Ultimate 6.2/6.5 engine build questions

[Matt Bachand]

well.................. I fabricate, and I just like to do it. I like to make things better and make it look just as good as it works. It is just something I do. It is what makes me, me. Plus what fun would it be to just buy something you have no idea what the clearences are? You could hope the assembler had a good day and not a bad day. I'm not trying to degrade anyone, and in no way am I suggesting Penninsular doesn't know what they are doing. I just like to know what is what. Plus with the economy the way it is it is easier to do steps instead of forking out 7K. BTW this is my other toy hand built completely by me.

Carrera TT... quite nice there bud...

I went broke just looking at the picture I think

 

[GJF]

Thanks Matt,
Your sharp, yes it is Carrera based.
Good thing it is done I can't afford to build another one.

 

[Turbine Doc]

Turbine Doc, Do you regret not going 18:1? If you had to do it all over again would you stay 21:1 ?

I am thinking hypothetically, that a 18:1 motor would have less block stress since the cylinder pressures would be less off load which the motor is seeing most of the time anyways.

Next question on concrete filled blocks.... How do you contend with a block heater and concrete fill?

To be honest if one would actually build a REAL girdle that would tie the oil pan rails in and combine a windage tray into the same unit IMHO think it would be just as strong as splaying the caps. This method would add triagulation to the main caps and tie all the main studs together and take care of harmonics at the same time if there are any.

At elevated boost 15+ I see maybe need for lowered CR, that was reason many did it, especially when going with a hi boosting turbo, more better boosting with ATT and boost pressures matching those capabilites of GM-X turbos I don't think 2x about that now.

So no regrets staying at 21:1, I spent a lot of hours pondering that question, but after reading issues of the many who went that route and experienced issues, and hours with Heath talking about it on various calls when I was building my project engine; I think I made the correct decision. FWIW I have a set of new never installed 18:1 "shave top" Mahle pistons on my shelf I was so committed to that possibility, and very close to going that route.

Slim Shady has 18:1 & ATT he's told me he'd probably go 21:1 if he had to do it over, he's in Detroit, I'm in South Ms/Ga/Al 95% of my driving, so I could manage with the lowered CR and probably not have cold start issues, but combustion design for this engine was optimized for 21:1 figured I stay with that.

As far as filled block and winterblock pre-heating, I'm not sure with a fully functional glow system & 21:1 it's a issue, Heath is probably best to ask that of, but he's in the mountains of Wa State, and gets purty cold there so I've heard, if artic cold and no block heater, maybe one of those epoxy on oil pan heaters.

X2 :thumbsup: on full oil pan rail girdle & custom pan, IIRC a guy on Diesel Page did just that, awesome machine work, but not something that could be done for 6.5ers economically, & I doubt with vintage of these tucks one would find somebody willing to produce en-masse to get the cost in what passes for "affordable" on a "vintage no longer manufactured truck", (heck guys gripe at the price of the proven best DS4 long term FSD fix, try to sell a custom girdle/pan setup)

As a pet project, improving strength for monster race/sled puller (not really much you can do anyway once IP is out of fuel delivery capability), or love of the challenge have at it.:thumbsup::thumbsup::thumbsup:

As I said about my splays, ain't hurting nothing, as a do-over, I probably wouldn't, it's overkill for what I do with mine and what most guys will do with theirs.

Shucks the factory engine is still in it, and is still capable of pulling 18K loads 80+ mph flat grade & 70+ mph up minor hills to my camp 160 miles from home with 176K on the engine and nothing done inside the block.

I don't run that hard, I have tested it just to see, and it's capable of doing it if I needed to.

 

[bison]

It seems every one has its own opinion about girdles or splayed mains or billet caps.(they are welcome to it)
The real issue is how to prevent web cracking.IMO, none of the above solutions are really adressing or curing that,altough the splayed mains would offer more protection if the outer main bolt holes did not exist.The block construction,metal composition and/or the casting methode itself are prob the culprit.Wheather curing the blocks for a yr or so before machining would prob help a great deal,but is most likely no longer done.
As the webs are simply proven not beefy enough to withstand the downwards and twisting forces and/or vibrations occurring for whatever reasons, metal fatique is often the result.Cracks occur as often at the boltholes as closer to the panrail.
Tying the webs more to the panrail,and resisting block twist can only be done by casting or billet machining a solid bottom end that includes the panrail and all main caps like in that new AMG block (dont know what they call it)
Altough i would have placed the outer mainbolts in the panrail,as i am planning in my block (see bottom of sig)I wish i had the time to finnish it.
Now, that dont mean the engine becomes indestructable,but i bet the bottom end will be.

