Measuring for pushrods with a flat tappet hydraulic cam

[timmycharger]

Looking for someone to confirm if the method I used was correct  before I order pushrods.  I am in the process of changing cams after a lobe failure and I want to be sure my valve train is set up properly first.

I am putting the stock stamped rockers back on and Lunati recommends lifter preload to be between .020 and .060.

Here is what I did:

I made sure the lifter I was using was on the base of the cam lobe, then I used my measuring pushrod tool and tightented the rockers/shaft down.  I then took up all of the slack with the adjustable pushrod until I could just barely spin it with my finger rolling over it, then locked it down.

I then pulled the rocker shaft off and measured the pushrod

My measurement was 9.243. I did this three times and got pretty much the same number.

I want to be in the middle of what Lunati recommends for preload so I will use .040

Do I just add the .040 to the 9.243 to get the size push rod I need so in this case, does that mean I need a 9.283 push rod?

I have stock pushrods (9.315) already which according to this may have been too long?  so that would mean I need a push rod .032 shorter according to my math.

Appreciate any insight here, I would like to get them ordered. Thanks guys!

[PRH]

That is how you do it.

If it's a dual pattern cam with different lifts for in/ex, then the cam base circle can be slightly different for the two.

You should measure for pushrod length on both and see if there is a slight variation.

Often you can get a set of pushrods made that will work on both(average length between the two).

[timmycharger]

Thank you, I will double check that.  I am running the below Lunati Voodoo cam:

•Advertised Duration (Int/Exh): 268/276
•Duration @ .050 (Int/Exh): 226/234
•Gross Valve Lift (Int/Exh): .494/.513
•LSA/ICL: 110/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1800-6200
•Includes: Cam Only


Part Number: 10230703
Previous Part Number: 60303

[timmycharger]

Anyone have a source for custom length pushrods?

[BLK 68 R/T]

I used Smith Brothers, they are located in Oregon. There is also Trend Performance and Manton. Those are the only ones I have ever read about and all seemed to have good reviews from what I remember. Whoever you go with will also want to know if you need solid or oil through pushrods.

[timmycharger]

Thank you.  The ones I had before were solid. Is one more desirable than the other?

[BLK 68 R/T]

Thank you.  The ones I had before were solid. Is one more desirable than the other?

Just depends on if your rocker arms require pushrod oiling or not?

[timmycharger]

Hmm ok. Stock stamped rockers, were the pudhrods solid from the factory?

[BLK 68 R/T]

Pretty sure they were solid from the factory and oil through the rocker shafts. Need to double check the FSM to be certain unless someone else that knows for sure can chime in?
Edit: looked at the fsm oiling system. They oil through the rocker shaft, so solid pushrods from factory, in 69 Anyways.

[timmycharger]

Thank you 

Checked out Smith Bros, I will be calling them today once they open and ordering a set. I did another measurement last night and didn't see any differences in pushrod length with the intake side of things.

[68CoronetRT]

That's how you check the length  . Smith Bro's will set you in the right direction.

Yes, the factory used the rocker shafts to oil the pushrods. Remember when installing the shafts to make sure the oiling holes are DOWN AND OUT(pointed towards the headers)

[timmycharger]

 

Thank you!


Called Smith Bros, super easy to get my custom pushrods ordered, I should have them this weekend!

Yes, thanks for the reminder on the shafts.  I have screwed this up in the past 

[BSB67]

Yes, thanks for the reminder on the shafts.  I have screwed this up in the past 

Remember it this way.  One rocker shaft can be installed on a head 4 different ways.  Only one is the right way