Technical Camshaft break in

Hi,

So I’ve been reading and watching lots of videos on how to do a camshaft break in. Now I have to questions:

1. Is there a way to determine push rod length without actually using a push rod checker?
I ask this because my current set up is old and, I would assume if the engine’s lifters and lobes are very worn.

2. How do you set the timing when breaking in a cam? Comp Cams says lifters will mate to the camshaft and if that is the case then it will require manifold and distributor removal.

 

just install the old pushrod in the engine, rotate the engine by hand, and when the valve is at full lift, the rocker should be very close to the center of the valve stem.
#2- set the timing to factory specs to start with, then play with it until you get the best performance. as far as manifold removal question, please explain what you mean.

 

Removing the manifold for dropping the lifters?
Also aren’t I supposed to start it and bring it up to 2000-2500 rpm immediately? I’ve played with timing before but is it an issue to adjust timing during break in?

 

Tell me more about what you are doing and why. Is this a running engine? Are you having trouble starting it? Does it run like shit? Did you change the cam?

Generally speaking, the pushrods that left the factory in the engine should be just about perfect unless you have changed something. Also, an assumption about how worn you engine may or may not be could be wildly inaccurate.

Give us some details, we'll get this sucker figured out.

-Abone.

 

Well, I’d like to switch to full roller rockers (1.5) at some point but in the meantime I am putting in a higher duration and lift cam and mechanical lifters.

Since the arms currently on it are stock I just want to make sure I break the cam in properly. The engine already runs fairly hot, despite having an aluminum intake.
The idea of estimating or actually calculating pushrod length was just a time saving hope.

But following that direction could you not calculate it based off cam lift, lifter length, spring height and tangent on the arm?
I almost wonder if you could get it by Sin.
Following angle A) with the length of the rocker and staying on the valve lock at 1/2 radius would be our point of max lift.

 

Possibly you've never heard of the KISS Principle? If you buy(or make?) a pushrod checker, the checker will have been used & rusted away, & the motor will have 200K miles on it by the time you've finished all those calculations(& corrected your math errors?), & the motor won't care how much math you've done. The checker will take no more than an evening & will be more accurate due to less possibility of measurement & computational errors.

 

There is a small possibility you may be overthinking this.

Unless your new cam has a much different lobe centerline, your original pushrods are going to be fine. I am going to ASS-U-ME your new cam is a mild to moderate performance grind somewhere around 480 degrees gross valve lift, maybe 280 degrees duration. I base this on very little information other than 480/280 is a pretty popular Chevvie cam profile. A cam of that category is going to be fine with the original pushrods. I am also going to ASS-U-ME that you have adjustable rocker studs, which if correct, will compensate for any minor differences in cam profile, compressed head gasket thickness, deck height, etc.

My advise is to use plenty of break in cam lube, Valvoline NON-synthetic VR-1 race oil (high in zinc) and use a proper cam break in procedure and you will be fine.

-Abone.

 

WTF over.

 

Yes I have hear of the KISS principal.
Gene Simmons kicks all the dumbasses out of the band and becomes a millionaire due to intelligence.

I live in BF nowhere Manitoba. I’m 2 hours away from a speed shop with a tool that I can buy. That means 4 trips ( 1 there 1 back for a tool and 1 there 1 back for the rods).

If I can calculate the length I’m going to try that instead of tearing apart a motor and making lots of trips

 

You could do both over the phone(or computer) from Speedway in about 20 minutes(tops), save your time(& gas), & wait for the mail?? KISS was not about a heavy metal band, bur rather "Keep It Simple Stupid" : The simpler you keep it the less trouble it will give you!

 

Have you put a hydraulic roller cam in the engine? Have you installed aftermarket aluminum heads? Have you put rocker arms with a different ratio on the heads?
If the answers to the above questions are no then I would expect you will be OK with the factory pushrods.

 

Why are you so worried about the pushrod length? Is there some detail that we don't know that has you losing sleep about it?

-Abone.

 

I just figured it out

Inches:
The Cam intake lift is 4.60,
The Stud length I pulled with a measureing tape and it was a rough pull mind you. But if I’m wanting rocker arms @ 1.5 then we can use A2 + B2 =C2.
7.3125 before cam lift.
7.7725 inches with lift factor.
That’s pretty dam close to stock.

This gives us the distance from the rocker arm perched with no spring pressure.

 

^^Reminds me of an old saying, “The figures don’t lie...but liars figure “.

 

KISS and Gene Simmons !! KISS stands for ''Keep it simple stupid'' but thanks for giving me a good laugh, i don't think you are going to be a ''Millionaire'' any time soon. JW

 

Just color the top of the valve tip with a dry erase marker turn, put the rocker arm on and adjust. Then turn the motor over 2 revolutions this will show you your contact area on the valve tip in relation to the rocker arm and tell you if the push rods are the right length or not

 

I just wanted to save driving. I do appreciate the responses though.

 

I am speechless!

 

Yeah, that was the measurement of arm height on the stud centered on the valve spring.
I bet if you were to take a 1.6 ratio or 1.7 they would move down on the stud slightly in order to center it. As it is a 1.6 Ratio at 2.25 centered height usuing the same lift cam tells me an 8.08 rod is necessary.

I wonder if someone does take a measurement of rocker stud position if that will hold true

 

Just put the old fucking pushrods back in and follow what flamedabone said....


Sent from my iPhone using H.A.M.B.

 

You cannot calculate pushrod length like that.

 

Looks like I just did. After all pushrod geometry is calculated using a checker, which is just the missing side of a triangle.

 

It's your engine. Have at it!

 

Building a running, driving hot rod is usually equal parts of thinking and doing. My suggestion is a little less think and a little more do.

Good luck, -Abone.

 

I think you will need the rocker arm fulcrum point to calculate this, which may be kinda hard to determine. I guess I'll go search the net and see if I can find it.

 

If you haven't changed from factory steel heads to aluminum heads, the push rod length should be fine, stock for a Chevy 350 is 7.794. Most aluminum head applications will be .100" over stock length. This is from when I was deciding on my push rod length.

 

An adjustable pushrod is $15.

 

You also need a solid lifter .......

 

You can use a hydraulic lifter. Take out the plunger and replace it with a short bolt then put the clip back in.