And that folks, is my take on the matter.

 

[ak diesel driver]

Slim Shady has 18:1 & ATT he's told me he'd probably go 21:1 if he had to do it over, he's in Detroit, I'm in South Ms/Ga/Al 95% of my driving, so I could manage with the lowered CR and probably not have cold start issues, but combustion design for this engine was optimized for 21:1 figured I stay with that.

As far as filled block and winterblock pre-heating, I'm not sure with a fully functional glow system & 21:1 it's a issue, Heath is probably best to ask that of, but he's in the mountains of Wa State, and gets purty cold there so I've heard, if artic cold and no block heater, maybe one of those epoxy on oil pan heaters.

When I talked to Bill about his block fill he said he couldn't use block heaters. He fills them too full. But he did say he has used an intake grid heater IIRC.

 

[Ratman]

So you are saying the time and money myself and some others have spent building main girdles are a waste of time?

Nope, didn't say that.

MY OPINION IS, it isn't going to prevent mainweb cracking.

Nothing I said was intended to be offensive. :thumbsup:

 

[Ratman]

Actually if you go back and read what he said he initially went on a rant about girdles. Then on a rant about how the metalurgy does not match between cast iron and steel. Then indicated what he said does not apply to race engines because they are different.

I do agree that the angle iron girdles are probably not worth the money and I do know that I will never bother to put one on my engines but, I have built enough race and diesel engines of wide varieties to know that he is steering people in the wrong direction with his statements. In the same post he praises one method yet says there is nothing we can do to save our junk. Really?? I might be stuborn, but I have yet to figure out why some people have to be so negative when solutions like this are being discussed. It is discouraging to the new guys.

Nothing was meant to be negative, -it is negative only if it is taken that way.

If having those rails bolted onto the main studs makes you sleep better at night, -and your stuff ain't scattered in the road, -then by all means it was worth it.

I myself, personally, (am a machinist), and won't be doing it.

To each their own. Let's just agree to disagree, -no harm, no foul.

 

[Ratman]

It seems every one has its own opinion about girdles or splayed mains or billet caps.(they are welcome to it)
The real issue is how to prevent web cracking.IMO, none of the above solutions are really adressing or curing that,altough the splayed mains would offer more protection if the outer main bolt holes did not exist.The block construction,metal composition and/or the casting methode itself are prob the culprit.Wheather curing the blocks for a yr or so before machining would prob help a great deal,but is most likely no longer done.
As the webs are simply proven not beefy enough to withstand the downwards and twisting forces and/or vibrations occurring for whatever reasons, metal fatique is often the result.Cracks occur as often at the boltholes as closer to the panrail.
Tying the webs more to the panrail,and resisting block twist can only be done by casting or billet machining a solid bottom end that includes the panrail and all main caps like in that new AMG block (dont know what they call it)
Altough i would have placed the outer mainbolts in the panrail,as i am planning in my block (see bottom of sig)I wish i had the time to finnish it.
Now, that dont mean the engine becomes indestructable,but i bet the bottom end will be.

And that folks, is my take on the matter.

Yep, -what he said.

 

[Jasonsmack]

I am all for agreeing to disagree. I am a journeyman automotive mechanic, and separately certified diesel engine and gasoline engine machinist. I believe that properly built and installed main girdles have to increase lower block core rigidity in the 6.5, or any other engine for that matter. Every time a new engine is produced, you see more and more companies following through with cross bolting main caps through the lower skirts of the engine block. That is the way big diesels are built. Heavy main girdles are as close as we are going to get with the 6.5.

 

[Missy Good Wench]

I have owned 6.2/6.5 from waaaaaaaaaaaaaaaaaaaay back in 82 when the Little red block 6.2's came down the line.

I have had my fingers into all of them over the years.

Any and all of these little critters can and do crack in the main web areas.

The Buzzword used to be that the Red blocks were the real deal.

Nope, sorry to say, they too will crack in the webs just like all the rest.

Got one with about 150K on it that has every center main cracked in it.

The 599 blocks were used during the transisiton from 6.2 to 6.5 and could be found with either bore size.

My 94 6.5 (599) had 230K on it at teardown time (head gasket) NO cracks at all.
The next 599 I took apart was a crack heap.

The squirt blocks with 12mm outer bolts were notorious for cracking and the main webs breaking.

