Cam repair/replace

[jhg41977]

I am not sure how I could have missed this during tear down but here it is.

Exhaust lobe of cylinder 3 is pitted heavily. Looking at the rocker, it is 'flat spotted' on the edge closest to the pivot point.

I had a very noisy lifter, part of the reason for the tear down. My guess is that the lifter had collapsed completely, allowing the rocker to float. The float created a constant harsh impact against th cam, resulting it the pitted appearance.

What are my options at this point? The motor is very nearly reassembled.

The drain plug was free of debris or small particles for every oil change I have done. Teardown did not show any metal debris. All piston squirters and cam squirters flow freely.

So where does this leave me? New cams? Is repairing possible and advisable?

[safe]

A new cam and reconditioned rockers and if you haven't removed and cleaned the cam spraybar now is the time....

Doesn't need to be a new cam, a good used cam will do fine.

[jhg41977]

I sprayed brake cleaner through the cam spray bar and then blew it out with the compressor. All holes seemed to flow well. Is it still necessary /advisable to pull and brush clean?

I was just reading a rennlist thread about regrinds from John Doherty, any thoughts on regrinds?

[safe]

Originally Posted by jhg41977

I sprayed brake cleaner through the cam spray bar and then blew it out with the compressor. All holes seemed to flow well. Is it still necessary /advisable to pull and brush clean?

I was just reading a rennlist thread about regrinds from John Doherty, any thoughts on regrinds?

I would pull them, could be loose debris in the bar that clog up a hole from time to time. Its not that difficult to do.

A regrind is fine, an updated grind is also a lot more fun than just stock. But I don't know if John is the man for the job these days, do a search...

[jhg41977]

Thanks for the heads up. I did the search and the last year is concerning. I hope he is able to get his business back together.

[moneymanager]

Elgin reground and re heat-treated mine 50k miles ago and they are perfect still. He is among the best.

[JFairman]

If you don't want to remove the cam spray bars there is a way to get some more dirt out if there is any in there.
Remove the 17mm bolt inline with the spray bar down at the far end. That bolt has a pointed end that fits into a hole in the end of the cam spray bar.

You can take some approximately 3/8" thick tubing, I used clear pvc tubing so i can see the oil in it and stick it into the threaded hole after removing the bolt and then spray carb cleaner into the spray bar where the oil line banjo fitting goes on at the front end.
Then take a rubber tipped blow gun with 120psi air pressure and blow into the banjo fitting hole and the solvent will shoot out all the spray bar holes and the tubing you stuck in the threaded hole at the far end.

I stuff wadded up paper towels into the oil return tubes so solvent and dirt doesn't go down into the case while doing that.
If you don't want to do all that with solvent etc. you can also just stick the tubing into the threadedhole down at the firewall end of the cam tower and run it down through the engine tin into a container under the car and then start the motor and let it idle.
Oil will run out the tubing down into the container and flush out the cam spray bar in the process.
There is a little more spray bar tubing beyond that hole though so some dirt could stay there at the far end but you'll get most of it out this way is there is any in there.
You can look to see if any dirt (or oil coke particals from running lousy oil in a 911 turbo) is sitting in the bottom of the container afterwards.

This process isn't a total soloution or for everybody but it worked well for me.

[Sboxin]

We had good service from WebCams in Riverside, CA
(not connected - our Indie engine builder uses them all the time)
Web Cam Inc. - Performance and Racing Camshafts

Call and talk to them -- very good customer service.
They will tell you if they have vacation/holiday shut downs, etc that may slow the work
completion date.

We had 964 Cams redone to 20-21 spec (better torque) and rockers reconditioned for race car -
so far all is good.

Regards,

[camgrinder]

I don't see too many 993 cams with worn lobes like that. But the cam looks repairable.

[jhg41977]

I ended up finding a set of low mile cams through Rennlist. They are on their way to Steve to get checked out. Anybody want a set of used, slightly damaged but most likely rebuildable cams as a core set?

[sunlion]

Sure. PM sent .

[KTL]

WebCam does do a very nice job of reconditioning cams and turning around in a very timely manner. I highly recommend them.

Removing spray bars is not that hard but you have to be careful when they are reinstalled that:

1. You have the holes oriented properly. It's very easy to think you've got them installed properly because the holes at the ends line up with the banjo & plug locations. But if you don't look closely, you may have the tube flipped 180 degrees lengthwise and you can miss that the cam oiling holes are NOT lined up. You'd get no oil to the cam bearing bores starve them of oil when the engine was run.

2. The tubes need to fit tightly in the cam housing. If too loose, the oil spits out of the interface between the tube and housing and you're losing oil/pressure that should be going into the cam bearing bores.

A good approach to start is to remove the end plugs in the housing by drilling and tapping an M6 screw to pull the small aluminum plugs out. This will let you look down the tube and clean out any debris thoroughly. You can use a sewing pin in the very small holes to clear out any blockages. A long piece of 14 ga. stiff copper primary wire (solid core, not stranded) can be used to push some cloth material thru the tube to swab it out.

I used to remove the tubes but don't feel comfortable doing that anymore. I'd rather leave the tubes alone (some are quite stubborn to pull out) and clean them in-situ.

Some good info here about various spray bar issues

How to remove cam tower spray bar

Soda blasting engine case