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1992 Chevy Silverado crazy timing

Tiny
DADSTRUCK1
  • MEMBER
  • 1992 CHEVROLET SILVERADO
1992 Chevy Silverado V8 Two Wheel Drive Automatic

What would cause the engine to want 53 degree's of timing to run just ok. It is a 355, the original block with trickflow heads and roller cam. It also has a 4bbl 4 venturi aftermarket tbi. The cam has been degreed and is timed perfectly. When I set initial timing (with wire unpluged) and then plug it back in it runs at about 22 degree"s advanced but will not run worth a crap. All sensors are new. Distributor is also new (stock). I have even replaced spark advance module to no avail. Massive tuning done by Lt1pcm. Com to no avail. With wire pluged in I can advance it to about 53-60 advanced and it runs much better. It seems as if the spark timing is malfunctioning. As I said all sensors are new and nothing abnormal coming accross data log. I am able to log the ecu but we cant find anything a miss. Is there any way to work on distributor to fix this or does this sound like tuning issue. Compression check done and all is well. 50 psi of fuel pressure with no drop off. How do I fix this problem? Has anyone ever had this type of problem before? Please Help. I am a pretty good back yard mechanic but this is beyond my comprehension. How could I just convert over to carburator or can i?
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Friday, February 19th, 2010 AT 3:04 PM

9 Replies

Tiny
RACEFAN966
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You have a few issues happening here. First off you have nothing stock and trying to run with the computer that is disigned to run stock. You are running a higher fuel pressure on a truck that was disigned to run on 15 psi. You are now running roller rockers that will make noise that the knock sensor will see so it will try to retard the timing. Did you get the computer with the aftermarket 4bb throttle body system? How large of a cam are you running (specs please). What rocker arm ratio are you running? To answer you question is you go to regular HEI distributor and eliminate the computer then yes you can go to carburation. Get back to me.
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Saturday, February 20th, 2010 AT 9:15 AM
Tiny
DADSTRUCK1
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The ecu has been upgraded from a 20 pin chip to a 24 pin chip with the addition of a g2 socket purchased from http://www.Moates.net This was done to get the wider parameters. I am running 1.5 ratio rockers. The cam has a centerline or lsa of 110. 528 lift on intake and 539 on the exhaust. Duration at .050 is 234 intake and234 exhaust. Cam timing @ .004 is 36.0 btdc and closes at 76.0 abdc on intake side. exhaust is 78.0 bbdc and 38 atdc. Advertised duration is 292.0 - 296.0 Cam timing at .050 is intake 9.0 btdc and 41.0 abdc with max lift of 106. Exhaust is 51.0 bbdc and 3.0 atdc max lift 114. Hope this helps, thanks.
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Saturday, February 20th, 2010 AT 10:23 AM
Tiny
RACEFAN966
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Ok so you timing is going to be very high with a 528 lift that is over 500 and also requires a stall converter too. Now when you refer to the timing is it overall timing or base timing?
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Monday, February 22nd, 2010 AT 10:25 AM
Tiny
DADSTRUCK1
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  • 5 POSTS
This the base timing with the wire plugged in:
it advances to about 67 from there and am already running a 2200 stall
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Tuesday, February 23rd, 2010 AT 1:58 PM
Tiny
RACEFAN966
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Ok good stall on the converter. Now the timing you say 67 deg at what rpm with the timing wire plugged in or not? Are you using roller rockers and or lifters?
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Wednesday, February 24th, 2010 AT 10:01 AM
Tiny
DADSTRUCK1
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Yes, roller rockers and roller lifters. That timing was at idle and 67 at 3000 rpm. Weird thing though, I unpluged the knock sensor thinking that it was picking up the rockers even though they are fairly quiet. It did not even trip the check engine light. I am now able to time it to 38 at idle and at 3000 rpm it advances to 48. It runs much better but not yet perfect. I started loging again and it is still picking up knocks even with the knock sensor unpluged. My tuner is going to disable the knock retard function in the next chip to see what happens. I am working with Solomon at Lt1pcmtuning. Com. It is not an lt1 engine but he does tbi stuff too. Also in the log it shows that it sometimes picks up crank signal and sometimes does not. It has no crank or cam sensor. I thought that was all controled in the distributor right? The program I am using to log is tuner pro. I also noticed in the logging that it does not always pick up tps % though it does get the voltage changes. Also the voltage shows in the log that it drops off to about 6-8 volts but the guage in the truck shows nothing of the sort. Could I have a Short in the system that would affect things in this manor?
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Wednesday, February 24th, 2010 AT 9:44 PM
Tiny
RACEFAN966
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That is what I am thinking the knock sensor is picking something up with the roller rockers and such. So once the advance it disabled lets see what it does. I also would like to know if you checked the timing control module see pic below.


https://www.2carpros.com/forum/automotive_pictures/249564_ESC_Module_1.jpg

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Thursday, February 25th, 2010 AT 9:07 AM
Tiny
DADSTRUCK1
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It runs better with out the wire pluged in. It has to be timed manualy to about 36-38 advanced. Problem is there is only the mechanical advance from there and it goes to about 40-42 then which is not near enough. Sort of like runing without vacume advance connected on a regular hei. Yes I just replaced the advance module and it did not help. Well then again maybe a little, but not much. This is what I thought the problem was at first, but when I replaced it, really no changes took place.
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Thursday, February 25th, 2010 AT 6:39 PM
Tiny
RACEFAN966
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I has to be that knock sensor picking up the sounds from the lifters and rockers. I would also check the timing control module that I included in the previouse response. If you need the test procedure just let me know and I will include it.
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Friday, February 26th, 2010 AT 10:19 AM

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