Tune & Log. Gen VI CBB 1999 Vortec 7400

[oldpartsnrust]

Darn, they're booked up till after the holiday... Well, HAPPY 4th. EVERYONE!!!

[99k2500]

OMG I read all of this a wtf.... I have a 1999 BBC suburban. 411 pcm with a mild cam. I had a shop rebuild it after it had a crack in the crank. Everything is new all the way through the motor and sensors. I am hunting it running rich but it runs and pulls well. I use it as a response vehicle where I volunteer as a firefighter/EMT. 6mpg isn't great but it is fun lol. One day I'll go through the tune more. Now I am just reading and figuring things out on how. Thank you so much for this awesome thread! Can't wait to read more!!!!!

[oldpartsnrust]

Well, one thing I learned is that you should not 'set the bearings loose' even if someone tells you to. I was told to order 'extra clearance bearings' for the rods and mains which seems to have led to low oil distribution even though the pressure showed 60PSI at the gauge. There was the valve train noise and then after stripping it down the bearing wear and cylinder scuffing became apparent. So, my catastrophic mistake of leaving the EGR bolt where it could (and did) fall into the intake when swapping lifters, was almost a blessing in disguise. I do know that the 454 to 496 stroker DOES absolutely work with the Comp Cams upgrade, injector upgrade and roller rockers all with completely stock vortec appearance. Well, besides my Scooby Doo Mystery machine paint choices.

[oldpartsnrust]

Shooting for tomorrow to drop off the block for the machining. My visual inspection has it as better than my original block! Just overall with the lack of casting flash around the oil return holes and such, but the line hone/check will tell the true story.

[oldpartsnrust]

Dropped off.... drum roll...

[SiriusC1024]

Should show before/after pics for the fans.

[oldpartsnrust]

Crap, I forgot to get pics before. It really looked just like the old block before. Here are some pics of that.
Engine01.jpg Engine02.jpg Engine03.jpg Engine04.jpg Engine05.jpg

Fans? Everyone likes destruction right!?

[oldpartsnrust]

I keep alternating between "lighting a match" and "finishing this thing up". At this point, if I do it right it will seriously outlast me! I guess I will keep pushing onward. I only wish I was retired and this could be my 'hobby' but I need this bad boy to tow some stuff around and haul all of us to and from our place in NY.

[oldpartsnrust]

Shouldn't be long now till I can start putting this back together again...

[oldpartsnrust]

Machine work complete. Block is solid. Should be picking it up this week! Decked 0.020" to 9.780", bored 0.060" over to 4.310", line checked OK. I'll post picks once I pick it up. Side note: Spent 3 days in the hospital from a freaking tick bite!

[oldpartsnrust]

Quick question. One of the things I noticed on the old block is that there was some significant scoring on the piston skirts and cylinder walls. I am thinking that when I had first slapped this together if I recall, it was running really rich. I believe this may have caused that scoring as the walls are splash lubed no? There was also some pretty significant carbon build up on the piston tops when I took it all apart. I also believe that during the tuning process, one of the first things you noticed was that there was a lot of leaning that had to be done as it was running rich. Does this sound correct? I am asking because I think you had gotten pretty ball-parkish with the tune and that I should worry too much about this recurring with where we currently are with the tune? Is that a pretty fair assessment? Thanks. Starting to get pretty psyched now that time has dulled the impact of my f'ups. I think I am now able to categorize it as a different project mentally!

[SiriusC1024]

Yes, that's a fair assessment. Low oil pressure was also a contributing factor. Bores are splash lubed in a way, but not from the crank throws getting into the oil in the pan. Windage is something to be avoided. That heavy oil you were forced to use doesn't mist too well, either.

We'll go double check the tune and build sheet when you're ready. The tune we have won't have such a fueling issue. Couple that with a correctly built bottom end and there's the recipe for success.

