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Camshaft Break In

  
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Camshaft Break In

 
tuffnuff tuffnuff
Moderator | Posts: 322 | Joined: 03/11
Posted: 02/03/13
04:26 PM

Prior to installation:

Check the compatibility of the camshaft with the remainder of the valve train components, particularly the valve springs.
On high load spring applications you will need to use lighter load springs, or alternatively remove the inner spring (for dual spring applications) just for break-in.
The most critical time in the life of a flat tappet camshaft is the first 20 minutes of break in, during which time the bottoms of the tappets mate-in with the cam lobes.
This is true for both hydraulic and mechanical flat tappet camshafts.
Due to the EPA's mandate of Zinc being removed or having less of these high pressure additives in a lot of Todays engine oils needed for flat tappet camshaft break in,There for Proper Flat tappet camshaft break in is more critical then ever before. Therefore choose your motor oil carefully as some engine oils are not suitable.
A race only oil usually will work just fine for proper break in of a flat tappet camshaft as these oils have higher levels of ZDDP in them.
Prior to installing the camshaft and lifters, it is recommended that the crankcase be drained and filled with new, clean oil, as aforementioned. The oil filter should also be changed at this time. Proper flat tappet camshaft break-in starts with the cam installation and includes these steps:
Before installing the camshaft and lifters you must wash them thoroughly in clean mineral spirits or solvent to remove the rust preventative that is placed on the cam prior to shipping. NOTE: As a "rule of thumb", always thoroughly clean any part before installing it in an engine. Never "assume" that the parts are cleaned before packaging.
WARNING: NEW LIFTERS MUST BE INSTALLED WITH YOUR NEW CAMSHAFT AS WELL.

Installation Procedure

DO NOT "pump-up" hydraulic lifters before use. This can cause the lifters to hold a valve open during engine cranking, resulting in low compression. The low compression will delay engine start-up and is very detrimental to proper camshaft "break-in".
With the supplied moly paste lube, coat the bottom of the lifters, cam lobes and distributor gear.
Set your valve lash or lifter preload. Try to minimize the number of times that you rotate the engine, as this can displace the moly lube paste from the lobes and lifters.
If possible prime the oiling system. When priming, rotate the engine at least one complete revolution to assure oil gets to all valve train components.
Valve covers should be off to assure that all rockers are oiling.
Preset the ignition timing to start the engine at a fast idle. It is important that the static ignition timing is as close as possible and if the engine has a carburetor, it should be filled with fuel to insure the engine starts immediately. The engine needs to start quickly without excessive cranking to insure immediate lubrication to the cam lobes.
Start the engine and immediately bring to 2,800 rpm. Timing should be adjusted, as closely as possible, to reduce excessive heat or load during break-in. Get the engine running fairly smoothly and vary the engine speed from 1500-2800 RPM in a slow acceleration/deceleration cycle. During this time, be sure to check for any leaks and check out any unusual noises. If something doesn't sound right, shut the engine off and check out the source of the noise. Upon restart, resume the high idle speed cycling. Continue the varying "break-in" speed for 20 - 25 minutes. This is necessary to provide proper lifter rotation to properly mate each lifter to its lobe. Should the engine need to be shut down for any reason, upon re-start it should be immediately brought back to 2800 rpm and the break-in continued for a total run time of 20 - 25 minutes.
Let the engine cool, and then drain the crankcase and properly dispose of the oil and oil filter. Refill the crankcase with premium conventional oil do not use a synthetic oil. At this point the initial "break in" is complete. You can drive the vehicle in your normal manner. I recommend changing the oil and filter after 400-500 miles.

Additional Information

Spring Pressures: For extended camshaft life, flat-tappet cams should not be run with more than the recommended open valve spring pressure. Racing applications will often need to run more spring pressure at the expense of reduced camshaft life. In order to "break-in" a camshaft with high open pressures, the inner springs should be removed to reduce "break-in" load. The inner springs can then be reinstalled after initial "break-in" is complete.
Lifter Rotation: Flat tappet cams (both hydraulic and mechanical) have the lobes ground on a slight taper and the lifter appears to sit offset from the lobe centerline. This will induce a rotation of the lifter on the lobe. This rotation draws oil to the mating surface between the lifter and the lobe. If it is possible to view the pushrods during "break-in", they should be spinning as an indication that the lifter is spinning. If you don't see a pushrod spinning, immediately stop the engine and find the cause.
Never use old flat tappet lifters on a new cam. On flat tappet cams, the lobes and lifter bottoms mate together and if the lifters are removed from the engine, they must go back on the same lobe from which they were removed. Most Cams manufactures recommend the use of high quality tappets to prevent premature cam or lifter wear.  

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

yvdz yvdz
User | Posts: 118 | Joined: 12/08
Posted: 02/04/13
01:38 PM

Tuffnuff,

Thanks for all this technical info, very interesting. I actually never knew lifters & pushrods need to rotate. I friend of mine rebuild my 360 years ago but I don't recall him talking about this. It never had a cam/lifter issue so I assume it's ok...the valve covers were on the engine during break in so how would you check, seems kind of messy to leave the valve covers off while revving the engine...  

tuffnuff tuffnuff
Moderator | Posts: 322 | Joined: 03/11
Posted: 02/04/13
01:57 PM

yvdz,

You are very welcome and I have many more tech articles.,. but I'm not sure how well they are/will be received on this forum.Anyone
I Moderate on numerous other sites and so far you are the only one here, who has offered a thumbs up.
The reason flat tappet lifters rotate, lies in the fact that the lifter is offset on the cam lobe.,. as you can see in the pic.
If it did not rotate, the cam and lifter would wipe out in minutes.

