When installing heads that have been milled .030" how do you know if you need a shorter pushrod or not? I don't want to shim my rocker arms, I want to use a pushrod of different length if necessary when installing my heads. How do I tell what length I need to get. I know that the stock length will be slightly too long with the milled heads, but with my B1 cam, which apparently has a smaller base circle, wouldn't the smaller base circle reduce the need for a shorter pushrod? <img src="images/icons/confused.gif" border="0"> I am really excited to get the new heads on the car, but I can't until I get this figured out. Hopefully someone can shed some light on this subject for me.

Later,
Jordan <img src="images/icons/cool.gif" border="0">

 

What you're trying to accomplish by shimming the rockers, or using a shorter pushrod, is getting the lifter preload correct. Personally, I run Comp lifters, which like only a small amount of preload, unlike the stock lifters.

I have mine set up around .010" of preload on the lifters. The way I set mine up is like this;

You'll want to do this with the crank in a position such that the valve you're working on is closed. With everything pretty much set in place, drop a pushrod in and tighten down the rocker arm until it just starts to get snug, and all mechanical slop is taken out. It shouldn't be "tight" but you shouldn't be able to move the pushrod up/down any. This should be zero lash. Set up a dial caliper somehow, so it reads zero on the pushrod side of the rocker arm. Now, tighten the rocker down all the way, and note how much the gauge reads (but do it quckly before the lifter starts to bleed down and throws off your reading). The measurement you see is your lifter preload. All you need to do is shim the rocker, or shorten the pushrod until you achieve the amount you're looking for (someone else will have to chime in with stock lifter specs). An adjustable checking pushrod would make this job easier.

I know my description is probably pretty confusing, but I'm not good at explaining **** like this with a keyboard <img src="images/icons/smile.gif" border="0"> I hope it at least helps you some...

 

I went thru the same dilemma when I installed my heads (milled .030). Basically, everyone told me to "Guess" and hope that they worked. <img src="images/icons/rolleyes.gif" border="0"> Yes...I know, that's not the way I do busines either. Fortunately I was able to talk w/ Mikey @ Rapid Motorsports and he told me that w/ my cam's base-circle (It's a Comp grind), I would need 7.350" length p-rods.

Do you know the exact Base circle of the B1? If so, just call MTI. I'm sure they can give you an exact answer.

(BTW...summit has the best prices on 7.350 rods if you end up needing them. <img src="images/icons/grin.gif" border="0"> )

 

My heads were whacked about .030". Mine have .030" shims under the rockers PLUS the shorter 7.350 pushrods. For most, the pushrods alone will be enough, but like George, I like running a very shallow plunger depth for high rpm safety.

 

Ok, my heads were milled .025.

Basically, here's what I did to find the right preload. Get the rocker set to zero lash...the rocker should be tightened just enough to where the pushrod won't turn with your fingers, now the correct preload should be one full turn to 23 foot lbs of tq. To achieve the one full turn I used .060 shims with the stock length 7.40 hardened pushrods. Also I am using a B1 so you may try a .060 shim to begin with(if you go the shim route)

 

Thanks for the help guys. <img src="images/icons/smile.gif" border="0"> I'm understanding a little better, I think. Another question...Couldn't you just install a pushrod that was short enough so you wouldn't need to shim the rockers any? <img src="images/icons/confused.gif" border="0"> I was kind of wanting to avoid installing shims because they change the way that the rocker arm contacts the valve. Could I just get a pushrod length checker and find out exactly what length I need and then custom order a pushrod of that length?

Later,
Jordan

 

Yes Jorday you can...most people like me like to just shim it and go.

 

The heads I'm getting from MMS are milled .030". I asked them if there was anything I needed to do because of this and was told they would just bolt right up??? <img src="images/icons/confused.gif" border="0">

 

milled .030" heads 7.350" push rods work just fine