Cwarta

iTrader: (12)

Well after talking with VS, I ordered the billet 78. Goal is 650whp with some room to grow, but it's a street car so I didn't want a laggy setup. So he said this would be perfect

coltboostin

I highly doubt it, mayyybe on a 4.8? Maybe...

aggie91

Well he had issues on the second pull on the dyno that resulted in letting out before he got to 5200 rpm...first pull was WAY rich and did not make power.

Second pull was a 12:1 ratio, much leaner but pushed out part of the head gasket that created a nice gyser out of the head/block at the #2 cylinder. Oh well, used gaskets and reused bolts will get you sometimes. Anyway at about 4800-5000 it was making 515 ft-lbs (9-10psi and 14 degrees of timing) at the tire before letting out of it.

The shop owner offered up some gaskets and tools for him to make the repairs to get back on the dyno that day, but Korbin passed on the offer and is looking to upgrade to some head studs and LS9 gaskets before going back. The tuner wanted to lean it out a bit more, but that will be for another day.

chiaj144

iTrader: (4)

Leaner than 12:1???

ddnspider

iTrader: (26)

It's not an NA motor, you need to keep that tune in the low to mid 11:1 A/F on pump gas.

aggie91

We know it is not a NA motor, these are the numbers that I was told, I was not there at the shop when this all went down. It was really rich on the first pull and made **** for power, shooting a 6 foot flame out of the down pipe while it decelerated on the rollers. They leaned it out a bit and then it pushed out the gasket on the second pull. I know he has a wideband gauge on the dash, not sure where the numbers he told me came from. Not sure what the dyno reading was or if they even had another wide band on it at the time.

Next time I hope to be at the shop when its on the dyno...

ls1charged

iTrader: (8)

91 octane the only thing available in your area?

ddnspider

iTrader: (26)

Than it sounds like whomever is tuning it doesnt know what they're doing....

truckdoug

iTrader: (25)

dang sounds like he was on the way to making some pretty good numbers and pulled too much fuel. **** happens. glad it was only a gasket. remind him when he eliminates that weak link, the next one is much more expensive

aggie91

Its the most common, some places have 92...I don't think I have ever seen 93 around here....

My son has had a ton of local places that claim to be the best in the area tell him that they won't even attempt to tune it. One shop could not even make it do anything but idle. One other blew him off because of how his truck looked (was not a late model vette or Camaro). This shop has turned out a ton of fast cars and the tuner has been doing this stuff since the before LS motors even came out. I have faith in them to treat my boy right and make it all good. I don't blame the tuner for the head gasket issue, that's on my son for putting in damaged used MLS gaskets, reusing the stock bolts and not torqueing them properly. The plan now is to swap to some head studs and use new LS9 gaskets and get it back on the dyno to make some real power.

See my comment above, not 100% sure that fuel mix was the real issue. He has already broken a converter that took out the trans. That was by far the costliest mistake to date. The new converter was around $900, the used trans was another $200, plus all the time and gas to get and install the parts...

Its all good, for the amount of money he has in the truck he has been embarrassing a good number of higher dollar cars around here.

ddnspider

iTrader: (26)

If you say so. 10psi on 91 octane, 14 degrees of timing, and 12:0 A/F could have caused detonation, which pushed the gasket out. Usually its not best to start making full pulls to redline before you have the AFR in the ballpark. You sort out the AFR first with low timing and then start creeping up on timing once you can make a full pull with the AFR doing what you tell it. Hope it gets sorted out and lasts a long time. Keep embarrassing those high $$ cars.

NicD

iTrader: (7)

C'mon guys, he had used head gaskets on there along with used factory head bolts, I wouldn't be surprised if it would have puked a head gasket at 0 psi on a full pull let along throwing any boost at it. Now I would have started with lower timing than that especially on a 2nd pull but I can't really blame that nor would I blame the a/f since a 12:0 isn't lean even on 91 for head gasket issue on the 2nd pull with used parts like that.

aggie91

Ok, I did have some info wrong above. Korbin found some 93 octane in Tyler for his pulls. The AFR gauge was reading 11.2-11.5 before letting out at just before 5200 rpm on the pull when the gasket let go. It did seam to creep towards 12:1 on the street as it approaches 5500 rpm. Boost was limited to 10psi.

The gasket was bound to let go anyway. After talking to him, he did not even use a torque wrench on the bolts when he put the used gaskets in. Sloppy Style to the extreme. The tune seems fairly safe for now. I just want him to fix it right. You can get on ebay and have new studs and new MLS gaskets to you door for just $155. Not sure what he is going to do. He is in college full time and this should not be his priority.

Once it is fixed, back to the dyno, if it makes 550+ to the tire, he claims that is where he will stop for now and just have some fun with it.

Thanks for all the input, We are still learning this turbo stuff and have to trust the tuner as he seems to be one of the best in the area.

Back to the OP's original question. Korbin and I would vote for the 7875, if you can wait for the billet wheel version, then you will have a turbo to meet you goals and have some room to grow a bit...We are very please with the 7875 unit.