Addressing poor performance after internal engine work (CHECKLIST)
04-22-2002, 07:56 PM
#1
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Addressing poor performance after internal engine work (CHECKLIST) Okay, now that I've got your attention, let's look at what you should do to a poorly performing modified LS1.
Let's say you just did heads and cam, did not/ cannot dyno the car, and went to the track.
... And you only picked up 4mph from heads, cam, headers, after market cats and a y pipe.
Before you douse the car in gasoline, check out these points...
-----------------------------------------------
Best way to tune a car is of course on a dyno. Wideband tuning is invaluable when trying to dial in a performance car.
-----------------------------------------------
Let's say you don't have access to a dyno, what should you do?
1. Always check over engine for obvious mistakes. Did you forget to plug in a sensor? Is the EGR, AIR, and EGR all plugged in correctly? Any big vacuum leaks?
2. Excessive ticking? Well, I can tell you from personal experience that a heads/cam/header'd LS1 will sound sometimes like a solid 302ci Z28. And you can get a bit of that sewing machine sound. Keep in mind that your stock exhaust manifolds were designed for maximal sound attenuation.
But another goofy thing to check? I had a brand new spark plug with a cracked ceramic section. Plug ticked and would visibly arc in total darkness. I'm guessing the plug box got dropped at some point.
If your car is making any weird noises, ie ticking, popping out the exhaust, sputting etc., try to figure what is going on.
3. Maybe you are shifting your combo too low. Remember, your new combo might be making peak HP at 6200 rpms! I'd shift any M6 car at 6400 rpms or higher to make sure you are making use of your power band.
4. Maybe you have other problems. Maybe you low timing, or run too rich? What are ideal #'s?
I'd say that 25 degrees of timing is the mininum you need. I'd shoot for 27-29 degrees of timing. How about 02 readings. Well, I am not a fan of 02 readings off Autotap per se, but I'd shoot for mid 850's or higher. I've experimented with a MAF Translator, both the base and the WOT settings, and I was able to improve both part throttle and WOT acceleration by leaning out my old combo. If you are using a MAF T, try tuning at the track. I lent my MAF T to a buddy with an M6, and he picked up a solid 2 mph by adding fuel to his combo. Turns out he was lean.
But maybe your setup is now too rich. If you drilled out your idle air hole to the same diameter as everyone else on here, maybe you need to use the MAF T or LS1 Edit or aftermarket tuning to lean it out OR to add more idle and part throttle timing. Excessive surging at idle is a screwed up AF ratio and means you a) need more air coming in to help the idle or b) you need to lean it out because you can't make the hole any bigger.
5. I've got 28 degrees of timing at WOT, and my 02's at WOT are 860mv and I am still too slow.
Now it's getting serious.
Questions to ask:
-Am I running the right length pushrods? For most popular applications 7.350 is the way to go. Lifter preload with stock lifters should be around .050-.060. With Comp R lifters it should be between zero lash and .050. I have talked to very senior folks at Comp and they said that extra preload woun't be a problem.
-What is the car exactly doing? Is it slow all the way down the track? I have had at least one friend not realize that his clutch was dying and that it was slipping slightly in 3rd and 4th and he was only going 111mph with heads and cam.
-Do you have excessive knock retard? Might be from running too lean and you are getting detonation. Could be from excessive valvetrain noise. Try resetting the pcm. Does it come back? Now try adding more fuel, or run some race gas. If you have audible detonation you need to address that immediately.
There are a lot of reasons why a car might not perform after major work. Sometimes it's not the engine but it's the tune (most of the time), the racer not making shifting changes to work with the new power range, or other mechanical problems.
Another problem I have realized in the last 12 months is how often we foul out 02 sensors during a heads/cam swap. We let coolant run down the exhaust. We start up the motor after it's been sitting and you get that nice cloud of junk that comes out of the tail pipe. Maybe your car just runs kind of rich.
What is the result? Lazy o2's because they are coated and are not switching back and forth as fast as they should. Your car can end up running overly rich from this. Will make your eyes water and make your lowend really soggy.
Let's see some other tuning tips.
PSJ
<small>[ April 22, 2002, 08:06 PM: Message edited by: Pro Stock John ]</small>
Let's say you just did heads and cam, did not/ cannot dyno the car, and went to the track.
