Camshaft break in

[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]

Break In ?

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.

[speedbuggy]

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.

The way they reduce the rocker ratio is by lengthening the short side of the rocker. This will push the pushrod out towards the outer part (intake side) of the head.

[speedbuggy]

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.

I just assumed .551 lift for my guesstimate since the OP didn't say. I calculated the reduced lift like you said. Don't you also have to take into account that the reduced rocker ratio will exert less pressure on the lobe for any given lift? For example, at .500 lift, wouldn't a 1.3 rocker actually put less pressure on the cam than a 1.5? I am not an engine builder, but I would think so.

[DANNY]

The way they reduce the rocker ratio is by lengthening the short side of the rocker. This will push the pushrod out towards the outer part (intake side) of the head.

Humm,

I'll have to see like I said it's pretty opened up in there but I'll take a look.

Either way I am pulling the springs so shouldn't be too bad... Been a while since I have done a cam break in.