timing camshaft

[grape]

Anybody actually checked the lobe centers on their cam after a timing gear install, or new chain install? Just curious

[grape]

shocking..............no answers :rolleyes:

[JoeyD]

Have you?

[grape]

Originally posted by Joey D:
Have you? umm, of course, why would i ask if i haven't?

[Bobbie Martin]

Are you talking about only GM diesel cams or any cam? No on the first, yes on the second. Why are you asking?

[JoeyD]

It's a game he plays. He is looking for an edge in life

[dieseldummy]

Does it really matter? We only have a very small margin of clearance before the valves are implanted into the piston so anything more than stock is bad and anything less is bad.

[Dvldog 8793]

Howdy
Just wondering...Why would you ask if you have? Seems like if it was valuable info it should be posted and skip the I/I...

a few years ago did you have pictures on your web sight of a front mounted IC that was a work in progress? If so how did it pan out? Any problems with added heat to the cooling system?

L8r
Conley

[john8662]

I'm curious what checking lobe centers is all about?

I recently assembled a 6.2 engine and have put no further thought into whether the roller on the lifter is going to be centered on the camshaft lobe. There is, however, a certain amount of endplay on the camshaft that allows the cam to walk. Fortunatly, in the design of these engines a plate is added to one end of the camshaft that keeps the cam from walking much, but only the amount of endplay, which is controlled by the thrust washer below the key on the camshaft.

[rjschoolcraft]

What he's talking about is the angular position of the lobes on the cam shaft. What he's worried about is the valve timing relative to the crank/piston position.

In racing applications, this becomes very critical (especially very high rpm applications). The tolerances allowed in normal production are inadequate for racing so engine builders check and adjust the cam/valve timing to optimize it. This is usually done by making an oversize hole in the cam gear/sprocket so that a plug with offset hole may be inserted to adjust the timing of the cam to the crank. I'm sure you've seen degree wheels in hot-rod magazine photos before. The slang term for this is "degreeing in" the cam.

I'm probably wrong, but I didn't think it was that critical in an engine that turns 3500 rpm max. However, as picky as I was with everything else I did on this project, I probably should have checked this. Especially since The Lone Ranger is playing cat & mouse about it. He's probably found that the cam timing is off by quite a bit.

I doubt that he will report what he has found, however.

I just had the front cover off to fix an oil leak. The bolt holes had stripped where the pan mates with the front cover. Pulled the cover to repair the threads with inserts and re-seal. Should have checked it then. Oh, well.

[john8662]

Thanks Ron!

I'm familiar with degreeing the cam, haven't done it myself but am familiar with whats going on.

Why couldn't he just say that in the first place, afterall being involved the "racing" -Rhetorical Question.

I agree, no worry at our RPM, I've run these engines ~4100 - 4300 though (DB2 6.2 governor).

[grape]

Originally posted by dieseldummy:
Does it really matter? We only have a very small margin of clearance before the valves are implanted into the piston so anything more than stock is bad and anything less is bad. That's why i asked, to see if anybody had found out for themselves what they had room for. I'm just trying to get a grasp on how much real engine experience the people here have that are telling me how to do things. I have over 20 degrees more intake duration and .060" lift and still have over .040" between the intake valve and the piston at the closest point. However, put a gear drive in that advances the cam 2 degrees and it will crash.

[rjschoolcraft]

Using a stock cam so I have no trouble. With your custom cam that's different.

I'll be interested to see how much effect your cam changes make for your effort. My bet (and it's a pretty good one) is that in the world of turbo Diesels the bang for the buck is not very big compared to the parameters of boost and fuel.

But what do I know?

[john8662]

Somewhat related,

The Diesel Depot offers a custom cam for these engines that changes the duration in the valve timing. To use the cam, requires degreeing the cam to their specifiation, and using decompressed pistons. If the cam is not degreed and standard height pistons are used, there is a possibility of interference between the valves and pistons.

So, I'd bet part of the interference possibility comes in when using the gear drive, due to the advanced timing built into the cam gear on the drive. Using a chain would probably not cause the problem.

[G. Gearloose]

Peculiar, I thought the advance was only machined into the reluctor, no the gears.

[dieseldummy]

I can say that I've ran Avant's reground cam and they never mentioned measuring anything or setting it at a different angle. I had no problems with it either when timed like the stock cam and with high compression pistons. I think that most of the gain from a custom cam will be in EGT releif and not necesarily in power.