The V8 Owners Forum -

I’m trying to install a JP chain and gear set (JP 5984 RPi) for a Rover v8 3.9l. I’ve installed a new Crower CAM and had the crank reground and the measured crank end play was ok. When I look at both timing gears (on crank and cam) from the side you can see and measure that the smaller gear on the crank is closer to the front face of the block than the larger cam gear. This difference is a bit less then 1mm. See photo attached.

Is this (mis-)alignment done on purpose the keep the cam back in his valley or do I have a problem?

Many thanks for your help.

Kind regards,

Frank de Kleuver
The Netherland - Europe

Hi Frank,
I don't think this is done on purpose. The gears are normally in line and the drag from the oil pump tends to keep the cam "in the valley" as you put it.

Assuming the gears are the correct way round and you have checked that the cam is snug against the block, the fix would be to introduce a shim behind the small gear.

It's seems you have been unlucky with all the normal tolerances.

Regards Denis

I've measured and compared some dimensions of original Rover parts from the old engine. They are worn but I think the numbers are good enough for comparison.

Cam thrustface/plate thickness - identical
Distance on crank between but thrust faces of the center bearing and the timing gear thrust face - identical (for 3.5l, 3.5l, 4.0l and 4.6l)
Offset CAM gear VERSUS Crank gear is:

- for a Kent Cam chain set 0.0 mm
- for a Standard Rover set (3.5l) 0.0 mm)
- for the JP Timing set 0.35 mm

The difference between the CAM thrust face and the Crank thrust face is approx. 0.85mm

This in combination with the already 0.35mm of the JP timing set give a whopping 1.10mm misalignment which can be spotted by eye.

Now I can do 3 things;
- Shim the Crank gear (pain in the butt because of the inner radius at the crank thrust face)
- Machine the CAM gear which upsets my Thrustbolt setting
- Turn the CAM gear front to back. The offset at the front is aprox 1mm larger than at the back so will align my gears nicely.

But can this be done in regards to the teeth of the gears. They look symmetrical but at closer inspection you can see small differences in the angles of the teeth when looking at the gears from the side. I've mailed JP if I can turn over the CAM gear but no response jet (to soon)

The only thing I didn't check is the dimensions of the block itself (center bearing to front face)

Kind regards,

Frank

Hi
If they are new then the teeth should be symetrical, you should certainly be able to treet them as such, however have you tried contacting the people who sold you this set as it sounds like a manufacturing error, ie someone stamped up the wrong face when they made it
Best regards
Mike

I bought it from a guy that stopped with his hobby. He hat it sitting on a shelf for a couple of years. It was still in it's plastic blister packaging.

He bought it from RPi

So no invoice, no nothing ...

I'll try to make a close-up of the teeth.

Kind regards,

Frank

DEVONMAN wrote:Hi Frank,
I don't think this is done on purpose. The gears are normally in line and the drag from the oil pump tends to keep the cam "in the valley" as you put it.

Assuming the gears are the correct way round and you have checked that the cam is snug against the block, the fix would be to introduce a shim behind the small gear.

It's seems you have been unlucky with all the normal tolerances.

Regards Denis

Thats what just came to my mind Denis. One of the cogs on back to front maybe ?? Just a thought

I've checked if one of the gears were the wrong way around.

Also I compared my gears to the photo's on the RPi website and this would confirm that the marking is not at the wrong side. Or we both have ;-(



Crank gear


CAM gear



What do you think.....could I just flip over the CAM gear with these teeth?

Kind regards,

Frank

JP gave me the following numbers, but I'm not sure what the difference is between offset and counter bore and between a gear and sprocket. My technical Englisch is not good enough I guess. I'll do some homework.

"The teeth angle does not change but there are other reasons I would not recomend turning the cam gear around.

The JP5984 crank gear when facing the block has a counter bore of .015"

The JP5984 Cam gear when facing the block has an offset of .045"

The cam sprocket front face has an offset of .007".

When fitted correctly onto our 3500 block the Cam and Crank Gears line up perfectly"

They try to help and react to my mails within a day

Hi
I'll try and help with the terms used.
A gear is a round thing with teeth where the teeth mesh with and push against other teeth on another gear to transpher load.

a Sprocket also has teeth, but these engage with a chain that in turn transfers load/power to another sprocket.

The JP5984 crank gear when facing the block has a counter bore of .015"
a counter bore is a hole (bore) that is at the end of another hole, larger i size and usually gives onto a shaft inserted in the first hole (bore). . . generally a hole is in the ground/ water pipe /your trouserd, it is not always a precise round shape use is poorly defined and use is imprecise . A bore is generally round (unless otherwise stated) of a designed shape and has tollerances, it will often have another component that fits in it to form a system, it is an engineering term (generally) and generally it's use implies all of the above.
People often use gear when they should use sprocket (as in the case here)

The JP5984 Cam gear when facing the block has an offset of .045"
He means that the Sprocket is .045 inches out of alignment with the other sprocket (sticking out too far?)

The cam sprocket front face has an offset of .007".

It needs .007 inches machining off the front face.

When fitted correctly onto our 3500 block the Cam and Crank Gears line up perfectly" You need to find some shims.

Looking at your pictures I would only mount them with them this way round in relation to each other, the teeth are not symetrical and reversing one relative to the other would increase wear rate. I would also tahe a piece of 800 grit (very fine) emery cloth and go round each tooth and give it a light polish to remove the rather nasty machining swarf and edges from each one (about 10 - 15 seconds rubbing per tooth edge).
I hope this is of some help. If you don't understand a term or use of a word or phrase it is always good to ask, it also gets me thinking about using the right terms and it is very easy for me to be sloppy.
Best regards
Mike

Frank.
I believe you have fitted a standard set to your engine and the sprockets lined up ok.
If that is the case then there is nothing wrong with your engine and the fault must be with the JP set.

I have inspected a new set (Cloyes true roller type) and the teeth shapes are machined symmetrical so it should make no difference which way the sprocket is fixed. I note JP's response which confirms this in their first line.
I think your close up pictures of the teeth give a false impression of the teeth as I assume they all have a machined chamfer on both sides.
Your pictures make the teeth look like rough castings before machining.

If the cam sprocket is in line the other way round then if it was me I would fit it that way round and punch a new the timing mark. (Sorry to disagree Mike).

It would be good to establish the reason for your problem but that would need someone to measure another JP sprocket.

Regards Denis


l

I'd agree with the teeth being symmetrical when new.

Ages ago, I bought a steel set off RPI and a new cam, and the dots couldn't be made to line up. Exactly in the cracks between teeth. Never did discover what was wrong - either wheel keyway, or the dots.

Hi Denis
Disagree all you like mate it is fine with me , I have been wrong many times before and will be again in the future. . However I will stick to my belief that those teeth are not symetrical and are in need of a bit of cleaning up before use.
Best regards
Mike

They look rounded on one side and angled on the other dont they??

mgbv8 wrote:They look rounded on one side and angled on the other dont they??

They certainly do.
I think it's a trick of the camera due to the fact that the camera is so close to the object and not showing a true parallel image.

If Frank could look at the teeth and clarify if they are symmetrical to the naked eye.

Regards Denis

Hi,

They are indeed rounded at the rights side. The left side is straight.

Sorry for the slow response but I was up all night. And hitting 42 years that's not that easy anymore

Tomorrow more...

Frank