My heads/cam/fast 90/90,stalled LS1 runs 12.7's
09-27-2007, 10:49 AM
#1
My heads/cam/fast 90/90,stalled LS1 runs 12.7's 109 mph 
Sure does. How? I dont know. My car ran 12.8 with headers and street tires ONLY automatic. I gained a tenth and gained 2 MPH and 60ft'd the SAME with 325 MT et streets and the same with 245 street tires. The car dead hooked but when you make no power how do you 60ft though. I had a set of ported heads 1st of this year and they started leaking. Then I ran cam only and it ran fine then I swapped over to my new set of heads a few months ago and have been fighting this problem till now. I have no fuel its not there. The tune in my car has PLENTY of fuel it should be so rich. It made almost 420rwhp through a pt4000 converter with the 1st set of heads now it has NO power. Ive swapped pcm's, swapped injectors around on the car, checked fuel pressure at wot/idle. checked voltage at the fuel pump, checked voltage at the injector harnesses, changed fuel pump, fuel filter, done a compression test and all the cylinders were 173-175 psi ( I dont think the motor is bad b/c it turned slow immediately after a 2 day head swap). Ive gone through 3 cans of starter fluid looking for vacuum leaks. Checked tps voltage, checked all grounds under the hood/under the car, changed o2 sensors, changed the alternator out thinking I had a voltage issue, changed tps, had the intake off 3 times in a week inspected it, changed gaskets. I've unplugged the front o2's to keep the car in open loop to see if the fuel would show up and rich pig rich...nope. I dont know anymore. Im having my 42# injectors sent off this week sometime some think my injectors are bad but I have fuel on cold starts and idling the plugs are drenched in fuel b/c of the rich tune but it just dissapears at wot leans out and makes NO power. I want to blame the heads but I can't b/c where is the fuel? Also on the #6 cylinder primary off my headers my primary temperature is 650 deg F idling!! Ive swapped injectors on that cylinder and the heat stays there. All the other primarys are about 260-270 idling. All my inj harnesess have about 13.8 volts idling and it goes up as the motor revs. Is there somewhere in these fast intakes you could have a HUGe vaccum leak that would not be able to be picked up by spraying from the top of the motor to get it to ramp up?
Last edited by AutomagicLS1; 09-27-2007 at 12:12 PM.
09-27-2007, 12:52 PM
#3
Youve Answered Your Own Question..if All You Did Was Swap Heads And Everyting Else Was The Same And Working Before Then Its Apperent You Got A Problem With The Heads.. If Not That Then Its Something That Plugs Into The Heads... Bad Spring? Leaking Intake Runner.. I Dont Think Your Injectors Or Electerical Is Gonna Be The Culprit
Ovbiously You Got A Problem With Cylinder 6 Start There...and Yes You Could Have A Intake Leak That Dosent Show Easily.. There Is A Tq Sequence For Fast Intakes That I Know Tony Form Afr Was Just Preching To Some Other Guy About On This Board B\c He Had A Intake Leak.. But Being Your Problem Is Only With 1 Cylinder And You Didnt Complain About A Drifting Idle Im Gonna Guess You Have A Mechaincal Issue With The Valvtrain (mabye Collapsed Lifter, Bad Spring, A Valve Issue??)
Im No Engine Expert But If It Were Me Id Start With Pulling The Heads And Inspecting Them Along With The Valvetrain..
Ovbiously You Got A Problem With Cylinder 6 Start There...and Yes You Could Have A Intake Leak That Dosent Show Easily.. There Is A Tq Sequence For Fast Intakes That I Know Tony Form Afr Was Just Preching To Some Other Guy About On This Board B\c He Had A Intake Leak.. But Being Your Problem Is Only With 1 Cylinder And You Didnt Complain About A Drifting Idle Im Gonna Guess You Have A Mechaincal Issue With The Valvtrain (mabye Collapsed Lifter, Bad Spring, A Valve Issue??)
Im No Engine Expert But If It Were Me Id Start With Pulling The Heads And Inspecting Them Along With The Valvetrain..
09-27-2007, 06:12 PM
#4
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Originally Posted by AutomagicLS1
Sure does. How? I dont know. My car ran 12.8 with headers and street tires ONLY automatic. I gained a tenth and gained 2 MPH and 60ft'd the SAME with 325 MT et streets and the same with 245 street tires. The car dead hooked but when you make no power how do you 60ft though. I had a set of ported heads 1st of this year and they started leaking. Then I ran cam only and it ran fine then I swapped over to my new set of heads a few months ago and have been fighting this problem till now. I have no fuel its not there. The tune in my car has PLENTY of fuel it should be so rich. It made almost 420rwhp through a pt4000 converter with the 1st set of heads now it has NO power. Ive swapped pcm's, swapped injectors around on the car, checked fuel pressure at wot/idle. checked voltage at the fuel pump, checked voltage at the injector harnesses, changed fuel pump, fuel filter, done a compression test and all the cylinders were 173-175 psi ( I dont think the motor is bad b/c it turned slow immediately after a 2 day head swap). Ive gone through 3 cans of starter fluid looking for vacuum leaks. Checked tps voltage, checked all grounds under the hood/under the car, changed o2 sensors, changed the alternator out thinking I had a voltage issue, changed tps, had the intake off 3 times in a week inspected it, changed gaskets. I've unplugged the front o2's to keep the car in open loop to see if the fuel would show up and rich pig rich...nope. I dont know anymore. Im having my 42# injectors sent off this week sometime some think my injectors are bad but I have fuel on cold starts and idling the plugs are drenched in fuel b/c of the rich tune but it just dissapears at wot leans out and makes NO power. I want to blame the heads but I can't b/c where is the fuel? Also on the #6 cylinder primary off my headers my primary temperature is 650 deg F idling!! Ive swapped injectors on that cylinder and the heat stays there. All the other primarys are about 260-270 idling. All my inj harnesess have about 13.8 volts idling and it goes up as the motor revs. Is there somewhere in these fast intakes you could have a HUGe vaccum leak that would not be able to be picked up by spraying from the top of the motor to get it to ramp up?
