petro55

Hello,

This is my first build. Looks a little low however it is going through a 9 inch and 4l60. Any suggestions? I need to drive it some more to see how well it runs.


1971 Nova
TR6 Plugs
Firecore wires
6.0L LQ4 motor-10.7:1 compression
1.7 Yella Terra roller rockers
Johnson Lifters
Manton rods 11/32
Ported 62ccDart LS1PRO 225 Heads 2.06 intake 1.6 exh .700PAC springs
Ported Fast 102 intake and throttle body
Kook 1 7/8 headers
Custom CAM- CAM MOTION 232/236 .626"/.626" 112LSA +4
Transmision- Finishline 4l60
Stall- FTI3800
The donor vehicle for the 6.0L engine, -02 Suburban
-trans, PCM and engine harness -01 Silverado
-MAF sensor, 5.3 truck maf
-Injectors, Racetronixs 42
-Rearend gear, 370

petro55

tech@WS6store

iTrader: (2)

You need ALOT of tuning. That middle squiggly part is prob knock and the plateau is prob from fueling. So rich it couldn't make any power. Have your tuner turn COT off and look for 26 degrees and 12.5 afr. That cam has too much adv honestly imo. It should make somewhere in the 430-450 range.

thunderstruck507

iTrader: (18)

Agree with above.

Also it seems rare I see engines with aftermarket rockers do well unless the builder took care to setup the pushrod length and valve spring installed height very well. Could have unstable valvetrain above about 4700rpm.

It also looks like the pull might have been with a locked converter based on the lower end of the graph. If so those are pretty disappointing results.

Are you sure on the compression? Is this a stock piston lq4?

What exhaust is after the headers? I hope it's 3" duals of some sort.

I'm assuming the pull was done in 3rd gear?

petro55

Hello,


Please see replies below, please keep in mind I am a pure amateur and having a blast learning about LS engines and doing burnouts.


Also it seems rare I see engines with aftermarket rockers do well unless the builder took care to setup the pushrod length and valve spring installed height very well. Could have unstable valvetrain above about 4700rpm. I spent a long time setting up PR length and ordered custom length rods. This was my first build but I am fairly confident I did this part correct. Are the wavy lines indicative of valvetrain instability or is that a characteristic of the dyno sampling?

It also looks like the pull might have been with a locked converter based on the lower end of the graph. If so those are pretty disappointing results. Once again nooby here isn't it standard to lock the converter in 3rd gear to read dyno?

Are you sure on the compression? Is this a stock piston lq4? Stock piston .41cc gasket 62cc chambers in the heads. After using a couple calculators I am right around 10.8 please correct me if I am wrong.

What exhaust is after the headers? I hope it's 3" duals of some sort. 3inch 10 series flowmasters dumped after axle, Loud as F.... I have some new exhaust on the way that does not rattle your insides.

I'm assuming the pull was done in 3rd gear? I did not ask, however I think that is standard.

thunderstruck507

iTrader: (18)

Sounds like you have all your eggs in a basket as far as everything on my comment goes.

Which leaves me with 2 thoughts: Either the tune is not spot on as suggested by tech@ws6store or it could just be a stingy bitch of a dyno. Or both.

I've personally seen a dynojet consistently read 5% lower than other dynojets. (E.g. a car that normally makes 400rwhp would make 380rwhp on it)

I've also made some minor mistakes in my car's fueling which made it run .15 slow at the track which is a pretty easy 15-20rwhp loss at my level.

You could always get a wideband on it and double check the fuel at WOT. That along with a OBDII scanner which can show timing at WOT will tell you a ton about the state of the tune. It could be fine too. Sounds like you're enjoying the car either way.

tech@WS6store

iTrader: (2)

Something else is wrong in the tune there is no way it should plateau like that esp with that cam and engine and intake. If it were way larger cid maybe but not stock ci or 370 even.

Darth_V8r

iTrader: (4)

OP, glad you posted your build list here. That answered some questions I had. I'm with "Tech" something is going on. Its possible that squiggly section is knock - I'll also throw out the additional possibility of the converter locking and unlocking. Certainly, those are relatively easy to check, however...

On the cam, I have a slightly different thought. The IVC calculates out to 44 degrees. Now, a 44 degree IVC on a fast102 intake should pretty much always hit 4800 rpm peak torque and 6300 rpm peak HP. Those are values you can pretty much hang your hat on based on the intake and head runner lengths. They tend to force those peak RPM's. Your peak TQ RPM is impossible to determine due to the waviness right where it matters most. Your HP definitely peaked at least 400 rpm early. If everything was sorted out, I'd say you were heading for 385-390 TQ and 420-440 HP just based ont he power curve carrying properly.

