Dirty-Maxx after 600hp build regrets

[reese600]

Last summer I had to rebuild my LBZ after a bad injector cracked the #3 piston, so I did my usual, and asked advice from some builders on how to correct for broken pistons and cranks (my 09 LMM had a broken crank also). One of the builders, owns a diesel performance shop and he truck pulls a Duramax, so I figured he should know what it takes to keep one from braking. So after consideration, this is the build I put together.

07 LBZ block bored to 4.075" over to fix damage in cylinder #3
Entire rotating assembly balanced
Fluidamper
LBZ crank keyed
LBZ rods
Fingers Oval Bowl pistons w/ valve reliefs
SoCal 6480AF stage 2 cam
ARP main and head studs, rod, flywheel, exhaust bolts
S&S 10mm CP3
60% injectors
65mm STG2 Danville turbo
Profab manifolds and up pipes

That covers the meat of the build, Mark at Danville does my tuning and in November '21, I went to Danville's shop and had the truck dynoed at 620rwhp and 1197 ft/bs.
That is all great and well, but after putting 10,000 miles on it and driving it thru a Northern NY winter, I am beginning to regret some of the parts I put in this build. This truck is my DD and I tow heavy most every weekend over the summer and plow snow in the winter.

My 3 biggest complaints are:
1. cold start and idle - it is extremely dirty, takes forever to warm up, and blows blue smoke terribly when cold even when the outside temp is above 70 degrees. I am told the pistons, cam and injectors are to blame, but mainly the pistons. Once up to temp, the haze clears up, but not completely, burns your eyes terribly.
2. fuel mileage - before I broke the piston, daily driving I would average 18.5-20.5mpg depending on conditions, now I see 13.5 avg, and if I baby it , 15 is the best I've seen. Towing, is about the same as before 10-11.5mpg with a combined weight of 26k.
3. overall throttle response - I really want to get the engine to react quicker, Mark has tried tuning revision after revision, and its slow to react to throttle input. From a dead stop, if you mat it, you can almost count , one-one thousand, two-one thousand, three...before it takes off and goes. Half throttle launch reacts much quicker, which makes sense. once rolling, if i lay into it, it reacts much quicker.I tried one of those throttle sensitivity boosters, and it did nothing to help off the line performance. If i boost it a little before launch, its much better, but a PITA for a daily driver.

So now I'm trying to figure out what I can do to take care on these complaints, but I'm in no hurry to pull the engine back apart and starting to replace parts, I spent enough on this set up, and I totally screwed the daily driver aspect of it up. So looks like i'm living with it the way it is, unless anyone reading this has a good suggestion.

 

[Chevy1925]

What converter are you running? your builder should have taken that into consideration when building that engine or changed it for one that matches the new cam/engine setup. yours sounds far too tight for that cam and turbo.

as for engine:

i would have stayed on a stock cam or at min - the smallest AF cam socal offers, done a durastar crank and done no valve reliefs in the pistons. We need to know the piston to head clearance and piston to wall clearance from the machine shop to see if they are too far open and hurting fuel econ as well as part of your cold start issue.

whos injectors are you using and did you only do 60% over tips or the whole injector is set for 60% over?

crappy injectors can cause you issues and loose tolerances for those fingers pistons can cause the cold start and mpg issue. the oval bowl is not known for being efficent BUT it can be midigated by keeping p to h tight, p to w tight, and playing with tuning on GOOD injectors. you wont ever get back to that 20mpg on those pistons though imho, then add in 60% overs. its already hard enough to get mpg back on big injectors. not saying it cant be done but it takes alot of seat tuning time.

 

[2004LB7]

as James said, the converter is the first place I'd look into for responsiveness. but I also like to adjust the shift points too. closing the downshift and upshift points so it more easily kicks down when you want to go faster helps get the RPMs up to spool the charger. if you can keep the converter locked on the downshift it can make it much more responsive. the only big issue with this is it can cause gear hunting so getting the numbers just right can be a pain. took me probably 50 revisions to dial it in

 

[TheBac]

Since you do not race or sled pull, the people you asked shouldve recommended simply upgrading the crank and pistons with stock compression ratio.
Their recommendations did not take into account what you actually use the truck for.
IMO, there was no need for cam, turbo or injectors on a stock truck, esp one towng heavy.

 

[08lmm72mm]

What do you have for a torque converter? That will be what is making your truck respond like a dog for sure.

