Buckshot

I've got a set of MMS 5.3l pnp heads and a 229/229/112 LSA cam that I'm installaing on my 2002 C5. 4 rocker shims, .020" thick, came with the setup. I need to establish between .030" and .050" of preload. What's the best way to measure the preload height?

TIA

mikey

iTrader: (6)

I don't know why they do that with the shims <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

You would be better off with the right pushrod lenght in the first place. Anyway, here's what to do.

Bring the exhaust pushrod on any cylinder up until it is at it's peak. Install pushrod on the intake and bring the rocker bolt down until there is no play (zero lash). Now count how many turns of the bolt it takes to completely tighten the bolt. Should be 3/4 to 1.25 turns for acceptable preload.

Mikey

Buckshot

Thanks, Mikey.

MMS sent me the Comp Cam Hitech 7.350" pushrods for this setup. When I asked Mike Morgan about the shim kit he said, "Sometimes the 229 will need two to get the preload just right. You want to see about .030 to .050” preload." When I initially spoke with him about the pushrods, he indicated the 7.350" are the correct length. I guess not?

I appreciate the quick response. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

mikey

iTrader: (6)

Most of the time a 7.350 rod is correct on an LS1 head cut 0.030 with the stock cam base circle.

Mikey

Buckshot

That's why I asked about the pushrod length before I ordered. Aren't pushrods sold in .050" increments? In that case, I could see why shimming would be necessary if the correct preload fell in between consecutive pushrod lengths.

mikey

iTrader: (6)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Buckshot:
<strong>That's why I asked about the pushrod length before I ordered. Aren't pushrods sold in .050" increments? In that case, I could see why shimming would be necessary if the correct preload fell in between consecutive pushrod lengths.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Exactly. Every head and cam package we sell is checked for pushrod length
on an engine core.

Mikey

<small>[ October 25, 2002, 03:59 PM: Message edited by: mikey ]</small>

Buckshot

So with a .030" milled head and a 7.350" pushrod I should be at the correct height. Base circle on the cam is unchanged and I'm using stock lifters, stock rockers and Rev dual springs.

Scalpel

iTrader: (4)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Buckshot:
<strong>So with a .030" milled head and a 7.350" pushrod I should be at the correct height. Base circle on the cam is unchanged and I'm using stock lifters, stock rockers and Rev dual springs.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yep yep <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Tin Indian

mikey...

Joe Prince stated in another post that 2.0 to 2.2 turns of the rocker bolt past zero lash would equal the correct factory spec preload.

You say its 3/4 to 1.25 turns for acceptable preload.

<img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

AFTICA

iTrader: (8)

2.0 to 2.2 turns, 3/4 to 1.25 turns, 22ft/lbs <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Tin Indian

ttt