There is not any real good GM blocks out there.

I have spent many hours contemplating the cause of the issue.

Green blocks that were not cured properly ??
Tortional stress due to poor cyl to cyl timing ??
Bad ballance ??
Cranks with issues that cause stress in the block ??
Vibration dampener issues ??
Poor metalurgy ??

I have considered it all and still scratch my head.

One things for sure and has been stated, if the block is high mile and has not cracked it probably won't.

Studs in the lower end are not a bad idea.
Girdles are a JOKE as far as whats available for these engines.

Two fixes seem to work well.

Splayed main caps (Spendy but good)

I currently install the Lock and stitch inserts in the 6 center main outer holes.
I do it even if the holes are not cracked.

These inserts reinforce the area and assure that there will be no wedging action from the bolt threads.
The insert has angled threads that pull the area together and eliminate the forces that add to the likelyhood of a break.

To date the reports are good that there have been no failures of a 6.5 bottom end with the inserts.

A squirt block in my opinion is a bad choice for an engine thats going to be asked to give its all.

The main webs are too small anyway and to drill more holes though them is ludicrous.

If the block was cast from some very good Iron, this would be a moot point.

The new AMG/GEP blocks are reported to have far better material plus the HMMWV engine are getting the huge main cap one piece girdle assembly.

The new engines are also getting a forged steel crank too.

The Iron cranks from GM were basically a limp noodle and IMHO may very well be flexing far too much under some conditions and causing stress in the block.

I have pulled down several 6.5's that had some real wierd wear patterens on the main bearings. This had to be caused by the crank moving around.

Poor injector POP pressure (uneven from cyl to cyl) will cause wild swings in timing from cyl to cyl.
This issue can cause an uneven power flow and the crank to flex more than it should.

Coupled with driving habits and other issues that can't be controled after the sale,this could be the reason some fail and some don't.

Any 6.5 thats being asked to go into the 300HP arena is living on borrowed time unless much attention is paid to the build.

A crack free block thats been inserted
Steel crank
Ballanced rotating assembly including flywheel and ballancer
Carefully setup injectors (all pop pressures equal)
Head studs a good idea.
Aftercooler a must for pressures over 12 PSI
When working on the lower end, all main bolt holes need to be lightly chamfered and all sharp edges on the machined surfaces of the main webs broke and smoothed.

The bottom end of these are like a razor and this is just poor engineering to say the least.

A prayer won't hurt either.

Best

MGW

 

[bison]

I am all for agreeing to disagree. I am a journeyman automotive mechanic, and separately certified diesel engine and gasoline engine machinist. I believe that properly built and installed main girdles have to increase lower block core rigidity in the 6.5, or any other engine for that matter. Every time a new engine is produced, you see more and more companies following through with cross bolting main caps through the lower skirts of the engine block. That is the way big diesels are built. Heavy main girdles are as close as we are going to get with the 6.5.

I agree with the cross bolting.However that can only be done to some extent with the existing 6.5, if one extends the skirt by casting it in with the maincaps and bolting it to the panrail,or re disign the block.
IMO,anything else are bandaids

 

[Ratman]

I am all for agreeing to disagree. I am a journeyman automotive mechanic, and separately certified diesel engine and gasoline engine machinist. I believe that properly built and installed main girdles have to increase lower block core rigidity in the 6.5, or any other engine for that matter. Every time a new engine is produced, you see more and more companies following through with cross bolting main caps through the lower skirts of the engine block. That is the way big diesels are built. Heavy main girdles are as close as we are going to get with the 6.5.

First of all Jason, I would NEVER be one to question your technical credentials, or discredit your opinion.

Cross bolting is a GREAT idea that WORKS. Unfortunately, it ain't gonna happen for us.

There are MANY different theories about what causes the blocks to crack in the webs, -and unfortunately, I don't think any of us are 100% sure what the root cause of failure is, -or if it isn't a combination of things going on.

We're all here to draw off each other's opinions and experiences, -the hard part is doing it without offending anybody.

In all seriousness, I think that if they would have used better materials and went with the 10mm outer bolts instead of the 12mm's (506-style), -we likely wouldn't see what we're seeing. I agree with MGW on the squirt holes, -although like some have said, there doesn't seem to be any real hard evidence that one without holes is any better than one with holes.

The failures seem to be all across the board, -almost like there may have been something wrong with the way they were casting/cooling them, -and undoubtedly the selection of material. Machining the castings while they were too green may have also been a contributing factor as well.

