Pathetic 427 numbers...help!
I agree with Patrick. I would start the car up and start pulling plug wires off one by one and see which one does not cause a miss. If nothing changes then I would disconnect each injector connector one by one and see if you develop a miss. I had a similar issue post installing injectors and one was leaking and fueling intermittently. This was on my Vette when it was a nitrous setup.
I agree with Patrick. I would start the car up and start pulling plug wires off one by one and see which one does not cause a miss. If nothing changes then I would disconnect each injector connector one by one and see if you develop a miss. I had a similar issue post installing injectors and one was leaking and fueling intermittently. This was on my Vette when it was a nitrous setup.
At this point, I'm wondering if the cam is indexed incorrectly or ground wrong. I think the next step is for me to drain the coolant, pull the radiator & pump and have a look at the cam.install.
Ryan
Have someone confirm the pushrod length. Make sure the intake bolts are tight, fuel filter isn't clogged. It is very easy to pull out a connector on the plug side of a wire. Make sure they are intact, click firmly into place, even measure resistance and make sure they are even.
Are you running a straight shot style intake or does it have a 90* bend in it? That will suck up 35-40rwhp right there.
This is my intake setup on my FD with an LS7 K&N air filter on the end. 11.25:1 427, stock LS7 heads with minor exhaust side clean up, 243/256 .650" cam, 90mm TB, mildly ported LS7 intake, ZR1/LSA injectors, JTR 1 7/8", Random Tech 3" cats. SD tune running Holley HP EFI.
520rwhp/472rwtq on e85/91 blend (e30 maybe?). I was disappointed in my #'s also... but it runs the number at the strip.
Are you running a straight shot style intake or does it have a 90* bend in it? That will suck up 35-40rwhp right there.
This is my intake setup on my FD with an LS7 K&N air filter on the end. 11.25:1 427, stock LS7 heads with minor exhaust side clean up, 243/256 .650" cam, 90mm TB, mildly ported LS7 intake, ZR1/LSA injectors, JTR 1 7/8", Random Tech 3" cats. SD tune running Holley HP EFI.
520rwhp/472rwtq on e85/91 blend (e30 maybe?). I was disappointed in my #'s also... but it runs the number at the strip.
Last edited by gnx7; Oct 30, 2014 at 12:26 PM.
It sounds like you've tried all the obvious and low cost options, time to pull cam and heads and measure.
do you really have an 11.5 CR?
are you really getting the valve lift you think you're getting, at the correct point in crank rotation?
do your heads really flow what was advertised?
random thought- you said you were not using MAF, but if you had one connected just to diagnose then you would know the air flow thru the motor. your tune would not use it, only the computer would read the signal and you could plot it afterwards, could knowing that help in this type of diagnosis? isn't airflow directly related to hp output? or mathematically could you compare it to other known engine data like a LS7?
and if you were down a cylinder meaning not firing, wouldn't that be caught by the wideband and be in a data log, how could you still maintain a consistent 12.6 to 13.0 AFR with that happening?
or are you running E85 for fuel? what are you running for fuel?
https://ls1tech.com/forums/advanced-...-troubles.html
https://ls1tech.com/forums/advanced-...-troubles.html
Have someone confirm the pushrod length. Make sure the intake bolts are tight, fuel filter isn't clogged. It is very easy to pull out a connector on the plug side of a wire. Make sure they are intact, click firmly into place, even measure resistance and make sure they are even.
Are you running a straight shot style intake or does it have a 90* bend in it? That will suck up 35-40rwhp right there.
This is my intake setup on my FD with an LS7 K&N air filter on the end. 11.25:1 427, stock LS7 heads with minor exhaust side clean up, 243/256 .650" cam, 90mm TB, mildly ported LS7 intake, ZR1/LSA injectors, JTR 1 7/8", Random Tech 3" cats. SD tune running Holley HP EFI.
520rwhp/472rwtq on e85/91 blend (e30 maybe?). I was disappointed in my #'s also... but it runs the number at the strip.
Are you running a straight shot style intake or does it have a 90* bend in it? That will suck up 35-40rwhp right there.
This is my intake setup on my FD with an LS7 K&N air filter on the end. 11.25:1 427, stock LS7 heads with minor exhaust side clean up, 243/256 .650" cam, 90mm TB, mildly ported LS7 intake, ZR1/LSA injectors, JTR 1 7/8", Random Tech 3" cats. SD tune running Holley HP EFI.
520rwhp/472rwtq on e85/91 blend (e30 maybe?). I was disappointed in my #'s also... but it runs the number at the strip.