09-28-2007, 10:21 AM
#5
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Did you change the valley cover bolts with the ones that fast gave you. I have read some where that the stock bolts stick out too much on the valley cover and can possibly crack your intake.
09-28-2007, 01:46 PM
#6
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Originally Posted by tilly
Did you change the valley cover bolts with the ones that fast gave you. I have read some where that the stock bolts stick out too much on the valley cover and can possibly crack your intake.
i would have to say that it is the injectors. but it could be anything.
who's heads are they?
09-28-2007, 05:35 PM
#7
Originally Posted by WS6TransAm01
that is true, but a cracked intake would only cause an idle issue, since the injector is in the intake runner, a crack in the center plenum would not cause a loss of fuel.
i would have to say that it is the injectors. but it could be anything.
who's heads are they?
i would have to say that it is the injectors. but it could be anything.
who's heads are they?
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10-01-2007, 09:47 PM
#10
little update did a leakdown on the hot #6 cylinder and it held about 92-93 psi and did one on the other side and it was about 95 so about 2-3% difference. Also did the cylinder balance test with HP tuners and they were all 93-95% held at about 1500 rpm. still dead in the road with what to do
10-01-2007, 11:26 PM
#12
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Originally Posted by Jpr5690
Youve Answered Your Own Question..if All You Did Was Swap Heads And Everyting Else Was The Same And Working Before Then Its Apperent You Got A Problem With The Heads.. If Not That Then Its Something That Plugs Into The Heads... Bad Spring? Leaking Intake Runner.. I Dont Think Your Injectors Or Electerical Is Gonna Be The Culprit
Ovbiously You Got A Problem With Cylinder 6 Start There...and Yes You Could Have A Intake Leak That Dosent Show Easily.. There Is A Tq Sequence For Fast Intakes That I Know Tony Form Afr Was Just Preching To Some Other Guy About On This Board B\c He Had A Intake Leak.. But Being Your Problem Is Only With 1 Cylinder And You Didnt Complain About A Drifting Idle Im Gonna Guess You Have A Mechaincal Issue With The Valvtrain (mabye Collapsed Lifter, Bad Spring, A Valve Issue??)
Im No Engine Expert But If It Were Me Id Start With Pulling The Heads And Inspecting Them Along With The Valvetrain..
Ovbiously You Got A Problem With Cylinder 6 Start There...and Yes You Could Have A Intake Leak That Dosent Show Easily.. There Is A Tq Sequence For Fast Intakes That I Know Tony Form Afr Was Just Preching To Some Other Guy About On This Board B\c He Had A Intake Leak.. But Being Your Problem Is Only With 1 Cylinder And You Didnt Complain About A Drifting Idle Im Gonna Guess You Have A Mechaincal Issue With The Valvtrain (mabye Collapsed Lifter, Bad Spring, A Valve Issue??)
Im No Engine Expert But If It Were Me Id Start With Pulling The Heads And Inspecting Them Along With The Valvetrain..
I would guess the valvetrain. Bent pushrod, bad/broken spring. I've never heard of this happening on a GenIII engine, but maybe something went wrong with installation and the cam has a flattened lobe. Hope you get it figured out!
10-02-2007, 03:56 PM
#15
I had the same problem with the 5.3 in my truck. I changed the fuel pump, injectors, intake, fuel rail, O2 sensors, map, maf, and TPS. I also checked voltages, grounds, and did lots of data logging; all to no avail. When I was finally at my wits end I swapped the engine harness, and to my surprise it fixed the problem. I tore into and inspected the old harness but couldn't find a problem with it. I actually used that harness on another S10/5.3 swap I did this past spring, and it is still working fine. My best guess is that one of the grounds was making poor connection on the back of the head and simply reconnecting to the new harness fixed the problem. I would check your grounds on the heads very well. Disconnect them from the heads and inspect the terminal carefully also. Good luck, I hope this helps.
10-09-2007, 12:27 PM
#19
Still nothing. I messed with the grounds it didnt change anything. Pulling heads this week and putting stock heads back on. I hate to pull them but ive tried everything, and it all changed after this new set went on. All I can say is if the car goes back to normal and I can prove somthing is wrong with those heads im taking a weeks vacation at work and taking a little road trip down to dirty texas...... I'll also probably have my fast 90/90 up for sale this week sometime. Im just going to buy a ls6 intake.
Last edited by AutomagicLS1; 10-09-2007 at 12:56 PM.
