verbs

First off a big thanks to Louis of LG motorsports for helping me troubleshoot my problems. He's spent a lot of time with me on this during his crazy schedule, and it's much appreciated.

The original thread with my initial progress can be found here:
https://ls1tech.com/forums/generation-iii-internal-engine/146431-please-help-missing-over-50rwhp-after-g5x3-lsx-intake-install-dyno-graph-inside.html

I just redynoed after a few changes and came up with exactly the same #'s as before for the most part. The changes included getting rid of the YT rockers/shims/different length pushrods (7.4 intake/7.35 exhaust), and going with all 7.35 pushrods and stock rockers.

Well, it looks like the YT rockers caused no valvefloat with the G5X3 cam and Crane 832 dual springs, as the power is identical up top with stock rockers vs. YT rockers. Since I'm not experiencing any valvefloat, the YT rockers will likely go back on.

Tested the MAF weatherpack plug by going into speed density mode (via pulling the MAF plug) to see if I had a bad weather pack. The #'s in speed density mode were much worse than with the MAF plugged in.

I'm now down to 3 possible options.

Option 1: The cylinder heads got a valve job on the valve seats by a local machine shop while they were replacing my 7 bent valves (2 intake 5 exhaust). It's possible the airflow could have been severly disrupted by this process. My cylinder heads are going back to TEA in the coming weeks for testing with and without the LSX manifold in place. If they aren't fixable, I will be sporting a brand new set of Stg. 2.5 LS6 Massengale Series heads with a 2.055 intake/1.6 exhaust and the special nitrous port (since the nitrous port makes more power under the curve) and hand finishing to competition level. This is the option I will be exhausting first. If I only pick up say 15rwhp or so, I know something is still wrong.

Option 2: Cam is one tooth off. If it was one tooth off, that could explain the huge dropoff in power down low compared to up top (I'm down at least 70rwtq down low). If the cam was one tooth off giving me more advance, I'd have destroyed my engine by now. If the cam was one tooth off giving more retard to the cam, then my p/v would be fine, but I'd be way down on power. However, if my cam was retarded too much, then my cam wouldn't be peaking at 6200rpms like it is now...and 6200rpms is lower than where it should peak.

Option 3: Cam was misground by Comp. Cams. If options 1 and 2 yield no results, I will be swapping in another G5X3 112LSA cam to see if that fixes anything. It's very rare this is an issue, but it has happened before.


Hopefully one of these options will yield the desired results. I should know for sure in the coming months.

CHRISPY

Good luck!

DenzSS

Who installed the cam? Did they use a degree wheel? Not too long ago I saw a cam installed 8* advanced even though it had 4* advance ground into the cam. Talk about making no real power. Looked good on the dyno, but was absolute crap in the real world.


I agree. Possible, but HIGHLY unlikely.

verbs

Xtreme motorsports in Tempe AZ did it. They are Corvette/LS1 specialists. The did not use a degree wheel, but said it was dot to dot and they used a leveler to help. They also installed my last cam which had no problems. They've installed hundreds of ls1 cams.

DenzSS

Well, then #2 should be off the list.

You are down to bad luck or airflow problems. Tracking these problems down is always a pain.

verbs

The other reason I find it hard to believe that the cam is off a tooth (causing extra retarding) is that my dynograph peaks at 6200rpms, which is too low to being with. If my cam were retarded at all, it would probably pull all the way to the redline of 7000rpms.

gomer

iTrader: (13)

I vote for option #1, I have seen two sets of LS1 heads that had a local NAPA machine shop do their "valve job" on when rebuilding and completely screwed them up. One set was an ex vendor's stage II's and after the valvejob they flowed 250ish, Terry at patriot redid the valvejob on them and they ended up flowing 290, so that is a hell of an increase from just a valve job. I good valve job is KEY to flow.

DenzSS

fully in agreement there. Plus, one tooth is a hell of a lot of retard.

IMO, if you're expecting 480rwhp, that probably isn't going to happen. At least not without an incredibly narrow power band.

6200 is way low for a cam that size. Where is the torque peak?

Did you ever post a dyno graph?

30th TA 0219

wouldn't #3 be the easiest and cheapest to test?

DenzSS

#3 is practically impossible, especially for a common grind like the G5X3. Misgrinds are incredibly rare to begin with.

verbs

Torque peak is at 4700rpms or so, which is the proper torque peak. Again, if my cam was severely retarded, I'd expect this number to be a lot higher. There is a dynograph on the link to thread at the top of the page.

As far as 480rwhp, no I'm not expecting that, but I was realistically hoping for 460rwhp with all the new mods, and if I go to LS6 heads I would hope to see 470rwhp.

KGSloan

good luck to you. my guess would be that the heads arn't flowing properly due to the valve job. didn't you also say that they only did a valve job on the seats with the bent valves? this could make each port flow different which would not be good for power. best of luck to you, i hope you can get it figured out

99 Black Bird T/A

iTrader: (4)

Gomer and I tend to agree again. I think the valve job was messed up when the heads were "fixed". The valve job either makes or breaks any set of heads.

Has a leak down test been done to make sure everything is sealing up as it should with the motor? You may have posted this, I dont recall.

DenzSS

Damn, after looking at that graph I'd be more worried about your torque. You basically don't have any. I still wouldn't expect even 460 realistically, but you definitely do have some major issues.

I would take a look at your tuning first, then dig into the heads. It looks like you're hitting some pretty good KR on one of those graphs. Each point of KR can kill up to 10rwtq, so it can eat it up quick.

What kind of timing are you running?

verbs

The did a valve job on the valves that replaced the bent ones because they said they couldn't get it to seal properly without doing that.

Leakdown test was done, and it was 4-8% on the entire motor. The leakdown test is what clued us in to the bent valves.

verbs

The tuning should be dead nuts on. Look at the A/F ratio for example, just about perfect, and I have 26-27 degrees of timing until 5500rpms or so, and then 28 degrees to redline. I'm getting 0 knock retard throughout the entire runs, which makes the wavering of the graphs even more perplexing.

DenzSS

4%-8% isn't bad at all for a street motor.

Do you have a copy of your ls1edit file?

DenzSS

The wavy grapg isn't that unusual. Depending on the wires used and the rest of your mods, that can be pretty normal. Basically it is just a not-so-good tach lead.

The two dips on run 14 are likely detonation. You can detonate pretty easily and pick up no KR.

I'd make a bet that your tuning isn't dead-on.

DenzSS

As far as the A/F goes, you generally want to be your "richest" at peak TQ and "leanest" at peak HP.

I'm leaning toward a timing and a/f issue.

verbs

You must not have read the whole story. Runs 14 and 15 were with 2 bad spark plug wires that I changed out. Go further down and you'll see this graph making 430rwhp with better plug wires.