Why no gains after head install?
something besides the gear swap is not right, imo. i have seen way too many people not gain a single bit of et or mph going from 3.23's to 3.73's or 4.11's (with a computer calibration) in these ls1 autos.
Okay i'll ask, OP what was ur difference in trap b4 and after ur changes? mph and E.T.? that will help..maybe i missed it,4 every combo , use track or dyno to figure out where u are peaking in h.p. etc, and figure out max effort regarding current gears, tire height and stall, and trans tune(shift points , etc.), they all need a relationship 2 make stuff work..
Man it's hard for me to believe that the change in gears offset the power he gained in the head swap. I should have just put in some 4.10's and forgone the TEA heads I threw at my car.
OP how much lifter preload did you have?
OP how much lifter preload did you have?
I am not questioning whether that is true, I am asking why it is true. The only answer offered up so far consists sole of the words "torque converter." So why does a torque converter render rear gear selection irrelevant?
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
I was shooting for .08 on the preload. I measured to 0 lash and got 7.25 and with .08 added that got me to 7.33. So i went with the 7.325 PR.
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
Okay i'll ask, OP what was ur difference in trap b4 and after ur changes? mph and E.T.? that will help..maybe i missed it,4 every combo , use track or dyno to figure out where u are peaking in h.p. etc, and figure out max effort regarding current gears, tire height and stall, and trans tune(shift points , etc.), they all need a relationship 2 make stuff work..
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Are you 100% sure you were on the base circle of the cam when you took this measurement? Did you confirm on more then one rocker?
Thread Starter
Joined: Sep 2005
Posts: 741
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From: North Little Rock, Ar
I can't give you a 100% answer, it probably relates to a lot of little things. The autos just don't respond to gears like M6s do. An M6 going from 3.42s to 4.10s would make a nice improvement, going from a 4.10 to a 4.56, probably not so much. I guess there is a point in every setup where more gear just doesn't help anymore. Autos seem to be a lot closer to that point.
Are you 100% sure you were on the base circle of the cam when you took this measurement? Did you confirm on more then one rocker?
Are you 100% sure you were on the base circle of the cam when you took this measurement? Did you confirm on more then one rocker?
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I make no claims to be an expert but if it were mine my train of thought would go:
Is it noisy? It seems most people end up with 7.375 or 7.4 pushrods so perhaps you measured wrong?
From the way you talk about the tune I would also expect there to be a bit to gain there. You are tuning with a wideband correct? Tuning based on the LTFT or STFT or factory o2 sensors is not a good way to do it. I've had a friend pop pistons doing that.
If you aren't tuning with a wideband I would point my finger 1000% at the tune being fucked. That would explain why the car won't take timing.
If you are, make sure you have good fuel pressure all the way to redline under load. You want ~58psi at the rail.
Make sure the IAT are reading accurately. If something is wrong and it's reading high triple digits for the temp that could also be pulling timing.
Did you reset the calibration for the gears? If not is the car shifting where you want? If it's short shifting due to improper MPH readings that could affect your track times too.
What are you shifting at? If you aren't revving high enough the gains will also be minimized.
Is it noisy? It seems most people end up with 7.375 or 7.4 pushrods so perhaps you measured wrong?
From the way you talk about the tune I would also expect there to be a bit to gain there. You are tuning with a wideband correct? Tuning based on the LTFT or STFT or factory o2 sensors is not a good way to do it. I've had a friend pop pistons doing that.
If you aren't tuning with a wideband I would point my finger 1000% at the tune being fucked. That would explain why the car won't take timing.
If you are, make sure you have good fuel pressure all the way to redline under load. You want ~58psi at the rail.
Make sure the IAT are reading accurately. If something is wrong and it's reading high triple digits for the temp that could also be pulling timing.
Did you reset the calibration for the gears? If not is the car shifting where you want? If it's short shifting due to improper MPH readings that could affect your track times too.
What are you shifting at? If you aren't revving high enough the gains will also be minimized.
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
I make no claims to be an expert but if it were mine my train of thought would go:
Is it noisy? It seems most people end up with 7.375 or 7.4 pushrods so perhaps you measured wrong?
From the way you talk about the tune I would also expect there to be a bit to gain there. You are tuning with a wideband correct? Tuning based on the LTFT or STFT or factory o2 sensors is not a good way to do it. I've had a friend pop pistons doing that.
If you aren't tuning with a wideband I would point my finger 1000% at the tune being fucked. That would explain why the car won't take timing.
If you are, make sure you have good fuel pressure all the way to redline under load. You want ~58psi at the rail.
Make sure the IAT are reading accurately. If something is wrong and it's reading high triple digits for the temp that could also be pulling timing.
Did you reset the calibration for the gears? If not is the car shifting where you want? If it's short shifting due to improper MPH readings that could affect your track times too.
What are you shifting at? If you aren't revving high enough the gains will also be minimized.
Is it noisy? It seems most people end up with 7.375 or 7.4 pushrods so perhaps you measured wrong?
From the way you talk about the tune I would also expect there to be a bit to gain there. You are tuning with a wideband correct? Tuning based on the LTFT or STFT or factory o2 sensors is not a good way to do it. I've had a friend pop pistons doing that.
