#7 way way lean
TECH Apprentice
Joined: Dec 2008
Posts: 333
Likes: 0
From: Westbank of N.O.
This is not the 1st LSX engine to have these issues w/ cyl. #7........at 1st, it was thought to have something to do w/ intake manifold flow tendencies. But, when the intake was installed backward on a dyno engine, #7 still had issues. The best theory out of a discussion we had was that there is some kind of coolant flow disruption or cavitation around the #7 cylinder. A colder plug and if u can, a bit more fuel for that cylinder under WOT/max load.
Whatever caused your detonation, you had it.
A melted ground strap will often take out a piston with it, so you definately need to get a plug that will live in there.
I'd switch to a race style plug that will give you a better chance to see what's going on before it disintegrates on you.
Autolite makes the AR-472 plugs that fit LS1 style heads.
I would have the injectors flow tested. If they are all good I'd assume you have a hotspot back there.
A melted ground strap will often take out a piston with it, so you definately need to get a plug that will live in there.
I'd switch to a race style plug that will give you a better chance to see what's going on before it disintegrates on you.
Autolite makes the AR-472 plugs that fit LS1 style heads.
I would have the injectors flow tested. If they are all good I'd assume you have a hotspot back there.
So as not to confuse the noobs. !2.1-12.5 AFR N/A is safe as a rule of thumb on most street driven LS cars. I target 11.5:1 for my big shot (DP w/ 35N jets) and run a #8 plug. I think that once I get my new intake plumbed, I'm going to run 1 jet bigger for fuel in cyl 7. When I do have a plug issue. That's the one.
just throwing this out there for further discussion (again).
regarding the newer intake/coolant routing as the OP has in his 2002 fbody, there is a different coolant line routing setup in the newer LS1's which some people speculate has something to do with the cylinder #7 issue.
when i did my LS6 intake swap, i had the coolant pipe kit on hand, but decided to grind the ribs down and keep the older coolant routing intact to help prevent the cylinder #7 issue.
i know GM must have done extensive testing before going with the new coolant routing setup, but maybe they didn't account for FI/N2O?
here's a photo of the older LS1 coolant line routing where you can see the coolant line running under the intake manifold to the back of the block.
regarding the newer intake/coolant routing as the OP has in his 2002 fbody, there is a different coolant line routing setup in the newer LS1's which some people speculate has something to do with the cylinder #7 issue.
when i did my LS6 intake swap, i had the coolant pipe kit on hand, but decided to grind the ribs down and keep the older coolant routing intact to help prevent the cylinder #7 issue.
i know GM must have done extensive testing before going with the new coolant routing setup, but maybe they didn't account for FI/N2O?
here's a photo of the older LS1 coolant line routing where you can see the coolant line running under the intake manifold to the back of the block.
Last edited by BobDoLe; Jan 1, 2009 at 11:38 AM.
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just throwing this out there for further discussion (again).
regarding the newer intake/coolant routing as the OP has in his 2002 fbody, there is a different coolant line routing setup in the newer LS1's which some people speculate has something to do with the cylinder #7 issue.
when i did my LS6 intake swap, i had the coolant pipe kit on hand, but decided to grind the ribs down and keep the older coolant routing intact to help prevent the cylinder #7 issue.
i know GM must have done extensive testing before going with the new coolant routing setup, but maybe they didn't account for FI/N2O?
here's a photo of the older LS1 coolant line routing where you can see the coolant line running under the intake manifold to the back of the block.
regarding the newer intake/coolant routing as the OP has in his 2002 fbody, there is a different coolant line routing setup in the newer LS1's which some people speculate has something to do with the cylinder #7 issue.
when i did my LS6 intake swap, i had the coolant pipe kit on hand, but decided to grind the ribs down and keep the older coolant routing intact to help prevent the cylinder #7 issue.
i know GM must have done extensive testing before going with the new coolant routing setup, but maybe they didn't account for FI/N2O?
here's a photo of the older LS1 coolant line routing where you can see the coolant line running under the intake manifold to the back of the block.
The single plain intakes have helped with the lean cylinder issue, over the front entrance plastic style intakes. better distribution.
Robert
So has anyone tried the ideas given to see if they help/work for a dry shot or other FI?
a) 1 step colder plug in #7 and #8 (i.e. tr6 in #1-6 and tr7 in #7-8)
b) Different flowmatched injectors as you go back (i.e. #1-2 normal, #3-4 at 1% more, #5-6 at 2% more, #7-8 at 3% more). Direct Port can get around this with tuning each cylinder, but dry can't
c) Some sort of different coolant setup for the rear cylinders?
These of course would not substitute for a better fuel system, as the injectors/pump/etc should be upgraded
a) 1 step colder plug in #7 and #8 (i.e. tr6 in #1-6 and tr7 in #7-8)
b) Different flowmatched injectors as you go back (i.e. #1-2 normal, #3-4 at 1% more, #5-6 at 2% more, #7-8 at 3% more). Direct Port can get around this with tuning each cylinder, but dry can't
c) Some sort of different coolant setup for the rear cylinders?
These of course would not substitute for a better fuel system, as the injectors/pump/etc should be upgraded
So has anyone tried the ideas given to see if they help/work for a dry shot or other FI?
a) 1 step colder plug in #7 and #8 (i.e. tr6 in #1-6 and tr7 in #7-8)
b) Different flowmatched injectors as you go back (i.e. #1-2 normal, #3-4 at 1% more, #5-6 at 2% more, #7-8 at 3% more). Direct Port can get around this with tuning each cylinder, but dry can't
c) Some sort of different coolant setup for the rear cylinders?
These of course would not substitute for a better fuel system, as the injectors/pump/etc should be upgraded
a) 1 step colder plug in #7 and #8 (i.e. tr6 in #1-6 and tr7 in #7-8)
b) Different flowmatched injectors as you go back (i.e. #1-2 normal, #3-4 at 1% more, #5-6 at 2% more, #7-8 at 3% more). Direct Port can get around this with tuning each cylinder, but dry can't
c) Some sort of different coolant setup for the rear cylinders?
These of course would not substitute for a better fuel system, as the injectors/pump/etc should be upgraded
The other thing that we can do is to get rid of the front entrance plastic intakes and go with a central entrance single plain. this will go a long way in curing our couple cylinders that tend to run lean.
Flowing th injectors and using the richer ones in the lean holes is a good idea.
Robert
