Thanks for having me first of all. Long story shorter version is I received a 01 extended cab stepside 2wd with no rust and a broken timing chain. Tore into engine to find cam tightened up due to lack oil sludge and neglect. I pulled engine and found rotating assembly not damaged whatsoever and heads have bent valves. I have stock heads off my GTO that had 20k miles when I went aftermarket with it. I also have 90mm throttle body and timing chain from the LS2. I want to mill the heads .075 and use .040 headgaskets , Truck Norris cam,Trailblazer SS intake,LS2 injectors,4L60E with Zpack clutches and converter with apx. 2300 stall. RPO code shows 373 locker diff. The truck is kinda a retirement gift to myself and I need to keep cost down as much as possible. that is why I want to leave rotating assembly as is except rings and bearings and oil pump. I have long tube headers and true duals for it also. I have searched for weeks and cant find any reasons it shouldn't work. Anyone have any input? Thanks

 

I wouldn't mill those heads more than .030", and honestly wouldn't worry about the thinner gaskets. Splitting hairs trying to get the compression to a certain number - not worth the hassle. As for cam, it'll work... but if you're going to do a 3200 stall - there are better options for less money. (Summit Pro LS cams come to mind) Just my $0.10

 

Pretty much nailed it. The thinner you make the decks, the more likely you will have sealing problems.

 

Agree with everything, except you transposed the stall (OP stated 2300rpm). He could probably step up to the Summit 8720R1, and it'll probably work out even with the extra money for the higher lift springs.

 

I left out Truck Norris BTR NSR cam is also in the recipe and I will tow with it occasionally. So I am thinking a little bump over stock on converter to keep trans temps down. The truck will never see a track unless towing my car or sons car there. I have heard of 243 being milled over .100 N/A without issues. At the end of the day if for some reason it doesnt work Im only out my time and cost to mill. I really appreciate the input and Im looking for someone that has tied it or something similar. I dont want to raise the start of the torque curve much over a few hundred RPM over stock.

 

I don't know much information on the 4L60e, but have read the "Z-pack" is not a great idea from some builders, but can't recall why? Maybe some other clutches are supposed to be better? IDK. It may have to do with like performance (racing) vs towing? Do some reading about it, maybe on the LS1TECH forum?

I'm assuming you are going to get the transmission built? Talk to your builder about it.

 

Its there now and he recommended along with so altering of valve body. I actually put my trust in him and did not research that. I retired from wrenching for 40 years and automatic internals were not part of it but am Master certified with L1. I know 4l60E isnt the stoutest but I am not thinking I will be at the level to break it with sensible driving. Going to have to keep fingers crossed

 

oops... guess my brain saw what it wanted to see

 

OP,

You've received some great advice from the community. We agree with everyone about the milling. We wouldn't go more than .030". At .030" your heads would be roughly 60cc from 65cc. One thing to remember is the intake lining up with the head. .030" is what we've found to be about the limit for the intake to still line up with the head. At 60cc with a .051" head gasket you're LM7 would be around 9.6:1 compression. With .040" head gaskets, you'd be around 9.8:1. We like using a thinner head gasket to reduce the quench distance. Reducing quench into the optimal range helps promote a more efficient combustion cycle and reduces the chance of knock.

Regarding the cam. Added lift is your friend for added power and torque across the range. We'd take a look at our SUM-8728R1 "Big Torkinator" for this combo and goals. Specs on it are .600/.585, 212/218, 110+3 with -5* of overlap. It'll have a steady lope and will require a custom tune. It's spec'd similarly to the TN but with added lift. The 8728R1 will make great torque from 2,000 on up and pulls well to 6,500 while remaining easy on the valvetrain. Pair it with the Trickflow by PAC .600" lift beehives. Your other planned upgrades will help get everything out of the cam.

You'll need upgraded pushrods. A 7.400" or 7.425" typically works with the 8728R1 but we always recommend measuring first, especially when milling the heads. We recommend a minimum of a Chromoly 5/16" pushrod with a .080" wall. You can typically find a set of 16 for around $100.

Let us know if we can be of any further assistance.

 

Additionally, if you're really trying to add compression, use an 862/706 head instead. Can get 'em rebuilt for less than $500 shipped off eBay. Sell the 243 heads ya got. How much time do you plan on spending above 6,000RPM where those 243 heads are more useful than the 243s?