... And you only picked up 4mph from heads, cam, headers, after market cats and a y pipe.
Before you douse the car in gasoline, check out these points...
-----------------------------------------------
Best way to tune a car is of course on a dyno. Wideband tuning is invaluable when trying to dial in a performance car.
-----------------------------------------------
Let's say you don't have access to a dyno, what should you do?
1. Always check over engine for obvious mistakes. Did you forget to plug in a sensor? Is the EGR, AIR, and EGR all plugged in correctly? Any big vacuum leaks?
2. Excessive ticking? Well, I can tell you from personal experience that a heads/cam/header'd LS1 will sound sometimes like a solid 302ci Z28. And you can get a bit of that sewing machine sound. Keep in mind that your stock exhaust manifolds were designed for maximal sound attenuation.
But another goofy thing to check? I had a brand new spark plug with a cracked ceramic section. Plug ticked and would visibly arc in total darkness. I'm guessing the plug box got dropped at some point.
If your car is making any weird noises, ie ticking, popping out the exhaust, sputting etc., try to figure what is going on.
3. Maybe you are shifting your combo too low. Remember, your new combo might be making peak HP at 6200 rpms! I'd shift any M6 car at 6400 rpms or higher to make sure you are making use of your power band.
4. Maybe you have other problems. Maybe you low timing, or run too rich? What are ideal #'s?
I'd say that 25 degrees of timing is the mininum you need. I'd shoot for 27-29 degrees of timing. How about 02 readings. Well, I am not a fan of 02 readings off Autotap per se, but I'd shoot for mid 850's or higher. I've experimented with a MAF Translator, both the base and the WOT settings, and I was able to improve both part throttle and WOT acceleration by leaning out my old combo. If you are using a MAF T, try tuning at the track. I lent my MAF T to a buddy with an M6, and he picked up a solid 2 mph by adding fuel to his combo. Turns out he was lean.
But maybe your setup is now too rich. If you drilled out your idle air hole to the same diameter as everyone else on here, maybe you need to use the MAF T or LS1 Edit or aftermarket tuning to lean it out OR to add more idle and part throttle timing. Excessive surging at idle is a screwed up AF ratio and means you a) need more air coming in to help the idle or b) you need to lean it out because you can't make the hole any bigger.
5. I've got 28 degrees of timing at WOT, and my 02's at WOT are 860mv and I am still too slow.
Now it's getting serious.
Questions to ask:
-Am I running the right length pushrods? For most popular applications 7.350 is the way to go. Lifter preload with stock lifters should be around .050-.060. With Comp R lifters it should be between zero lash and .050. I have talked to very senior folks at Comp and they said that extra preload woun't be a problem.
-What is the car exactly doing? Is it slow all the way down the track? I have had at least one friend not realize that his clutch was dying and that it was slipping slightly in 3rd and 4th and he was only going 111mph with heads and cam.
-Do you have excessive knock retard? Might be from running too lean and you are getting detonation. Could be from excessive valvetrain noise. Try resetting the pcm. Does it come back? Now try adding more fuel, or run some race gas. If you have audible detonation you need to address that immediately.
There are a lot of reasons why a car might not perform after major work. Sometimes it's not the engine but it's the tune (most of the time), the racer not making shifting changes to work with the new power range, or other mechanical problems.
Another problem I have realized in the last 12 months is how often we foul out 02 sensors during a heads/cam swap. We let coolant run down the exhaust. We start up the motor after it's been sitting and you get that nice cloud of junk that comes out of the tail pipe. Maybe your car just runs kind of rich.
What is the result? Lazy o2's because they are coated and are not switching back and forth as fast as they should. Your car can end up running overly rich from this. Will make your eyes water and make your lowend really soggy.
Let's see some other tuning tips.
PSJ
<small>[ April 22, 2002, 08:06 PM: Message edited by: Pro Stock John ]</small>
04-22-2002, 08:09 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) One of the most important tuning tips:
1) If you don't know what the heck you're doing, take it to someone who does. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
1) If you don't know what the heck you're doing, take it to someone who does. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
04-22-2002, 08:15 PM
#3
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Re: Addressing poor performance after internal engine work (CHECKLIST) I drove a heads/cam M6 car a few years ago that crawled. I mean, I drove my old 98SS M6 to 109mph back in 1998 with boltons and I was a nondriving' MFer. But I could not get this M6 car (which was heavy) to trap better than 108mph with heads, cam, headers, aftermarket cats, catback, and programming. It audibly pinged which I wanted to address but it was not my car. It should have went about 114mph at 3900 raceweight and 1000 elevation.
Also remember that a car that crawls at the track might only be running on 7 cylinders. Maybe you have a bad plug, or heck, you pulled on the wiring harness and you have a problem with one of your injectors.
My current car saw so much engine work in 2001 from problems (with the old 346ci setup) that I had to rewire the crank position sensor since the wire was either damaged or broken somewhere down the wire.
John
422ci
450rwhp / 502rwhp unlocked on pump gas
31 degrees of timing
13:1 AF on wideband
NGK TR6's at .050
Also remember that a car that crawls at the track might only be running on 7 cylinders. Maybe you have a bad plug, or heck, you pulled on the wiring harness and you have a problem with one of your injectors.
My current car saw so much engine work in 2001 from problems (with the old 346ci setup) that I had to rewire the crank position sensor since the wire was either damaged or broken somewhere down the wire.
John
422ci
450rwhp / 502rwhp unlocked on pump gas
31 degrees of timing
13:1 AF on wideband
NGK TR6's at .050
04-22-2002, 08:26 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) WoW John! looks like you covered almost everything! I only have a couple of power killers to add, Check MAF screen and filter for debris, check the MAF grids heat elements for caked over black gunk from over oiled K&N filters. Something I learned to make the low end a bit cleaner under 174 F is to unplug the air pump, or block off the inlet. Over ported TB's hurt power, never re-install the stock spark plugs after a S2 high performance install, NGK TR55's are great. Don't chase the 02's around with the translator under computer LT/ST heavy + to - compensation, Auto Tap the crap out of it on the street before you go to a dyno session and translate it as close as possible to minimize your pulls when you get there. Alot of S2 packages will need to be launched 2,000 RPM higher out of the hole than before to get the 60' out of it. Higher milage cars, ALWAYS change the fuel filter before you even start tunning. Low rail pressure under WOT is another "ghost" power killer. If you tunning on the dyno or the street, never let the car audably detonate under WOT for more than a second or so, let out of the GAS! your destroying the plugs/gasket firing rings/ring lands.
04-23-2002, 02:05 AM
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Re: Addressing poor performance after internal engine work (CHECKLIST) great thread, you learn something new everyday <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
04-23-2002, 06:45 AM
#7
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Re: Addressing poor performance after internal engine work (CHECKLIST) 1 Q..
Last time I talked to Comp, they said .025-.050 Preload on the stock lifters helps at higher rpms and they don't like seeing more than .050, altho up to .090 might not hurt.
Do you think .025-.050 is best for 6400-6800 with stock lifters? I always get a different answer from Comp each time I call. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
Last time I talked to Comp, they said .025-.050 Preload on the stock lifters helps at higher rpms and they don't like seeing more than .050, altho up to .090 might not hurt.
Do you think .025-.050 is best for 6400-6800 with stock lifters? I always get a different answer from Comp each time I call. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />
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04-23-2002, 10:19 AM
#8
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Re: Addressing poor performance after internal engine work (CHECKLIST) I think anything around .050 is fine with stock lifters. Beyond that I don't think about it, because nobody else really has done any research into stock lifters. I recall Craig from GTP saying to me on the fone a few years ago that it's not a bad idea to run extra lift because the stock lifters are probably getting some bleeddown at higher rpms so your 580 lift cam is probably more like a 560 lift.
Anymore tips for fixing troubled cars?
------
6. Car stalls when coming to a stop after cam (+ heads) swap.
Autotap your IAC counts. They are supposed to be 30-40 stock. Based on my experience you can get around with 50-70, but when it's it's like 85-130 then the car will stall out at lights, after a burnout, when you crank the power steering. You can try cranking up the TB screw under the throttle which will crack the blade, but you can only do so much of that before you set a 'TPS voltage too high' code. Really what I do is this: I take off the MAF etc so I can get at the TB. I put a rag behind the TB blade, and I trial fit a drill bit into the idle air hole. I then find the next biggest one and drill out the hole. I use the rag to catch the shavings. You really should take the TB off but I am lazy. If you are impatient I would go no more than two sizes bigger to start. Put it back together and drive the car a bit. If you still have to two-foot the car AFTER it's warmed up you might need to go one more.
