Hey Guys,

Been browsing the forums for quite some time but this is my first post. Hopefully yall can provide some valuable info for me.

I have a 2004 Chevy silverado 1500 w/ an LM7 5.3. I recently discovered it has some cracked castec 706 heads. It began ticking and had a puff of smoke on startup so I began researching the cause. Coolant was disappearing so it led me to the castec issue. I pulled the rockers and confirmed that they were in fact the castec 706s.

Fast forward a couple weeks and I've got the heads removed and some parts waiting to be installed. I got a set of reman'd heads from Cylinder Heads Int, ARP head bolts, LS7 lifters, new lifter guides, and a felpro gasket kit. When the rain stops, I'm gonna swap out the lifters/guides and start putting it back together. My main concern at the moment is the topic of pushrod length. Can I put it back together like normal with the LS7 lifters, Felpro head gasket, stock pushrods & Rockers, or must the pushrods be measured and possibly swapped? I'm also a little confused as to preload as I thought these motors weren't really adjustable. If anyone can help with the process of what to do from this point it would be greatly appreciated. Thanks!



IMG_5224.mp4 video by redrdrfmx | Photobucket

 

It should all go back together the same. I believe the LS7 lifters are the same height as stock and the flepro gasket is the same thickness.

Some will say the right way is to always check it with a pushrod checker. But I dont think you'll have any problem at all.

Side note: I stay away from any 706 cast for this reason and when replacing I go with the 862 cast. Even though not all 706 crack. I just try to stay safe with a completely different cast.

 

Toss the stock Pr's back in there as long as your putting the stock cam back in. I think I would have went with OEM gaskets, but the FP's are good..

 

You will want to measure the pushrod length. With a stock LS1 cam, stock 706 heads, stock head gaskets, stock rockers, and LS7 lifters, I needed 7.350" pushrods to get around 0.070" preload. Many people use the stock length pushrods without issues, but it's always best to measure.

 

Thanks guys for the quick replies. I really appreciate it.

It is the stock cam, in fact I didn't pull it out. (nor do I plan to)

I just ordered a comp cams length checker (7702-1. COMP Cams Hi-Tech Pushrod Length Checking Tools 7702-1 - SummitRacing.com) that goes from 6.8" - 7.8". As far as preload and how to check I am at a loss. Even the process of measuring I don't quite understand. Anybody care to learn me some knowledge?

 

Good call on measuring it...

As for the tool, each full twist is 0.05" I think, so if it takes you 10 turns to take away the slack on the rocker without preloading the lifter, your pushrod length will be 6.8+10*0.05=7.300. Now you add the desired preload to your measurement for your final length. So if you want 0.075" preload you need 7.300+0.075=7.375" pushrods.

 

Those lifters and head gaskets are direct replacements, there is zero reason to measure the PR length. I don't care what anyone or any internet post says.....lol

 

Agreed, no reason in this instance, IMO.. Al stock replacing parts..

 

TXSZ66AVALANCHE, that is exactly what I wanted to hear. I'm thinking about measuring them just to learn the process but can everyone agree that I would be fine with just putting it back together with the stockers. Everything I've read so far tells me that the LS7 lifters are an OE replacement on these motors.

Now as far as setting preload, can anyone give me a little more info on the process and what is involved. Sorry for the noob questions. I know my way around a wrench but when it comes to engine building, and valvetrain stuff I have a lot to learn.

 

Double agreed.