Timing Chain sets

[BobND]

I have two 6.2 timing set projects going on, a DSG gear set, and another engine on which I am replacing the timing chain set.

After some of the posts on this board about a timing change after the installation of a new timing set, gear drive, or gear (sprocket?) and chain set, I decided to do a simple check of two new timing sets against each other, and against the used, stock gears.

I used a long piece of square keystock to match up the keyways of 4 crankshaft gears. As you can see from the photos, one of the gears is WAY OFF from lining up with the others.

(The 2 new timing sets are fresh out of the boxes, and supposedly direct replacements for the oem sets, they are not "spec'd" to alter timing.)

http://ndtc3500.stellarnet.com/~blweltin/Bob/timing%20gears1.jpg

http://ndtc3500.stellarnet.com/~blweltin/Bob/timing%20gears2.jpg

http://ndtc3500.stellarnet.com/~blweltin/Bob/timing%20gears3jpg.jpg

I figured perhaps the camshaft gear was also "off" to compensate for the crank gear, but as you can see in the photo of the cam gears, the teeth all line up pretty closely, compared to the crankshaft gear.

I realize installing each set, and "degreeing" the cam would be a LOT more scientific, but it is clear from the photos differences between sets DO occur. I really should take the time to install and degree all the chain drive sets, and the DSG gear drive.

The Melling crankshaft gear that is "off" from the others is "off" in the "cam retarded" direction.

I can't say just what the error is, degree-wise, but it seems it would be significant, and perhaps some of you guys that have had problems with setting the pump timing after a timing set replacement have run into this, also.

I wonder if it is intentional on the part of the gear manufacturer, or an "out of spec" part?

[john8662]

Great work Bob,

You've confirmed something I've thought about Melling Engine components. I have had little success with Melling products, besides oil pumps.

I really don't like to see that the gears were off that much!

The sealed power seems to be pretty close to OEM.

J

[Warren96]

I couldnt even guess how far off that Melling Crank Gear is off compared to the others!! Does Melling make any claims of "..advanced timing right off the crankshaft.."???

[BobND]

Originally posted by Warren96:
Does Melling make any claims of "..advanced timing right off the crankshaft.."??? AFAIK, that set is sold as a direct OEM replacement.

And it would RETARD the cam.

There is another problem with that set. I will post a photo later.

Funny part is, the used OEM gears are marked with an "M" with a circle around it. Isn't that Melling's trademark?

Did they "forget" how to make the gears?

[CleviteKid]

Well, ya see, Ol' George in the sprocket department retired a couple of years ago, and things just haven't been the same. Seems no one else knows the machines like Ol' George did . . . . . ;)

Dr. Lee :cool:

[More Power]

Diesel Services Group advertised a built-in timing advance for their gear sets... This would explain what you're seeing. If so, it would add timing to both the cam and injection pump. The pump timing advance can be compensated for, but perhaps someone with performance engine experience can explain how a cam timing advance of a few degrees affects overall engine performance.

I know DSG did a lot of dyno work during the development of their gear sets.

Jim

[chickenhunterbob]

I wonder though, (and sometimes this gets me in some trouble) that the real time work of the chain is when it is running on the lower part of each cog, or the valley of the cog on the sprocket.

It's hard to say, but the bottoms of each appear close enough.

Then again, I may be out to lunch, hope they can hire George back if that is the case ;)

[Bobbie Martin]

The difference in the gears shows why degreeing the cam is so important. There are production tolerances in all the components and even more so with some reground cams. In all our Mini engines, we always set the cams to within 1 degree. On the 6.5's it may not be so critical.
Generally, advancing the cam gives more low end power and retarding gives more high end. Here is some good reading on Cam Timing. (http://www.babcox.com/editorial/ar/eb90252.htm)

[MaxEgli]

Hy,
When mounting a DSG Dual Idler Set on my 1983 6,2L with banks Turbo, I noticed a difference in the cam gears (about 1/2

[DmaxMaverick]

I've always thought of Melling to be at least "in the middle" when it comes to quality parts.

If the cam was off by the same amount, it might offset the difference, and might in fact, be right on. It is good practice to replace these parts in sets, and you shouldn't mix brands, which could be an angle.

On the same note, these engines are so sensitive to anything outa' whack, they really don't need help with inferior parts. Just the same, the variance may be well within spec, whatever that could be. What is the translation of the crank sprocket to the cam? 2:1. If the crank sprocket (or gear) is off by .5

[BobND]

Here's another photo of the timing gears.

http://ndtc3500.stellarnet.com/~blweltin/Bob/tooManygears.jpg

The cam gear from the Melling set is not machined on the front face, where the lower IP drive gear mates up to it.

As a matter of fact, there is actually a raised bump in one area the prevents the lower IP gear from seating tight and true, against it.

I will be returning the Melling set to the supplier.

I wish I knew of an email contact at Melling to forward these pictures to.

Either this set slipped through quality control, or they do not realize the face of the gear needs to be machined true because the lower IP drive gear butts against it, and would wobble badly, if set up against this gear!