Yo I got a tick bite earlier in the summer while mountain biking. Little bastard was only about the size of a strawberry seed. Not like a normal size one. I picked it off then put it in rubbing alcohol. It was still alive even after 15 minutes of marinating, so I lit it on fire. Might as well have been a spider bite. Spread in red streaks up my neck over the course of a few days after. I don't remember ticks being like this growing up.

[abc]

Knock can cause the marks you describe on the cylinder walls.

[oldpartsnrust]

I have a couple of days off after my unplanned excursion to the hospital and I will try to get some pics of the pistons that I had taken out. If I don't have to move too much stuff, I will try to get some pics of the cylinder walls too. This time I also sent the pistons out with the block so they can measure and fit each one. Thanks guys.

[oldpartsnrust]

Compression-001.PNG Compression-002.PNG Compression-004.PNG Compression-003.PNG
Compression-001A.PNG Compression-003A.PNG Compression-002A.PNGCompression-004A.PNG
First batch of calcs don't take into account the gasket bore.... BUT show the other details. The second set were run on a different calculator, with the gasket bore, but don't show the details, but the rest are the same as the first batch. I tried to make it that if I wanted to boost it later for some insane reason, I could add a different head gasket, and lower into the range to take a modest boost from a supercharger (NO TURBO). That was my logic anyway,,,, see how far that got me! Back to square one.

We were seeing the knock sensor going nuts the whole time I believe. I was attributing it to the valve noise, but that might not be the case. I put 0.030" thick head gaskets with a tight bore to actual, thinking I may be able to make a slight lowering if necessary by going to a thicker, larger bore gasket if needed.... HOPEFULLY setting the correct clearances will allow the proper oiling and lower the valve noise thus leaving any knock to be actual knock. I calculated the actual compression to be between 9.5:1 and 10:1 with my intro-level expertise with big blocks (domestic V-8s in general).

Will the casting #s on the heads indicate whether they are 100CC or 110CC? I think I was calculating on 110CC.

[oldpartsnrust]

Currently trying to run again (unless the Combustion Chamber CCs are 110):
Bore: 4.310"
Stroke: 4.25"
Combustion Chamber (Casting#10141279) : 100CC/120CC not sure? Any input?
Piston Dish: 3CC
Gasket Bore: 4.370"
Gasket Thickness: 0.030"
Deck Clearance (Decked -0.020" for absolute 9.780"): 0.00"


IF my heads are 100CC, that means I am at about 10.2:1 compression.... I believe I can lower it by using the following:
I was shooting for like 9.5:1, but if the heads are 100CC, I may be at 10.2:1
100CC
9.005 - C5634-092
9.294 - C5634-075
9.568 - C5634-060
9.859 - C5634-045
10.172 - C5634-030 <-- Current

This is going to be a tow vehicle, do you guys think I should use the gasket that would provide the lower compression ratio?

[oldpartsnrust]

I ordered a set of these: C5634-075 which should yield a 9.294 compression ratio, considering the high IAT readings and the fact that I plan to tow through the mountains. I always run premium gas, which is usually 91+ octane. I have run across 89 as premium in our travels, but don't mind running octane boost for a fill here and there. This is really a vacation and tow vehicle only. This is all assuming 100CC heads. Anyone have an authoritative source to verify the castings?

[abc]

Everything I have read in the last 20 years states: your much better off to adjust the compression ratio with combustion chamber volume and/or pison top shape/volume rather than change the quench depth via gasket thickness or leaving the piston recessed in the bore. With that being said, do what you have to to get the comp. in check, will be much better than dealing with knock.

[edcmat-l1]

Quick question. One of the things I noticed on the old block is that there was some significant scoring on the piston skirts and cylinder walls. I am thinking that when I had first slapped this together if I recall, it was running really rich. I believe this may have caused that scoring as the walls are splash lubed no? There was also some pretty significant carbon build up on the piston tops when I took it all apart. I also believe that during the tuning process, one of the first things you noticed was that there was a lot of leaning that had to be done as it was running rich. Does this sound correct? I am asking because I think you had gotten pretty ball-parkish with the tune and that I should worry too much about this recurring with where we currently are with the tune? Is that a pretty fair assessment? Thanks. Starting to get pretty psyched now that time has dulled the impact of my f'ups. I think I am now able to categorize it as a different project mentally!

