of it. I found a Noridcar video showing the process for swapping the timing gear and there is no washer between the nut and gear.

So, I wonder why this nut moved forward? How did Volvo think it wouldn't move forward? There is a fix to the problem but no answer for the why. Loctite and drill a hole!

There shouldn't be a need to bang the gear on. I'm surely spooked by the image of the cam coming out the back!

link to cam gear parts with video: https://shop.nordicar.com/en-gb/volv...enas-ring.html

[tdz840]

Originally Posted by gothamus

I've been fixated on the cam nut washer. I don't think they went on the b20 engines. I have at least verified installation without from a number of places. The manuals make no mention of it. I found a Noridcar video showing the process for swapping the timing gear and there is no washer between the nut and gear.

So, I wonder why this nut moved forward? How did Volvo think it wouldn't move forward? There is a fix to the problem but no answer for the why. Loctite and drill a hole!

There shouldn't be a need to bang the gear on. I'm surely spooked by the image of the cam coming out the back!

link to cam gear parts with video: https://shop.nordicar.com/en-gb/volv...enas-ring.html

Hi Happy New Year
Confirmed, no washer on the Cam nut. There is a spacer behind the cam wheel that maintains the correct tolerance between the thrust plate and cam gear.
This may be different for OEM volvo cams but the cams supplied by KG Trimning specify 65pound foot and emphasise it on the box along with loctite green.
I believe there have been several instances of the cam nose thread shearing.
Re the cam gear moving:
Clearly the nut not being secured has enabled this but could the movement be a combination of the helical cut gears along with the oil pump skew gear adding a lateral thrust?
Just a thought but if so suspect the thrust plate/spacer is there to deal with it
Russ

[arcturus]

From VP Auto. Note lock washer

[arcturus]

Originally Posted by arcturus

From VP Auto. Note lock washer

And from parts book.