It's been said already in the thread but I'll say it again, that's a lot of timing at that boost level on **** gas.

 

wow thats a lot to ask of 91 octane. must have some logs of the dyno runs monitoring knock?

 

Sounds like a to much boost n too much timing for 91.

 

I don't know how much timing it had but looking at the main timing table in the tune the highest it could have been would be 19*. It was probably less though but 19 is the highest number in the table without taking into consideration IAT's, coolant or other factors that could reduce the timing more.

Don't have the crossover in the back. I looked into that a couple years back when I built the 408 in my Silverado after reading about the #7 running hot but there was no clear consensus as to why #7 fails the most. I had read they even tried installing the intake backwards and a couple other things.

Is the crossover from the LS6? Do you have a part number?

Since the engine is being rebuilt it certainly would not hurt to install it.

I had it towed to the dyno and then towed back home afterwards. They shut the dyno down after the very next pass netted 200hp less with no changes to the tune. Plus is was already close to 9PM.

When I went to pick up the car it was smoking really bad so I towed it home. he tuner made me some notes to check the passenger side because he flt something was wrong causing the low hp numbers on the last pass. I removed the plugs and that's when I found the #7 plug had burned.

The smoke I later found out was from the shop pinching the oil return lines with the skid plate. The oil from the turbos had no where to go so it went past the seals and into the exhaust and intake. I found oil all the way to the TB and intake. I replaced the oil return lines with new SS lines and added a reservoir while I was at it. I cleaned the pipes the come off the compressor housing because they sit the lowest and the charge pipe attached to the TB. After that I let it idle for 30 minutes then let it cool over night then another 30 minutes until almost no smoke was coming out of the exhaust from residual oil. I took it around the block but it started smoking again and it felt funny. Turned out to be the intercooler full of oil so I cleaned it(drained and degreased) and flushed it out by driving around the block with the pipe from the IC to the MAF pipe not hooked up. That cleared up all remaining smoke so i hooked the charge pipe back up and drove it to the shop o do a leak down test which showed 28% on cylinder #4.

I had already left because it was late and I live about 2 hours from the dyno but the tuner said he did not save the logs and that it never knocked.




BTW, I wanted to clear things up.

The engine was built to years ago and was originally 10.38cr but a couple months ago I replaced the WCCH L92 heads with some WCCH LSA heads. The old heads were 62.5cc vs the new heads 75cc so that lowered the cr of the engine over a full point so I could run more boost safely after the turbo install. I also changed the cam that was recommended by the turbo kit manufacturer.

The old motor was run hard and had many 200 shot 1/4 mile runs but everything still looked good when the new heads and cam went in. The new combo made like 12 less tq but 7 more hp on the same dyno after. Only switched heads and cam to lower the cr and make it more boost friendly.

After the swap I ran it NA at Fontana(1/4) on the 22's with street tires and managed a 12.30 @ 113.63(vs 12.18 @ 118.02wih sock 20's on Nitto DR's) hen I sprayed a 100 shot and ran 11.64 @ 122.13 rolling into the throttle.

I was invited to participate in an exhibition race at Pomona(1/4) for the finals so I went and made two uninspiring runs. Then I ran it at Irwindale(1/8) twice once with the 22's and once with some 18's with DR's that I borrowed from another Camaro owner. I managed 7.8 on the 22's NA, 7.6 on the 18's NA and finally 7.1 on the 18's with 100 shot.

After those runs I started the turbo install so the engine only has 200 miles running after the install of the turbos and most of those miles were from after the dyno tune. I did drive it from the shop to the tire shop to take off the 18's with DR's. Then to the muffler shop to extend the turbo DP to connect it to the existing exhaust because it was pretty load and then to my house. From there I drove it to a fabricator that was going to make me some brackets and stuff. That was about 20 miles total of local driving and all of it at part throttle as I was still on the stock injectors and old NA tune. From the fabricators shop I had it towed to the dyno and back home.

 

I just check and looks like 18* would have been the highest on the table under boost. For all I know i could have been 10* though as I was not there and I don't have the logs.

Here is what the table looks like.

 

18* is still too much for 16psi...if I was your tuner I would have "lost" those logs too!

 

Sorry for the mis-hap op..Hope you can get her rebuilt sooner than later..I agree with 1999black Z28, if I were the tuner I would have lost the logs as well.

 

Again I am not saying it was 18* just that in the table 18* is the highest. For all I know it could have been a lot less and probably was.


Hoping that a hone will fix it up as I did not want to bore it so the walls could be as thick as possible. Currently running a 4.070 piston and the next size up would be 4.080 which would make the engine go from 416 to 418.

Here is a picture of the cylinder #4 from the top and from underneath.

 

I don't think that timing is high enough to toast a motor on a 3 sec dyno run. Maybe at the track on a hot day. I think you got a bad tank of 91.

 

The car was never taken to the track after the turbo install. After having it towed home from the dyno I replaced the spark plugs with a colder(8's) set and fixed the smoking by replacing and upgrading the oil return lines. I then drove it without the charge pipe connected to a GTG 40 miles away. I then installed the charge pipe and drove it 60 miles to the shop to get a leakdown test performed. From there I drove back to the house and then straight to the engine shop about 65 miles away where they pulled the head off and later the whole engine. It is now being going to be rebuilt.

In all that time it felt perfectly normal except for the surging/bucking(never got a chance to finalize the tune with some street driving) and I even got in it about 3/4 throttle and up to 7psi and it felt great and pulled strong. That 7psi run was after I found out about the 28% on the leak down and was driving back home. I got on it a bit passing a car on a two lane road and even though I way already going 50mph it spun the tires a little and pulled hard. At that point the engine was already hurt.

 

i heart E85

good to hear the LSAs stayed down through that abuse, impressive

 

If oil got into the combustion chamber under power (from the pinched oil drain lines) it could have caused the damage.

 

[QUOTE=SRTKLLR;16295796]The smoke I later found out was from the shop pinching the oil return lines with the skid plate. The oil from the turbos had no where to go so it went past the seals and into the exhaust and intake. I found oil all the way to the TB and intake. I replaced the oil return lines with new SS lines and added a reservoir while I was at it. I cleaned the pipes the come off the compressor housing because they sit the lowest and the charge pipe attached to the TB. After that I let it idle for 30 minutes then let it cool over night then another 30 minutes until almost no smoke was coming out of the exhaust from residual oil. I took it around the block but it started smoking again and it felt funny. Turned out to be the intercooler full of oil so I cleaned it(drained and degreased) and flushed it out by driving around the block with the pipe from the IC to the MAF pipe not hooked up. That cleared up all remaining smoke so i hooked the charge pipe back up and drove it to the shop o do a leak down test which showed 28% on cylinder #4.[QUOTE]

That's a lot of oil going where it don't suppose to go.

 

The oil problem did not happen until after the dyno session when they reinstalled the skid plate. After that though it did ingest some oil but during normal part throttle driving. When I saw the oil in the TB I removed the IC and drained/cleaned it.

The engine is being torn down right now and I need to replace the pistons. It had Weisco pistons before and I thought about just buying a new set of the same but the engine builder does not like the brand. He wanted to get some Ross pistons but they would have to be made and that could take 4-6 weeks.

Are the Weisco pistons good/bad? What is better?

 

I had the exact thing happen (but on a 4cyl turbo motor)....too much timing with 91oct. My plugs looked the same as well as cylinder wall scoring and piston skirt wear. It was using a base tune with safe timing but we did not verify timing at 0deg with a timing light...ecu thought it was at zero but actually was 5deg advanced.

I know it's not the same engine but I got déjà vu looking at your pics..

 

Detonation does that, and/or lean mixtures which can lead to detonation. Then the tip of the plug gets chewed up down the side of a piston causing more damage

The wear on the skirts isnt that uncommon, especially if it's a stroker. Have the bottoms of the bores been chamfered properly ?, what sort of bore clearance are you running on the pistons ?

My last 402 with Wisecos had a huge 7 thou clearance for some reason. The skirts were visibly polished like that at the bottom. Not ideal, but dont see it as a major problem either. But being so loose in the bore, ring seal wasnt great either.

Does look like a simple tuning issue though.

 

Damn, sorry to see that.

 

Its not the piston itselfs problem. Yes those are fine pistons,its def not the norm for them to look like that after one dyno run or 2000

 

A few problems going on here. First that is a TON of wear on a COATED piston skirt. There is definately a piston to wall clearance issue going on, or the motor was overheated bad.

91 octane, 16 psi, and 18 degrees is not a good combination. That car should have been tuned with 10.5-11.0 afr on that kind of pumpgas with less timing.


Providing the motor is done right, it is ALL in the tune.

A build motor will only last .5 seconds longer than a stocker if the tune is wrong.

 

this sux to hear man. I am not going to repeat whats been said a 50th time, but you may want to consider going e85. I am doing that, plus methanol, plus a tune in between safe and aggressive, and coolant crossover lines, even putting the highest flowing injector on number 7. Anything You can do to cool that thing down, and avoid detonation is going to make you smile in the longrun.