6.5 N/A vs 6.5 turbo

[greenmeanh1]

This was asked earlier in the thread,, don;t know if it was answered
J127 is equal to Oct 12 1997 casting date. I am assuming that number came off the rear passenger side of the block where the bell housing connects. In the Hummer world we call that an at risk block and has the cylinder 8 flaw in the casting. My engine does too and its still going at 127kmiles
I think all 6.5s have web cracks from the factory!! LOL As long as thery are short!

 

[Will L.]

Pretty much all the blocks risk cracking in the main webs until you get a Navistar block (GEP; optimizer)I believe in 2004 is when they were available. That's one of the good things about the take-out engines from the military Humvees is some of those are the Navistar blocks. Another thing that was included in that is a better crankshaft. That's when they went to the three Center main caps having two different size bolts to mount them instead of all the maincaps taking the higher torque that attributed to the cracking. Same crappy cam bearings though:mad2: idk about the main and rod bearings. Same rods, pistons, rings, lifters pushrods, rocker arms. Better camshaft. I know there were more changes made I just can't remember them at this time.

There was questions whether it also had an upgraded oil pump. after many hours of research I can tell you there's only one manufacturer making the high-volume will oilpump for the 6.5 -Melling. You can order it with different pressure springs depending what (relabeled) company you buy it from if not melling.

Iirc When they changed the metallurgy in the block they also changed it in the heads in the attempt to alleviate some of the cracking heads, and a slight difference in the water flow. The two guys I was talking to agreed the water flow change was minimal and was one engineer just mopping up a little OT, so of no real value. I spent a bit of time talking to a couple of the engineers. It's amazing what a free lunch will do when you're trying to get information.

You really ought to search the older posts in this forum - there's a lot of information about it. I remember one interesting one that Missy did about some blocks that weren't supposed to get out (still wandering how you pulled that one off Missy...)

Btw, According to the engineers, It's not really a cylinder 8 defect, it's just that's where most of the heat gets trapped because that side of the engine gets the worst waterflow with the old water pump system and the cylinder head is closest to the transmission amplifying the problem so it absorbs most of the heat out of all the cylinders. If you take your engine right now and shoot it with temp gun and you do not have The "HO" water pump on it you will see the difference After pulling a hill that heats up the ECT's.

The cylinder eight temperature issue is also why a lot of people were switching locations for the two coolant temp sensors, so the gauge read the hotter temperature for the driver to see instead of getting that information to the Cold advance system.

I hope I didn't hijack your thread or steer it too far off course, just hoping to put out some useful information for the people that might not learned it yet.

 

[ak diesel driver]

the diff size main bolts started with the 506 block in 97 IIRC which is also when the HO water pumps came into the mix

 

[Will L.]

I stand, in this case sit, corrected. I new the water pump, but couldnt remember the main bolts. Was the optimizer 04? It was summer of 08 when i met the engineers, so all of the conversation was based in past tense.

 

[ak diesel driver]

hard to say when the "optimizer" came in to being. there was some changes going on as early as 00

 

[ak diesel driver]

technically the waterpump and dual stats came into the fray in 96 but not all trucks got them and it doesn't seem to follow a mid year time frame more of which factory it came from. case in point my truck has both

 

[turbovanman]

Pretty sure the GEP came out in 01. Camshaft is the same. Crappy cam bearings???????

Reason for the block failures wasn't really bolt size, but casting, simply too thin, crappy metal and apparantly, the cutters for the squirters cut into the side of the blocks, creating stress risers. I have the article saved at home.

 

[Will L.]

Yeah, they went with a metallurgy change because they were trying to build in a larger room for error with the history of heating errors. The cams have same lift/duration but they changed how they were making them. I'll look for some pictures, but be patient. I am not a pictures organize person. Iirc there are groove looking areas in between the lobes and a little more meat there on the newer ones. Idk why I never heard of any cam problems that didn't have bearing failure as culprit.
The cam bearings are still the gm stamped rolled and pinched style. They (gm) went to them in mid 90s to pinch pennys. There isn't a lot of problems with them, but they wear and spin much quicker. That is the number one cause when oil pressure would drop from 20 range to 8-10. That's when they lowered the min oil pressure to 6 psi as basis to tear down under warranty. Tsb on it back in the day. They later killed the tsb when a state ( Texas iirc) filled suit against them for a fleet with multiple trucks on it. Then they said it was just a fluke to have over 20 psi at idle. I have my cam bearing that I lost this year still, I'll try to find it a take pic to post.