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4.8 LR4 dyno results and build evaluation

 
Old 12-20-2018, 10:01 PM
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Default 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?


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Old 12-21-2018, 10:33 AM
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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.
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Old 12-21-2018, 10:33 AM
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Nevermind, I see the Pacesetter part
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Old 12-21-2018, 10:41 AM
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I wouldn't have expected 300 wheel out of a BTR truck cam on a 4.8.
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Old 12-21-2018, 11:18 AM
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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!

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Old 12-21-2018, 11:31 AM
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id take it to someone who specializes in tuning LS stuff.
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Old 12-21-2018, 12:12 PM
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Do you have a before dyno? Interested to see what YOUR truck did on THAT dyno before.
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Old 12-21-2018, 01:18 PM
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Originally Posted by LSleeper1500 View Post
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.
2wd; rebuilt a 4l65e trans with all the bells and whistles (hd shift kit, servo, hd sun gear, trans pump update, etc.); tire size was like 32.5Ē I believe; no other mods that I didnt list besides a transmission cooler, I did a few other repairs and preventative maintenance but no other performance mods
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Old 12-21-2018, 01:21 PM
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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
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Old 12-21-2018, 01:36 PM
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Originally Posted by stockA4 View Post
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!
Got the heads pretty cheap I think. paid $450 for the pair. Some guy was selling them milled and with the bigger valves already installed. Now that I think about it I see that they were probably overkill considering the lack of displacement but seemed like a hard deal to pass up considering price and availability of other heads in my area.

I was a little bothered to see it peak at 5400. while I dont have very much personal experience with modifying these motors I have spent A LOT of time looking up information, build threads on similar engines, and data on results from similar mods. so when I saw these numbers I felt like I got robbed of some performance.

I was able to get some information from the tuner. He said the afr is about 12.7 in the low end and goes to 12.0 in the top end. He said timing is advanced 20 degrees. And he said the duty cycle on the injectors is 74%

Not totally ecstatic with my results over all so Iíll see what I can do considering my current circumstances
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Old 12-21-2018, 01:38 PM
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Originally Posted by LSleeper1500 View Post
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
I have heard that as well. I was originally going to get a TSP cam but theyre turn around time for a cam was nearly 4 weeks due to a large number of black friday orders. Maybe next build I do Iíll go woth a TSP and see how it does
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Old 12-21-2018, 01:39 PM
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Originally Posted by 00pooterSS View Post
Do you have a before dyno? Interested to see what YOUR truck did on THAT dyno before.
Sadly no. I will try to contact the tuner and see if he has the sheets for each run saved and see what kind of improvements were made throughout the session
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Old 12-21-2018, 01:45 PM
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Originally Posted by JoeNova View Post
I wouldn't have expected 300 wheel out of a BTR truck cam on a 4.8.
Originally Posted by stockA4 View Post
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!
Originally Posted by todoslosdiaz View Post


Sadly no. I will try to contact the tuner and see if he has the sheets for each run saved and see what kind of improvements were made throughout the session
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.
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Old 12-21-2018, 01:53 PM
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Originally Posted by 00pooterSS View Post
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.
you have a point. that would probably be a better reference point than the final number. Also I understand my goals were a little high haha. I was crossing my fingers for about ~290 but was realistically expecting ~270 (give or take a few hp due to dyno discrepancies)
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Old 12-21-2018, 01:55 PM
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the truck is going to be spending some time in Mexico pretty soon. Out of curiosity anybody know any tuners out there?
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Old 12-21-2018, 02:58 PM
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20 degrees total advance??? thats extremely low if thats the case
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Old 12-21-2018, 03:32 PM
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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
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Old 12-21-2018, 04:53 PM
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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.
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Old 12-21-2018, 05:26 PM
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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.
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Old 12-21-2018, 08:13 PM
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I shot the tuner an email asking for more information concerning his decision making process on the tuning parameters. Hopefully Iíll get some info by tomorrow. Iíll keep you guys updated
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