September 2, 2024 Update - Rough Country, High Mountain Lakes!
Here are 3 photos we took on a camping trip about a month ago.
https://www.thedieselpageforums.com/...4&d=1725317166
The above photo shows the Blazer on the road to a pair of lakes here in Montana's Bitterroot Valley called "Twin Lakes", elevation about 6500'. It's a 20 mile drive from US-93 to the lakes, about 15 of it on gravel. This mountain valley was formed via glacial action during the last ice age. Lotsa granite boulders... Those BFG's really did improve the appearance of the Blazer... ;)
https://www.thedieselpageforums.com/...6&d=1725317166
The above shows the lower of the two lakes. The fish were biting! Cutthroat Trout... Access was not that great, forcing boaters to scramble across the boulders to put in. Not a lot of "scrambling" at my age... ;) Just over the hill beyond the lake is the border with Idaho - and the roadless Bitterroot-Selway Wilderness.
https://www.thedieselpageforums.com/...5&d=1725317166
Here's the Blazer at the camp site we chose. Lots of vacant sites to choose from. The CG had 12 sites in total, but just 3 were occupied. Our site's fire-ring and nice picnic table are just out of sight behind the Blazer. The well kept FS outhouse is just a stone's throw away to the left.
The 270 degree Oztent awning was deployed here. On the way out we stopped to pick wild berries (Oregon Grape and what looked/tasted like Blueberries - actually Service Berries). Didn't see any bears... :eek: Fun Trip! The 6.5TD did a great job! Sarah drove both ways.
6.5L Turbo Diesel Blazer Project - "Back from the Dead"
https://www.youtube.com/watch?v=9Il2deqwXLA
Introduction: This "Murdered Out" 1994 6.5L Turbo Diesel Chevy Blazer was brought "Back from the Dead" after the engine sat in a thousand pieces for over 11 years. Here, we solve the problems caused by a melted piston, a gouged crankshaft, and cracked cylinder heads that were unrepairable. The Blazer has been back on the road now since the fall of 2021. This YouTube video will show you how well this GM 6.5 diesel currently runs and performs, and what we think of the Fluidampr harmonic damper replacement. Segments of this video put you in the driver's seat, so you can experience what a proper 6.5L Turbo Diesel is supposed to be like on the highway.
Had fun with this one! Check it out. There are some new video clips that haven't been shown here before... including at the very end. :)
Jim
Update: 10-20-2024 - 6.5L diesel cylinder sleeves and cam bearings
This next photo is one I used in the video, showing a faint line around the #8 cylinder's deck, which indicates the close fitting cylinder sleeve - nicely installed. Notice the "M033" block date code on the "599" block used in Sarah's 6.5L diesel...
https://www.thedieselpageforums.com/...7&d=1729464069
The close fitting cylinder sleeve in the #8 hole can also be seen from below - in this next photo.
https://www.thedieselpageforums.com/...8&d=1729464069
The other 7 cylinders were still within std spec (even after 187k miles), needing just a glaze break for the new rings. By using a sleeve that was bored to std, we were able to install a matching set of eight standard size pistons, which were acquired as new "take-out" pistons. One of our members had recently upgraded a brand new 6.5 engine by replacing the original pistons with lower compression 18:1 pistons, and sold us the "like new" original (20.3:1 compression ratio) piston set for a really good price.
A few of the original pistons may have been OK to re-use. Aside from the destroyed #8, a couple of other pistons showed degrees of scuffing and heat damage. If on a tighter budget, I might have re-used the few remaining pistons that looked OK (assuming they also mic'ed OK), just replacing the ones that looked/measured bad. But, they all had near spotless crowns, having been burned clean by high/excessive EGT - kinda like how I prepare my BBQ grate. ;) - It was best to replace them all - glad I did.