Camwear

Wiped out cam lobe and lifter.

Wipedoutlobelifter

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

pepsi1 pepsi1
User | Posts: 150 | Joined: 10/11
Posted: 02/05/13
09:47 AM

Icon Quoteyvdz:
Tuffnuff,

Thanks for all this technical info, very interesting. I actually never knew lifters & pushrods need to rotate. I friend of mine rebuild my 360 years ago but I don't recall him talking about this. It never had a cam/lifter issue so I assume it's ok...the valve covers were on the engine during break in so how would you check, seems kind of messy to leave the valve covers off while revving the engine...


Back in the day a friend had a brand new 67 GTX 440.
  Those engines idled so lopey it was hard to tell if they had a problem. Now remember this is brand new car. It didn't have 100 miles on it he was pulling into the club parking lot. The pushrod hit the valve cover. They found the pushrods on that one cylinder were longer then needed. They installed the correct pushrods, and it was okay after that.  
  The point I'm trying to make. The Dealer thought the factory guys had union problems, and did something like that. On purpose of course.

Bob  

pepsi1 pepsi1
User | Posts: 150 | Joined: 10/11
Posted: 02/05/13
09:56 AM

Tuff
Thats a great shot of how the lifter rides the cam lobe.
Thanks
Bob  

tuffnuff tuffnuff
Moderator | Posts: 322 | Joined: 03/11
Posted: 02/05/13
12:47 PM

Thanks Bob, by the way, are you able to login at CHP or HPP yet.
If not, send me an email.

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

69GTX 69GTX
New User | Posts: 7 | Joined: 01/13
Posted: 02/20/13
10:05 AM

Another thumbs up here, just went through this with another post.  I dug all this info up from other sites piece-mail!  

3404spdvaliant 3404spdvaliant
New User | Posts: 20 | Joined: 01/14
Posted: 01/05/14
09:35 AM

Actually its not about the lifter being offset to the lobe so much, its the lobes taper that rotates the lifter. all the lobes are at a slight angle in order to rotate the lifter...Cams do walk btw, thats part of why the pic shows the lifter in the position its in.
See the slight angle of the lobes also lets the lifter's fixed position force the cam to move backwards.

Roller cams have no lobe taper and the cam moves both forward and back wearing the thrust plate and timing sprocket.  

tuffnuff tuffnuff
Moderator | Posts: 322 | Joined: 03/11
Posted: 01/09/14
07:29 AM

Icon Quote3404spdvaliant:
Actually its not about the lifter being offset to the lobe so much, its the lobes taper that rotates the lifter. all the lobes are at a slight angle in order to rotate the lifter...Cams do walk btw, thats part of why the pic shows the lifter in the position its in.
See the slight angle of the lobes also lets the lifter's fixed position force the cam to move backwards.

Roller cams have no lobe taper and the cam moves both forward and back wearing the thrust plate and timing sprocket.


Yes, the flat tappet cam lobe has a slight taper that corresponds to the crown on the lifter face.,. this is usually .005".,. so if you placed 2 flat tappet lifter faces together, there would be .005" clearance on each side.
Or if you placed them so the edges would touch, you would have .010" clearance on the other side.
Correct, roller cams do not have any taper and a torrington thrust bearing behind the cam gear is a prudent choice.,. driving the oil pump and distributor is sufficient force to move the cam towards the rear of the engine.

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

tuffnuff tuffnuff
Moderator | Posts: 322 | Joined: 03/11
Posted: 01/09/14
07:30 AM

Icon Quote69GTX:
Another thumbs up here, just went through this with another post.  I dug all this info up from other sites piece-mail!

Thank you.

Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

3404spdvaliant 3404spdvaliant
New User | Posts: 20 | Joined: 01/14
Posted: 01/27/14
11:38 AM

Yep, and hyd lifters have less ''crown'' than solid lifters, something to the tune of .002 vs .005

Great post for the beginners and experienced whom need a refresher.  

marcohotrod340 marcohotrod340
Enthusiast | Posts: 459 | Joined: 09/08
Posted: 01/28/14
11:17 AM

the 1989 mopar engine book on page 76 by L. Shepard states "the tappet radius gives the tappet a crown. a solid is sometimes called a flat-tappet because the tappet radius is so large it's virtually flat. mechanical cams have much lower lobe tapers to go with the "flat" tappet. hydraulic tappets have a short enough radius that the crown is noticeable." With this in mind, which type should last longer? those old "flat" tappet mechanical slant sixes and early mechanical Mopar V8s lasted many miles  

marcohotrod340 marcohotrod340
Enthusiast | Posts: 459 | Joined: 09/08
Posted: 01/28/14
11:18 AM

the 1989 mopar engine book on page 76 by L. Shepard states "the tappet radius gives the tappet a crown. a solid is sometimes called a flat-tappet because the tappet radius is so large it's virtually flat. mechanical cams have much lower lobe tapers to go with the "flat" tappet. hydraulic tappets have a short enough radius that the crown is noticeable." With this in mind, which type should last longer? those old "flat" tappet mechanical slant sixes and early mechanical Mopar V8s lasted many miles