I wish we all had a bona-fide answer.

 

[Non Typical]

I think bottom line in finding one that's crack free is simply going to be luck of the draw. I have seen some absolutely phenomenal girdles that have been built that completely encase the bottom end. Unfortunately, they are custom works and I am sure would cost a lot of $$ to get them replicated.

That being said, provided my build block is crack-free, I will be looking to do what I can to beef it up. :thumbsup:

Keep the opinions rolling people.

 

[Matt Bachand]

I wonder where/when in the rpm most of these cracks happen? Under smooth acceleration? Under Hard acceleration / downshift?

Don't hear standard shift blowing more... of course by numbers alone they are only probably 10-20% of 6.5's and maybe 50% of 6.2's?

Also, why can't that hummer bottom end be used in our rigs? crossmember in the way?

 

[Ratman]

I wonder where/when in the rpm most of these cracks happen? Under smooth acceleration? Under Hard acceleration / downshift?

Don't hear standard shift blowing more... of course by numbers alone they are only probably 10-20% of 6.5's and maybe 50% of 6.2's?

Also, why can't that hummer bottom end be used in our rigs? crossmember in the way?

Matt, I think it'll fly in a 2WD rig.

I think the diff is in the way on the 4WD stuff.

Nothing a 6" RCD lift won't cure ):h

 

[Missy Good Wench]

The New Hummer engine with the built in Girdle can be used. Ya just have to rebuild the pan using the lower part from the stock pickup pan and the uppper part off the new pan from AMG.

Cut and weld them together and custom build the oil pickup for the rear sump.

Just $$$$ is all

MGW

 

[Missy Good Wench]

Had the 6.5 been designed with a deep skirted block like the Old 390-428 Fords and the cross bolted mains like the 427 side oilers and the 427 cammers had.

That design would have been super tough and could have been done easily.
The reason it was not was simple, it costs money to do stuff the right way.

The engineering folks knew all along that the 6.2/6.5 was a time bomb ticking away and that it was not failure proof at all.

The whole pacakage was designed to hopefully make it out of warranty before it grenaded.

Some did quite well, some bit the dirt.

Then came the aftermarket and many good fixes to the rescue.

Deep skirted block
Forged steel crank
Cross bolted center mains
decent iron that has good metalurgy

OMG what concept.

MGW

 

[mattthebrat]

Had the 6.5 been designed with a deep skirted block like the Old 390-428 Fords and the cross bolted mains like the 427 side oilers and the 427 cammers had.

That design would have been super tough and could have been done easily.
The reason it was not was simple, it costs money to do stuff the right way.

The engineering folks knew all along that the 6.2/6.5 was a time bomb ticking away and that it was not failure proof at all.

The whole pacakage was designed to hopefully make it out of warranty before it grenaded.

Some did quite well, some bit the dirt.

Then came the aftermarket and many good fixes to the rescue.

Deep skirted block
Forged steel crank
Cross bolted center mains
decent iron that has good metalurgy

OMG what concept.

MGW

My, for someone who owns quite a few of these motors you sure do hate them!?:smile5:

 

[bison]

My, for someone who owns quite a few of these motors you sure do hate them!?:smile5:

 

[Ratman]

My, for someone who owns quite a few of these motors you sure do hate them!?:smile5:

The love affair with the 6.5 is truly a LOVE/HATE relationship!! ):h

When they are running the way they're supposed to, they do VERY well, -especially considering what they cost.

And, let's not forget what made these things so damned affordable in the first place, -it is because most people are scared to death of them. (because of all the horror stories -PMD/DS4 crap, gasket issues, cracked block issues).

If it wasn't for these "issues", we'd surely pay a lot more for our stuff.

But, the 6.5 has a following like NO other, and there is a HUGE knowledge base, -much of it right here at DTR.

Nothing brings more pleasure than passing a PSD or a duramax on the freeway going 105 mph and seeing the grins, -especially if they're old-timers old enough to know what's under the hood of my "vintage" GM diesel truck.

The guy that works at NAPA saw me burn a little rubber leaving the lot one day. I went in to get power service one day and he remembered who I was, -he asked, is that a 6.5 in that thing? I said yep. He responded by saying "I didn't think you could make one of those things run like that" ):h

The fact is, -for all the "pain in the a$$" stuff we get to deal with sometimes, -hands down, the 6.5 is the KING of affordable diesel, -and yes, they can run WELL too.

So, there's that love/hate thing.....:thumbsup: