View Poll Results: Have you ever lost #7???
Yes
81
29.45%
No
194
70.55%
Voters: 275. You may not vote on this poll
How many of you guys have lost number 7....
04-20-2006, 07:40 AM
#44
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Working at my old job at a GM dealer here in Norway, I saw a 2001 Tahoe with the LM7 5.3l lose the ringland on the #7 piston. It was equipped with a Whipple twin screw supercharger kit, with those two additional injectors in the adapter where the TB was stock. The longblock was swapped, and it blew the #7 again after that... It had the stock truck intake, no other mods.
04-20-2006, 07:33 PM
#46
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Originally Posted by 92SilverSHO
this thread has me a bit nervous, but theres so many modded ls1s out there with no problems at all.
06-01-2006, 08:53 PM
#48
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Originally Posted by V-10 Killer
Isn't there somewhere in the ECM that you can bias injectors per cylinder? Couldn't you run a little more fuel to #7?
Thats what Im wondering also...
In my tuning program for my GTP, it has a profile called 'Injector Skew Rate" where you can adjust each individual injector to flow more or less than the rest. i.e., Cylinder 1 - 105% Cylinder 2 - 97% Cylinder 3 - 97%, etc....
06-03-2006, 09:12 AM
#49
It's common...
Originally Posted by NHRAMAN
is this the official answer?? does this happen to other engines also.?? With F/I SBF's, this happens as the t/b is on the side, and the cyls opposite get more air, and the same thing happens.
The same phenomina would apply to an N/A application, but to a lesser degree. [CAI]
On the higher HP combos, the solution appears to be a 4 BBL manifold conversion, or, as mentioned above, the use of individual cyl tuning on an aftermkt ECM.
As for #7 being the "last to get fuel", is not the case, unless the system cannot keep up with demand.
Dirty injectors? Maybe, but not likely. I've cleaned hundreds, and seldom see a major increase in flow rates, short of the injector being totally stopped up.
06-03-2006, 10:01 AM
#51
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The rear cylinder is going lean because of it's getting the bulk of the ram air from the intake, not because of fuel. Matter of fact, it should be getting more fuel than the other bank. Also with it being at the back of the motor, it is going to be the hottest cylinder.
I would suggest getting all of the injectors flow balanced, and put the richest injectors at the back of the motor, and the leaner ones in the front. And then run a slighty rich AFR.
Has anyone Dynoed a motor with a O2 in each exhaust runner to see what the AFR differential is between all cylinders?
I would suggest getting all of the injectors flow balanced, and put the richest injectors at the back of the motor, and the leaner ones in the front. And then run a slighty rich AFR.
Has anyone Dynoed a motor with a O2 in each exhaust runner to see what the AFR differential is between all cylinders?
10-07-2006, 03:58 PM
#54
My #7 and #5 went... probably a comination of reasons.. one beign that I foolishly didn't have the tune checked after I swapped heads, and I know the compreeion was higher... even though we added fuel to the car... and I had a **** tune done on teh car when it had about 5000 miles on it, and it was in teh car for about 4000 miles.. the first place I ever went to did a diablo tune on teh car after I ahd them put headers on it.. and it never really felt right... I brought the car to eastside 6 months later, and they dyno'ed the car.. a/f was at 15.7 
I suspect the #5 and #7 were probably slightly hurt then, it didn't show up when teh cam went in the car, still ran pretty good with the cam... but as soon as the heads went on, no more then 200 miles later it went. My guess is the added compression was enough to finish teh #5and #7 tp ringland off. When the heads were off everything looked fine, but apparently, they weren't.
I suspect the #5 and #7 were probably slightly hurt then, it didn't show up when teh cam went in the car, still ran pretty good with the cam... but as soon as the heads went on, no more then 200 miles later it went. My guess is the added compression was enough to finish teh #5and #7 tp ringland off. When the heads were off everything looked fine, but apparently, they weren't. 
10-07-2006, 10:38 PM
#56
12 Second Club
So what can we do to prevent/protect ourselves from this problem. Dial in our tune a little rich, clean the injectors dosen't sound right, new intake, don't spray, if this happened to me the car would sit in the garage for at least a couple of year till I could fix it. Car is not DD BTW.
10-08-2006, 10:35 AM
#57
Originally Posted by MyTA99
So what can we do to prevent/protect ourselves from this problem. Dial in our tune a little rich, clean the injectors dosen't sound right, new intake, don't spray, if this happened to me the car would sit in the garage for at least a couple of year till I could fix it. Car is not DD BTW.
Tie the rear coolant passages on the heads to the radiator.
10-26-2006, 11:39 AM
#59
Originally Posted by LS1-450
Tie the rear coolant passages on the heads to the radiator.
that's been tried, doesn't make a differnece. The only real thing that can be done is to go to the single plane intake, so all cylinders are getting the same amount of air. But, most people aren't willing to hack the cowl/hood to get it on there, as well as all the other things that have to be done.... so the only real thing to do is stop pushing the stock shortblock so hard.... or at least keep the tune more towards the safe side. Won't put up the #'s that everyone gets so hard over.. but if you can't afford to replace the shortblock, then you shouldn't eb racing anyway, so power #'s shouldn't really matter that much.
10-26-2006, 04:24 PM
#60
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Originally Posted by JoeyGC5
lost #7 a day after a VERY bad clutch slip on the highway, while hitting it with 100hp shot. My heads and cam #'s were starting to drop from couple of past dyno runs. So I knew something wasn't right. Car ran good, just after the clutch slipped at 4300rpms in 4th it just went south from there. Car smokes like a choo-choo train out of the oil fill breather. Need to finish pulling it out for the forged relacement though. Compression test showed 195psi in all cylinders, except #7, which had 70psi 