parish8

iTrader: (6)

2 years ago i ran a 10.08 with my truck. since then i have dumped a pile of money and time to get it to the next level and i seem to be stuck. truck will run 10.20's prety easy but just doesn't want to go any quicker without hurting itself.

2 years ago... single pt88 near it's limit, smallish intercooler, 408, afr225's, cometics or sce ics head gaskets, 7 heat range plugs although i have tried 8's with the same results, 234/232 114+1 600lift, stock truck intake, 8.7-1 compresion.

scan tool shows knock and i pop a head gasket very quickly as i aproch 20psi. that was 2 years ago and still the same today. in those 2 years i have done many things that i thought would help me get a little more out of the set up but i seem to be at exactly the same place(hp level and et)

since then i have done these things in the power adding dept.

twins, turbos should be right in the heart of their eff range.

much larger intercooler, more air filter, larger charge pipes, more down pipe area...

single plane intake and 90mm tb to help get rid of #7 problem, now when i push the head gaskets it seems to push out of 3-4 cylinders so rather than just one so it would seem things are more even.

tried cometics and sce ics gaskets. had the heads checked to be true and had them surfaced when i used the cometics.

my latest round of improvements were to completely overbuild the fuel system, fuel presure is rock solid and to tune it on c16.

last night i poped the head gasket again. tuned to the 11.5 a/f range with c16 fuel. running 19deg of timing and 18psi. the truck is heavy. 5000lb's so i know i am asking alot out of it. after many rounds of thinking i know how to push it to the next level and geting to exactly the same place i am running out of ideas.

i have always thought i was geting into knock and that was pushing out the head gaskets. does anyone think i might just be lifting the heads(flexing head or stretching the studs) and after they lift i see the knock. maybe it isn't the knock hurting the gaskets but the lifting and then showing me knock?

if not that then any other ideas for me to consider.

Josh@MASPORT

iTrader: (3)

6 bolt heads

parish8

iTrader: (6)

wouldn't 6 bolt heads only help if the knock i am seeing is not real or is caused by the head lifting? if i am seeing real knock for another reason wouldn't the 6 bolt heads just cause something more expensive to break?

Texas_WS6

iTrader: (9)

I agree. With that much boost and the kind of power your making, and taking the type of fuel/timing your running into account, I would have to say your lifting the head, stretching head bolts, something along those lines. Once the head gasket is blown you will see nock. I bet it is realy not detinating or else you should see signs of it on the pistons or rings. Look into the new LSX block by GM. It has provisions for 6bolt heads. Good luck.

TS6

iTrader: (41)

I'd bet you're just lifting the heads, with a good tune on 116 I'd have a hard time believing you are seeing real detonation.

O-ringing might be the next logical step.

blacktransam

iTrader: (13)

i may be totally off base but did you consider pulling some timing out of her.. i know that set up may work for some LS1 cars but you just increased airflow plus you also have the added load of not only a 5000lb vehicle but the 4WD drivetrain and a huge aerodynamic load as well.. maybe just to much.. pull a few degrees out and start upping the boost..

once again i'm unsure but you have a good bit more load then the cars do.. and i'm wondering if shes firing just to early..

Mike

kp

iTrader: (34)

Is it always popping the same cylinder or is it random?

Have you ever checked your timing with a light/indexed damper?

parish8

iTrader: (6)

i have had the same problem with less timing and more boost. ~15deg and an extra psi or so. infact i have always ran around 15deg of timing but that was with cheaper race fuel. from what other have seen posted i thought 19deg was prety safe with c16.

my dyno charts look prety rough at the low timing with race fuel. with the c16 at lower timing(15-16deg) the chart was prety wavy but bumping it up a few deg smoothed it out(smoothed out the hp and the a/f reading). going from 16 to 19deg i only gained 20hp but the chart looked so much cleaner i thought it was a good idea to keep it.

keep the ideas coming.

i have never confirmed my timing but i am still on the stock ecm for timing.

i wouldn't say it is random cylinders but it isn't just one either. most of the time i can see one obvious one that is causing it to over heat and 2 to 4 more where the gasket is pushed out a little into an egg shape.

NA$TY-TA

iTrader: (21)

Id say its lifting the heads..... with that good of fuel and low timing.. thats what id say... your putting quite a load on that motor with the wieght u have...

I was pushing water when i last blew my gaskets... was still using GM MLS gaskets....

O-Ringing now....
That might be your only hope.. if ya dont want to spend the $$ on the 6 Bolt stuff....
Id be with KP..... Your still running the stock PCM with a Piggy back correct??
Timing might not be what it says it is...

Kyle

kp

iTrader: (34)

Just because you can run say 15 degrees on cheaper race fuel doesnt mean you can run 19 with C16. I run the same timing with 112 or C16, I just up the boost a little with C16. And 15 degrees is all I run, I know exactly when this starts detonating and when I'm pushing it hard I cant go over 15 degrees of timing.

Ever had your injectors flowed?

hellbents10

iTrader: (10)

The log manifolds could definatly be the problem. What kind of pressure ratios are you seeing? You might need a better flowing exhaust side and wheel, and tubular headers. Camshaft selection may need to be revised also.

cablebandit

iTrader: (37)

I AM WITH kp on the 15 degrees. I am only running 11-13 on 9psi..on 110!!! I am being very conservative now but dont plan on over 15 deg with 20psi and c16 myself. That truck is hevy and an aerodynamic brick....i bet you are putting a lot more load on it than us fbodys

qqwqeqwrqwqtq

On your latest tune, have you made a run and pulled/read all of your plugs? If so post pics.

parish8

iTrader: (6)

i have never flow checked my injectors but they were flow matched when i got them. since it is a multi cylinder problem i dont think i will worry about that one just yet.

seems some people see 19deg as low timing and other see it as too high. i can and will certainly run less timing in the future. i have an excess of turbo so i can run 10deg and tons of boost if that is the way to get the most power out of it without poping a head gasket. i run 15deg on pump gas with a touch of meth and am in the 750-800rwhp range. it will be easier to not change the timing. has anyone tried running very low timing and lots of boost? would i get farther with 10deg and max out the boost to the edge of knock or 15deg and a little lower boost?

i am using the stock pcm to control timing. is there a chance that the stock pcm timing is not what it says it is?

my turbos are gts70's with .81ar(maybe it is .83?), i dont want it to spool any slower than it does. i dont think it is the logs but you never know. i am not changing that. i did check my pr awhile back and at higher boost it was around 2-1 wich i thought was prety good. with two 3" open dp's and a seperate two 1.5" wg pipes there is a lot of area for the exhaust to get out.

i have never really looked at my plugs. i have no idea what i am looking at but the next time i push it i will pull a few and take some pics. what i have seen is the ground straps still have sharp corners on them, no black specs, nothing obvious like that.

i am hearing lots of ideas here and it seems i might be a little off track with my timing. i will work on that and maybe do the lsx later on down the road.

2000TurboVert

iTrader: (17)

I think that the 6 bolt heads are probably the route I would take!

kp

iTrader: (34)

My stock PCM was off by six degrees +/- 1 degree. I used to run nearly 20 degrees on pump gas and that just didnt seem right so I checked it with two different timing lights. The BS3 is correct according to my light and TDC mark, thats all I can say. Thats why I dont like throwing timing numbers around. I just keep going up until I see some signs of detonation and back it off some. These things are pretty dynamic so a lot of experimenting is in order.

A lot of backpressure will usually kill power to the point that detonation shouldnt be an issue. All that charge dilution (think EGR) actually helps with detonation control unless its excessive.

At your power levels i would probably start looking into some way of monitoring all 8 cyl EGTs plus the ability to control individual cylinder fueling. A single wideband just isnt that precise. You can pull the plugs on dyno pulls and get a good idea whats going on as well but its a little time consuming.

cablebandit

iTrader: (37)

wow 6 degrees!!!! that is a bunch.....

kp

iTrader: (34)

I double and triple checked everything, whether its the PCM or the reluctor or even the crank sensor I dont know. But unless there was a hidden table somewhere pulling timimg out that wasnt reported in the log the log I have no idea why it was so far off. With the stock PCM If I ran 15 degrees of timing the car would slow down considerably.

I have been degreeing camshafts and finding TDC for over 25 years so its not a guess. Granted timing lights can be off some as well but I have two of them. Thats why its best to just let the engine be your guide to max timing sometimes, start low and go up until power stops picking up then backing off a little has worked for a long time..

NXRICKY

iTrader: (1)

Check your head studs, is they are still torque'd or not. If you are lifting the head, you may also see a different ringed area on the heads surface, from the head lifting and slamming back down.(in extreme cases)
The head studds might need to be changed out, if this problem has happen time and time again, the studs could becoming weak.
If your heads and block are flat, gasket pushing with no other damage makes me think the heads are coming up.

Your plugs sounds fine with the sharp edges etc.

To bad you donot have a stretch gauge to compare the stretch between the block and heads, under that much stress.

Ricky

LASTLS1

iTrader: (7)

I agree with the others, there's no reason to go over 15 deg of timing. You said your self you only picked up 20 hp, stay at 15. I wouldn't waste your time or money on o ringing, stick with the mls gaskets. Also I run tr9's when I'm running it hard, 8's for street driving. Your very close to the limits of the 4 bolt heads on the ls1, in my opinion. Good luck!