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Author Topic:   cam break in
garyl
Member
posted May 07, 2004 02:02 PM
whats the best way to break in anew camshaft to prevent lobe failure.?

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gl


dirtbuster
Member
posted May 07, 2004 02:22 PM
If you do a search for cam breakin there are several topics on here related to that.


iowa_dirt_track_girl
Member
posted May 07, 2004 07:00 PM
i feelthat if you dont let it stay at one rpm during break in your fine
lets say 2000 to 2500 back down then up do that for 30 minutes and then let it cool ALL the way down dont start it until it has cooled all the way down.Dont let it get above 190 during break in.


supwitchew
Member
posted May 07, 2004 09:26 PM
I would follow manufacturer's recommendations. Each one seems to be a little different. I installed a Howard's cam. They said to run it at 3000 for 10 minutes, let it cool, then run it at 3000 for another 10 minutes. Whatever you do, do not let it idle. That's probably the most important thing.


Rat Trap
Member
posted May 10, 2004 09:09 PM
Most of the oil the cam gets is thrown off the crankshaft. By letting it idle you are cutting back the amount of oil it gets. Even after breakin a race engine with pretty agrresive cam shouldnt be idled less than 1500 for the same reason.


racerguy500
Member
posted May 11, 2004 08:20 AM
The cam lobes are not pressure fed, the only oil they receive is from splash from the crank and rods. Therefore an engine at idle doesn't "sling" enough oil to properly lubricate the cam lobes and could allow it to start wearing. Like it was mentioned, I would follow the cam manufacturers suggestion. If nothing else, just to make sure you are familiar with how they say to do it in case you ever need to talk to them directly. Most are pretty much the same anyway. But I just fire them up and vary the RPM from about 2500 to 3500 for about 15 minutes before even thinking about idling. The main thing to me is to have some help. Other eyes looking for leaks, watching pressures and temperatures, making sure the water is still in it, and someone able to shut it off if need be. Good luck.



hms
Member
posted May 11, 2004 10:41 AM
Last summer JRs had 40% of the lifters sold that were flat on the ends. Needless to say it doesn't matter how you break these in they still go flat. This is supposed to be industry wide with only one company making solid lifters now. Keep this in mind and check that the lifters are not flat on the ends.


racerguy500
Member
posted May 11, 2004 10:08 PM
Very good point there, I personally wouldn't buy a cup of water from JR in a heat wave anyway, but it may help him. Trying to keep it clean there.


whiterabbit
Member
posted May 12, 2004 01:44 AM
When using a flat tappet cam I always try to obtain a valve on seat spring presure of 135 lbs. per sq. in. at the recommended installed spring height. In process always be sure never to have any coil bind and to have sufficent clearance between top of guide and bottom of retainer. When breaking in a new cam always have engine rpm above 2000 and occasionally 'wing' throttle as cam lubing is from oil that relieved through rod side clearance's. It is adviseable to reduce the valve spring presure for initial breakin. This can be accomplished by one of two ways. Assuming you are using a 1.460 diameter spring which are double springs I remove the inner spring on buildup and install after cam breakin. You will need a valve spring compressor that you can screw onto rocker stud with handle that swings over top and locks in compressed position. Also you will to fill cylinder with compressed air to keep valve from dropping out guide into cylinder when spring is removed. You can also spring valve up to final presure and order rocker arms from several cam manufacturers with reduced ratio's I believe some around 1.2-1.3. there by elimating ecessive presures on intial breakin.
Good luck
whiterabbit


Raz_900
Member
posted May 12, 2004 09:44 AM
Spring open pressure is more critical for breakin than seat pressure. 350# 'over the nose' is considered the most for a good breakin on flat tappet cams. Rollers doesn't matter. 250# closed and 300# (just an example, there is no such spring) wouldn't be any problem as the open pressure wouldn't wear the lobe down.

Pulling inner springs on multi spring applications and breakin rockers are good ideas for high pressure applications.

Main thing is to keep rpms over 1500 and make sure the oil system/oil pressure are in good working order.

Just my $.02

dirtbuster
Member
posted May 12, 2004 09:56 AM
I'll throw in to use a good quality conventional oil. Id go 30wt or heavier. Also make sure everyhting is ready to fire before you start and dont spend a lot of time cranking it. If it wont fire stop and figure out why then proceed. Once it fires bring it up to 2000 or so and if you have to shut it down make sure when you refire you get it right back up. Dont mess with idle speed ro timing at idle until you get 20-30 minutes runtime on it.

At assembly make sure you use the proper cam lube and also make sure the lifters are free to rotate in their bores. I had a block once that a lifter would not slip all the way in because it had a little bur on the block and i had to polish the bore lightly so it was free.... would have had a ruined cam for sure.

outlawstock17
Member
posted May 12, 2004 12:17 PM
build a ford.....they hardly ever knock a lobe down on break in...


racerman707
Member
posted May 12, 2004 02:25 PM
Second that on the Ford. Not enough of them!


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