Camshaft break in

[ford396]

I am looking for opinions on the proper break in procedures for my flat tappet cam SBC.

What I have is a billet steel cam that has been micro polished. The lifters are DLC billet also. I have 155 psi on the seat and 460psi over the nose. I am using 1.9 ratio rockers. Pan filled with Joe Gibbs break in oil.

My question is: do i leave all the spring in to break in or do I run just the outers? I am afraid of bouncing valves with that large rocker ratio and just the outer springs. On the other hand, if I leave the springs intact, is it too much pressure to properly break this assembly in. I am very concerned with this due to the large cost of parts and want to ensure I do not screw up.

Any thoughts and help from those who have gone down this road will be appreciated.

[perfconn]

Take the inner springs out and keep the engine under 2000rpm.

[ford396]

If I keep the RPM below that 2000 window, will I get enough oil onto the foot of the lifter to keep it alive?? This is one of my concerns.

Thank you for your thoughts.

[Dirtrunner35]

I always leave the springs alone and never had a problem. Make sure you have some zink additive .

[perfconn]

You will have plenty of oil.

[usafracer]

I have a set of 1.3 rockers for break in and pull the inner springs. Keep the RPM between 1500 and 2K and add a zinc adative to your oil after break in. You never can be too carefull.

[sj valley dave]

Gibbs break in oil has plenty of zinc, and if you go to their synthetic afterward, it has plenty of zinc also. We ran a Crower flat tappet with 150 lbs/400 lbs for years with no additives other what was in the oil with zero problems...

[perfconn]

The cam and lifters that he has can be run in without pulling the inner springs out but I would pull them anyway.

[DANNY]

I know that this is an older thread but it's right up along with what I'm doing.

Questions are:

Would you use synthetic oil like Mobil 1 and comp additive or a conventional oil with the same additive?

Also with relation to the spring pressures I'm around 140/450 will I be ok just using a set of break in rockers vs taking the inner spring out and using the break in rockers too?

Finally RPM I seen anywhere from 1500-2500 I even seen step it from 1500 and end up at 2500 and the other way as well. All of which giving it a quick crack on the throttle here and there and running for around 25-30 mins.

Just looking for some consistency as far as a standard.

Thanks in advance.
Danny

[speedbuggy]

We've never used synthetic for initial fireup, but always put in the Comp additive. You will be fine with break-in rockers and leaving the springs alone.

We prime the heck out of the engine before firing and do not let it drop below 2000 rpm or get above 2700 for the first 20 minutes. Ok to crack the throttle every so often. Also, make sure to get the timing set as soon as you can after the engine fires. Fill the fuel bowls through the vent tubes so you don't have to crank so long to get fuel.

I have a set of rockers I would sell, but they are 3/8 studs...

[dereksehi]

I agree with speedbuggy except I would take the innerspring out 450 open is quite a little I don't think just goin from a 1.5 to a breakin rocker would get your open pressure down to 325 which according to my cam grinder is the max recommended open pressure for breakin just my 2 cents its always cheaper to switch springs than take a lobe off.

[speedbuggy]

I agree with speedbuggy except I would take the innerspring out 450 open is quite a little I don't think just goin from a 1.5 to a breakin rocker would get your open pressure down to 325 which according to my cam grinder is the max recommended open pressure for breakin just my 2 cents its always cheaper to switch springs than take a lobe off.

You got me thinking about this and I tried to calculate it out. The number I came up with for the nose pressure going with 1.3 rockers was 363#, which is still more than the 325 you are saying. Sounds like he does need to remove the inner spring. You are right...450# is a lot.

Anybody know of a calculator you can use to do this? I just stuck some numbers in a spreadsheet that take into account the reduced lift and the lower ratio that the springs will exert on the cam through the rockers.

[DaveBauerSS6]

I've found the breakin rockers sometimes interfere with the head. Now I always pull the inner spring.

[DANNY]

How so Dave? I seen the push rod hole gives issues. Mine are hogged out lol.

Thanks guys, got me thinking too. Think I'll pull the inners and still use the break ins. Then I'll put the springs back and go another 20 mins just to be safe after that should be good to go.

[DaveBauerSS6]

Push rod hits the head depending on how its cast. Open holes may work; I've ran into some that still hit. I make it a habit to change the spring. I have a couple light spring setups for known combs that I put on, like for beehive setups. No big deal, just a little more time. Set idle/ timing at 2000, and dont crack the throttle, till the springs are changed out.

[DaveBauerSS6]

I also set the timing at 30 degrees to keep the water temp down during break in.

[stockcar5]

Anybody know of a calculator you can use to do this? I just stuck some numbers in a spreadsheet that take into account the reduced lift and the lower ratio that the springs will exert on the cam through the rockers.

you will need to know lift and open/seat pressures to do this Or know the spring rate. If you dont know the spring rate then use this..
rate=[valve open load(lbs)-seat load(lbs)]/[seated length(inches)-open length(inches)]

then you simply multiplty the lift by the rate and add the seat pressure to get your open pressure.

[forty40]

You got me thinking about this and I tried to calculate it out. The number I came up with for the nose pressure going with 1.3 rockers was 363#, which is still more than the 325 you are saying. Sounds like he does need to remove the inner spring. You are right...450# is a lot.

Anybody know of a calculator you can use to do this? I just stuck some numbers in a spreadsheet that take into account the reduced lift and the lower ratio that the springs will exert on the cam through the rockers.

Thanks to the advice of a now departed engine builder, Bill Hendren, we have not removed inner springs or used break-in rockers for the past 8 years. Start-up with 1.85:1 rockers, Joe Gibbs BR oil, PSI Late Model springs 500lb OTN, billet cam, PPPC billet hard coat lifters, run to operating temp for 10 minutes, set timing 36 deg, shut down and check lash. Drain oil, cut filter, if OK, put in XP3, run again, check timing and go racing.

[DaveBauerSS6]

Doubt he's running a billet cam and hard coat lifters. Good advice but for the wrong application. RIP Bill.

[DANNY]

Nope sorry not billet, I maybe just use both 1.5 if the others give trouble. Where does it hit inner or outer part of the head?

I am going to pull the inners (grrrrrr) and do it to it.