lq4 broken pistons?
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Teching In
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lq4 broken pistons? Wondering why my pistons chipped, i had my vacum hooked up straight from throttle body to the valve cover did that cause this or do i have other issues timing never exceeds 36 deg, was running super rich when it happened 10:1 during full throttle im thinking it was the vacum scenario but unshure any confermation will be great. I also cant figure out how to post my tune?? Was running a 12 lb spring and only getting 3 lbs boost. iats never over 150deg ushually 100deg is that bad? Im also running all stock internals.
Last edited by eddierm250; Sep 16, 2014 at 09:49 PM.
Somebody with more boost experience will chime in but I don't think you should be anywhere near 36 degree's of timing under boost. I know the 6-71 blown 408 that I am rebuilding had serious issues with only 24 degree's of timing and 10lbs of boost.
Most people seem to run 14-20 under boost https://ls1tech.com/forums/forced-in...-able-run.html
Most people seem to run 14-20 under boost https://ls1tech.com/forums/forced-in...-able-run.html
Thread Starter
Teching In
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Thanks for the reply appreciate that and yea i have been unshure about my timing table i start off idle at 16 deg then at full throttle max 36 deg. Was the 24 deg at idle or max timing? Three of my pistons are broke they broke on the top side of the motor but on the opposite side the spark plug, and the spark plug closed but doesnt appear to have hit anything, and there is no sign of any piston chunks any where???
Last edited by eddierm250; Sep 17, 2014 at 07:21 PM.
You might want to post this in the forced induction section https://ls1tech.com/forums/forced-induction-9/ to get more exposure and hopefully the answer you're looking for.
This piston chunks most likely went out the exhaust so I would have the heads checked when you rebuild.
Timing varies from engine to engine but you'll likely need pull timing as you make more boost. So you may start at 16*-18* at idle and end up at pulling 4*-6* or more depending on boost levels.
This piston chunks most likely went out the exhaust so I would have the heads checked when you rebuild.
Timing varies from engine to engine but you'll likely need pull timing as you make more boost. So you may start at 16*-18* at idle and end up at pulling 4*-6* or more depending on boost levels.
On The Tree
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My experience with boosted engines is the 3800 series 2 supercharged motors. I have 2 cammed 3800's at the moment. One of them runs on pump gas and idle timing is around 20* cruise timing is around 20-45* depending on engine load. Wot timing on is around 16-18*. The other car is on e85 with a higher compression motor and again idle timing is around 20* and cruise timing is around 20-50* depending on engine load. Wot timing on this car is around 20-22* because of the higher octane. Now these cars do not have ls motors but i would think that the timing would be similar on a ls motor. Most boosted motors ive played around with i shoot for an air fuel ratio of 11.4:1-11.8:1 at wot. Once i get the air fuel ratio dialed in i start messing with timing. I usually start low and slowly add more till you see some detonation then i back the timing off a few degrees so it no longer detonates
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My experience with boosted engines is the 3800 series 2 supercharged motors. I have 2 cammed 3800's at the moment. One of them runs on pump gas and idle timing is around 20* cruise timing is around 20-45* depending on engine load. Wot timing on is around 16-18*. The other car is on e85 with a higher compression motor and again idle timing is around 20* and cruise timing is around 20-50* depending on engine load. Wot timing on this car is around 20-22* because of the higher octane. Now these cars do not have ls motors but i would think that the timing would be similar on a ls motor. Most boosted motors ive played around with i shoot for an air fuel ratio of 11.4:1-11.8:1 at wot. Once i get the air fuel ratio dialed in i start messing with timing. I usually start low and slowly add more till you see some detonation then i back the timing off a few degrees so it no longer detonates
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Teching In
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Thank you for the replies after checking out some of denmahs advance tables im shure mine was way off my timing would only increase as load and rpms went up looks like as you go from vacum to boost is where you need to bring the timing way down the more boost the more your timing should retard and start with low numbers to play it safe ill fix and try again this is my hobbies so be it if it cost me a lil money. Thankx again to all who replied really appreciate the responses.