Phil99vette

iTrader: (11)

How many of you guys have lost the dreaded number 7 pistons. If you got time give me a brief rundown of setup.
Phil

Tony Mamo @ AFR

iTrader: (13)

Losing #7 before you post dyno results would certainly suck (and probably be a first)....hopefully thats not the case.

I lost a small piece of my #7 ring land with my stock short (52k on the clock), but considering the handful of nitrous bottles ran thru it, many late night blasts on the street (and some track time), over 400 logged chassis dyno runs, and the fact I shifted it for a year at 7K (with the AFR headed combo), Im thinking why didn't it fail long before that.

I speculate that I might have slightly hurt it (the ring land) on a spray pass, quite some time before it actually failed in the car, but who the hell knows. One thing for sure is that shortblock was a good one and didn't owe me a dime.

Bottom line however is that alot of engine builders and tuners feel that the rear two cylinders get the most air due to the layout of the intake, with #7 probably the worst offender. I dont have conclusive facts to back that up and look foward to hearing from others who might have looked into that situation a little more closely.

Tony

V-10 Killer

iTrader: (22)

I'm in the same boat Tony was in. Damaged a ringland on a spray pass.

Phil99vette

iTrader: (11)

Naw, my motor will take alot more than what I am throwing at it right now. Its running like a champ. Just had a friend lose #7 in a blower motor.
Phil

2c5s

iTrader: (11)

Now that would BLOW!!

Ryan02SS

iTrader: (3)

Wondering if that could have been prevented with a richer A/FR and backed off timing? I used to spray but have had the kit off the car for over a year now.

SUX2BU

iTrader: (14)

i lost # 7 twice. once with a dry shot and once on motor bolt ons only (thanks FAST TB)

JoeyGC5

iTrader: (24)

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

Ragtop 99

iTrader: (7)

Exactly what happened to me a few years ago.

camarokid94

iTrader: (2)

If the intake is the problem, and you have it ported and flowbenched and get all the runners to match, like my headporter says that he can after i get my FAST 9, there shouldnt be any problem for running the #7 lean.

Hennytime

iTrader: (33)

are there any good precationary methods to keep our #7 from going? im using a 125 shot and a few boltons, mayb ea cam this summer and really dont want to buy a new motor jst yet

camarokid94

iTrader: (2)

yeah read one up!!! what i wrote LOL
or buy 2 WBs and put one in the #7 header tube to make sure its not to lean
also take to a local chevy dealer and have them do an INJECTOR CLEAN. Im a GM tech and we hook a chemical up to the fuel rail and blow the injectors out works awesome. i did it on my old 94 3.4L camaro went from 210mi a tank to 300 unreal huh but it works and keeps them clean.
a plugged #7 injector ( wich happens alot more than people realize will make it go lean. we have tahoes in al the time with a plugged #7 the fuel rail seems to collect dirt back there and plug them up i have seen like 10 done in one week.
so theres the two thing to keep in mind

MTN_Z

iTrader: (7)

I'll second the clogged injector. I blew a #7 ringland on a bolt on motor with a hair over 50,000 on the clock as well. My #7 injector was pretty clogged up. I looked at the piston and it was pretty scorched and the ring land looked like it was melting. Pretty sucky.

Wnts2Go10O

iTrader: (12)

would an invl tb setup fix the #7 problem or is there some other weird issue with it?

Orange Juice

iTrader: (3)

H/C with all the bolt ons no nitros maybe 20 passes on the track and 15,000 with the heads and 60,000 total on the motor.

Fireball

iTrader: (21)

I lost mine on an all motor 346. made a stupid mistake and ran 93 octane on a 11.5+:1 setup in -2000 ft DA. Ran fine on 93 all summer but the better air killed it.

http://home.comcast.net/~tfranklin5580/piston2.jpg

BB396

At the risk of sounding retarded, couldnt you run a slightly larger injector in that cylinder? I.E., go from a 42 to a #46? Or would that overcompensate?

GenIIINova

I would not suggest an injector change like that. A good technique I have used on the Supra's 2JZ, is to add about 5% to the cylinders that tend to go lean; #1 and #2 on the 2JZ. Of course, you will need to use an EMS that will support this, such as Motec, AEM, FAST, etc.

And as far as Wide-Band O2's, they are not too accurate in header primaries. The heat and pressure will skew the readings. And even if you are lean in any given cylinder, you can't change it without a high-end EMS.

Fireball

iTrader: (21)

you could always flow match the injectors and put the highest flowing one on #7

slt200mph

iTrader: (42)

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