This last photo shows the cam bearings that had been installed by the engine shop. Unfortunately, the pictured cam bearing set had to be removed and replaced with another new set. It really wasn't that big a deal. The machinist did a great job otherwise. Just glad I caught it. Why did the bearings have to be replaced???
https://www.thedieselpageforums.com/...6&d=1729464069
It's what's not in this photo that illustrates the problem... Some of the oil holes in the cam bearings should have been visible in this photo, but none can be seen here. Oil hole positioning is called out when viewed as though the engine were sitting upright and you're facing the front of the block. This necessitated installing a new set of cam bearings. I didn't want to trust re-using the cam bearings after they had been removed. They go in tight enough that the OD may have been tweaked a bit going in/out. In any case, new Clevite cam bearings were only about $50/set. Seemed like cheap insurance to just replace them. Jim
We need your help too! Did this forum thread or YouTube video help you with your 6.5L Turbo Diesel? Would you like to share this information with others or help us get the word out about the 6.5? It's easy! Simply link to us in your own YouTube video, or post the link(s) shown here in a forum post, email message or social media site. Thank you!
thedieselpageforums.com/tdpforum/showthread.php?46770
https://youtu.be/9Il2deqwXLA
Update: 11/1/2024 - Boost Pressure & Gauges
https://www.thedieselpageforums.com/...5&d=1730491410
As mentioned earlier in this forum thread, Sarah's 1994 electronic 6.5TD is equipped with an aftermarket mechanical "Turbo-Master" wastegate actuator (shown here), which can be adjusted to manage maximum boost pressure. Currently, the Turbo-Master is adjusted to allow the factory GM-4 turbocharger to produce about 12-psi during a full-pedal run, and that boost pressure is relatively constant throughout the rpm range - assuming a more or less constant full-pedal accelerator position is maintained.
When originally stock, the electronic engine management system controlled boost pressure using the OE vacuum controlled wastegate to produce a boost pressure that varied across the rpm range even with a constant acc pedal position - with boost pressure maxing out at about 2400-rpm with around 7-psi max and then trailing off as engine speed increases above 2400-rpm. Various theories exist for why that's so... I suspect boost pressure, when stock, trails off as engine speed rises above 2400-rpm for a couple of reasons... 1- These electronic DS fuel injection pumps decrease fueling as engine speed increases due to both limitations in mechanical design and the EFI programming being used, thereby reducing the need for more boost pressure as fueling decreases. 2- And, reducing engine power/torque as rpm rises may help with emissions control and engine durability.
https://www.thedieselpageforums.com/...6&d=1730491410
The above photo was taken by Sarah just last week while cruising on the Interstate at 75-mph - showing 7-psi boost pressure and 550-degrees F exhaust temperature. The EGT pyrometer is located in the crossover pipe a couple of inches below the flange where it connects to the driver's side exhaust manifold.
Not surprisingly, with the current Turbo-Master adjustment, there is almost no smoke produced by the 6.5 - under nearly all driving conditions. It's easy to experiment with boost pressures when using a Turbo-Master, and I'd like to experiment with a lower boost pressure for three reasons - say around a 7-psi max. 1- The current fuel rate doesn't need that much boost pressure to burn clean. For example, a stock Duramax when driven at these speeds/loads only produces about 3-psi boost pressure. 2- These factory GM-series turbochargers are not very efficient above about 7-psi - and it really needs an intercooler at 12-psi boost pressure. 3- The engine may be more fuel efficient when the wastegate is allowed to open more - to reduce turbine drive pressure while in a light load cruise.
Incidentally... with more than 5K miles since the rebuild (it's on its 3rd engine oil service), the engine oil still darkens at around the usual 3000 mile mark (this is typical for the 6.5TD), which indicates that a higher than stock boost pressure may not have a lot to do with how soon the engine oil darkens from soot. I thought it would have made more of a difference... I do know that there is no visible blow-by at the oil fill pipe (when the cap is removed) while the engine is idling.
Did I miss anything?
Jim
Update: 2/21/2025 more Shortblock details
Time flies! The last update was the first of November last year... Time for an update.
