Camshaft worn?

[Westfield 129]

The cam probably wasn't processed properly after grinding. I have had numerous re ground cams over the years without problems. Cam failure is really quite rare. I find it hard to believe that a reputable cam grinder would send out an unprocessed cam. What followers did you use after installing the old cam?

If you use the correct cam lube (copious application to the cam and follwers, including the follower bores, is customary), the setting of the cam timing should not cause any problems. Note that if that little bit of rubbing when turning the engine by hand did cause a problem, the cam doesn't have a chance in hell of lasting more than a few miles. I always use a good assembly lube as well. The lube wont rub off...

One thing that can cause problems with the cam wear you describe is improper valve train geometry. That all of the lobes were damaged might point to those valve springs again, and the rockers. If the cylinder head has been milled a little (say, you have combustion chambers at around 21 cc), you would need to shim the rocker towers or the springs will get close to packing up solid, and the pushrods may bend. I had to do this with my last Longman race head when I checked the clearances after cam timing and assembly. Valve float can be hard on the cam, lifters, rockers and pushrods as well. Make sure that you have the correct ratio rockers to match your new cam. Improper valve train geometry is not unusual with some cam combinations when used with a modified cylinder head. You may have to put a few thou shim under those towers to correct it.

Note that many roller rockers wont fit properly beneath an alloy rocker box cover without machining the internal ribs from the inside of the cover. Just another thing to look at. Stock steel boxes work fine with most roller rockers.

Make sure that you have full oil pressure prior to the first engine start. This often requires a couple of minutes of cranking to ensure that you have oil pressure. I pull the oil pressure sending line to see the oil coming out, and to eliminate any bubbles in the line. I do the start once I have a solid oil pressure indication at the gauge during cranking. If you can pre lube to bring up the pressure prior to cranking, all the better. Anyway, this will ensure that the cam is bathed in oil as well as cam lube.

Most cam grinders recommend 20 minutes of running at 2000 RPM for cam break in. I suggest that you break in on conventional race oil, with a ZDDP break in additive. If the engine heats up, stop the break in, let it cool, then continue when it is safe.

That said, I have started a few engines, and just took them for a drive. This resulted in a good break in of the cam, without problems. I did this with my current 1380/scatter pattern regrind cam engine, which now has 18,000 miles. I still recommend the 20 minute, 2000 RPM break in.

I have not had to adjust the valves in more than 12,000 miles.

You might also check to ensure that you have proper cam lubrication, and that all the oil passages in the block are clear. Your block should have threaded plugs to make blowing out the passages easier. Check the cam bearings and make sure that there is clear passage for the oil.

[adamwilkinson]

We use Snot [technical term there and cant remember the actual name of it] assembly lube, very very sticky and green - brilliant stuff.

Is your oil nice and sparkly Charles?

Sounds like you were unlucky and got a sub-standard cam shaft - might be worth contacting the company and letting them know, you never know they may offer to replace it.

[biggles]

it's not unknown, this chocolate cam syndrome. The Locost racers had a very bad run of it using Kent cams in Ford crossflows inthe early days of the series, around 2000 - 2001. The cams would wear out from new in one race in some cases!

Rest of the valve train was standard then (well, it should have been )

[adamwilkinson]

I was in the Locost series at the start and yes some did suffer, we never had an issue with them though.

[erictharg]

It was a Piper re-grind. But clearly something not right early in its life. I run a steel rocker cover to ensure clearance (an alloy one adds no useful purpose other than weight). Rocker pedestals shimmed by 1.2mm to compensate for head skimming. Ran engine initially for 10 mins at 2000 rpm plus after using Torco red lube on cam and followers.
This time I'll use Graphogen on all contact points and be even more conservative on break in procedure.
The bottom line, I suspect, is that we are pushing the limits of a flat tappet cam and anything not quite right will lead to early life failure. The new cam is drilled with oil bleed holes in each lobe that can only help, as long as it survives the first few minutes withour galling. It can only be better than what I've been running for the past year!
Hopefully back together and running for the weekend. Will keep y'all posted.

[erictharg]

Engine re-built with the new cam etc. All set to go back in but just noticed the pilot bush in the rear of the crank is loose. Replacement ordered... on hold for a £3 bush.
Used copious amounts of Graphogen on the followers and cam lobes this time.

[Westfield 129]

Torco Red is an engine assembly lube, but not really suitable for cams and followers, which require a moly based lube specifically for cams. We use Torco here as well, along with various other thick assembly lubes in blue and green (I love the colors). But Cam lube is always very dark gray, and very sticky. At least it has in the cases where I have used it. Mine has always come direct from the cam grinder, even in the case of aircraft engine cams.

This is probably what caused your problem. Your cam should have come with suitable cam lube, or a specific recommendation.

A 20 minute break in at 2000 RPM should do the job, but the cam grinder may have another procedure.

I am assuming that Graphogen is a recommended cam lube. You might also add a ZDDP break-in additive to the oil as well.

It sounds like you have fixed the problem. Good thing you caught that pilot bush.

[erictharg]

Graphogen is a colloidal graphite paste, according to the tube. Gets good press as a valve train and general engine build lube. Very black. Very sticky. Feels a lot more up to the job than the Torco red jelly!
Surprisingly new Piper cams don't come with any of their cam lube. Bit dissapointing on a £200 new cam I think. turning the engine over to set the clearances shows a lot more lift than before (as you'd expect) but still plenty of spring coil clearance.
Managed to get a slot on the rolling road the morning before I head off for Anglesey, so fingers crossed that all goes well up until then. Spigot bushes not arrived in today's mail so nothing for it but go to the pub. It is Friday, after all...

[erictharg]

Ran the car up for 20 mins at 2000 rpm plus. All seems OK but sounding very different - hardly surprising with an extra 27 deg of exhaust duration. Much lumpier low down. Let it all cool, re-torqued the head and checked the clearances - all OK. Piper advise an extra 002" to allow for the high lift rockers so set at 016" in & 018" ex at present.
So, road test in order. Seems to have undergone a Jekyll to Hyde transformation. Won't take anywhere near full throttle below 4000, but after that it's positively scary on our little back roads. Still pulling well at 7000. No more Mr. Misfire. No more Mr. Nice guy!
Suspect I'll have noise limit problems as it is noticeably noisier. Feels like, dare I say it, a racing car.
Rolling road booked the morning I'm heading off to Angelsey (no more holiday to take) so hopefully all is well. Better start practicing the circuit.
The old oil pump was pretty scored - it would have taken the bits of old cam through it before the filter did its job. Hopefully. If it holds together the rest of the season I'll check the crank and rods over winter and fit new pistons.

[erictharg]

Rolling road Friday AM. Started out with 117 hp at 7250 (self imposed redline). A bit of playing around with timing and fresh plugs and we now have 121.5 hp. Happy with that. Torque peaks at 5000 then dips a little and plateaus from there. So maybe some scope for tweaking cam timing to push the torque peak a bit higher up. Running well though - see race report.