Horizontal misalignment of JP timing gear

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Fri Mar 02, 2012 8:07 pm

Many thanks for all your help. Tomorrow I'm have the most of the day to play with the engine. I've a couple of older block laying around and I'll try to find why this has a misalignment.

To be honest I don't really get the numbers JP gave me. I now know the terms (thanks for the help) but if I do the measurements I only recognize one number.

I've spoken to some people and the general consensus is that it's not advisable to flip the cam sprocket over because they are not symmetrical.

Still a little voice in me tells me that it won't matter that much but I don't want to risk it. Tomorrow I'll measure the misalignment exactly and I'll measure a vernier sprocket set from Kent Cams that I have for my next project, the 5 liter

But first things first... tomorrow we're going to tackle the mystery of the CAM sprocket and we're going to try to dregree in the CAM. This is for me the first time so I'm excited.

Kind regards,

Frank

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Sun Mar 04, 2012 1:45 pm

I've done my measurements with a feeler gauge:

JP stated:
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".

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 Crower 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

DEVONMAN · Post by **DEVONMAN** » Sun Mar 04, 2012 2:12 pm

Frank,
Hopefully you haven't got the runt of the litter.

I believe the teeth should be symmetrical.
If the teeth were machined (chamfered) on a wheel having an incorrect offset then the teeth would end up unsymmetrical.

This is a possibility.

Hope you get some joy from JP

Regards Denis

DaveEFI · Post by **DaveEFI** » Sun Mar 04, 2012 6:59 pm

Could anyone explain the theory behind asymmetrical teeth?

sidecar · Post by **sidecar** » Sun Mar 04, 2012 7:04 pm

DaveEFI wrote:Could anyone explain the theory behind asymmetrical teeth?

Yeah....bad machining!

kiwicar · Post by **kiwicar** » Sun Mar 04, 2012 7:33 pm

JSF55 · Post by **JSF55** » Sun Mar 04, 2012 8:43 pm

DaveEFI · Post by **DaveEFI** » Sun Mar 04, 2012 11:32 pm

And there was me trying to be polite.

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Mon Mar 05, 2012 6:58 am

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

kiwicar · Post by **kiwicar** » Mon Mar 05, 2012 9:58 am

Hi Frank
I think you will find that there is no such thing as "too much single malt" you may find that for some strange reason ocasionally the evening was just a little short.

Best regards
Mike

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Wed Mar 07, 2012 6:53 pm

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

sidecar · Post by **sidecar** » Wed Mar 07, 2012 7:14 pm

Have I missed something here? How come they will reply to your question about flipping the sprocket round yet you have not asked them or they have not answered why the sprockets don't line up?

I think that you could file of the sticky out bit on the casing by the way.

Did I mention that I don't like thrust buttons!

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Wed Mar 07, 2012 7:28 pm

The problem is that I'm asking more than one question in the mail. This because they are 'down under' it takes 24 hours to reply since they are asleep when I'm typing.

What happens is that they answer one of the three questions. It's like a kind of game

But my last mail I've only asked one question (again). That if I could solve all the issues regarding flipping over the sprocket if it would be allowed because of the shape of the teeth.

We'll wait and see. Every time it's a race for me to find solutions during the week so I can continue working on the engine one day in the weekend with my son.

But building an engine without issues is no fun either

Kind regards,

Frank

unstable load · Post by **unstable load** » Fri Mar 09, 2012 5:18 am

It could also be that they are hoping the main question of what to do about the gear misalignment will go away and save them the cost of fixing it.....

Frank.de.Kleuver · Post by **Frank.de.Kleuver** » Fri Mar 09, 2012 6:45 am

It looks like it.

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