The way this sounds, you rebuilt this engine and then took it apart again at some point? And the cylinders had significant scoring? Depending on the mileage my first reaction would be it's a less than sterile rebuild. But I'd have to see/know more to know for sure. That would be the most common cause. If there's any debris floating around the cylinder walls and piston skirts are the first to show signs.

[oldpartsnrust]

SUMMARY TO DATE

Fair enough assessment given the length of this thread so far! I will give a quick summary:
~~~
1. 180,000 miles on stock 1999 L29 Vortec 7400, spun 4 rod bearings seemingly at once while towing through the Appalachian mountains. Still running, towed home, torn down.
~~~
2. Decided to rebuild and upgrade. Sent block out for boring to 0.060" over, decking to 9.780, line hone/check. All clean and good. Followed engine builder's recommendations on what bearings (extra clearance), boring sizes (4.315"), etc. to put together ("these big blocks like it loose" - engine builder).

a. Eagle 496 stroker kit
b. F.A.S.T. injectors
c. Comp Cams towing cam for 7400 Vortec
d. Roller tip Comp Cams rockers (fit under stock Vortec Valve Covers)
e. Couldn't find any local tuners as they "don't work on that old chit". So I bought HPTuners
f. Adjustable rocker studs
~~~
3. Assembled all, programmed in the new injector flow rate and it started! Oil pressure 60PSI, but apparent lifter noise from the get go. Running very rich, but running. Knock sensor all over the place, but so was lifter / rocker noise.
~~~
4. Tried all kinds of things to quiet the lifter noise all while getting tuning assistance (Thanks SiriusC1024!) to back off the richness and get closer to final tune. This is all complicated by noise in valvetrain and Knock sensor.
~~~
5. Oil pressure still 60PSI on start and 18-20PSI after hot. Lifter noise no matter what I did. Decided to get lifters that had additional oiling at the top end. Took apart intake to swap lifters, knew I dropped a 10MM EGR bolt and planned to retrieve it later. Promptly forgot about dropped bolt, even searched for a new one when I couldn't find it. Was re-assembling and using a starter button to bump the engine over to adjust the valves when I heard a lockup, and then a ping, and then a crack. Sat for a second wondering what I just heard... then bumped it again and it spun freely. Decided something not so good happened so I got out a borescope and saw that a piston met its demise. #3 hole.
~~~
6. Tearing down motor revealed the following:

a. coolant in oil, didn't register initially as I pulled intake and coolant migrated, but it was A LOT
b. broken piston
c. rod bearings had some scoring as well as rod journals had a touch of scoring, (was able to be polished out)
d. mains looked pretty good, slight (less than rods) scoring and journal scratches
e. Piston skirts and cylinder walls had vertical lines/scratches/scoring, cannot catch a nail, but obvious sight wise.
f. CRACKED cylinder on #3 when went to hone cylinders for re-ring!
~~~

At this point, with some lessons learned (and probably a few more to come!) new used block, fresh line hone/check, fresh 9.780" decking, fresh 0.060" bore, NEW pistons/rings and polished crank (scoring was superficial and polished out), going to re-assemble. The more research I do, the more I am thinking that the knock readings could be valid as I think these heads have a 100CC chamber instead of a 110CC chamber which is what I used to calculate everything. IF 100CC, the new head gasket should give me 9.4:1, which is where I wanted to be and thought I was initially.

Corrective actions from first swing:

1. Thicker head gasket
2. Factory clearance specs for mains/rods
3. straight 0.060" bore, rather than 0.065" that engine guy recommended
4. Thinking rich issue is mostly gone thanks to SiriusC1024 getting it close to "Ship it!" tune.

Still researching the head casting # unless someone can definitively tell me the CCs of the heads I am going with 100CC this time instead of 110CC.
Casting #10141279