I've seen a graph very similar to the one you posted about three years ago -- on my own engine. It was a cam only plus typical bolt ons LS1. Underperformed, wavy through the midrange, torque fell FAST past 5500, HP peaked early and fell fast... I found that the timing set was off. Took forever to diagnose, because at the time I didn't know anything. The tuner was the one who figured it out, actually, because he COULDN'T put timing into it. Well, rather, the tuner figured out the cam timing was off. But after I degreed it, I found the set was off by 9-degrees. The really effed up part is I swapped back to the stock cam and it was off by the same amount, roughly half a tooth, which pointed to the timing set itself being off. Cam motion is an incredibly reliable vendor for the their cams being spot on and actually got my car right after all that stuff. $38 cloyes timing set fixed it. Car went from 345 to 370 HP just from the timing set. BTW - the bad timing set I pulled? It was the one the car came with. I had reused it when I did the cam swap.

So, I'm going to recommend that you verify the cam timing with a degree wheel or ask the shop that installed the cam to do it. If it's way off, it might be a tooth off. if it's something like six degrees off, it's likely a bad timing set.

The wavy lines could indicate valvetrain instability, but I'm thinking that's not it. The waves are far to regular and rhythmic. it is definitely NOT a characteristic of the dyno sampling, as evidenced by the rest of the curve being fine. Usually, valve float is far more random and rough looking - like a EKG. It is standard to dyno in third, locked converter on an auto.

Sorry for the length of the post. Since you're learning, I wanted to take the time to explain why I came to the conclusion I did. I really do hope WS6Store is correct, because the tune is an easier fix. Best of luck.

(Edit) PS - consider a 100mm MAF also (/edit)

speedtigger

iTrader: (16)

What is the part number on that valve spring?

axld

jumped over to here to hear more on this build/ tune.

petro55

Speedtigger- I was told it was pac 1207 .700 springs. I never verified(is there a way to verify?)

speedtigger

iTrader: (16)

Not without the package. That is a good spring.

If those heads have a good port job and the tune is right, that combo ought to be able to make 425-450. But dynos are dynos. So, I would not sweat it too much if the car runs good.

tech@WS6store

iTrader: (2)

That dyno graph is proof enough to not drive the car until issues are determimed and fixed.

petro55

tech@WS6store That dyno graph is proof enough to not drive the car until issues are determimed and fixed. Near term I plan on bringing it back to the tuner to talk about the dyno and to touch up the drivability.

Darth_V8r Thanks for taking the time to post a thought full response. I nvr thought a timing gear would be off by that much. I also did not degree the cam and just reused the double roller that was on it before. After another attempt at tuning I might give that a look.

Is there anyway to test valve train stability? Could I not have enough preload on the lifters causing some float? I also reused the truck maf and sensors could any of those cause something to be off?

tech@WS6store

iTrader: (2)

You dont have stability issues im sure. the only issue may be to shim the springs to .080-.050 from coil bind. Otherwise thats it.

Darth_V8r

iTrader: (4)

I agree. You're using 11/32 pushrods and cam motion lobes are very smooth. Typically valve floats more of an issue at higher rpm. Your issue is more midrange.

Here's an example of valve float.

Darth_V8r

iTrader: (4)

[COLOR="RoyalBlue"]After another attempt at tuning I might give that a look.
I also reused the truck maf and sensors could any of those cause something to be off?[/quote]

Yeah. I mean I'd look at trying to tune it again. If you can, stay with the tuner and just listen when he gets pissed at the car. He says things like -"why won't you take any timing?" Or "you shouldn't be knocking like this" or even more a giveaway "I'm putting it in safe mode", then you'll know it's mechanical, not software. Alternately, he says something like "who the hell did THIS in here?" You'll know it's possibly just a tuning issue. Definitely a better first step.

I'll say this too. A good tuner can at least point you in the right direction. If it isn't something he can tune out, he can usually tell you why. My tuner nailed that the cam was off timing, and six months later nailed a plugged catalytic converter from the runs and logs.

I don't think any of your sensors are bad honestly. I suggested a bigger maf because you have a 102 throttle. No reason to run a maf smaller than 100mm. The maf can limit airflow with the throttle wide open if it's smaller than the throttle.