The Blazer is currently tucked away in the garage. I had my trickle charger on the batteries for a month or so, just to make sure they were being kept fully charged. I'll likely do this again before spring gets here. Sarah decided to leave the Blazer with me this winter. Her Malibu has grippy studded snow tires all around, and does a great job on icy roads, and it fits well in her single car garage, so she hasn't needed the capabilities of 4WD and fairly new BFG tires. We talked the other day about the upcoming camping/kayaking season. With a couple feet of snow on the ground and sub-zero temps (last week) where she lives, it's easy to think about warmer temps and green grass... I'll likely start the 6.5 in a week or so, and put a few miles on it, just to keep things limbered up... ;)
https://www.thedieselpageforums.com/...5&d=1740166052
The above pic was taken as the engine short-block was in its final assembly in 2021. I'm not sure if I mentioned this in an earlier post, but the 12mm threaded holes for each head-bolt were chased with a tap (before the short-block was assembled) to prepare the threaded holes to accept the new Fel-Pro TTY head bolts. The threading process was done when each head deck was upside down - so any metal particles would fall away instead of into the engine. This was followed by a good vacuuming using my powerful shop vac.
Chasing the threads in the block deck ensures that all head bolts have an equal opportunity to reach the same torque value (clamping load) during the head(s) installation, and that the GM Teflon pipe thread goop would have the best opportunity to seal the head bolt threads. I've not had any sort of coolant leakage because of a head bolt sealing problem with any of the 6.5s I've worked on - including this one, when using this (GM recommended) method. These threaded 12mm bolt holes are open to the coolant passages below the decks, so proper sealing is important.
Also, you can see in the above photo that the #6 piston is at TDC. The piston protrusion seen here was well within specs, when considering I installed +.010" thicker Fel-Pro head gaskets that TDP recommends when the block decks have been machined. Both of these head decks had been machined .005". Otherwise, I recommend the standard Fel-Pro 9701PT head gaskets when the head decks can just be reconditioned (or prepared) for new gaskets. The pistons/rings used here were new "take-out" units purchased from a member who upgraded his 6.5 using 18:1 pistons. These (standard compression) take-out piston crowns showed a light coating of soot residue, but the rings/ring grooves, skirts and undersides were still shiny clean aluminum.
Jim
You can help! Did this forum thread or YouTube video help you with your 6.5L Turbo Diesel? Would you like to share this information with others or help us get the word out about the 6.5? It's easy! Simply link to us in your own YouTube video, or post the link(s) shown here in a forum post, email message or social media site. Thank you!
thedieselpageforums.com/tdpforum/showthread.php?46770
https://youtu.be/9Il2deqwXLA
3/24/2025 Update - Piston & Rod Assemblies
https://www.thedieselpageforums.com/...8&d=1742856251
This photo shows the assembled pistons and rods, arranged in the cylinder positions they would assume after being installed in the block. Pistons 1-3-5-7 are nearer the camera here, numbered right to left in this photo. Pistons 2-4-6-8 are on the far side - also right to left.
The factory "J" stamp on most of the pistons indicate a "standard" bore diameter. The other markings were my writing with a Sharpie, my codes correspond to their measured diameter and which cylinder they belonged to. I developed a couple of charts in my notebook during this process - to help prevent a mistake.
All 6.5L pistons are "barrel-shaped". These piston diameters had been carefully measured using a micrometer (measured where GM said to measure them), then matched to the cylinder bores to produce the best fit. Seems making pistons and boring cylinders can produce a few ten thousandths difference between what might be identical parts. As luck would have it for our Blazer project, the end result was a near perfect match-up, with piston clearances being in the center of the prescribed tolerance range for all eight holes, even including the slightly larger factory specified piston clearance for #7 and #8.
