Another myth

[grape]

seems when you slide a stack of feeler gauges between the cylinder liners on a 6.2 and a 599 6.5 block, they are exactly the same. Hmmmm, guess that means you can't bore a 6.2 out to a 6.5...... :rolleyes: why am I not surprised.

[dieseldummy]

Care to elaborate some more Grape? Me and another on this board have been having a conversation on this exact subject.

[grape]

the OD of the cylinder liners is the exact same distance apart in my red 81 6.2 block and 599 6.5 block. If you take the block heater out of the driver side center you get direct access between the center two cylinders. Everybody always said that a 6.2 block doesn't have thick enough cylinder liners to bore the 2 mm out to the 6.5. Well, if the OD is the same distance apart, I would assume that means they aren't any thicker.

[DmaxMaverick]

That doesn't make sense.

If the distance between the cylinders is the same at the water jacket, then the difference would be the bore. Cranks are interchangeable, so the bore index would be the same. It would mean that 6.2 block could be bored to 6.5L, and maintain the same cylinder wall thickness, as the 6.5.

Myth is right. It's as accurate as saying an Olds 350 Diesel is a converted gasser.

[tom.mcinerney]

I thought the capability to overbore the 6.2 to 6.5 was what justified Avant's purchase of a (couple) thousand ex-UPS 6.2L blocks.

[mhagie]

Frito Lay not UPS besides he probably got them dirt cheap.
Hope someone takes this a little further and checks the next block in succession, The 506?
Maybe this has been a myth all this time.

[arveetek]

I am convinced that the 6.2L and 6.5L blocks are essentially the same, and that there are no cylinder wall differences between the two. After examining the evidence that Grape has mentioned here and before, and after talking to Benny Avant, I do believe that a 6.5L is simply a bored-out 6.2L, with some other minor differences for the DS4-equipped engines, and of course the later piston-oiler blocks.

Benny Avant has an '82 Suburban with a pre-599 6.2L that they bored out to a 6.5L. I saw this truck in Ohio at the DP Rendezvous in 2001. It's still going strong.

This would also explain why the 6.5L blocks crack more frequently than the 6.2L blocks. I've never seen or heard of a 6.2L that cracked from the main webs up into the cylinder walls, but I've heard of several 6.5L's that have. It makes sense: if a 6.5L is a bored-out 6.2L, and you increase the power output with less meat in the walls, then you're asking for trouble. Weaken the block even further with more oil ports for the piston-oilers and then make the outer main cap bolts smaller, and what do you expect? Block crack city.

I'm not sure why so many people have persistenly stated that the 6.2L could not be bored to a 6.5L. Ford/International did the same thing with the progression of the 6.9L into a 7.3L. Everyone knows that a 7.3L is just a bored-out 6.9L, and a lot of people believe that the 7.3L cavitation issues are a direct result of boring the 6.9L out too far, leaving thin cylinder walls. If you read over at The Diesel Stop, Ford's equivalent to The Diesel Page, you'll a see that a lof of the guys will recommend a 6.9L over a 7.3L, due to the fact that the block is stronger. Apparently the 6.9L's had more head-gasket issues, but that's another story.

Casey

[john8662]

Interesting!!

I didn't think of just taking feeler gauges between the cylinder liners in the specified spot from freeze plug access. Makes sense though.

I was going to get a chunk cut out of the cylinder block on an 82 cracked engine, but now I'm wondering what this would tell me, just save the trouble eh.

Just as stated above, I'd like to see some measurements of later blocks and compare 6.2's not just the early 82 hi-ni blocks with that of the 6.5's (various castings would help).

82 '660 block (1st generation) 6.2
83-87 '660 block (2nd generation) 6.2
88+ '660 block (3rd generation) 6.2
92-93 '599 block (4th generation) 6.2

97+ '506 block
AMG '506 block

[More Power]

Using feeler gauges inside the block to compare a 6.2 to a 6.5 is interesting, but not definitive because the sacrificial mold used on the inside may not be positioned exactly the same - block to block.

In 1992 & 1993, 6.2's and 6.5's were being built on the same production line - using the same cylinder block casting number, same crank casting, and same rods. Heads & pistons were different.

A few years ago I heard from a fellow in Australia who had bored a number of 6.2's (80's blocks) out to std 6.5. He had one or more that split the cylinder walls soon after being put into service.

Avants have been boring 599 6.2 blocks to std 6.5 for a few years now. I believe Dr. Lee's is one of them.

Jim

[dieseldummy]

Just for kicks and grins I'm going to measure between the cylinderwalls of my 2nd design '660 block. I'm still going to cut a chunk out of my '599 6.5 block just incase anyone has a piece out of a junk 6.2. That will settle the argument for sure... Just for the record I do agree with Grape that the 6.2 and 6.5 are the same blocks, just bored out differently. Grape, what were your measurments between cylinders? I would like to see if my '660 6.2 block is the same.

Justin

[GMC Hauler]

If the blocks and all parts are interchangable except for pistons and bores, then why not make a 6.5 in every respect except for the pistons and bores, which would be made 6.2? I would be willing to sacrifice .3 ci to make the block more reliable. You could make up for the lost cubes in boost/fuel.

[arveetek]

Originally posted by GMC Hauler:
If the blocks and all parts are interchangable except for pistons and bores, then why not make a 6.5 in every respect except for the pistons and bores, which would be made 6.2? I would be willing to sacrifice .3 ci to make the block more reliable. You could make up for the lost cubes in boost/fuel. That's what my engine basically is. My engine is actually a 6.35L. If the 6.2L can be safely bored .080" over to std. 6.5L pistons, then my 6.2L bored .040" over should be stronger than a std. 6.5L, but more powerful than a std. 6.2L. With the timing gears, lower-compression pistons, and 6.5L fuel system, I should have more power than a stock 6.5L, even with a little less displacement. With 17 lbs. of boost, it sure does scoot down the road!

Casey

[Cowracer]

Originally posted by More Power:
Using feeler gauges inside the block to compare a 6.2 to a 6.5 is interesting, but not definitive because the sacrificial mold used on the inside may not be positioned exactly the same - block to block.

In 1992 & 1993, 6.2's and 6.5's were being built on the same production line - using the same cylinder block casting number, same crank casting, and same rods. Heads & pistons were different.

A few years ago I heard from a fellow in Australia who had bored a number of 6.2's (80's blocks) out to std 6.5. He had one or more that split the cylinder walls soon after being put into service.

Avants have been boring 599 6.2 blocks to std 6.5 for a few years now. I believe Dr. Lee's is one of them.

Jim 'zactly!

Core shift is almost a given on GM castings. I have seen some gasser heads that were rediculous.

Do the same measurement on 10 engines and see if the average backs up the claim.

Tim