Alright, I've decided (and received Wifely approval) to do a *mild* cam swap in my 07 Trailblazer 5.3 4WD.

Originally was just going to be some gaskets and a wear component replacement, but the "Since You're in There's" bit me and now it's turning into a build.

Goals/rules:
Retain as much stock-like driveability and reliability as possible. This is a DD for both myself and my wife, and one promise I had to make was that, aside from some chop at idle, she would barely be able to tell the truck has been modded.

Run on 87 Octane, and minimize MPG losses. I know deleting DOD is going to cause a drop in mileage, and any cammed motor is also going to drop. As long as I can stay within the teens for average MPG then I get to continue to sleep in my own bed.

Minimize the amount of mods needed. Again, being that this is a DD (and my budget is limited anyway) I'm not looking to build a *****-to-the-wall motor. Stock manifolds (until I find some 1-3/4 headers or someone convinces me 1-7/8 will be fine) and stock converter are a must. Also, not looking to make so much power that it disintegrates my 4L60E

The parts list:
LS7 lifters
New lifter trays
Pushrods
Ls2 valley cover and gasket
Stock 5.7/5.3 MLS head gasket
Head bolts
1-3 bolt cam conversion kit
Timing chain
Cam
Cam Retainer plate
Timing cover gasket
Front main seal
Oil pan gasket (needs replacing)
Crank bolt
Catch can
Valve seals
spring kit
retainers
Rocker trunnion kit
Inspect/rebuild oil pump


I am still considering my cam selection. Based on some of Richard Holdener's videos, I'm torn between the Truck Norris cam, or the BTR Torque Cam. For those far more knowledgeable about cam selection, I'm open to feedback as well as other options.

Is it worth having the heads milled to bump compression a little? I'm still trying to stay within 87 octane but I know compression will help combat any bottom end losses from the cam.

I have a set of bare 243 heads from a TBSS LS2 I got a few years ago. To assist with turnaround time my plan was to send those heads to be decked and/or milled, then when I disassemble the Lh6, take the valves out of my current heads and put them in the fresh decked/cleaned ones. Are there any issues with this? I figured I would be lapping the valves, but wasn't sure if moving seasoned valves (cleaned up of course) into a different core was a big no-no. If it is, I'll see about sourcing a set of new valves. My goal is to reduce the amount of downtime, hopefully to no more than 2 weeks from start to finish (minus tuning time).

Thoughts? Feedback? Anything I missed?

 

"New lifter trays" - Genuine GM? If not, they need to be, as lesser brands DO fail

 

BTR torque cam will drive very tame and make great power with the 243’s..plus is stock converter friendly. You’re going to get recommended a lot of cam recommendations here, from mild to wild. It doesnt take a lot of camshaft to make the LS platform respond…do not overcam this…you’ll regret it. Regarding the 243s, to minimize down time, go ahead and have them built before you start the process. This will save you downtime. I know you want to stay 87 pump friendly, but increasing compression will increase fuel mileage. With the right tune, the trade off between the extra mileage increase on 93 octane, vs the increased cost per gallon becomes worth it. Plan on a .040 headgasket (efficiency) and shoot for 11:1 or more. The only way to go farther on a gallon of gas is to squeeze it harder. It’s why the OEMs are making everything these days a high compression engine…fuel economy. Power is simply a nice byproduct.
Id plan on a new Melling M295 pump…toss the old pump, it not worth it on this investment.
​​​​​​…edit…LS7 lifters are a crapshoot these days. The BTR LS7’s are quality. They cost $210 but are quality. Use with confidence.

 

Scott-
Good advice on compression.
On that, it never fails to amaze me how these engines can run as high a compression as they do even on 87 octane!
Much less what it will do on 91 or 93!

 

Good point on the melling pump. For 100 bucks its a cheap upgrade.
I was looking at the GM lifters listed on ICTBillets website. They're in stock vs BTR being on backorder. I would assume that the OE and Delphi lifters are basically the same?

