The dreaded #7 destruction...
 

... no... not me:D ... hopefully never:eek: :blueangel:

... just would like to discuss how many of you have had it happen... and whether or not you actually found the problem or chalked it up to bad luck or some other "common" problem.

Could it really be a intake manifold flow issue? FWIW, truck #7's are dying too...

Could it be a coolant flow issue concerning the rear vent ports being blocked off on the 01-up vette's? Trucks also have their rear vent ports plugged. What about the older 97-00 vette's with there coolant "manifold" that ties all 4 vents together? Is the destruction common to 01-up vettes... and less so with the older C5's or the same?

Could it be a fuel flow characteristic within the fuel rail where the #7 injector just happens to see most of the fuel line contaminants?

Can this problem be attributed to stock returnless fuel rails?

What are your thoughts and/or experiences?

Bill :)

MikeD just picked up his 20k mile LS1 motor Friday, 2 of the rings were gone/shattered on #7

Does he still have all the injectors? Would he be willing to flow test the injectors and/or inspect the screens? Any hard "input" evidence, if possible, would be helpful:)

Bill :cheers:

This is the reason I was adamant in setting up my fuel system with front and rear crossovers on the rails... for fear that #7 was caused by inadequate fueling. Not that it can't happen now but I think it's less likely to.

as a matter of fact, i do; i removed them prior to tuning at Don's shop, didn't # them:(

Well... thats too bad... but if you find something wrong with ANY of the injectors I think it would still be a good data point...

Bill :)

While I wont spoil all the fun.

#7 is an issue on all GenX motors whether or not the coolant crossovers were plugged or not over the various years.
Scratch that one.

#7 is an issue on Trucks (with return rails) and 97/98s with return rails.
Scratch this on too.

Also, Statistically speaking, how could a low flow rate injector always wind up in #7? As for contaiminants its very unlikey as it would rear is head on the rebuild but never does.
Scratch that one too ;)

Phil

Hi Bill,

Happened about 9 months ago to my wife's '02 WS6. Went through the side of block. 22k miles, no mods to motor other than a air filter, header and exhaust. We were not happy but we had it covered under ext warr. co. thank goodness.

Shahram

OK spoiler... spill your beans:D, so did GM strike out multiple times on different iterations of all GENIII based intake manifolds? How many truck manifold iterations? I know of 2 LS1/6 variants... widely discussed here. I find it odd that 2 completely different intake manifold designs (and their supporting fuel rails - return style or returnless) would wind up with the same problem...

Is this an inherent design flaw in coolant flow in the earlier GENIII based block castings? Can't see how it could be a design issue with the heads themselves... otherwise #2 failure would be proportionate, eh?

Do LS2's and LS7 or any new derivitive GENIV based motor have the same issue? ... or too soon to say?

Bill :)

Thanks for the input Shahram. Sorry to hear about your troubles good to know GM took care of you. Wonder if the motor was sent back to corporate for a failure analysis (?). FWIW a former GM Dealer Service Tech in Georgia said he noticed, I would assume abnormally high, #7 injector clogs... I suppose often enough for it to stick in his head and comment about it on another forum...

Bill

Actually Bill, when I got a hold of brass at GM, they acted like they knew already about it and they really didn't care to help. Also, I am a huge advocate of BG injection cleaners and Redline SI 1 injector cleaner for years. I have the injectors of that engine and they are and were spotless. And, Its not like we killed the car. My wife drove it like it was a Honda and it was an auto.

Shahram

I lost #5 and #7 was on its way out while running 10.6:1 AFR. My 2 cents..First it seems like the factory drilled dot to mark forward is a bad design. Then #5 and #7 have more cylinder pressure by design of the intake. Well my fuel rails feed from the rear, so #7 is first in line not last anymore like the factory rail. I do believe the rear cylinders tend to get hotter with less water flow in the rear.. I had no signs of detonation. Looks like a stress riser from the factory drilled dot to mark forward caused the failure. #5 was broken and #7 had a crack that was about all the way through that started at the dot.. I think the Dot is just a weak spot in the ring land. I think it would be better if they moved it further away from the ringland or didn't drill it so deep.

Now thats not to say alot of guys don't lose #7 from detonation. If you run it border line on AFR #7 will be the leanest and prone to detonate..

Mine...

#5
http://i112.photobucket.com/albums/n...x/DSC00026.jpg

#7
http://i112.photobucket.com/albums/n...x/DSC00025.jpg

An old trick is to have your injectors flow-tested and put the highest flowing injector on #7 then the next highest on #8, and so on, working you way forward...

:cheers:

my #7 died in january. destroyed the block, cam, 1 cylinder head and damaged part of the other when piston fragments tried to ender the intake valves. plus the #7rod and piston. I'm still on the fence about the crank I have to take it to the machine shop to see if I can salvage it. still true I hope.

I don't see how GM made the mistake.

GM never intended for the engine to do any more than it is from the factory. What surprises me is that people are surprised they break a piston on a stock motor with a supercharger... :lol:

Been plenty of stock motors loose #7 as well...

My theory is the blame is on the intake manifold design. It gets a ram air effect straight to the back. Which means the rear cylinders gets more air than the front cylinders. More air, more lean.
The only way to really test this is to have 8 equally flowing injectors, a fuel pressure gauge and each end of the fuel rail, and a Wide band sensor at each exhaust port.

I'm guessing a cooling deficiency since the Vette has a "reverse-flow" cooling system. The coolant has to travel the length of the head, picking up heat all the way before it reaches #7.
Why not number 8 first? Maybe there's a bit more flow on that side.

Edit:

The LT1 engine was reverse cooled, LS1 is not. My boo-boo.
Original info came from a dealer service department. I should know better. :willy:

Toasted 5 & 7. The usual suspects.

:iagree: The tunnel ram manifold for a carbed engine has the carbs sitting in the middle so that paths to each cylinder are roughly equal. The manifold is designed to create a "supercharging" effect and push more air into the cylinder than a low rise manifold (at upper rpms). In the LS1, Its possible that with cylinders 1-6 creating velocity in the incoming air, momentum carries the air to cylinder 7 and it runs into a dead end and actually compresses until cylinder 7's valve opens and then you get too much air and it goes lean. If its true, why doesnt number 8 go bad as often as number 7?.