<small>[ April 23, 2002, 10:24 AM: Message edited by: Pro Stock John ]</small>
Anymore tips for fixing troubled cars?
------
6. Car stalls when coming to a stop after cam (+ heads) swap.
Autotap your IAC counts. They are supposed to be 30-40 stock. Based on my experience you can get around with 50-70, but when it's it's like 85-130 then the car will stall out at lights, after a burnout, when you crank the power steering. You can try cranking up the TB screw under the throttle which will crack the blade, but you can only do so much of that before you set a 'TPS voltage too high' code. Really what I do is this: I take off the MAF etc so I can get at the TB. I put a rag behind the TB blade, and I trial fit a drill bit into the idle air hole. I then find the next biggest one and drill out the hole. I use the rag to catch the shavings. You really should take the TB off but I am lazy. If you are impatient I would go no more than two sizes bigger to start. Put it back together and drive the car a bit. If you still have to two-foot the car AFTER it's warmed up you might need to go one more.
<small>[ April 23, 2002, 10:24 AM: Message edited by: Pro Stock John ]</small>
04-23-2002, 10:46 AM
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Re: Addressing poor performance after internal engine work (CHECKLIST) Excellent thread!!
How do you fix low rail pressure?
What is the "idea timing" - anything over 28 or should I really shoot for 31. What's the highest you should go?
What's the easiest way to figure out A/F ratio on a 98' ( A-tap won't tell me). What are my options for cures? (no MAF-T)
- too rich then flip MAF around?
- too lean then replace ported TB
and MAF back to stock.
With the intake off what's the easiest way to clean the injectors to where they perform like new? Is there a visual inspection that could let me know if I should replace them? If I need to replace them what would be good alternatives for a bolt-on/cam car? (SVO 30#)
Thanks for all the help!!
Eric
How do you fix low rail pressure?
What is the "idea timing" - anything over 28 or should I really shoot for 31. What's the highest you should go?
What's the easiest way to figure out A/F ratio on a 98' ( A-tap won't tell me). What are my options for cures? (no MAF-T)
- too rich then flip MAF around?
- too lean then replace ported TB
and MAF back to stock.
With the intake off what's the easiest way to clean the injectors to where they perform like new? Is there a visual inspection that could let me know if I should replace them? If I need to replace them what would be good alternatives for a bolt-on/cam car? (SVO 30#)
Thanks for all the help!!
Eric
04-23-2002, 03:01 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) Throwing strange codes after a head swap, check your ground straps.
The PCM has 3 primary grounds that terminate at the back of the driver's cyl head onto 2 studs. 1 is the main computer ground and 1 is for the heated O2 sensors. A loose ground will drive you nuts!!! Make sure all 3 are hooked up and tight!
Mark
The PCM has 3 primary grounds that terminate at the back of the driver's cyl head onto 2 studs. 1 is the main computer ground and 1 is for the heated O2 sensors. A loose ground will drive you nuts!!! Make sure all 3 are hooked up and tight!
Mark
04-23-2002, 04:24 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) and what if you have horrible compression in 4 of the cylinders? would bad tuning causing you to run too lean, possibly burn out some valves? I have 4 bad cylinders in my engine. After the heads and cam went in the car pulled pretty good but then lost its "pull" all together after awhile. I assume this was when the engine lost its compression and NOT BEFORE the heads went on. Its my daily driver and only car so i don't want to pull the heads off unless it is absolutely necessary.
04-23-2002, 04:54 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) Pro Stock John, please take a look at this these graphs ( link ).. I would love to figure this one out
Check the sig and you will see what I mean...
http://home.attbi.com/~sawacs/t1dyno.htm
Thanks, Awacs
__________________
2000 Ralley Red SS M6, Ebony Int, T-tops, FRA!, CAGS!, MAFT, lid, cutout, T-1 Cam, ARE oil pump , Lou's short throw shifter, RT catback, BMR stb, and many coats of Zaino.
SAE Corrected...cutout open
before T-1:
330.9 RWHP
335.6 RWTQ
After T-1:
338.5 RWHP
338.4 RWTQ
Check the sig and you will see what I mean...http://home.attbi.com/~sawacs/t1dyno.htm
Thanks, Awacs
__________________
2000 Ralley Red SS M6, Ebony Int, T-tops, FRA!, CAGS!, MAFT, lid, cutout, T-1 Cam, ARE oil pump , Lou's short throw shifter, RT catback, BMR stb, and many coats of Zaino.
SAE Corrected...cutout open
before T-1:
330.9 RWHP
335.6 RWTQ
After T-1:
338.5 RWHP
338.4 RWTQ
04-23-2002, 05:42 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) My S2 H/C is suppose to be here first week of May. This thread is invaluable but, it is scaring the **** out of me!! It seems there are so many potential problems. Im afraid I am taking a bolt on car that runs perfect, spending a small fortune, and possibly having major headaches! Please give me some words of encouragement. This will be our first H/C install. Ive got some great mechacic buddies, but this will be our first internal mod LS1.
Paul <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />
Paul <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />
04-23-2002, 05:44 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Amarillo2:
<strong>Excellent thread!!
How do you fix low rail pressure?
What is the "idea timing" - anything over 28 or should I really shoot for 31. What's the highest you should go?
What's the easiest way to figure out A/F ratio on a 98' ( A-tap won't tell me). What are my options for cures? (no MAF-T)
- too rich then flip MAF around?
- too lean then replace ported TB
and MAF back to stock.
With the intake off what's the easiest way to clean the injectors to where they perform like new? Is there a visual inspection that could let me know if I should replace them? If I need to replace them what would be good alternatives for a bolt-on/cam car? (SVO 30#)
Thanks for all the help!!
Eric</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">-Stock timing will be in the 25-28 range. I'd shoot for 27-29 degrees. I see a gain of HP with more but it might be at the cost of pinging in July, we'll see.
-Rail question, I have no clue.
-You can get injectors flow matched and cleaned for about $200. You can run injector cleaner thru the motor to see if that helps.
-You can flip the maf ends around it appears to richen it up. If you go to lean and cannot correct it you will set an SES code.
<strong>Excellent thread!!
How do you fix low rail pressure?
What is the "idea timing" - anything over 28 or should I really shoot for 31. What's the highest you should go?
What's the easiest way to figure out A/F ratio on a 98' ( A-tap won't tell me). What are my options for cures? (no MAF-T)
- too rich then flip MAF around?
- too lean then replace ported TB
and MAF back to stock.
With the intake off what's the easiest way to clean the injectors to where they perform like new? Is there a visual inspection that could let me know if I should replace them? If I need to replace them what would be good alternatives for a bolt-on/cam car? (SVO 30#)
Thanks for all the help!!
Eric</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">-Stock timing will be in the 25-28 range. I'd shoot for 27-29 degrees. I see a gain of HP with more but it might be at the cost of pinging in July, we'll see.
-Rail question, I have no clue.
-You can get injectors flow matched and cleaned for about $200. You can run injector cleaner thru the motor to see if that helps.
-You can flip the maf ends around it appears to richen it up. If you go to lean and cannot correct it you will set an SES code.
04-23-2002, 05:47 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 98F-1camaro:
<strong>and what if you have horrible compression in 4 of the cylinders? would bad tuning causing you to run too lean, possibly burn out some valves? I have 4 bad cylinders in my engine. After the heads and cam went in the car pulled pretty good but then lost its "pull" all together after awhile. I assume this was when the engine lost its compression and NOT BEFORE the heads went on. Its my daily driver and only car so i don't want to pull the heads off unless it is absolutely necessary.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">In early 1999 I saw unequal lifter preload, .090 on one bank of cylinders, and .100 in the other. Car ran shitty. You might have a similar problem. Might not have the valves closing all the way on one side of the motor. Car ran superrich and had terrible power. I have no idea why it was unequal, maybe the heads were not decked the same amount or the block surface was not equal. It's a reasonable theory since it's just one side of the motor.
<strong>and what if you have horrible compression in 4 of the cylinders? would bad tuning causing you to run too lean, possibly burn out some valves? I have 4 bad cylinders in my engine. After the heads and cam went in the car pulled pretty good but then lost its "pull" all together after awhile. I assume this was when the engine lost its compression and NOT BEFORE the heads went on. Its my daily driver and only car so i don't want to pull the heads off unless it is absolutely necessary.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">In early 1999 I saw unequal lifter preload, .090 on one bank of cylinders, and .100 in the other. Car ran shitty. You might have a similar problem. Might not have the valves closing all the way on one side of the motor. Car ran superrich and had terrible power. I have no idea why it was unequal, maybe the heads were not decked the same amount or the block surface was not equal. It's a reasonable theory since it's just one side of the motor.