I don't know if where I live an increase in mileage from upping compression and requiring premium would make sense. Where I live 92 Octane is about a dollar more per gallon than 87.

and overcamming is the last thing I want to do. This motor lives most of its life between idle and 2500RPM. The only time top end power is going to matter is if I'm towing or passing someone (or when my son says "Daddy go fast!"). Thanks for the recommendation.

 

So lots of companies offering “LS7” lifters, with very few being quality. Knockoffs are everywhere. Finding a cheap set on Amazon or eBay often means they are counterfeit knockoffs. I mentioned the BTR Delphi set because they are genuine lifters and quality is great. I build a lot of engines, and I’ve seen a lot of junk lifters. I’ve also used the BTR Delphi and they are high quality pieces. Here’s a link at Summit…https://www.summitracing.com/search/...SABEgJg6PD_BwE

 

That's fair. Ordering now.

I did some digging in my garage, and I happened to find the valves that were originally on the 243 heads I bought. Despite living in a ziploc bag, they look pretty decent. Going to clean them up and give them a solid once-over and see how they look. Found the retainers and keepers, though somehow I'm missing 2 retainers and a pair of keepers. Oh well, those are at least cheap to replace (vs valves anyway).

Started ordering parts, main focus is getting parts for the cylinder heads so I can get them machined and assembled. Trying to figure out if I need to have the heads milled or just decked. From what I read online, both the TBSS and the LH6 had the same combustion chamber volume (65cc). They also had flat top, 0cc pistons. Yet there's a full point difference in compression (10.9 vs 9.9). Did the lh6 pistons have a lower compression height and that's why compression was lower? I know to get accurate compression numbers I would need to measure deck height, but given the time constraints, is there an amount I can tell the shop to knock off the heads that'll get compression up to near 11:1?

 

LH6 is a flattop piston engine. Your 243 heads…IF they have never been cut…are 65cc chambers. To get to 11:1ish you’ll need a 58cc chamber. Figuring this with a .040 headgasket, pistons out of the hole .005…which is normalish for most LS engines. To get those heads down to a 58cc chamber, you’ll need to cut .039-.040” off of them. You’ll end up with a 10.92ish compression number, but that’s close enough for what you’re doing. Intake will fit fine with .040 off the heads. I’ve been .060” off of heads and intake still fit correctly.

 

I have a TBSS, orig owner👍. My suggestion for combo on yours is 862 heads cnc'd and a Hawks Cheatr cam I ran the Lingenfelter version of that cam and it's amazing the driveability and power it gives. Do the Speed Engineering 1 7/8 headers and a full 3.5in car back. It will be a new truck, perfect driveability and still gets decent mileage.

 

1-7/8 are way overkill on a mild 5.3

 

You might want to consider summit 8728 big torkinator cam. -5 degrees of overlap, 212/218, 600, .585, 110+3. Same power curve of the truck norris cam with a lot less overlap. Higher lift and more aggressive lobes, but since you are swapping lifters, I would think that shouldn't be a problem. If you were running stock lifters, I probably wouldn't recommend it.

 

I'll add that to the list of consideration. Though one question that comes up is longevity. Part of the reason I'm doing this is to increase the reliability of the motor (figure a fresh top end and no DOD should make it go for another 1-200k), and I wonder if anyone has ran/DD'ed a car with an "aggressive" cam enough to actually wear out the springs and/or lifters.

 

ok i re-read the thread. Everything is screaming btr torque cam. Easy on the valvetrain and your wife won't mind it. We're you going to use a converter? Wouldn't need one with the torque cam. The truck would be a monster with a 3k converter and the truck norris cam, but everyone including your wife would know it is cammed, and you would lose low end torque if you didnt install a converter. For a dd, I say torque cam and no converter.

If it was a weekend car, I would say truck norris and converter. That would give a massive torque curve and pull so hard from 3k to 6500 but for your goals, I say btr torque cam. It should be better everywhere I think.

 

My plan was to stick with the stock converter. This is definitely a budget build (unless I fall into a pit of money tomorrow).

 

btr torque cam for the win