 

[Bdsankey]

What converter are you running? your builder should have taken that into consideration when building that engine or changed it for one that matches the new cam/engine setup. yours sounds far too tight for that cam and turbo.

as for engine:

i would have stayed on a stock cam or at min - the smallest AF cam socal offers, done a durastar crank and done no valve reliefs in the pistons. We need to know the piston to head clearance and piston to wall clearance from the machine shop to see if they are too far open and hurting fuel econ as well as part of your cold start issue.

whos injectors are you using and did you only do 60% over tips or the whole injector is set for 60% over?

crappy injectors can cause you issues and loose tolerances for those fingers pistons can cause the cold start and mpg issue. the oval bowl is not known for being efficent BUT it can be midigated by keeping p to h tight, p to w tight, and playing with tuning on GOOD injectors. you wont ever get back to that 20mpg on those pistons though imho, then add in 60% overs. its already hard enough to get mpg back on big injectors. not saying it cant be done but it takes alot of seat tuning time.

^James is spot on. Is the oval bowl a great piston? It sure as hell is, BUT they are not efficient and are notorious for having issues with hazing. You put a 1500hp capable piston on a 700hp-ish capable rod, you would have certainly been much better suited with either a delipped LB7 piston (from GM) or a set of off the shelf Mahle motorsport cast pistons without reliefs as reliefs also hurt efficiency to an extent.

This is the exact reason my tow rig has a very small cam (wagler stage 1), motorsport non-reliefed cast pistons, good rods/hardware everywhere, good balance job, and a stock keyed LB7 crank.

Since you do not race or sled pull, the people you asked shouldve recommended simply upgrading the crank and pistons with stock compression ratio.
Their recommendations did not take into account what you actually use the truck for.
IMO, there was no need for cam, turbo or injectors on a stock truck, esp one towng heavy.

^Great advice!

 

[moparkxracer]

Did you talk with more then just the one diesel shop, being honest abt your “needs” for the setup? Did you talk with SoCal specifically on the cam? Do you have the high flow veins in the turbo? Truck pulls and street pulling (towing) is not the same, “most” people are not boost launching and singing very high RPM when towing. What compression did the setup end up being when finished?

 

[reese600]

I had a couple people help me pick the parts I bought, one a machine shop that's been in business since the 50's that specializes in truck engines and my guy at the diesel shop that pulls. I screwed up then, I just had 2 catastrophic engine failures in 6 months, so my mindset to get the strongest pistons out there, and do everything I could to keep the crank in 1 piece. So naturally they basically gave me the set up for a good pulling engine, daily drive-ability never crossed my mind, so that is where I messed up. The injectors were new from GM and I sent them to S&S to have the 60% Exergy tips on them and properly tested and set up.
I have often wondered about the converter. I had the trans built by the same shop that I am talking about in 2020, and then the engine was your basic tuned, deleted, piped setup that most do. The trans is supposed to be good for 700-750hp, but I was told that the converter is a Goerend "C" stall, which i cant find any info on. But I vaguely remember being told that it stalled below stock rpm, and that was chosen for towing with a stock-ish engine. I think a different converter will get it out of the hole a lot better, and that is my #1 bitch. Being dirty and crap mileage, I think I will have to live with.

 

[Bdsankey]

I had a couple people help me pick the parts I bought, one a machine shop that's been in business since the 50's that specializes in truck engines and my guy at the diesel shop that pulls. I screwed up then, I just had 2 catastrophic engine failures in 6 months, so my mindset to get the strongest pistons out there, and do everything I could to keep the crank in 1 piece. So naturally they basically gave me the set up for a good pulling engine, daily drive-ability

^I personally would disagree. You have a rod that is not exactly "strong" compared to the piston. What we're getting at is money was spent on things that are a bit backwards for your goals. Are fingers ovals a great piston? Hell yeah, but not for your build. Is a 6480AF a great cam? Hell yeah, but IMO it's larger than what I would use for your build. Beyond replacing the crankshaft with a better than OEM crank there isn't much we can do beyond a good balance job/good damper to mitigate the snapping risks.

never crossed my mind, so that is where I messed up. The injectors were new from GM and I sent them to S&S to have the 60% Exergy tips on them and properly tested and set up.

^Are you sure on that one? I've never heard of S&S installing customer supplied nozzles. I know companies like Dan's, Bitterroot, and a few others will calibrate with customer supplied nozzles whereas S&S and Exergy will typically only test then install/calibrate their own nozzles.

I have often wondered about the converter. I had the trans built by the same shop that I am talking about in 2020, and then the engine was your basic tuned, deleted, piped setup that most do. The trans is supposed to be good for 700-750hp, but I was told that the converter is a Goerend "C" stall, which i cant find any info on. But I vaguely remember being told that it stalled below stock rpm, and that was chosen for towing with a stock-ish engine. I think a different converter will get it out of the hole a lot better, and that is my #1 bitch. Being dirty and crap mileage, I think I will have to live with.

^You would be well served switching to a Goerend R/DK/DL or a Limitless 1078. It will be a whole new truck with a properly specified converter. A Goerend C/X/G (below stock stalls) are great on stock fast spooling turbos but are a hindrance on larger drop in turbos. It also doesn't help that the C (1900-2200rpm) is a stock stamped stator and not recommended for heavy towing/boosted launches/drag racing.

 

[reese600]

What converter are you running? your builder should have taken that into consideration when building that engine or changed it for one that matches the new cam/engine setup. yours sounds far too tight for that cam and turbo.

as for engine:

i would have stayed on a stock cam or at min - the smallest AF cam socal offers, done a durastar crank and done no valve reliefs in the pistons. We need to know the piston to head clearance and piston to wall clearance from the machine shop to see if they are too far open and hurting fuel econ as well as part of your cold start issue.

whos injectors are you using and did you only do 60% over tips or the whole injector is set for 60% over?

crappy injectors can cause you issues and loose tolerances for those fingers pistons can cause the cold start and mpg issue. the oval bowl is not known for being efficent BUT it can be midigated by keeping p to h tight, p to w tight, and playing with tuning on GOOD injectors. you wont ever get back to that 20mpg on those pistons though imho, then add in 60% overs. its already hard enough to get mpg back on big injectors. not saying it cant be done but it takes alot of seat tuning time.

Unfortunately, I assembled the engine and I don't know the piston to head clearance, the piston to cylinder wall, all i remember is that it was in spec. Looking back, I wish I checked more than if the valves cleared the pistons.

 

[2004LB7]

you can always try a little more fuel pressure for the hazing and maybe a little more timing in the cruise area for mpg but I'm sure Mark already knows about that.

 

[08lmm72mm]

Given your converter ID recommend pulling it and sending it to georend to change it up to a R at minimum, or buy a Limitless 1078.

That's really the cheapest option and I guarantee the exhaust will cleanup a hellova lot quicker and will make it feel like a completely new truck. Stall speed of 2200 minimum. With a cam that big a georend k might be best but I have no experience with it.

 

[reese600]

^I personally would disagree. You have a rod that is not exactly "strong" compared to the piston. What we're getting at is money was spent on things that are a bit backwards for your goals. Are fingers ovals a great piston? Hell yeah, but not for your build. Is a 6480AF a great cam? Hell yeah, but IMO it's larger than what I would use for your build. Beyond replacing the crankshaft with a better than OEM crank there isn't much we can do beyond a good balance job/good damper to mitigate the snapping risks.


^Are you sure on that one? I've never heard of S&S installing customer supplied nozzles. I know companies like Dan's, Bitterroot, and a few others will calibrate with customer supplied nozzles whereas S&S and Exergy will typically only test then install/calibrate their own nozzles.


^You would be well served switching to a Goerend R/DK/DL or a Limitless 1078. It will be a whole new truck with a properly specified converter. A Goerend C/X/G (below stock stalls) are great on stock fast spooling turbos but are a hindrance on larger drop in turbos. It also doesn't help that the C (1900-2200rpm) is a stock stamped stator and not recommended for heavy towing/boosted launches/drag racing.

Again, looking back, the piston and cam choice weren't my best decisions, for what I am doing, but it's a little late now. That's why I am regretting the way I built it after driving it a while. I was going the right direction with getting everything balanced and using a Fluidamper.

I did send the injectors to S&S to have the nozzles installed last August. I had the parts, and when I called S&S to ask about ordering a 10 or 12mm CP3, I asked if they would do my injectors for me, and they said because it was all new parts, that they would do it and add it to my order.

I'm definitely going to look in to a converter...i would love to get this thing to come off the line a lot harder, hell at all, lol

 

[reese600]

you can always try a little more fuel pressure for the hazing and maybe a little more timing in the cruise area for mpg but I'm sure Mark already knows about that.

we are up to tune revision #14 since November, Mark has tried and tried...

 

[08lmm72mm]

..i would love to get this thing to come off the line a lot harder, hell at all, lol

Change up that converter then. Yours is choking the motor.

 

[Bdsankey]

we are up to tune revision #14 since November, Mark has tried and tried...

There isn't going to be much you can do about the haze cold, it's a natural part of ovals. I've only seen a few guys get it to go away and it took loads and loads of revisions if they even got it to go away.