Pushrod Length: Mic'd tip-to-tip, they are 7.675". At zero lash, I'm getting a half a turn to 22 ft/lbs. Common wisdom is 1 full turn ~.047" So it's off a little. Makes for a little noise on cold start but not likely to be costing 80hp.
Intake bolts are tight, it pulls a good vacuum @ idle.
Fuel Filter: 58 psi of fuel pressure throughout the pull on the gauge, IDC's are not maxed (52 lb'ers), it's clean & A/F's are consistent. It's got fuel.
Injector clips are tight. They were off recently when I pulled them for a compression check. If one cylinder was dead, I'd see it on the header primary temps.
Air intake: This one of the differences between this dyno & last. I'm now using a Samberg radiator w/the straight shot Vette K&N Filter.
Your setup & mine sound comparable. The only thing that sticks out to me is it sounds like you're running true duals. I'm running a single 3" Y off the JTR headers (no cat and straight through exhaust).
Good to see you're still around,
Ryan
Last edited by ryan23; Oct 30, 2014 at 03:54 PM.
or are you running E85 for fuel? what are you running for fuel?
https://ls1tech.com/forums/advanced-...-troubles.html
https://ls1tech.com/forums/advanced-...-troubles.html
Straight 93, no KR.
just read through the thread, and before you said it i was thinking what spock said in whatever star trek: If you eliminate the impossible, whatever remains however improbable must be the truth.
It sounds like you've tried all the obvious and low cost options, time to pull cam and heads and measure.
do you really have an 11.5 CR?
are you really getting the valve lift you think you're getting, at the correct point in crank rotation?
do your heads really flow what was advertised?
random thought- you said you were not using MAF, but if you had one connected just to diagnose then you would know the air flow thru the motor. your tune would not use it, only the computer would read the signal and you could plot it afterwards, could knowing that help in this type of diagnosis? isn't airflow directly related to hp output? or mathematically could you compare it to other known engine data like a LS7?
and if you were down a cylinder meaning not firing, wouldn't that be caught by the wideband and be in a data log, how could you still maintain a consistent 12.6 to 13.0 AFR with that happening?
It sounds like you've tried all the obvious and low cost options, time to pull cam and heads and measure.
do you really have an 11.5 CR?
are you really getting the valve lift you think you're getting, at the correct point in crank rotation?
do your heads really flow what was advertised?
random thought- you said you were not using MAF, but if you had one connected just to diagnose then you would know the air flow thru the motor. your tune would not use it, only the computer would read the signal and you could plot it afterwards, could knowing that help in this type of diagnosis? isn't airflow directly related to hp output? or mathematically could you compare it to other known engine data like a LS7?
and if you were down a cylinder meaning not firing, wouldn't that be caught by the wideband and be in a data log, how could you still maintain a consistent 12.6 to 13.0 AFR with that happening?
You are correct, If I was dropping a cylinder, you would think it would be audible but who knows :shrug: . Maybe an intake lifter is collapsing @ high RPM? In hindsight, I could have probably hit the header primaries @ WOT with the temp gun on the dyno...
Erik Koenig @ HKE assembled this engine. He's pretty well respected on here and while I don't personally know him (other than via phone cons), I would be extremely surprised if I tore this engine down and didn't find the components I paid for. I'd be more likely to believe a "switched at birth" scenario or something along those lines. Eric gave me the original CR, I let him calculate it. The heads were brand new LS7 castings ported by Greg Good. Once again, I didn't cut corners.
Funny you should mention lift, I did put my dial indicator on #1 Intake and measured .345 of lift at the push rod (multiplied by 1.8 LS7 rockers for .620). I didn't put a degree wheel on the crank because I don't have a lot of room nor the fixture to secure it on an LS crank pulley. If I end up pulling the whole thing apart, you can bet I will though.
Good stuff though. I'm debating whether I want to go weep in the garage tonight or just take a nap instead
Ryan
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
How about cry yourself to sleep in the garage? I feel for ya man. I want to do the same when I think about extending the engine harness about 5ft to move the PCM to the rear bin.....
I'm not too sure the cam is off by looking at the graph but it's certainly possible. One thing to keep in mind is that without a solid lifter or oil pressure the lifter will collapse from spring pressure while you turn it over. Makes the dial measurement off.
I'm not too sure the cam is off by looking at the graph but it's certainly possible. One thing to keep in mind is that without a solid lifter or oil pressure the lifter will collapse from spring pressure while you turn it over. Makes the dial measurement off.
Last edited by Exidous; Oct 30, 2014 at 04:36 PM.
Does that 8.8 have a trac-lock or something much better like a True-trac? Not sure how a dyno reacts to both wheels not applying torque (other than the driven wheel tire slipping on the drum), but a worn out trac-lock will not apply much torque to the otherwise non-driven wheel.
