12 Second Club - Help car too slow 117 over 550 hp

I don't know if clutch if slipping. It's an ls7 and I noticed I couldn't power shift with it. Anyway I used to run 108 with lid, long tubes and street tires. I ran 106 with over 420/415 with 2.0 60 ft. And only 117 on spray. I not sure if I need to check the spark plugs or clutch or tranny or what.. What would make a carslow down that is extremely impressive on dyne. Also the car vibrates every 3 secs at highway speeds as a side note. I have new tires and rims and just had my cam replaced because I didn't like the top end on the previous cam. C5 zo6scould walk away from my410 hp car if we started at about 80. Feels like something just hold it back at high speeds.

Did some reading. My car normally gets 26 mpg, however Ive only got 200 miles on the last two tanks. Ive heard some backfire and the lope is more noticeable. Also I didn't really spend the street tires when shifting under nitrous. So I'm guessing it's the spark plugs. Just hope I haven't screwed something up.

Sounds like you need to pay someone to fix this, because it looks like you don't have a clue where to start. Did you buy the car swapped?

Sounds like you need to pay someone to fix this, because it looks like you don't have a clue where to start. Did you buy the car swapped?

Sounds like you didn't help at all. Original owner, and just got the car shipped back from a sponsor.

Sounds like it needs to be hooked back up to a dyno and see if you have clutch slippage.

I changed the spark plugs and took off the 18's which are 4lbs heavier per side and put the stock wheels and street tires on the back. The car did 12.8 at 110. Still too slow for a 425/415 car. I'm still guessing its knock retard from the pipe banging on the floor board. Gotta get this thing logged.

425 to the wheels is low for a stock ls7.

425 to the wheels is low for a stock ls7.

Sorry I was misleading. It's an ls7 clutch. But head and cam ls1

I would contact the sponsor that did the work to the car first. If they did the work and something is wrong then they need to check it out.

Yea I have. The problem with shipping a car off is that you end up phone treating. Plus it's hard to get the guys on the phone. I don't think it's the motor or tune though. I think it's something external. My first setup made 410/386 and still only trapped 111 with two different tuners and air fuel 12:1. Just scanned the car and no kno k retard. The timing which I'm guessing is what advance means is a consistent 20.5 at wot. Could this be from motor mounts. The car does have a extremely noticeable vibration every 3seconds at 70mph. I hav e already replaced shocks lcas tires and wheels. I'm just grasping at straws.

I would still get ahold of the sponsor. If it ran fine before they got it and now it runs bad, well they should aid in it's resurrection or I would see about finding somebody local that has a dyno and see if the clutch is messing things up or something.

12:1 air fuel is extremely conservative. Seems a little rich. I would have it leaned out a little at some point. Also correct me if i'm wrong but isn't stock timing @ 25 or 26 degrees @ WOT? Your 20.5 seems low.

Maybe one of the tuners turned your knock sensors off. Might get that checked out.

Not sure where you are from or the weather and track conditions there but 410hp where I am from should trap at least 116 mph in the 1/4 in a M6.

Oh you are spraying it so it's a nitrous tune?

Yea its nitrous tune. The tuner said that it made within 5hp with the correct timing versus pulled timing. The 117 was on the spray in which the car makes well over 550 hp. The 110 is NA. However, this was done on two different nights. On the night that I trapped 117 on nitrous, I actually only trapped 106 NA. I changed the spark plugs, took off the heavier 18's and put on my stock ws6 17's with street tires and the MPH went up by 4 mph. So,i'm assuming I could actually trap about 121 on spray but I should be at 129 or so.

Can motor mounts do this?
I'll try to get another dyno, but remember my first setup never trapped as high either. When you guys log your runs, are you actually hitting the rev limiter on power shifts?
Any help helps.l

i'd find someone local with hptuners or efilive and pay for the credits to have them log the car. there is obviously a serious problem and driving it hard in its current state will most likely kill it.

have you tried cleaning the maf?

i'd find someone local with hptuners or efilive and pay for the credits to have them log the car. there is obviously a serious problem and driving it hard in its current state will most likely kill it.

have you tried cleaning the maf?

Haven't cleaned the maf. I have hp tuners now. Not sure what I'm looking at yet though. I know there is no knock. I know the timing is consistently at 20.5 at wot iat 77 194 coolant. But my buddies stock corvette is pulling harder as we just verified on the highway. I have a couple of emails in to the sponsor. We will see.

not sure what max timing on stock ls7 should be, but my ls1 with a lid and muffler was taking 28* pretty well. 29 is where we started picking up knock in the 4800+ range. this is with stock tstat and 93 octane. car has ory with no emissions, as well.

20.5 seems very low.

not sure what max timing on stock ls7 should be, but my ls1 with a lid and muffler was taking 28* pretty well. 29 is where we started picking up knock in the 4800+ range. this is with stock tstat and 93 octane. car has ory with no emissions, as well.

20.5 seems very low.

He has a heads/cam ls1 with an ls7 clutch.

He has a heads/cam ls1 with an ls7 clutch.meh. it makes a little more sense reading it on a computer. haha. so ya...20.5* timing seems low.

meh. it makes a little more sense reading it on a computer. haha. so ya...20.5* timing seems low.

I'm datalogging the car tonight. My tuner showed me where the car made 427/404 with 26* but 424/415 on 21*... So he left it at 21. I'm sending him the log tonight hopefully.

that seems odd that it would make more tq with less timing than the stock tune. good luck.

:cheers:I wasn't trying to be a dick lol. You are still where this was a few days ago. Some times it's best to leave it up to the professionals is all.

My tuner looked over my tune. Bank one reads low which he describes as valvetrain, ignition issues. I know that my old springs were beat up and my lifters beat the hell out of the cam rendering it unusable. When they put in the new cam. The lifters weren't changed. The car made good hp though. I'm just wondering if one of the bad lifters have bored a groove into the cam. Which would explain the car initially performing great on the dyno, then taking a crap. I'm not sure but looks like I'm back at square one of shipping the car back off. Even if I change the lifters, the new cam maybe shot.

I know that my old springs were beat up and my lifters beat the hell out of the cam rendering it unusable. When they put in the new cam. The lifters weren't changed. .


this confuses me?????

this confuses me?????

I may be confused about what beats what. I'll probably post a question in the valvetrain section. Anyway, the cam that they returned had grooves in it. Comp says the cam was too bad to be regrinded. They said the springs were worn out. They had 30 K on them. So I'm thinking, now, that the lifters may have had grooves after being used with the old cam. I'm not sure.

This is the cam that came out. I'm wondering if the lifters that did the damage to this cam have now worn into the new cam.

This is the cam that came out. I'm wondering if the lifters that did the damage to this cam have now worn into the new cam.

That is a good thought especially if the replacement cam isn't as stout of material as the old cam.

Are your 17" tires the same height as your 18" tires? Depending on power levels, gears, and a number of other factors a change in the height of the tires can easily make the type of differences that you describe you're experiencing.

Are the tires that are on there now nice and round? Even if they're balanced good they can still be the cause of a shake and shimmy if the tire it's self is out of round. Somebody once told me that you can balance a football but it doesn't mean that it will roll nicely.

I'd try swapping back to the 18's if for no other reason than to rule out the 17's as being part of your problems. The 17's could possibly be influencing both your speed differences and you're described shake/shimmy.


Good luck with getting this resolved.

Roach

What was the da on those runs?

What was the da on those runs?

da???
And the 18's only allowed me to run 106, I'm faster on the lighter 17's which are about a 1/2 in shorter