MaxPF's 6.2 build

[Russell]

These arn't Cummins diesels, they can't take the type of boost you can run through a Cummins without blowing out a headgasket or something...

By lowering the compression ratio, you can run more boost than stock, since stock compression is something like 23:1. Just makes the diesel harder to start, since it is an indirectly injected diesel, unlike the cummins.

 

[tRustyK5]

I dunno about 7 psi...Casey here (Arveetek) was running a non waste gated turbo set-up on gis 6.2 and reported he often saw 13-14 psi. I personally don't see a problem with that, and the way Max is building his I wouldn't think more would be a problem either.

In any case no 6.2 will take the boost a 6BT will...but this also isn't a 6BT build thread either.

Rene

 

[Russell]

Ah, I was kinda wondering why you were asking about that, I kinda see you as a major diesel guru, lol

As far as wastegating it goes, guess he just wants to play on the safe side

 

[mudman83]

Yeah, these are by no means high power monsters, but they are much cheaper to build than a cummins and much easier to install. That is why they are still around. If you are looking for 300+ hp you have to use a cummins, but generally for offroad use people want the cheaper 6.2 because you dont need the crazy cummins power and could spend the extra money on something else. It is better than a gasser though because it gets twice the milage, runs at any angle, has killer torque at low rpm, and diesels just sound better once you drive one. They might also be lighter than a 6bt but I am not sure. That is truly comparing apples to oranges, they may be diesels but are totaly different from eachother.

 

[mudman83]

On a 6.2 the head gaskets are not huge problems any more after felpro made their new ones. However, you still can't get huge power from them because of their inherent weakness. The crank and webmains are known to break and crack. If it is not making huge power with 15+ pounds of boost, and is kept under 7psi, you lessen your chance of breaking the weakest parts of the engine. It is a safety net. Some people have run up top 18 psi and higher, but that is too risky on an old engine designed for economy, not power.

I built my engine with everything new or rebuilt besides the cam for 4500 after spending a year buying good deals and still have spare parts to sell, which was easier for me since it was a dropin. I could not get a cummins for free or that would have been awesome.

 

[MaxPF]

The motor is strong enough for turbocharging... to a point. Even Cummins guys drop the compression when they start using really high boost. The difference here is that a stock Cummins 6BT has a CR of 17.5:1, while the 6.2 and early 6.5's are 21.3:1. Put 21.3:1 compression pistons in a 6BT with 32PSI boost and see how long your head gaskets last With 18:1 compression and a suitable DB4 marine pump (and a prepped block or a new AMG short block) 340HP is readily achieved - reliably. Even more can be had with more extreme mods: http://video.google.com/videoplay?docid=1641713166467266832 and http://www.thedieselpage.com/readers/kolkman.htm

The difference is that the Cummins stock block and crank will easily handle that amount of power, while the 6.2 will need to be built to handle it. It was designed as a light duty motor for good fuel economy, not brute power.

I am being conservative and shooting for a certain power target and good fuel economy. Right now my TBI 350 is rated at 210HP. The 6.2 I acquired was rated for 165HP, according to the sticker on the air cleaner housing. 5PSI boost is an increase of 33% over atmospheric pressure (1.33 bar). Not counting losses due to compression heating it would increase the volumetric efficiency by the same amount. Increase fuel flow accordingly and it will increase power output by 33%, giving me approximately 220HP. In reality it will be more like 200-210 - approximately the same as my current gasser (well, 100k miles ago ). It is a low enough amount of boost that I won't need a charge air cooler, and it won't beat the tar out of the 21.3:1 compression motor. Finally, since it will be wastegate regulated I can size the turbine for faster spool up, and I can maintain a constant 1.33 bar intake pressure regardless of altitude. This will make driving in the mountains much nicer The motor should live a nice, long, healthy life and I will be happy. Besides, I have an adjustable wastegate controller to crank up the boost if I want to play To go over 10PSI and still be rreliable the compression needs to be dropped. Lower compression = harder cold starting, which isn't an issue I want to deal with in the mountains at 10,000 feet in the middle of winter.

BTW, MudMan83 is correct about the weight. A 6.2/6.5 weighs about 700lbs, while a 6BT weighs in at about 1100 lbs.

 

[MaxPF]

Well, I spent more money this weekend. I ended up ordering rod bolts from my friendly GM guy. 16 bolts and 16 nuts cost me $144. I also spent $28 on a 4 foot long piece of 1.5"x1.5" 1018 cold rolled steel bar. This will get machined into a pair of stud girdle rails. I am still waiting on my friend to free up his manual lathe and mill at his shop so I can machine the seal surface on the crank and build the girdle. I still need to get main studs, head studs, a new flexplate, and a new harmonic dampener before I can send everything back off to the machine shop...

 

[tRustyK5]

That makes good clean sence. and I can see the glare of a light duty diesel Vs medium duty pretty clearly with how you guys talk of the 'ol 6.2s. right on. looks pretty slick though/

my '94 6bt was about 1250lbs fully dressed when I had it in the back of my truck.

