Cam Eval

Pulled my intake off and took some pictures of my Cam ... what do y'all think? I would dread taking apart the front of my engine to replace it ... I want to drive my Jeep in this weather!

Odd Cylinders are on the left in these pictures:

Cyl 1-2


Cam 5 - cyl 1-2 by Troy Davis, on Flickr


Cyl 3-4


Cam 4 - cyl. 3/4 by Troy Davis, on Flickr


Cyl 5-6


Cam 3 - cyl 5/6 by Troy Davis, on Flickr


Overall view 1


Untitled by Troy Davis, on Flickr


Overall view 2


Cam 2 by Troy Davis, on Flickr

 

Are you asking about wear?.........doesn't look bad from here. the only way to check wear is to put a dial indicator on the tip of each lifter and start rotating and recording the measurements...........hopefully you have a cam card or know the lift of the exhaust and Intake lobes to compare?

 

You already have the rockers off so pull out each lifter and look at the bottom. The high hump part of the cam should be polished with no grooves and the same as the bottom of the lifter.

 

Cool - thanks. lobes and lifters look pretty decent actually ... on the lifters, look at each end for wear and then measure overall length to see if one is collapsed?

 

Manual says use tool W-324 to time leak down of lifter ... what's the best alternative way to test since I don't have tool W-324? Also, does anyone know the lift specs for intake and exhaust?

 

As you have been told, it's sort of hard to determine anything from pictures, measurements are needed.
Back in the '70's I had a few cams go bad in some 198 V6s, it was fairly obvious, no lobe left and heavy scarring on the cam and lifter.
The guy I bought parts from said that the Buick V6 can be known to eat camshafts, somebody else mentioned on this forum that the 198 is worse that the 225 for cam damage.
I just hope both of mine keep running.

 

I have new pushrods and lifters - am going to put those in and keep the old ones and try to "recondition" them. Cam looks OK based on pushrod movement.

 

That doesn't make any sense to me.
Those two engines use the exact same camshaft, valve springs and lifters.

 

I know this,I had to replace 2 cams in my 198's, the 225's I have now seem to be holding up well.
I can't figure it out either. I've been running the 3B with the V6 since 1984, still the vehicle that always starts regardless of the temp.

 

Maybe oiling passages are different between the two?

 

I don't know, the cam lobes would be oiled from what comes off the crank in either case.
I just remember that Big Don at Mile High Jeep Repair said it was a common thing to happen.

 

So, someone correct me if this is wrong but:
I had always been taught that one should not attempt to replace just the lifters on a used flat tappet cam, instead replace the cam and new lifters as a set.
Reason being the wear profile on the cam lobe has changed to match the lifter that ran on that individual lobe.
Additionally, if the lifters are removed for inspection it is important to put them back in the same order they were removed, to keep the same matched lobe/lifter wear patterns.

Don

 

Now that one makes sense to me ....
I would certainly change the lifters if the cam is changed ..
If the cam stays in I would re-use the same lifters in their proper order.

 

Not saying your wrong but it is debatable to me. What I do know is that the lifters rotate when running due to a slight bevel ground into the cam. This allows lube to enter between cam lobe and lifter. That being said I don't see how one rotating lifter would wear any different than any other. Correct me if I am wrong and please explain why. Like Howard sez "inquiring minds want to know".

 

My understanding of the conventional wisdom:
New lifter(s) on old cam - ok as a repair, if the cam lobe(s) is(are) ok.
Old lifters on old cam - ok only if the lifters stay in their original location where they are worn in.


Also, looking at the cam, the lobe is ground so that the lifter rides on the edge of the heel of the cam lobe. You can see this looking down at the cam lobes. If the whole face of the lobe is polished bright, that is suspicious, because it says that the cam lobe has worn down enough to contact the full face of the cam lobe.

I would also pull each lifter (don't mix them up!) and take a look at how flat the face is. If the lifter face is obviously concave and the cam face looks ok, I would replace the lifter. If the cam is worn and the lifter is worn, I'd either replace the cam or get to measuring. You can measure the profile of the cam using a dial indicator on the pushrod. You can also measure the lifter preload. http://www.google.com/url?sa=t&rct=...S53NUXyztqJpFBBPBHGRVOA&bvm=bv.62788935,d.eW0 If the cam/lifter are badly worn on one cylinder, the preload should be way out of spec for that cylinder.

 

What Tim said.

Maybe it's just me, but you're a good ways into the engine already and if I had any doubts about either lifters or cam, the front cover would come off and both would be replaced. If either are marginal, you will be doing it again soon if they aren't replaced.

As to cam wear, I think it is mainly a function of proper hardening. If that is not up to snuff, they will not last. Given not many of us have a Rockwell hardness tester, it becomes more important to buy the cam a lifters from a reputable source.

 

Show us some pics of the bottoms of those lifters.
That will tell the tale.

 

I replaced lifters and pushrods and put it all back together. Looking for new rockers/shaft ... In the meantime runs much better. Old lifters than I pulled out actually looked pretty good. Saving them just in case.

I'm thinking I'm going to pull the thing next winter and do a full rebuild. Compression on Cyl 3 was 145 while the rest were between 165-175. Leak down test also showed weak #3 (sounded like rings to me).

 

Will try to take pics of the old lifters and post up soon.

 

Unless you have marked each old lifter for its original position on the cam they were run with, you might as well pitch them. A good way to check if used lifters are still serviceable is to put the wear face of one on the side of another. A good lifter face is slightly convex (rounded) so that it will rock on the flat surface. If the face is flat or cupped, it is trash and will lead to wearing out you cam very quickly. Lifters wear in to each individual cam lobe, and if broken in properly, will last for many years of service. They must not be interchanged once they have been run together. The exception to this rule is roller lifters that modern engines use.
When replacing the cam, always use new lifters, and a 30 minute break-in at about 2000 rpm is critical to a long service life. On our old flat tappet type valve train, it is also very important to use an oil additive with zddp (zinc) to prevent premature cam/lifter wear. Very few oils available today contain the zinc required for our vintage engines.
-Donny