need everyone's opinions

[ldyzluvdis06]

as most know, i have a H/C/I 98 trans am with a 6.0l (lq4) in it. ive been running slow at the track and have been trying to figure out why. well we put it on the dyno today to see if we could figure out what's going on, and we kind of did, and didn't...at first we thought it was the intake, but now that we put it on the dyno, the problem is obviously something else.

at 5200rpms there is a huge dip in my power band and it never really picks back up where it should. iv'e attached a picture, don't mind the power numbers because this dyno is known to read really low. i wasn't there for the numbers though, i was there for the info.

I have also been losing coolant somewhere. it has never had puddles and i last oil change, the oil looked good and nothing on the magnetic plug, but i change it well before 3k miles so it wasn't dark, so maybe it was hard to tell. i preformed a compression test and leakdown test when i first put it all together and all was good.

so.... im going to pull all of the plugs in a few and see what they look like, im going to pressurize the cooling system and see if i can visually find the leak, wether it comes out of the spark plug holes or it comes out in the oil. after doing them 2 things, i will retorque the heads and see if any of them possibly aren't at the correct torque specs.


sorry for the long read, just trying to get outside ideas and figure out what is going on here. here is a video of the dyno also just for the hell of it.

Click to read more...

 

[wolfe]

Does your car have enough fuel? Maybe the pump or injectors aren't enough to supply it as the rpm's climb

 

[SleeperLS]

I didn't know that shop was still open...dyno def. reads low. I hope you get it figured out.

 

[02BlueGT]

If the Air/fuel chart on that dyno was running (I can't see a sensor in your tail pipes in the pic), you were at 13.x : 1 that whole run, maybe bump it up in that 4750 - 5750 range.

Have a copy of a PCM scan from the same run? That could help us a lot more than the dyno sheet alone. We need to see what the car was doing, and what the PCM was commanding in that RPM dip.

 

[1quick]

id watch the fuel pressure also, did you have to get custom length pushrods with the heads and cam and did you measure to make sure they were the right length and you had the proper preload?

 

[ldyzluvdis06]

pump is a racetronix pump with hotwire feeding 42# injectors.

wideband was at 12.6 the whole time (aem wideband in car)

i did measure pushrods and ended up with 7.4's

ill get a copy of the scan as soon as my tuner gets a few extra minutes.

 

[Spivitz]

GL man, I hope you get it sorted out

 

[ldyzluvdis06]

here are the spark plugs if that helps anyone, im not sure how to read plugs. also, ive pressureized the cooling system up to 19.5psi, and in 30 minutes it had leaked down to 15. no coolant from the spark plug holes, but im going to do it a few times, and see if coolant ends up in my oil.

 

[Yaj Yak]

here are the injectors if that helps anyone, im not sure how to read injectors. also, ive pressureized the cooling system up to 19.5psi, and in 30 minutes it had leaked down to 15. no coolant from the spark plug holes, but im going to do it a few times, and see if coolant ends up in my oil.

problem number fucking one.

you have spark plugs where your injectors should be.


fix that.

 

[ldyzluvdis06]

problem number fucking one.

you have spark plugs where your injectors should be.


fix that.

haha! you would quote it, so i can't edit it...hahaha

im on 4 hours of sleep, and a lot of disappointment today

 

[Yaj Yak]

gotchu brah

 

[ldyzluvdis06]

okay so after 5-6 pressure test on the cooling system...no external leaks, no leaks in cylinders, and doesn't look like any in the oil, but im not 100% sure. it kind of looks milky and kind of not (i took a sample to send to Blackstone labs). also, the magnetic drain plug had some VERY FINE shavings on it.

here is a picture of the coolant bottle. the initial line is where is was before i added ANY, the second line is where it was after i filled it initially, the third line is where it's at after i filled the system after the 5-6 pressure test.

any help with what's next? im thinking pulling the intake/valve covers and start inspecting? come on guys, needing some help here before i decide to demod.

these pics were the first oil out of the pan after sitting over night. i drained the first initial sample into a clear vase (vases are for oil, not flowers!)

