Hello,

Do I need to replace my 6.2l pistons if I put in 6.5l heads/injectors and a turbo? Would it be a bad idea not to? Thanks.


-Erik

they won't fit. plus if you have the 19:1's in there why would you want to change them?

they won't fit. plus if you have the 19:1's in there why would you want to change them?
uhhhh HUH? http://www.dieselplace.com/forum/images/smilies/confused.gif

I thought that was the thing to do, place 6.5 heads on a 6.2. lower comp, means more boost. ???

Not a big deal, I have a 86 6.2 running right now in my daughters Blazer with a set of 6.5 heads, mainly because I was being lazy and one of the 6.2 valve stems was bad. Personally as long as you have post 84 6.2 heads, run them. You will have to do a lot of extra work(fitting injector lines, or purchasing new lines) and don't waste your money on injectors, at least until you run what you have. More important is what injection pump are you planning on running. Try to get a 4911 injection pump and adjust your fuel to match your air. If you are planning on running lots of boost you might want to consider ARP head studs. And like I have said before, 6.2 pistons are the weak link, the crowns crack, and skirts break. Call penninsular diesel and talk to one of their engine techs, they have played with every combination you can think of and they will tell you what will work durability wise.

Ah, I see, alright. Thanks.

[QUOTE=patracy]uhhhh HUH? http://www.dieselplace.com/forum/images/smilies/confused.gif

I meant that the 6.5 pistons would not fit the 6.2 block. I guess I didn't understand the question.

[QUOTE=patracy]uhhhh HUH? http://www.dieselplace.com/forum/images/smilies/confused.gif

I meant that the 6.5 pistons would not fit the 6.2 block. I guess I didn't understand the question.
Sure they will. Once it is bored out to 6.5 dimensions.
It is done plenty around here. I think it takes boring it juyst over .040 to get the right spec, but I would have to go look again.
Brian.

unless you have the 599 casting 6.2 i would not bore it out that big.

it's .080 or 2mm difference between a std. 6.2 and a std 6.5

Most machine shops around my area don't recommend boring a 6.2 out to use the 6.5 pistons. Unless you were to sonic test a few blocks and find a "thick one". Chances of that are slim to none, according to the machine shop techs.

Lupey6.5 is right about the 599 block. The "big guys" love to find 6.2 blocks with the 599 casting number. That's the easy way to make a 6.5. They are getting fewer and farther between. Most of the good ones have been gathered up and are being horded by the machine shops and core buyers around here.

I spent time on the phone to several good core people recently and was told, "Nope, none available" several times when I asked about a good 6.5 core block. If anyone finds one, hang on to it, it appears they are becoming "hard to find" in this area.

Where is the casting number of 599 found? Was it something that was primarily on J code engines?

If I remember correctly the casting # should be toward the left rear of the block(driver side) by the oil cooler outlet lines. Also, the desired block was made around 1992+ when 6.5's first came out it appears that 6.2's were made by simply underboring the 6.5 block. Also, in the front of the engine right side, there is a boss with a flat place right below the cylinder head, early 6.2's had a casting number that was 6.2 D, the ones built from a 6.5 block this spot is blank. One other thing, 6.2 blocks seemed to be a lot less likely to have the main bearing webs crack. The only ones that I have ever seen crack were blocks that suffered a crankshaft breakage. Most blocks that had a crank break have crack main webs resulting from the wedging force of the two parts of the crank. The last block I threw away was a 6.5 block with 599 casting and the main webs were cracked, very hard to see.:(

Remember, tho - how many 195hp turbo 6.2L's were built, between '82 to '92?

Reason why 6.2's seldom fail in that manner is because of the low oem hp rating - my '89 is fairly pristine, even with turned-up pump, advanced timing, and extreme abuse (oil field truck) before I got it.
It was an automatic, and the h\b and pulley are undamaged, so it may have some potential as an 18:1 6.2, which I am considering.

A considerable number of turbo-upgraded 6.2's lose the main webs due to the additional power - the number is comparitively low because of the hundreds of thousands of turbo'd 6.5's, and few want to upgrade a 6.2 beyond the 6psi Banks kit.

Upgrades are possible, but with same guarantees as with the 6.5 - it is fairly weak, and prior abuse weakens it drastically.

A half-ton Suburban, Blazer, or pickup, with 700R4 and no evidence of a trailer hitch, would be the best source for blocks, imo - no pre-stress.

'Tis a sad tale, folks - but true.

I ran turboed 6.2's for about 200,000 miles before I swapped in my first 6.5 in 94. I never had a bottom end problem other than 8 cracked pistons on a GM crate motor with 30,000 miles. GM replaced the engine no questions asked! Then I got the engine back, put in new pistons and had a spare engine. I ran 12-14 psi boost on this set up with good results. Never any cracks in the main webs.

Pistons with 6.2's are a weak link for turboed engines because they weren't designed for the added pressure. Beware of aftermarket pistons except for MAHLE as brands like silvolite are JUNK. There is a vender on ebay that sells sets of Mahles for about 350.00 for a 6.2 and 425.00 for a 6.5, a good deal considering they come with rings and are oem replacements.:)
I believe the underlying cause for 6.5's to crack the main webs is due to the way the cylinders under cut the main webs. The 6.2 due to it's smaller bore doesn't under cut the main webs as much. There are LOTS of 6.5's floating around with cracked main webs, some don't even know it. I didn't know that my 94 block was cracked until I read a post about cracks in the webs and went out to my shop at dark thirty with a flash light and looked real close and discovered cracks. Some people have worse luck. If I remember right John Kennedy had a 6.5 block fail shortly after putting it together, but his was bad and cracked into the water jackets. It boils down to luck of the draw. Maybe it will crack and maybe it won't. However, blocks built after 99 are suposed to be reinforced in the main web area to prevent this problem.:confused:

An additional factor to main web cracking, often overlooked, is engine balance. Most reputable balancers can correct these inherant problems. They oftentimes say, "This engine was off by Pounds, not grams!' It's always a good idea to balance an engine if you are looking for performance and reliability, but with the diesel, it's almost an engine saver.

Since the 6.2\6.5 is externally balanced, I would hope that they are balancing the crank with the flywheel and harmonic balancer installed - if not, it would be off by pounds.

I saw one professionally done crank, and the counterweights had a couple ~3/4" holes drilled and filled.

all the pistons and rods I've checked were within 1/2 of a gram on big end and small end weights.

Yep - I would have thought the cranks were more precisely balanced, particularly so for the 6.5 turbo.
The odd 6.2\6.5L firing order indicates an attempt at compensation for some severe forces at play, more so than a gasoline engine.

Any reputable shop that does balancing work should know the difference between internal and external balance. I would be worried if I took my parts to someone who didn't know!

Both shops that I use know these engines well. They have always turned out a smooth running rotating assembly. I've been able to tell the difference as soon as I start the engines. I'm convinced it saves engines in the long run and it makes a big hit with the customers!

If you look at the crank after balancing, you'll see the amount of work required to "make it right" is significant. Like gmctd says, "...holes, drilled and filled."

all the pistons and rods I've checked were within 1/2 of a gram on big end and small end weights.
Are they marked on the crank? just curious as to how you'd determine the cranks individual counter weight per piston/rod set

Defianetly didn;t say it was right, or that I would do it.
There is place around here (10 miles from me) that sells rebuilt 6.5 long blocks for $2950. I am afraid to ask what kind of parts go into them. I have seen one, even installed one for a customer trying to save money. I made him go buy the engine, that way he could deal with them when it failed.
he took them a 6.5, and got back a 6.2L in exchange. they thought it to be no big deal, do it all the time they said. Real nice, except we were expecting to reuse his flywheel and balancer!
My personal everyday driver isa 6.2L bored .040 over.
Never had an engine problem in the almost 500K it has on it (just 4.5k short). I have done a pump and injectors once, and it could probably be due again, mileage is dropped off.
Brian.

