I asked them at MMS if there was anything that needed to be done because the heads are milled .030", and they said "no, they would bolt right on". I was just reading a post about heads install and the topic is on shimming the rockers and pushrod length with heads milled .030"? Did I mis-understand them at MMS?
Now I'm concerned about doing the install myself. <img src="images/icons/confused.gif" border="0"> Can anyone point me in the right direction?

Thanks,
Jerry

[ November 30, 2001: Message edited by: Palm Beach Z ]</p>

 

my GTP heads were milled that much and Craig said that i would not have to do anything.

[ November 30, 2001: Message edited by: AAron ]</p>

 

u will be fine <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

 

i hope they are already bolted in <img src="images/icons/wink.gif" border="0">

 

As far as the heads being milled .030", I think that you will have to run 7.350 pushrods. The shims are to get the correct lifter preload. Call them back to double-check. Talk to Brad Giron about this!

Doug
00 Pontiac

 

Thirty thou extra crush on the stock crappy rocker set-up come on.... Don’t be so pedantic. It’s fine.

 

While I will agree that the stock length pushrod may be fine, the stock pushrods themselves probably aren't a good idea to use. I would spend the $100 bucks on a set of hardened pushrods.

 

I’ve been running that setup for almost 2 years now. My MMS stage II heads are milled .030, and I’m using the stock push rods. I’ve never had a problem with them. I’m keeping the stock P-rods because if something goes wrong it’s much easier to replace a bent push rod vs. a bent valve. My rocker arms are not shimmed either. Just torque the rocker arms down to 22ft# and be done with it. <img src="graemlins/burnout.gif" border="0" alt="[Burnout]" />

 

I have the Comp Cam Hi-Tech Pushrods and they are the stock length.
I e-mailed Mike to make sure that the information was correct.
I really appreciate the advice given, guys. I don't want to screw-up this install.

Jerry

 

I'm trying to figure this out, too. I'm not going to use any shims on my rockers when I do my heads install. I already have hardend pushrods of stock length, but if I have to I'll order a new set of shorder ones to install the heads. I think I'm gonna order a pushrod length checker because I've heard that it's the best way to see if you need shorter pushrods or not.

Later

Jordan

[ December 01, 2001: Message edited by: Jorday ]</p>

 

I never hurts to double and triple check stuff. Ecspecially something of this importance, that can make the difference between letting a ricer beat you or not ! <img src="graemlins/gr_jest.gif" border="0" alt="[jester]" />


Doug
00 Pontiac

 

Here is what Walt Donovan, an engineer at Jesel, said about milling heads and pushrod length:
_________________________________________________

"Shimming the stands is not desirable as it changes the rocker geometry, forcing the rocker into its most violent and severe sweep across the valve tip at maximum lift (and maximum spring pressure). The proper way to compensate for shortening the head is to use a shorter pushrod. If the heads are flatmilled .030”, the approximate decrease in pushrod length is estimated as follows:

A 1.7:1 rocker is 1 unit long from pivot to pushrod & 1.7 units long from pivot to valve (unit size is unimportant). This means the length from valve to pushrod is 2.7 units. Therefore, moving the rocker pivot down .030” moves the pushrod seat down .030” X 2.7 / 1.7 or an approximate total of .048". A .050” shorter pushrod should be perfect when the heads are flat milled .030”.

I also mentioned in my reply that lifter "preload" is not preload at all. You simply have to build the valve train so that you don't exceed the adjustment stroke of the lifter. One more thing; If the heads are angle milled, they won't move .030” at the pushrod, it'll be much less. If they're flat milled .030”, it'll move about .050” (don't forget the rocker ratio)."

Comp Cams pushrods P/N 7950-16 will get you 7.350” length rods. These are .050” shorter than stock.

Ron,

 

BTW, I believe the stock GM/LS1 cam and the Comp Cams both have the same base circle, so the above info would apply if the heads were flat milled .030" [and] an aftermarket Comp Cams shaft were installed togather as a package.

Ron,

 

Ron, that is excellent information!

ERic
www.installuniversity.com

 

[quote]Originally posted by Kimchee and Rice:
<strong>BTW, I believe the stock GM/LS1 cam and the Comp Cams both have the same base circle, so the above info would apply if the heads were flat milled .030" [and] an aftermarket Comp Cams shaft were installed togather as a package.

Ron,</strong><hr></blockquote>

My basecircle was not the same on my comp cam vs my stock cam. If I can dig up the measurements I'll post them. More lift = less basecircle at a certain point.

 

Well im just talking about the very heal of the cam (opposite the point of highest lift). Thats where the cam is set while checking lifter preload. I believe you will find that point the same dimension as a stock cam. (its [base] circle)

 

Thanks Ron for the information. Mike Morgan e-mailed me back and told me that yes I would need the shorter pushrods with the after-market cam.
I knew something didn't seem right when told that the milled heads would bolt right up. Sometimes it's good to get more than one opinion. <img src="images/icons/cool.gif" border="0">

 

Cam base circle dimension depends on cam lift. An '01 LS6 cam with .525" lift has a smaller base circle than stock LS1. The '02 LS6 cam with .550" lift has a even smaller base circle than than stock LS1. So I'm sure that the aftermarket cams with higher lifts, especially over .550", have smaller base circles, otherwise they would not fit into the block.

As far as using the stock length pushrod on a milled head, it will run fine, but unless you are using a smaller base circle cam that happens to offset the head milling, you will be running too much lifter pre-load for best performance. Remember, the goal is to run as little preload as possible, '0-lash'. This will allow the engine to rev to higher revs before the lifters pump up and you get into a float condition. Less preload is better.

 

I believe MMS suggests you check the lash, and shim as needed to get to their specs for the heads (I think they include a shim set with the heads). It's not hard or anything, just an extra 1/2 hr of work. Well worth it to check if you ask me.

 

How is lifter preload & lash measured? Should the shop that does the install know how to check this?
I already ordered the 7.350" pushrods.

Thanks,
Jerry
<img src="images/icons/rolleyes.gif" border="0">