04-23-2002, 07:43 PM
#16
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Re: Addressing poor performance after internal engine work (CHECKLIST) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>I think anything around .050 is fine with stock lifters. I recall Craig from GTP saying to me on the fone a few years ago that it's not a bad idea to run extra lift because the stock lifters are probably getting some bleeddown at higher rpms so your 580 lift cam is probably more like a 560 lift.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thx. So,.. more preload = more lift?
I believe I'm at .075-.080 right now.
Car feels great.. More preload would be more lift?.. right up until you cross some point where the valve starts to stay open and you lose power?
Anyone know what preload would keep valves open?
.100+?
<small>[ April 23, 2002, 07:44 PM: Message edited by: MelloYellow ]</small>
<strong>I think anything around .050 is fine with stock lifters. I recall Craig from GTP saying to me on the fone a few years ago that it's not a bad idea to run extra lift because the stock lifters are probably getting some bleeddown at higher rpms so your 580 lift cam is probably more like a 560 lift.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thx. So,.. more preload = more lift?
I believe I'm at .075-.080 right now.
Car feels great.. More preload would be more lift?.. right up until you cross some point where the valve starts to stay open and you lose power?
Anyone know what preload would keep valves open?
.100+?
<small>[ April 23, 2002, 07:44 PM: Message edited by: MelloYellow ]</small>
04-23-2002, 08:04 PM
#17
Re: Addressing poor performance after internal engine work (CHECKLIST) What does one complete turn of the rocker arm bolt equal in inches? I would like to measure my preload.
Eric
Eric
04-23-2002, 08:29 PM
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Re: Addressing poor performance after internal engine work (CHECKLIST) </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>I think anything around .050 is fine with stock lifters. I recall Craig from GTP saying to me on the fone a few years ago that it's not a bad idea to run extra lift because the stock lifters are probably getting some bleeddown at higher rpms so your 580 lift cam is probably more like a 560 lift.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thx. So,.. more preload = more lift?
I believe I'm at .075-.080 right now.
Car feels great.. More preload would be more lift?.. right up until you cross some point where the valve starts to stay open and you lose power?
Anyone know what preload would keep valves open?
.100+?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No preload would not add more lift, he was saying run more lift than you would otherwise, because lifters bleed some of it anyways.If you had adjustable valvetrain than you could adjust all of preload except for about .008",before bottomed, this would make lifter act like a solid and bleed would be limited. This is touchy though and you have to make sure lifterplunger doesnt close off oiling to upper end when doing this.
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>I think anything around .050 is fine with stock lifters. I recall Craig from GTP saying to me on the fone a few years ago that it's not a bad idea to run extra lift because the stock lifters are probably getting some bleeddown at higher rpms so your 580 lift cam is probably more like a 560 lift.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thx. So,.. more preload = more lift?
I believe I'm at .075-.080 right now.
Car feels great.. More preload would be more lift?.. right up until you cross some point where the valve starts to stay open and you lose power?
Anyone know what preload would keep valves open?
.100+?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No preload would not add more lift, he was saying run more lift than you would otherwise, because lifters bleed some of it anyways.If you had adjustable valvetrain than you could adjust all of preload except for about .008",before bottomed, this would make lifter act like a solid and bleed would be limited. This is touchy though and you have to make sure lifterplunger doesnt close off oiling to upper end when doing this.
04-24-2002, 04:35 PM
#19
Re: Addressing poor performance after internal engine work (CHECKLIST) if istalling aftermarket springs (especially double) or retainers and a crappy running car is the case, with no codes etc. check your rockers AND valvecovers for collision issues.. especially 98 valvecovers.
04-24-2002, 06:26 PM
#20
LS1Tech Co-Founder
Thread Starter
iTrader: (34)
Re: Addressing poor performance after internal engine work (CHECKLIST) Yeah do all the Crane springs require clearancing the underside of the rocker arms? The clearancing is very easy with a grinding, takes like 30 second to do each rocker.
