With all the information floating around regarding ZDDP levels (in particular decreasing amounts in newer oils), I hear warnings against wiping out a cam lobe. How do you know if a lobe is starting to wipe out? What are the symptoms??
from my days of working in a general repair shop and replacing many camshafts in small block chevies...yuk, you would get a backfire under accelleration. Not like a carb backfire where usually its just one "pop" initially, a bad camshaft will have a repetative backfire every time that worn lobe comes under fire. It pretty obvious.
During break-in, if a lobe even starts going away it's too late to abort and save the.....
April 30 2010, 4:57 AM
..........cam. Once the engine is in the 2,000 to 2,500rpm range and you notice a change in the 'music', it's too late. Loading your break-in oil with high concentrations of ZDDP lubricants is key, JMO, Rod.
In my cougar with a comp 270 -it developed a minor miss that I chased with wires, dizzy,plugs , carb adjustements etc. Could get it better , but would always break down at higher rpms, could never get it to pull hard above 4600 rpms. Friend actually noticed a rocker arm not moving one day when the breather was off. Hole through the bottom of #6 intake lifter...
When I lost #3 exhaust, it started farting through the carb. Not a back fire, but more of a fart sound. Was much worse under load. Happened after about 4-5 hours of run time.
Second time, I was adjusting rockers after break in run. Noticed #4 intake was loose, and not rotating. Engine still ran good, but as others stated, the damage was done.
My son bought a used motor with several completely flat lobes. We didn't know it and the thing ran good below 3000 rpm. Under heavy load or above 3000rpm it would pop. Because it ran so well it was difficult to diagnose. Seeing the cam, it is surprising it ran at all.
I believe he finally diagnosed it by measuring travel at the rocker arms.
I experienced a popping type of backfire in my tunnel port. Found one lobe wiped so I had my engine builder install a new camshaft. It ran great for several miles and then started doing the same thing again. We are assuming it wiped another lobe on the new cam. He hasn't been able to get it back in the shop yet to know for sure but we're wondering if possibly the valve springs are too stiff to break in a new cam? We added the ZDDP additive and did the break-in correctly. Hope to get it back in the shop soon so we'll know what it is.
I just think this whole thing about cam break-in is just B/S.
I was a diesel mechanic for many years and there is no such break-in procedure with diesels in my day. They were all flat tappet camshaft engines. Is there any more pressure at the lifter/cam lobe at idle than at 2000 rpm? It would be negligable if any.
Sure with higher lift cams there may be slightly more pressure but really, how much more?
I think some other problems may be more of a factor like lifter clearance which stops the lifter turning that is detrimental.
There are many myths in the automotive world and I believe this is one of them.
I think it is a "cop out" clause by camshaft manufactures because they can't or won't make materials to handle these applications.
Here in OZ in 1981 we had a 6 cyl Ford crossflow engine that wore cams & lifters fast. There was a grind that fixed that and Ford endorsed it. This was a std engine with a std cam & lifters and this new grind fixed the problem. There was no run in procedure.
They onlt have to rev to 2700 max, takes no valve spring to do that. Plus as someone else said they use high ZDDP in their oil.
Cams having issues is not BS, it is a real problem now that the oil changed. Happening way too often to be BS.
Slower revving diesels do have lesser spring pressure but Cummins 12 litre engines (back in the eighties)use an injector cam lobe to actuate each injector. Now that is real pressure on a cam lobe. They do use roller lifters though.
I enquired here in Australia about the ZZDP levels. Austrailan oil companys can still keep this stuff in their oils.
He told me in the US they had to remove it but it was replaced with other lubricants that will still do the same job & meet their emmission targets.