That's the only drawback I see with the 6BT, 500+ lbs more over the front axle...

Rene

 

[mudman83]

How are you planning to design your girdle?

 

[MaxPF]

How are you planning to design your girdle?

It will basically be like yours, except I want to tie it to the front and rear caps and put tie bars on it to tie the two sides together.

 

[BKinzey]

As for a harmonic dampner I haven't checked with FluidDampnr lately to see if their's is out yet. I'm hoping it is before I start putting mine back together

 

[MaxPF]

Today I spent another $355 on fasteners I had to contact ARP's special order department for the main studs since they don't have a main stud kit for the 6.2/6.5, and I needed 1/2" longer studs on the outboard holes to accomodate the girdle. They ended up having off-the-shelf parts that were close enough to work. I will need to trim the coarse thread side of the studs down a bit, but that's no big deal. I also ordered the head stud kit for the 6.2/6.5 application.

With the head and main studs and the rod bolts I now have $500 invested in fasteners alone . Building a custom motor sure ain't cheap, but it will be cool when it's done

 

[MaxPF]

I got my goodies in today.

Here's some pics of the main studs in place:

Right now you're probably wondering why there is a stack of washers under each outer stud. Well, that is where the 1/2" thick girdle will go. Hopefully it will clear the pan in the front. If not, I will modify the pan

Here's a pic of the head studs screwed into the block:

The head studs for the 6.2 app are interesting. They are a 1/2" stud with 1/2" fine threads on the top, but with M12x1.75 threads going into the block. I calculated the clamping force on the head with these studs, and it came out to 290,000lbs That's 145 tons of clamping load on the head gasket If that doesn't hold it in place, I don't know what will

 

[tRustyK5]

Swanky!!

Rene

 

[MaxPF]

Swanky!!

Rene

They are, aren't they

We finally designed the girdle on Solid Works today. It's pretty simple, but should do the job. My friend said he should be able to get it on the CNC this week. Once it's built I can install it, torque down the main caps, and take the block to the machine shop to have it bored and honed. The line bore will also be re-checked, and honed if necessary. Also, I may go ahead and have the deck surfaces touched, after I have them rechecked.

I will be taking my stuff to a new shop that just opened here in Mesa called Maximum Horsepower & Machine. I have talked with the owner at great length, and he seems to be a very knowledgable and decent guy. His equipment is first rate, and he knows what he is doing. In fact, I will be dropping my rods off Monday so he can recondition them. They will get shotpeened, magnafluxed, resized on the big end, and rebushed and sized on the pin ends. It's coming along, slowly but surely.

 

[colbystephens]

:drool:

question: what's the advantage to studs versus bolts? how do you install a stud so that it's properly torqued? or does it matter how tight the studs are into the block since the clamping force will hold them against the threads?

 

[tRustyK5]

Studs have the advantage of no radial stress, which means more strength to clamp with before yeilding. As far as I understand, studs are not torqued into the block, just spun in until they bottom.

rene

 

[colbystephens]

that makes sense. seems like if you put enough torque on the nut on the stud, radial stress could be created - but i guess that assumes that the yield strength of the part being clamped at some point gets to be higher than that of the radial strength of the stud.

 

[MaxPF]

The advantage of the stud is that it doesn't put radial stress on the threaded hole in the block. When you tighten a bolt in a threaded hole the camming action of the threads sliding over one another tries to push the threads in the hole away from the bolt. This puts tensile stress on the threaded hole. With a stud, you thread it all the way into the hole and torque the nut on the other end. Since the threads don't rotate in the block during torqueing, there is no camming action. The threads are locked together by friction, and the forces on the threads in the hole are mainly shear, as the stud tries to pull them straight up out of the hole. Why is this important? Well, cracks in 6.2 and 6.5 blocks start at the outer bolt holes on the intermediate webs. It is a region of highly localized stress, partially from the static stress caused by torquing the bolt, and partly from bending loads as the caps are rocked fore and aft during firing events. By eliminating the static stress caused by the torquing of a bolt, it leaves a much greater yield strength margin to resist fatigue and cracking due to cap loading. The stud girdle should control any fore and aft movement of the cap, minimizing any side loading of the hole. All that should be left is shear loading of the threads, which is what they are designed fore. In theory, this should eliminate block cracking under high loading. We'll see Oh, also the stock outer bolts only engage half of the threads in the block (only about .330"). The fewer threads that you engage, the more stress is created. The studs engage ALL of the threads in the block.

There are other advantages with studs, like minimizing wear on threaded holes (important for racing motors that are frequently torn down - not so important for non-racing apps), more reliable torquing due to lack of twisting, and the fact that the studs are made of stronger material to allow more preload. Is it worth it? I'll let you know in 500k miles

 

[colbystephens]

ah, makes sense. i was thinking stress on the bolt - not the block.