 

[Chevy1925]

Everyone is being quick to blame your pistons for ALL the issues but there is more to it than that.

The oval pistons are not THAT bad to make run right but having the valve reliefs are not helping your cold starts. you have high quench area in those areas when cold and causes your issues. Without knowing the rest of the piston clearances, that could very well be another big contributor on cold start up and mpg. too big of clearances means more area for blow by regardless of ring gap. There is also the fact that ring gap is probably much higher than stock which will increase blow by. if piston to head is .030 and higher, thats reducing mpg 1-2 or more mpg. All these things add up. tuning not dailed in for the injectors, loose clearances, the pistons you have, the turbo you are running and the cam you have are all going to decrease MPG without alot of work to bring it back but it will never be stock.

the hardest thing i found to tune on oval pistons is rattle. that took alot of pilot injection work but mpg wasnt much more than standard tuning. you may need more timing in cruise areas and that is hard to nail without being in the truck and listening for rattle. that can make a big difference in mpg.

@Mike L. would know the details on the converter you have. i have a feeling its like you are stating and might not even have a billet stator.

Could better choices have been made? yes and dont shoot yourself on the fact you put oval pistons in there, its just a small piece of the pie to the issues.

Get yourself a good converter in there. Its going to be the cheapest fix to a majority of the issues you hate and will bring a smile back. then start inching in on the rest.

 

[reese600]

Everyone is being quick to blame your pistons for ALL the issues but there is more to it than that.

The oval pistons are not THAT bad to make run right but having the valve reliefs are not helping your cold starts. you have high quench area in those areas when cold and causes your issues. Without knowing the rest of the piston clearances, that could very well be another big contributor on cold start up and mpg. too big of clearances means more area for blow by regardless of ring gap. There is also the fact that ring gap is probably much higher than stock which will increase blow by. if piston to head is .030 and higher, thats reducing mpg 1-2 or more mpg. All these things add up. tuning not dailed in for the injectors, loose clearances, the pistons you have, the turbo you are running and the cam you have are all going to decrease MPG without alot of work to bring it back but it will never be stock.

the hardest thing i found to tune on oval pistons is rattle. that took alot of pilot injection work but mpg wasnt much more than standard tuning. you may need more timing in cruise areas and that is hard to nail without being in the truck and listening for rattle. that can make a big difference in mpg.

@Mike L. would know the details on the converter you have. i have a feeling its like you are stating and might not even have a billet stator.

Could better choices have been made? yes and dont shoot yourself on the fact you put oval pistons in there, its just a small piece of the pie to the issues.

Get yourself a good converter in there. Its going to be the cheapest fix to a majority of the issues you hate and will bring a smile back. then start inching in on the rest.

I appreciate all of the feed back, and agree with most. As for the converter, I just spoke with Goerend and they verified that the "C" stall converter has the stock stator and it stalls below stock. So thats definitly not helping me out.
I wish I did more checking when I put the heads on it. So here comes the stupid question, is there a way to figure out the compression ratio on an assembled running engine to see if what your mentioning could very well be an issue? Mark had to do a lot of adjusting when we dynoed it for the rattle you speak of, the way all of the idle tuning is now with the timing and pilot adjustments makes it really noisy, which I don't care about. But right now, its 85 degrees out and the truck has been sitting for 5 hours, when I go out and start it, blue haze city, so bad you don't want to walk by it because of the smoke and it burns your eyes of raw fuel. And that's the best I have been able to get it to be.

 

[Chevy1925]

I appreciate all of the feed back, and agree with most. As for the converter, I just spoke with Goerend and they verified that the "C" stall converter has the stock stator and it stalls below stock. So thats definitly not helping me out.
I wish I did more checking when I put the heads on it. So here comes the stupid question, is there a way to figure out the compression ratio on an assembled running engine to see if what your mentioning could very well be an issue? Mark had to do a lot of adjusting when we dynoed it for the rattle you speak of, the way all of the idle tuning is now with the timing and pilot adjustments makes it really noisy, which I don't care about. But right now, its 85 degrees out and the truck has been sitting for 5 hours, when I go out and start it, blue haze city, so bad you don't want to walk by it because of the smoke and it burns your eyes of raw fuel. And that's the best I have been able to get it to be.

not without numbers like piston protrusion and hg thickness but thats kind of a mute point as the dynamic compression ratio isnt really going to give you the answers you are looking for.

 

[reese600]

not without numbers like piston protrusion and hg thickness but thats kind of a mute point as the dynamic compression ratio isnt really going to give you the answers you are looking for.

Roger that.