Rear brakes hanging up? E-brake cable improperly adjusted causing rear brakes to ride the brake rotor? Rear calipers gunked up causing the pads to ride rotors?
Rear brakes hanging up? E-brake cable improperly adjusted causing rear brakes to ride the brake rotor? Rear calipers gunked up causing the pads to ride rotors?
What trans are you using. Just wanted to make sure your 4th gear is 1:1 and thats not the mistake. I'm not familiar with RX7's. That power curve looks great. I would not believe there is anything significant wrong with the cam, valvetrain, or cam timing. I doubt it is an injector problem either if all the egt's are even although it is more accurate to test them at a higher rpm and some load if you can arrange that. I would agree with Pat and Erik that you probably have a bad plug wire or something in the ignition that is only droping when you are under a full load. Almost any plug wire will fire off at an idle under a zero load condition. A bad wire wont always show up on an ohm meter either. A single strand of wire will ohm zero but will drop all your voltage under a load. My unprofessional advice would be to buy a new set of Taylor thundervolt 50 10.4mm wires and new set of plugs too. Never hurts to have an extra set anyways. TR55's are hotter than I would run with your combo anyway. BR7's would be a good fit imho. Clean all the wire harness connections. Check grounds. I accidently plugged #8 wire onto the header stud instead of the spark plug once and the motor still ran smooth, didn't miss or studder so it doesn's surprise me that it still drives good. Big motors aren't easily phased. Good luck.
Sorry if this has been discussed already, but what does your exhaust consist of after the headers?
Edit: Just saws it up the thread a little. You think the single 3" is hurting you? That is not a lot of pipe for a well built 427. I was running a 4" custom Y-pipe on my lower compression 370ci, n/a.
Edit: Just saws it up the thread a little. You think the single 3" is hurting you? That is not a lot of pipe for a well built 427. I was running a 4" custom Y-pipe on my lower compression 370ci, n/a.
Last edited by 93camaro_zzz; Nov 1, 2014 at 12:07 PM.
Well I can olnly speak for myself, but I have been running 3 sets on 3 different LS engines for the last 10 years with zero issues. I have also used them on non LS engines without fail. I did use a set of they're cheaper spiro 8mm wires that I was not happy with the way they snaped on the plug. Felt a little loose.
Alright, let me catch up....
No, the heads are not stock. Do some reading about Greg Good. These heads were hand ported by him. The heads are capable of flowing enough air to support the HP.
Yeah, I do need to head back to the track. I just feel like I'm leaving something on the table and it's frustrating me.
Ya know, I've thought about it but I dunno.... I've opened up the dump (just after the Y) and picked up like 3hp. The headers themselves are certainly a compromise to fit the RX-7 chassis. However, there are some people putting down decent numbers with them.
The trans is a T56 out of an F-body, dyno'ing in 4th. Your thoughts on plug wires have merit and you are certainly correct on checking their resistance on the bench. I may in fact pick up another set but I'm not expecting any miracles. These still look new and haven't really been on the car that long. We'll see.
Originally Posted by Tuskyz28
Do you personally think it's the STOCK LS7 heads making those numbers?
Originally Posted by gnx7
See what mph it runs. That the true test.
Originally Posted by 93camaro_zzz
You think the single 3" is hurting you? That is not a lot of pipe for a well built 427. I was running a 4" custom Y-pipe on my lower compression 370ci, n/a.
Originally Posted by dtroike
What trans are you using. Just wanted to make sure your 4th gear is 1:1 and thats not the mistake. I'm not familiar with RX7's. That power curve looks great. I would not believe there is anything significant wrong with the cam, valvetrain, or cam timing. I doubt it is an injector problem either if all the egt's are even although it is more accurate to test them at a higher rpm and some load if you can arrange that. I would agree with Pat and Erik that you probably have a bad plug wire or something in the ignition that is only droping when you are under a full load. Almost any plug wire will fire off at an idle under a zero load condition. A bad wire wont always show up on an ohm meter either. A single strand of wire will ohm zero but will drop all your voltage under a load. My unprofessional advice would be to buy a new set of Taylor thundervolt 50 10.4mm wires and new set of plugs too. Never hurts to have an extra set anyways. TR55's are hotter than I would run with your combo anyway. BR7's would be a good fit imho. Clean all the wire harness connections. Check grounds. I accidently plugged #8 wire onto the header stud instead of the spark plug once and the motor still ran smooth, didn't miss or studder so it doesn's surprise me that it still drives good. Big motors aren't easily phased. Good luck.