If you aren't tuning with a wideband I would point my finger 1000% at the tune being fucked. That would explain why the car won't take timing.
If you are, make sure you have good fuel pressure all the way to redline under load. You want ~58psi at the rail.
Make sure the IAT are reading accurately. If something is wrong and it's reading high triple digits for the temp that could also be pulling timing.
Did you reset the calibration for the gears? If not is the car shifting where you want? If it's short shifting due to improper MPH readings that could affect your track times too.
What are you shifting at? If you aren't revving high enough the gains will also be minimized.
No the engine isn’t noisy and IAT are correct. It does have a slight ticking sound when it is first warming up but it did the same thing before I replaced the heads and lifters. Once it warms up there isn’t any excessive valve train noise.
I have been tuning using a wideband (LC1). At the track the car was running a little rich up top, because of the LTFTs being added in. It was in the low 12:1 area with about 26 degrees of timing. I have since turned the LTFTs back off and now the car is in the 12:3-12:8 AFR at WOT. But now it wants to pull 2-3 degrees of timing. I was going to try using a 2002 knock sensor calibration since I do have the new style knock sensors and see if that helps the retard. The car is a 99 and I think the sensors were a little sensitive in that year right? Fuel pressure is good. I have a new racetronics pump and hot wire kit and am reading about 58-60 psi at the rail. Tranny is shifting between 6400-6800 rpm so that is in range of where I want it to be and is the same when it was cam only.
Awesome, well that narrows things down a bit.
I would recheck the pushrod length and make sure it's correct for starters since that's an easy thing to do. I would also do a compression test and possibly a leakdown test.
Also be sure to thoroughly check the basics: plugs, wires, grounds, vacuum hoses, and anything else that would be disturbed during a head install.
Keep trying to find someone trustworthy to look at your tune/log files too.
Also, rather than trusting your senses grab a timeslip from before and after and calculate DA for each and compare the corrected times. You might be missing less than you think.
I would recheck the pushrod length and make sure it's correct for starters since that's an easy thing to do. I would also do a compression test and possibly a leakdown test.
Also be sure to thoroughly check the basics: plugs, wires, grounds, vacuum hoses, and anything else that would be disturbed during a head install.
Keep trying to find someone trustworthy to look at your tune/log files too.
Also, rather than trusting your senses grab a timeslip from before and after and calculate DA for each and compare the corrected times. You might be missing less than you think.
Do you have a before & after dyno? I wonder about your pushrod setup, 7.325" seems really short.
The heads will add 40rwhp no problem.
The heads will add 40rwhp no problem.
__________________
Jason
Co-Owner, Texas Speed & Performance, Ltd.
2005 Twin Turbo C6
404cid Stroker, 67mm Twins
994rwhp/902lb ft @ 22 psi (mustang dyno) www.Texas-Speed.com
Jason
Co-Owner, Texas Speed & Performance, Ltd.
2005 Twin Turbo C6
404cid Stroker, 67mm Twins
994rwhp/902lb ft @ 22 psi (mustang dyno) www.Texas-Speed.com
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
I guess i will pull the valve covers tonight and check the PR length again and give everything a look see to make sure there are no glaring problems. Maybe i measured wrong?
Measuring method:
Get lifter on base circle of cam. Snug rocker down and lengthen pr checker to zero lash. Count turns and multiply by .050 + 6.8 - .017 and add .080 for preload. Is this correct?
Thanks guys for all the help!
IIRC since you already have the 7.325 pushrods and know their length you can snug it down to zero lash then count the turns to 22ft lbs instead of using the tool at all.
It should be ~1.5 for the correct preload on ls7 lifters I believe.
It should be ~1.5 for the correct preload on ls7 lifters I believe.
You're pulling the same 60 ft. with taller gears, I would say that should speak for some power gains. I agree though, the trap doesn't make much sense.
FYI and not that it relates, but I gained .2-.3 tenths in the 1/8th going from 3.42's to 4.10's when I was bolt-on only. Most of it was gained in the 60 ft because I was in the powerband sooner than with the 3.42's.
FYI and not that it relates, but I gained .2-.3 tenths in the 1/8th going from 3.42's to 4.10's when I was bolt-on only. Most of it was gained in the 60 ft because I was in the powerband sooner than with the 3.42's.
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
You're pulling the same 60 ft. with taller gears, I would say that should speak for some power gains. I agree though, the trap doesn't make much sense.
FYI and not that it relates, but I gained .2-.3 tenths in the 1/8th going from 3.42's to 4.10's when I was bolt-on only. Most of it was gained in the 60 ft because I was in the powerband sooner than with the 3.42's.
FYI and not that it relates, but I gained .2-.3 tenths in the 1/8th going from 3.42's to 4.10's when I was bolt-on only. Most of it was gained in the 60 ft because I was in the powerband sooner than with the 3.42's.
Last edited by LeftySS; Sep 13, 2011 at 04:08 PM.
Were you spinning or easing it out or was that flat out launching the car?
Thread Starter
Joined: Sep 2005
Posts: 741
Likes: 1
From: North Little Rock, Ar
After reading some I am starting to doubt that a PR being too short would cause me to lose top end power. As long as the length gets me in the acceptable range of preload then the valves will lift all the way right?