Originally Posted By: BrocLuno
You had a very typical intake gasket failure. They love to loose gaskets and then suck oil like crazy ...
Or, the PCV system failed. Sometimes the valve covers do not have the right baffle configuration to minimize oil loss, and they will act exactly like you describe - when the bottom end is fine ...
On your build - yeah a lopy idle is nice, except that it means a lot of extra fuel down the drain and may be hard to control idle and slow speed heat build-up ... I'd really shy away from trying that with a ECM controlled engine.
So the way to make this work best in a big Burb is to make a really fat mid-range torque engine. Lopers almost always move the power band to high for the street and any off-road work.
Start with the heads and the block. 0.030" over is all you need for a street engine. You want killer more TQ, then think about a stroker crank. But it ain't necessary ... Sleeves no necessary unless one cylinder is thin on one side. If the machine shop sees any core shift, they can sonic test and do what's needed.
Put a piece of steel across the top of the cylinder with a piston at TDC. Use feeler gauges to measure the piston crown (cleaned) down the bore. If it's less than 0.005", you have power coming right there. The goal is to get just about 0.050" total quench. Your gasket is likely 0.038" or so compressed. So if the piston is down the bore much, you have given up a lot ...
Get the heads done at a good local machine shop. Iron guides are fine. Really good 3-angle valve job minimum. Better is 4 or 5, if you can find the folks who will do the work well. Most won't and have not done enough to know how properly.
Spend some time with a die grinder taking out casting flash and guide boss material in a streamlined shape. Don't go crazy. Study up, do homework. Take a 0.020" pass across the face of the heads. Your CR is going to come from the pistons, not the head. Have them CC the heads and give you real numbers - no Inet look-ups. GM was all over the place on chamber sizes.
Now pick your pistons with decked block in mind. The block must be decked to the actual piston/rod combo. You are shooting for 9.1 static CR max for future unknown fuel. Dynamic CR will depend on cam and installed adv. Have the block decked to calculated piston crown -0.005" for safety ...
Me, I'd go Howard's Cam all the way with a matching lifter set because it has a 5 year guarantee if installed per instructions. Nothing crazy. The more cam, the less fuel economy. Most guys over cam an engine and then cry - don't. The CR and the tight quench do the job.
If your used springs were not good (sagged, etc.), I'd get Howard's springs too. If your springs are good - fine, unless you look at a cam that will lift higher than stock springs can handle (which you should
not be doing on a real street engine ...). Call Howard's and get a recommended cam with your heads and pistons initially selected. Tell them it'll be a "Burb" ...
On a working street engine, I like steel roller tipped rockers. Those usually come from Comp. Crower is better, but way more expensive. OEM pushrods are OK if they are straight. If not, look at Crower.
Cloyes timing set. HV oil pump with low pressure relief spring. Drill the front two lifter gallery plugs 0.030" each. This will squirt oil on the back of the cam gear. That will over oil the cam chain. That will keep it all happy for many miles and reduce "chain stretch" which will keep your timing better longer.
Stock crank is fine. Nobody ever pushed a BBC crank out the bottom end unless they were stupid. Replacement H beam rods w/ ARP bolts are about the same price as fully re-cond OEM rods w/ ARP bolts, and may be lighter. Get it all balanced.
Change intake manifold for freer flowing unit. I like Wieand, but you can go wherever you want. Match the runner sizes to your heads. Wieand aluminum water pump. Now your motor is 50# lighter. Shorty Jet-Hot coated headers and you are another 40# lighter.
Even with a mild truck cam, this motor will spin 5,500 easy. One of the good "marine" cams will get you closer to 6,000. But you give up a bit of bottom end.
The bottom end grunt and mid-range will surprise a lot of folks. The tight quench means you can run more timing. So start looking at your distributor options. Rebuilt OEM is fine for these RPM ranges. But you may want to change the flyweights and the "scroll" to bring the timing in faster.
If you are rebuilding the tranny - I'd go with a Hughes Tow-Master converter. Same efficiency at cruise, but with more go off the line. You will be able to terrorize the tires with this build
This all sounds straight forward, but this is a serious engine. It'll make the OEM unit seem pale in comparison, and the gas mileage will not suffer
Make sure you speak with a tuner regarding what can actually be done with the stock ECM. From what I remember the 99-00 OBS has a modern ecm that is the same or similar to the later ones used on the NBS trucks with LS motors. This ECM lends itself to be tuned more than the earlier ones but you should check on fullsizechevy.com. You could always go stand alone like megasquirt but idk how far you want to go.
If you're going to build a 454 I would personally be looking at an LS swap. Even a stock 6.0 is going to vastly out perform a stock 454 and you already have the ECM that can run it. I know you probably want the big block torque but for a daily driver I think you will save a lot on gas. If you're willing to blueprint a 454, then you have to at least consider a 6.0 swap with a cam and a tune. Or you could be my hero and perform a cummins, OM series diesel or other small diesel swap.
The OBS is my favorite truck, my fam had a 95 burb 2500 4x4 350 TBI. My dad traded it in during the height of gas prices in 2005 for an 04 sierra z71. Wish we still had that heap, it had every option that a 2500 could have and was mega BA when my mom would pick me up from school where everyone else had mini vans and cars and we had a 2500 HD burb!
OBS burbs hold a special place in my heart, I would love a 6.5. Good job keeping that thing on the road, you have awesome taste in cars!
EDIT: I just wanted to add that you could do the intake gaskets/replace the PCV and then save up or do more research for a swap. I'm not a pro mechanic, but removing and rebuilding both a motor and trans and then putting them back together again seems like a troubleshooting nightmare waiting to happen. This would also allow you to put more time and money into the transmission, and give it a shakedown to see if it works properly after it is built. It would be awful to try to track down drivability issues when you have a freshly rebuilt trans and a freshly rebuilt upgraded mill installed at the same time. With automotive projects I have learned to take things slowly and methodically, as they can really bite you and cause you to loose interest in wrenching on cars period, which has happened to me in the past.
What are you doing to the trans? If you are planning to build the motor, I would be beefing that trans up to the max and getting a big cooler and a mag-hytec pan.