 

[ldyzluvdis06]

My tuner posted the tune in this thread: dyno/engine problems - LS1TECH

 

[Turbocharged400sbc]

no fuel...no extra revs....we did 608 fwhp at 13to1 and it just ran out of steam while it was running out of fuel, just lost power, tapered off and never really gained rpm's

12.6 seems lean enough for an NA motor to dropoff power output

 

[ldyzluvdis06]

no fuel...no extra revs....we did 608 fwhp at 13to1 and it just ran out of steam while it was running out of fuel, just lost power, tapered off and never really gained rpm's

12.6 seems lean enough for an NA motor to dropoff power output

I need to order a new fuel pressure gauge, mine sucks. But the Injectors and pump are new, I guess they could still be messed up, within this past week the pump has gotten really loud. But wouldn't I be knocking or something if I was running out of fuel?

Edit- new fuel pressure gauge ordered.

 

[Turbocharged400sbc]

We didn't knock at all....

Put a dso with current probe on that pumps power feed....noisy pumps seem to have really abnormal current form from winding to winding

 

[ktraver97ss]

Sorry to hear man, hope you get it figured out. Dont give up, I want to see this rear end in pieces before the end of the season.

 

[ldyzluvdis06]

If Iwwas dropping that much pressure to cause these issues, my afr wouldn't stay the same though...?

[MENTION=311]02BlueGT[/MENTION] did you get a chance to take a peak at the scans?

 

[Gone_2022]

Just asking a question not being rude.... its a 6.0 with heads cam and intake. and it only made 370-390ish? Maybe that is correct and Im totally wrong but ive seen ls1's make that with just a straight cam and tune. again just asking an honest question, maybe that is all part of this lack of upper end power

 

[ktraver97ss]

Its said more than once in here that that dyno reads very low. I would agree on a normal dyno those would be some shitty #s though.

 

[1quick]

We didn't knock at all....

Put a dso with current probe on that pumps power feed....noisy pumps seem to have really abnormal current form from winding to winding

You guys were running e85 tho I would expect you could lean it out even more and not knock on e85

 

[02BlueGT]

If Iwwas dropping that much pressure to cause these issues, my afr wouldn't stay the same though...?

[MENTION=311]02BlueGT[/MENTION] did you get a chance to take a peak at the scans?

Looking at your scan , It might just be my config, but your wideband seems to be static at 12.78 the entire scan. Maybe it is because your NA, but your maf does not go up as I'd expect, you only go from 9,100 hz to 10,800 hz in a 3,000 rpm gain (I see a 5khz+ ish change in a 3,000 rpm change in my car). You may be stalling airflow (In or Out could cause this issue), or your maf could be dirty. I'm not an expert by any means, so these are just my opinions.

 

[ldyzluvdis06]

Looking at your scan , It might just be my config, but your wideband seems to be static at 12.78 the entire scan. Maybe it is because your NA, but your maf does not go up as I'd expect, you only go from 9,100 hz to 10,800 hz in a 3,000 rpm gain (I see a 5khz+ ish change in a 3,000 rpm change in my car). You may be stalling airflow (In or Out could cause this issue), or your maf could be dirty. I'm not an expert by any means, so these are just my opinions.

the wideband on the tuner was not installed. we were just using my AEM wideband in my pod. ill relay this info to my tuner and see what he says. i know nothing about tuning. thanks!

and i don't know about the fueling because i don't understand why it would show on my wideband.

i honestly don't know if there is coolant in the oil because after 10-12 coolant pressure test, i had to add barely anything. so i could have possibly just had a bunch of air in the system. i honestly didn't spend a ton of time bleeding the system when i added coolant last. the last 6 coolant pressure test, i had the spark plugs removed and the oil drain plug out and not a drop of coolant was any where to be found.

so now im thinking something else. as mentioned earlier, possible broken/weak valve spring... they are good double springs, but i guess everything fails at some point? they are "cheap" enough i could just replace them, but i hate to waste 300 if not needed.

i will pull the valve covers tomorrow and inspect.

 

[DynaSlim]

I gave up reading did you find the problem?

My guess is...... Upper intake gasket leak fucking coolant into the cylinders. Ls motors are like that right? An upper and lower intake? I'm just thinking of the v6 in those cars that I've seen have that problem tho.

 

[Xtant12]

Head Gasket??