4.8 LR4 dyno results and build evaluation
 

How's it going guys, I did some performance modifications to my 2003 silverado for the first time. I noticed that the truck was consuming coolant a while back and decided to investigate. I did a visual inspection and found no leaks, did a coolant system pressure test and found no leaks, and decided to add some dye and reinvestigate at my next oil change. Upon doing my next oil change I found no traces of dye and when I drained the oil I noticed a difference in the consistency of the oil. After doing some research about common failures of the truck I discovered that I could possibly have faulty castech heads. I popped off the valve covers and sure enough they showed signs of head failure (butterscotch colored oil and coolant mixture all over the valve cover). I used this as an opportunity to do modifications I had been thinking of doing for quite some time.

Here is a list of what was done as part of the head cylinder repair/minor build:
-862 heads milled .020" to raise compression
-mild port and polish (mostly bowl work)
-2" intake valves
-blue GM springs
-Brian Tooley stage 2 truck cam (212/218 .553" lift)
-comp cams hardened push rods
-Timing chain and new oil pump
-8.1L truck injectors (gives me about 34 lbs/hr at my trucks 58 psi fuel pressure)
-Pacesetter long tube headers and off road y-pipe
-Airaid MIT w/ stock airbox and stock filter

After doing the repairs and modifications I took the vehicle to a local tuner. He did not specialize in Chevy's but he assured me they were not strangers to tuning them and that they could take care of me. I went ahead and bit the bullet and scheduled a dyno session. After getting the truck and dyno sheet back I have to say that I am a little underwhelmed. I was hoping to get close to the 300 rwhp range (270-290) although the torque is about close to what I was expecting. I will attach a picture of the dyno sheet and would like to hear some opinions on my results. Where my expectations realistic? Could a more experienced tuner get me better results? What should I have done to get closer to my goals?
https://cimg5.ibsrv.net/gimg/ls1tech...18e4185cf0.jpg

2wd? 4l60e or 4l80e? Tire size? Not going to lie, seems a little low. What other mods as far as headers and exhaust? I would've guessed it made a little more but the small cubes isn't the strongest setup to start with anyways.

Nevermind, I see the Pacesetter part

I wouldn't have expected 300 wheel out of a BTR truck cam on a 4.8.

I hate to say it but those 2.00" intake valves are completely unnecessary on a 4.8 build, they aren't really needed for a 5.3 either though in most cases imo. Stock injectors would have been fine as well.

That thing should peak a lot higher than 5400 though regardless, that's about where a stock cammed 4.8 peaks, so something could be off with the cam timing, like it's advanced to much? Or even more likely your tuner sucks.

I won't claim to know everything but I have been dailying a junkyard 2002 lr4 with 706 heads (never been off), blue springs and a comp 212/218-115+0 in an otherwise stock 2.73 geared camaro for 3 years. It has a great wideband street tune with just a stock 02 ls1 timing table and I only run 87 in it. Shifts at 6700, pulls hard to 7200 where we set the rev limiter. I've never dynoed it but I took it to the dragstrip last summer, (90 degrees and DA was about 2600 that day) and it was consistent 14.40's @ 104mph. Yes the et sucks, but that's due to the lack of low end tourqe and the stock ls1 converter (tighter than a stock 4.8 verter) and those 2.73's, it gets great gas milage though lol.

Anyways 104mph at about 3800lbs for my setup with me in it is easily 300 wheel so I would definitely say something is wrong. I'm also running stock exhaust manifolds on mine too!

​if it where mine I'd put the stock injectors back in, double check the cam timing to make sure it isn't advanced a tooth, and then find someone who knows what these engines want for a tune-up

Good luck and let us know what you figure out!

id take it to someone who specializes in tuning LS stuff.

Do you have a before dyno? Interested to see what YOUR truck did on THAT dyno before.

Not sure if it's worth mentioning.. But I have read that the TSP line makes more power than BTR truck stuff. Im considering the 216/220 low lift, high lift, or the 223/226 for my 5.3 rcsb

Yeah I'm curious if it's a low reading dyno or if you have something about your truck that makes it possibly read lower before assuming your power is down. I thought the 4.8 dynoed in the low 200's so it would seem you picked up some but to see if you're low or not it would be good to know how much you picked up.

300 is shooting pretty high for a small low lift cam. The head work should have helped but the large valve may have hurt it a little.

:burn:the truck is going to be spending some time in Mexico pretty soon. Out of curiosity anybody know any tuners out there? :burn:

20 degrees total advance??? thats extremely low if thats the case

It should easily be peaking over 6000rpms something isn't right . A 4.8 usually makes about the same same hp as a 5.3 just higher up in the rpm range given the same mods. I think the combo has another 30whp in it. 20 degree timing is conservative

I tend to find the most HP at 25-28* of timing and the air/fuel ratio at 12.5 to 1 from 3,500+. In the 1,500-3,500 rpm range I like the afr around 12:1. The torque curve looks honestly about what I would expect with that small cam. Leaning it out from 12:1 to 12.5:1 is probably only 3-4 hp gain. Its the 5-8* of timing that is missing that is hurting it the most. Probably down another 10-15 hp from that and matching torque.

I didn't even see the 20 degrees timing thing.

I wonder if the cam could be a hair advanced like off a tooth and causing some knock early on and that's why the timing was pulled. Otherwise not sure why the dude would stop at 20 unless he saw a little knock with a degree or two more of timing and brought it back to 20.

OP ask the tooooner if he stopped at 20 because he thought that was good or if he saw knock and brought it down to 20 to control it.