Most machine shops around my area don't recommend boring a 6.2 out to use the 6.5 pistons. Unless you were to sonic test a few blocks and find a "thick one". Chances of that are slim to none, according to the machine shop techs.

Lupey6.5 is right about the 599 block. The "big guys" love to find 6.2 blocks with the 599 casting number. That's the easy way to make a 6.5. They are getting fewer and farther between. Most of the good ones have been gathered up and are being horded by the machine shops and core buyers around here.

I spent time on the phone to several good core people recently and was told, "Nope, none available" several times when I asked about a good 6.5 core block. If anyone finds one, hang on to it, it appears they are becoming "hard to find" in this area.

Are they marked on the crank? just curious as to how you'd determine the cranks individual counter weight per piston/rod set
all i checked was the piston vs. piston, and rod vs. rod weight on the big, little, and total weight of the rod.

Brian, I went the other way once. Had my customer buy his own rebuilt engine. He came back with a 6.5 for his 6.2 core. I had fun with finding the right balancer, flywheel and pulleys to make it all line up and fit after the engine was installed. I, too was afraid to ask about warranty and quality of parts used. They even tried to take my installation away by offering him a longer warranty if they did the install. They told him they would have to recore his radiator, etc. They dreamed up all kinds of extra work to cover the cost of the extended warranty. Fortunately, I had already removed and disassembled his engine so was allowed to finish the job. Fred

You guys are making this stuff way harder than it has to be. Balancers and flywheels are interchangable from 6.2 to 6.5 as far as balancing is concerned. If you use a 6.2 flywheel you must use a 6.2 clutch. 6.5's originally came out with a dual mass flywheel, but they have issues. In 1998 GM went back to a single mass flywheel for the 6.5 and guess what, same exact part # as an 82 6.2. Rods are also interchangeable as are bearings. The biggest difference in the crank is the 6.5 all use a 1 piece rear main seal.;)

You guys are making this stuff way harder than it has to be. Balancers and flywheels are interchangable from 6.2 to 6.5 as far as balancing is concerned. If you use a 6.2 flywheel you must use a 6.2 clutch. 6.5's originally came out with a dual mass flywheel, but they have issues. In 1998 GM went back to a single mass flywheel for the 6.5 and guess what, same exact part # as an 82 6.2. Rods are also interchangeable as are bearings. The biggest difference in the crank is the 6.5 all use a 1 piece rear main seal.;)
Not the ones I have had here. The balancer and flywheel definatley did not interchange on any of the ones I have had apart.

I don't know what to tell you, but I was one of the first people in the country to do 6.2 repowers with new crate 6.5's. Granted all the new 6.5's came with balancers but every one I did I used the 6.2 flywheel and these have all logged hundreds of thousands of miles and been going since 1993.:cool2:

The balancers I've compared from a 6.2 vs a 6.5 have differences. The shape and size (thickness) are different. The casting #s also. Might be that the 6.5 was for a surpentine belt and the 6.2 was for the v-belt pulleys. Don't know the particulars as these were from used engines, but I do know they were different.

Believe me, I don't try to make my job harder. I just want it right. I hate comebacks! My customers have too many other choices. There's a shop on every block just waiting for me to make a mistake.

the only diffrence i have seen in 6.2 to 6.5 ballencers is the neck that goes in past the seal on a 6.2 is long for the narow timing chain crank sprocket and the 6.5 is shorter for the wide crank sprocket with the reluctor for the crank sensor the ballancer and sprocket from a 6.5 will fit on a 6.2 as you do not need the crank sensor but the 6.2 ballancer and sprocket will not work on a 6.5 as you will have no crank signal they will fit they will just not work flywheels are inter changeable but ballancer and sprocket must be used from same size engine:ro)

There are also some other differences as in the early 6.2's had holes drilled around the outer ring(they were real handy for installing bolt through magnets for Isspro tachometers.) What I am trying to say is that there are small differences but the balancing is the same. And mechanical 6.2's and mechanical 6.5's shared similar parts and parts could be interchanged without damage. You just need to know which ones and sometimes there is a companion part that goes with it.:grd: