Engine and Transmission Tech

Dear all,

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

Frank, Any measurable misalignment will only tend to accellerate wear on the chain and sprockets. How is alignment when you flip-over the crank gear ? Is the cam gear absolutely 100% seated on cam ? What does JP say ? I would compare thickness of flange for Crower cam vs. oem. cam. good Luck, roverman.

I've checked the distance between the thrust face of the middle crank bearing to the thrust face of the crank nose with this crank and a 3.5 and a 4.0 I had laying around and they look identical. Both gears are nicely making contact with both the crank and cam. And also the cam is sitting all the way in it's bearings and making contact with the front of the block.

I'll check the thickness of the CAM flange of an old CAM. I have an old early type and a SD1 type laying around. I'll also flip the gears around and check again. Now I can read both alignment markings from the front.

I mailed JP and they just said that this gear set was for a 3.5 and I have a 3.9 so that should make up for the difference. I also will try to check it on my old 3.5 SD1 block but I have to install a crank first..... and on my sons table :-)

But before I did this I was wondering if it was on purpose but as you mentioned it would just quicken the wear on the chain and gears. I'll keep you posted.

Kind regards,

Frank

WOW! Nice table.......

Jac

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

These are some pictures of the teeth. They don't look symmetrical.
CAM Gear


Crank Gear


JP Timing set

Frank, The chamfers on sides of teeth are not as critical, as actual side locations of teeth. I would flip the cam gear and check actual side of teeth locations. The chamfers are only "guides" to assist for/aft location of chain. Cheers, roverman.



Edited 1 time(s). Last edit at 02/29/2012 04:10PM by roverman.

Roverman,

I was hoping somebody would say that :-)

As soon as I'm able I will check if flipping it will bring the teeth sides at the same point. As you can see, the teeth have a straight chamfer on the left side and a rounded off type on the right. This got me worried somewhat flipping the thing over.

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

I've done my measurements with a feeler gauge:

JP stated:
The crank gear when facing the block has a counter bore of .015"
The Cam gear when facing the block has an offset of .045"
The cam sprocket front face has an offset of .007".

I've measured:
The crank gear when facing the block has a counter bore of .045"
The Cam gear when facing the block has an offset of .015"
The cam sprocket front face has an offset of .007"

When I install the cam sprocket backwards all align perfectly.

I've measured an old 3500 engine and found a similar offset on the crank versus cam trust face. These parts are all worn but not excessive.

Conclusion:
- Normal offset crank versus cam trust faces would be .045-.015=.030" (.762mm). Seem right on both my engines (3.9 with machined crank and new Cam and 3.5 with all original worn parts)
- This chain set is incorrectly machined in regards of the numbers JP gave me.
- If the chain set machined incorrectly and installed normally this would result in a offset error of .045-.007=.038" (.9652mm). This was approx. what I had.

Now I'm waiting on final confirmation of JP if I can flip the cam gear only in regards of the way the teeth are machined.

Kind regards,

Frank

Sorry, I made a mistake when stating my measured numbers. The conclusion etc is still correct (I hope)

I've measured:
The crank gear when facing the block has a counter bore of .015"
The Cam gear when facing the block has an offset of .007"
The cam sprocket front face has an offset of .045"

So back and forth of the CAM sprocket is flipped.

Sorry for the mistake. Too much Single Malt can do that you know :-)

Kind regards,

Frank

JP gave me the following info regarding why not the flip over the CAM sprocket. They didn't react to my question if it was ok to do this regarding the shape of the teeth. In their earlier mail one could conclude that's ok but I asked for a confirmation. They also didn't react to my measured clearance numbers.

They are very helpful and normally react with 24 hours.

The reason they advise not to install the CAM sprocket backwards is because of a recess in the front of the CAM sprocket that acts as a thrust area for a small boss in the casting of the inner side of the timing covers.

Since I'm using a thrust bolt on the CAM nose I thinks this can be removed. Is this correct?



Kind regards,

Frank

Have you tried flipping the crank gear the other way?

Sadly the crank sprocket has a very large offset and also has a recess machined at the engine side to accommodate the inner radius at the crank contact area.

Kind regards,

Frank

I now have an answer on my question; "Since I'm using a thrust bolt I don't need that casting thingy. So if I would find a way around it is it allowed to install the cam sprocket only because of the shape of the teeth?"

Last night I got the following answer:

Question:
I'm using a thrust bolt on the cam nose to prevent horizontal cam movement. See attached picture. The nylon head has a almost no clearance with the inside of the timing cover by maching this bolt down a small bit at the time.

If this casting thingy is mend to be a kind of thrust area than I can remove it from the timing cover.
But if I can find a way around this problem is it allowed to flip only the cam sprocket because of the shape of the teeth?

Answer from JP:
Hi Frank,

the gear teeth are cut the same on both sides.

So all I can say is "Good luck"

Regards

I'm thinking to remove or machine down the casting thrust area and risk flipping the thing around. I had a good look at a timing chain set from Kent CAMS and their teeth look symmetrical. Combined with the statement of JP I may conclude that the unsymmetrical teeth of the JP sprockets are unintentional.

I've installed the set and degreed in the CAM compared to the Crower Cam .050" angle numbers and everything is aligned spot on and it turns nicely by hand. I know this is not a guarantee.

Kind regards,

Frank

Frank,
I have also the timing gear and chain from JP so now I was wondering if I have the same misalignment. I have a 3.5 rover and standard cam. I checked the alignment but cannot see anything wrong. Both gears line up perfect. I do have a question. Do I need the button to keep the cam from moving forward and if so where can I get this button. Is it in delrin or metal ?
Also looked at the shape of the teeth on the gears but they look the same on both sides.
Bought the set at RPI on one of my many trips to the UK from the USA for work.
Hope to be back there in april 2013.
Werner

Hi Werner,

If they align well than everything is fine. There are two ways that I know to keep your cam for going forward during for example idling.

The thrust bolt can be made yourselves by using a cam bolt and drill and tap for a nylon bolt to be inserted and machined back to a nice round head.

Also you can machine your block to take the cam retaining plate but you can drill into your oil ways when not done right.

I bought my thrustbolt from v8tuners in the UK. v8tuner.co.uk

Grt

Frank

Frank,
What distributor are you using ?