Breaking in new cam shafts

[opethmike]

What do you fine folks recommend as a good cam shaft break in procedure?

[Ron]

The first 20-30 minutes are the most crucial for a camshaft. Similar procedures should come with the cam:
Set up everything you can before you ever turn the key.
Lash (error to the loose side, re-lash after break-in).
Timing (static time to tune up spec).
Use high zinc oil (ZDDP; eg. Shell Roetella T 15w-40, Castrol Tection Extra 15W40).
Use a high zinc break-in additive.
Pressure prime lubrication system.
Purge fuel and coolant systems (leave cap off at first w/ top-off coolant ready).
Start engine and immediately raise RPM to 2500 and vary +/- 500 for 20-30 minutes.
Do not run at lower RPMs.
Keep close eye on oil pressure, temp, leaks etc.
DO NOT STOP unless there is a significant problem.

Also if total rebuild, during first mile or so, help break-in/seal rings by putting the trans in 2nd for auto or 3rd for manual and bring it up to moderately high RPM and quickly let off accelerator and coast 5-10 times (MIN...This helps draw oil up around the rings). Vary speed/load for several hundred miles (avoids creating a ridge at top of cylinder). Don't baby or hot rod engine.

[David T]

There are a lot of different break-in procedures but they all have a lot in common. You should always go with the way the camshaft manufacturer says to do it but if there is no instruction this way is as good as most. It is assumed when the camshafts were installed you used the cam lube liberally on the lobes. You can also measure lift before and after break-in.
David Teitelbaum

[jerzybondov]

What are the consequences of not properly running in a new (or reprofiled) set of cams?

[Ron]

Extreme reduction of lifespan (bad wear pattern(s), flat spots, possible breakdown particles contaminate entire engine, etc).

[David T]

If you measured the lift before and after breaking in the camshaft you will know if you did it correctly. You would have less lift if you did it wrong. Not breaking in the camshaft you wear the lobes on the camshaft.
David Teitelbaum

[jerzybondov]

What would be the consequences of wearing the lobes on the camshaft? As the cam wore down would you notice any change in the valve clearances?

I mention this as I (a) didn't run my cams in according to this schedule (after being reprofiled) and (b) over the last 5,000 miles my valve clearances have opened up significantly a couple of times, but in an irregular fashion. The screws have not slackened, so it's either the tappets wearing down - or the surface it's impacting on.

[David T]

You would notice decreased lift and possibly more clearance if you are wearing your camshafts. If you were doing oil analysis you would see it as particles of the tappets and camshaft in the oil. Wear is a bad thing. It stays fairly constant for a while then then very quickly increases exponentially. Difficult to predict exactly when that happens. If you can't hold your clearances that is "Not a good thing". Are you using the correct oil? Are you changing it often? Are you running higher than stock spring pressures?
David Teitelbaum

[jerzybondov]

OK... the engine is a B28E that went in 18 months ago. Before the engine went in I took the cams out and sent them away to get reprofiled (to a 'fast road' setup). Since the engine has been in I've covered about 5,000 miles and have changed the oil twice (15W40 Semi-synthetic). Spring pressures haven't been adjusted.

Other symptoms are high HC readings at idle. When the cams were first in, I was getting about 600 (UK MOT limit is 1200, stock D should get 1-200). Now I'm getting about 3000. HOWEVER - I've used a different machine for the two readings (you never know, could be a sensitivity issue), and other things may have changed in the last 18 months too (e.g. I want to get the inlet smoke tested for a vacuum leak).

What I would say is that the valve clearance problem hasn't increased exponentially yet. After resetting them all last summer (when most of them were way out) I checked again after 500 miles or so, only two had increased from .25mm to .35mm ish (as opposed to several of them >0.50mm previously and some >0.80mm). I've since driven another 500 miles or so and the car isn't sounding tappety yet (like it did horrendously before the original reset).

The HCs issue has been a mystery that's stumped me for ages now. All the usual suspects have been ruled out (fuelling & ignition system all tested or replaced).

[tgraham]

Other symptoms are high HC readings at idle.

Varying measurements aside, your modified cam profile can certainly explain the high HC. It's "normal." High-performance cams have some degree of intake and exhaust valve overlap, where both are open (slightly) at the same time. This allows a little unburnt fuel to flow into the exhaust, which could put you over the limit for HC.

I have modified camshafts in my car and it definitely won't pass emissions at idle (the HC limit here is 220 PPM... I can't remember what my measurement was, but it was considerably over the limit). My solution was to raise the idle to a touch over 1000 RPM, which brought it down to under 220 PPM. They can't tell the difference between 750 RPM and 1000 RPM (and probably don't care - they're too busy looking for the gas cap anyway). In fact, I made the alteration in the parking lot before entering the emissions building, then I reset it on the way out! This solution won't work for everyone, of course...

Just to eliminate another variable, I'd use the same gas analyzer while you're troubleshooting.

Travis

[David T]

I agree with Travis, depending on the overlap you will never pass emissions at idle. In fact it may be hard to get it to idle, especially a low levels. You may also have very little vacuum at idle, again, depending on what they did to your camshafts. Camshaft profiles are a "Black Art". You want it to perform well over a very broad range of RPM's and that is impossible. It is all a compromise. For more performance you typically sacrifice low end performance for more high end performance. That is where all of the HP and torque is anyway. The original grind stressed emissions, fuel economy and durability. Performance was not high on the list. This is all assuming you timed and installed the camshafts correctly. I would check the clearances at every oil change for a while and use a ZDDP additive.
David Teitelbaum

[tgraham]

Just to eliminate another variable, I'd use the same gas analyzer while you're troubleshooting.

I should have also said, make sure the gas analyzer you're using is accurate! From your wildly varying measurements, it sounds like one could be off.

Travis