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View Full Version : Myth: run engine at 2200 rpm for 20 to 30 min



vettedog72
02-15-2008, 09:02 AM
I don't believe it for one second that you have to run in the cam and lifters UNLESS the replacement cam and lifters are different than the OEM. The reason is quite simple, they did not do it when the motors were made. Motors were tested for a very short period of time then passed on for installation in the car, not to be cranked until it got to the end of the assembly line where it was driven to its parking place waiting for shipment. What the heck has been done to cams and lifters that make them so failure proned?

DougF
02-15-2008, 09:23 AM
According to this article I referred to in the other post, Precision Engine Magazine, Jan.-Feb. '08, which I reread, during the 60's and 70's, camshafts were phosphate coated. This along with ZDDP worked well to protect new camshafts and lifters from premature wear, especially during break in.
ZDDP levels were at .07% in the 60's, and raised to .09% in the 70's. They were further raised to .2% in the 80's and 90's. Phosphorous levels were dropped to .1% which also dropped the levels of zinc sometime before 2004. Phosphorous was again dropped to .08% and zinc to .09% in '04.
It is also mentioned that if you plan to run a heavier valve spring and are afraid of the cam damage, to run a lighter spring during the break in period and swap out later.

YankeeTR
02-15-2008, 10:07 AM
After you wipe out a few lobes you will find that a short run-in procedure is good insurance against cam failure.

I used to feel as you do but not after seeing many cams fail both due to no break-in and cheap Chinese parts....

Brosky
02-15-2008, 11:51 AM
Richard Good recommends doing just that and draining the oil immediately after.

TR3driver
02-15-2008, 12:05 PM
The debate over early cam failure, especially with reground 'performance' cams, has been burning hotly since at least the 70s. Seems to me that the issue must be much more complex than simply lack of ZDDP in oil, particularly since the argument started BEFORE ZDDP levels started dropping.

I don't know where the truth lies; but with many engine builders (including Kas Kastner), plus cam makers like Crane and Edelbrock all endorsing the run-in technique, that's what I will continue doing as well. Call it cheap insurance, even if it only slightly reduces the chances of early failure.

TR3driver
02-15-2008, 01:07 PM
What the heck has been done to cams and lifters that make them so failure proned? Actually, that may be the crux of the matter. Whatever alloy and casting/machining/treating method they used then has no doubt been replaced many times over by now.

One example of that is the lifters that used to be chilled cast iron. By pouring a particular gray iron alloy into a cold mold, the surface of the iron is transformed into white iron with a high percentage of iron carbide and chromium carbide; which left a very hard and tough surface on the strong but more ductile grey iron in the rest of the lifter body. (The surface of chilled iron is literally so hard and tough that it's difficult to cut with machining tools; many of my old machining texts warn to make the first cut deep enough to get under the chilled layer to avoid ruining the tool.)

But no one makes lifters that way anymore (AFAIK), because it's a very time-intensive process and hence way expensive for mass production.

I don't really understand metallurgy much, just enough to know that there is a great deal I don't know. But there is far more to the properties of a particular piece of "steel" than just it's chemical composition (alloy), which in itself is almost infinitely variable. And most of the old way of doing things was determined solely by trial and error; with the scientists coming along behind to try to explain the results obtained by experimenters. They didn't always get it right ... AFAIK no one has ever identified the essential difference between a virgin's blood and non-virgin blood /bcforum/images/%%GRAEMLIN_URL%%/jester.gif but at least someone felt it was important enough to write down ...

Then once you fully understand metallurgy; you have to start studying tribology (science of rubbing surfaces & lubrication) which is an entire field in itself.

"Rocket science" is actually pretty simple compared to a car engine ! But lacking several lifetimes to understand it all, we're ultimately reduced to following the advice of others as to what they tried and found to work.

vettedog72
02-15-2008, 08:32 PM
If I change cam and lifters not only will I do all the "today" things, I will as Father Doug and Rev Roberts to bless it. TRDriver is the myth buster.

I do wonder how the lifters were cut or ground after the chill process as well as the final finish on both the cam and the lifter?

Brosky
02-15-2008, 08:44 PM
Count Dracula took the secret with him.... /bcforum/images/%%GRAEMLIN_URL%%/mad.gif

Bob Claffie
02-15-2008, 08:54 PM
I just pulled the lifters out of a 350 Chev with 2000 miles on a quality rebuild. Name brand new parts properly assembled and broken in "by the book". Already, at this low mileage there are wear marks on some of the lifter faces. It appears the lifters were not rotating in their bores. Very puzzling. Bob

MadMarx
02-16-2008, 03:25 PM
I grind my lifters dead flat.
The lifters are domed while the cam is not made for domed lifters.
The stock lifters were dead flat too...that's the reason why they last.

Since I grind my lifters dead flat all cam problem disapeared.

Cheers
Chris

hondo402000
02-16-2008, 04:37 PM
the problem could also be a material problem of the camshaft and not a runin problem, I know a guy who recently rebuilt a 66 corvet engine bought new cam and lifters after only 30 minutes of run in one of the cam lobes wore completely round, the place where he bought it sent him a new cam, kind of danced around what the problem, he had is checked and the hardness was no where near spec