I spent a lot of time trying to figure out the rod/cap match-up and orientation, because I didn't disassemble this engine and the rods/caps weren't marked before/after disassembly. I poured over all of the images/photos I had trying to figure out what orientation GM used when assembling the rods/caps. Pretty sure I got it right when this 6.5 went back together. At least the big-end crank bores in the rods were round and all eight rod/cap sets matched each other. Once satisfied with the choices... I used a carbide pen to mark each rod and cap as to orientation and which cylinder they belonged.
You can see the new rod bearings had been installed in the rods/caps, and assembly lube had been pre-applied. The crank journals received a liberal coating as well during its installation. I mentioned in an earlier post that the underside of these "take-out" pistons looked like new... You can see that here... ;)
On the right edge of the photo you can see two lengths of 3/8" rubber hose. I used those hose lengths on the rod bolts when the pistons/rods were installed in the block. The hoses protected the crank journals from damage as the rod bolts slipped past. All of the piston ring gaps had been positioned where GM indicated, and all of the bores had been cleaned with clean rags and brake cleaner before receiving a liberal application of new motor oil - right before the pistons/rods were installed in the block.
At the top of the photo, you can see the five main bearing caps oriented in their correct order - the same as the pistons/rods - numbered right to left. I'm not that experienced with engine assembly, so doing a little prep setup like this helped me keep things straight... Of course, the important thing here is not to let my daughter know that there was anything to worry about... :). I said, "It's all good. I got this!" She said, "OK", as she torqued the rod cap bolts... ;)
Update 4/11/2024 - Step Brackets
A Youtube viewer recently inquired about the steps we installed on the Blazer. I pointed him to this thread for more information regarding brand and more general information. He then bought a set of these steps and requested more info on the brackets. I haven't posted any details about how I adapted the steps to be used on the GMT-400 Blazer, so I thought I'd do that now.
As you may recall, the company that produced the steps didn't offer a bracket kit for the 88-98 GMT-400 OBS trucks, so I made brackets that allowed newer Jeep steps to fit the Blazer. So, here is some additional info regarding the special bracket adapters I made. :)
I originally used 2" angle steel to make these brackets. I knew once I purchased the steel and began the first bracket that 2" was way more than was necessary. I've since scaled the angle steel down to 1-1/4", which is still plenty strong enough. In any event, the mounted bracket adapters shown here were made using the original 2" stock.
https://www.thedieselpageforums.com/...1&d=1744410317
The brackets are attached to the steps using a single bolt (3/8" or 10mm), nut, flat washers and lock washers. The upper bolt (shown in the top left of the above photo - also 3/8" or 10mm) was inserted through an oval shaped hole in the body pinch weld. I used large flat washers large enough to capture the edges of the oval hole. You'll have to drill a 3/8" or 10mm hole through the body pinch weld flange to mount the rear step mount. I used a power drill with a 90 degree angle adapter for the chuck/bit.
https://www.thedieselpageforums.com/...9&d=1744410317
This photo shows the underside looking straight up, where the bottom bolt attaches to the original step's mount half. The two smaller 1/4" bolts shown in this photo secure the 1" angle steel that is used to overlap the pinch weld on the Blazer's lower rocker panels below the doors. (See below)
https://www.thedieselpageforums.com/...0&d=1744410317
A photo of the 1-1/4" and 1" angle steel parts ready for the cutting/welding process. Also, I made a thin sheet metal template that I used for a mock up. The 4 brackets you'll need are all the same, as are the smaller angle parts. Only one short weld is required on each bracket.
I'll re-do the photos (clean up the Blazer and to get better images) and have a drawing available in a week or two for the template shown here. In the meantime, this should be enough to get anyone started in the right direction. By the way, these steps/mounts are pretty solid. They don't deflect when I put my weight on them... ;) They've been on the Blazer for more than 2 years now, without a problem - or any sag.
By the way... The steps themselves did not need to be modified in any way. I did relieve a small amount from both front factory plastic wheel flairs where the forward end of the steps fit. That mod isn't visible. If your truck doesn't have the plastic wheel flairs, no mods required.
Jim
