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6.5 connecting rods

consaka

consaka

Active Member
Messages
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Location
Vancouver WA
Is there anything better? I am doing a rebuild of a performance 6.5. Actually I should say a buildup of a 6.5. I have one nice S shaped connecting rod that would seem to indicate a potential weakness. Granted it was shoving a piston too big for the cylinder through it anyway but I have heard of others having bent rods from other misc performance mods.

If there is something even marginally tougher I'd like to use that if possible. How about 6.2 rods? Where they any stouter?
 
I don't know if it is warranted. To my knowledge, the connecting rods are forged, so pretty damn strong for a 6.5L. If they kick the bucket, it's because of something else wrong. Usually incorrect timing or dropping something into the piston or something. Regular maintenance and a proper setup goes a long way. I got a pretty built engine and I've ran mine up to 4500rpm and 30+psi of boost multiple times and have nothing happen.
 
I have seen glow plug tips etc dropped in the cylinder and had a NA 6.2 still keep running for 100k miles. I also have seen pics and heard from others that they can head south above 30 psi.
I cant remember which forum but one forum has a carnage thread with some pics of rods tore up.
When I split the cylinder on my 6.5 I bent that rod into an S shape so like most factory things they work as they were intended and are engineered with no more than necessary.
I think I can say we are pretty far above what factory engineers envisioned for this engine.
 
I've seen a 6.5 motor bend c-rods trying to overcome hydrolock at 145mph... Put something in the hole that shouldn't be there and if the piston can't push past it, the rods are going to bend. Might want to take a closer look at the others and I wouldn't use that block either without a good deal of inspection too.
 
Paveltolz said:
I've seen a 6.5 motor bend c-rods trying to overcome hydrolock at 145mph... Put something in the hole that shouldn't be there and if the piston can't push past it, the rods are going to bend. Might want to take a closer look at the others and I wouldn't use that block either without a good deal of inspection too.
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That old 141 block? I was going to sleeve it but on disassembly discovered too many cracks in the main webs. Now I do not have a magnaflux setup and to see these I didn't really need one. The 3 middle main webs all had varying degrees of cracks with only one so bad it went to the bolt hole.
Now that is out of the way, please elaborate on your 6.5 going 145 mph and hydrolocking. Usually that much RPM can handle a pretty decent amount of liquids. For that to hydrolock it had to be bringing in A LOT of liquid. :) Sounds to me like someone was having way too much fun.
 
DSC01603s.JPG It was at the Bonneville Salt Flats in 2009, late September. The engine was donated by Diesel Depot out of Georgia to 'see what it would do.' At the time, they equipped all their builds with hi-volume oil pumps, which is fine for most applications running 'normal' RPMs. When you're pushing 5000 rpm at the shifts... its a bad thing.
It drains the oil pan PDQ, pushes the oil up into the heads where it aerates and gets into the tight spaces and eventually you have a very rough running 'low compression' engine. We'd seen the oil pressure drop during the previous event (World of Speed, 1st part of Sept) and had installed a very bright low pressure oil light on the dash and it came on before we were at speed (goal was 164 and it was popping up at 140-150) so off the throttle and back to the pits. One run too many and we 'saw what it [wouldn't] do.' Truck owner said the pump wasn't a good thing for what we were doing and wanted to swap it out of there but, the engine showed up too late to do anything about it as the race was only a few days away and there wasn't time. Best part besides not being our motor was we had the engine builder (Jamie Avante) out there when it folded.
 
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Paveltolz said:
View attachment 48600 It was at the Bonneville Salt Flats in 2009, late September. The engine was donated by Diesel Depot out of Georgia to 'see what it would do.' At the time, they equipped all their builds with hi-volume oil pumps, which is fine for most applications running 'normal' RPMs. When you're pushing 5000 rpm at the shifts... it's a bad thing.
It drains the oil pan PDQ, pushes the oil up into the heads where it aerates and gets into the tight spaces and eventually
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Whoa that sounds like a whole lotta fun though. Curious question though. Did you guys clean up the castings and enlarge the oil return areas? Did you use a high psi film strength oil in a lighter weight for the run?
hehehe I got a engine block that would be perfect for you guys. lol it has zero oil pressure at hot idle and only 22 at 2000 rpm. I reckon it could hit 40 maybe at 5000 rpm. lol maybe. That's with standard 15w-40 with a quart of 60 weight in there(long story).
Well pretty awesome the maker of the engine was there. And they saw what it could do. Mission solved. Now my question is did you guys manage to fix the problem and try again the next year perhaps?
 
The truck is based in Washington and I just crew for it and get to help tinker a little when passing through on a detour from work. That year was the last year though as the owner, Bill Heath, saw the Diesel Truck class record get higher as it was taken by a Dodge and then a Ford...both prepped for the runs by factory teams. Bill's plan was to run as near stock as he could but, that's not going to get the job done now. Business kept him from working on it and bad weather the last few years has too often made the salt unsuitable with either too much water from late rains (this week is rained out) or the deteriorating salt surface makes for unsustainable racing conditions. But, to your questions...
After the Diesel Depot failure, he went back to the motor he'd built and run the year before but, he hadn't gotten it ready for 2009 (hence DD coming to the "Rescue" in 2009). Then the record started getting faster (IDI trucks currently have to compete with the Direct Injection/fuel rail set ups so until SCTA makes a split in the Diesel Truck Classification, he's @#$%^& for trying to set a record with a 6.5). Still, he's the fastest recorded 6.5....
I don't know what voodoo stuff he does or what DD did to that motor but, I do know on his own motors he does clean things up as you mentioned and ports the intake and exhaust runners. I know he did NOT knife edge the crank or thin the oil etc. In the year's since, he's worked with GEP on their Optimizer series and P-400 series motors and one thing led to another and he's got a couple of motors on stands waiting for mating to a 4L85. Only there's all electronics and body mods to the firewall and a business to run and no guarantee that there will be a surface to run on... He's parked it in storage for now and is considering putting his built up 6.5 (not the P-400) in his 60's step-bed for a return to drag racing. He used to run a big block gasser in it and its been long parked too so we'll see. They run their street 6.5 trucks out there on a local track in Yakima and have a pretty good time taking people's money. He built my motor as a favor after another DD #$%^&* up but that's a long story and even longer thread(s) for all my banter (sorry, its what I do).
Basically it went from this Diesel Depot custom build for member 635 in 2009...
Ted Rich Custom Engine & Parts 0890.jpg
...to junk from using a King bearing on #7 (Clevites on everything else)...
00 Busted Diesel Depot cranks.JPG

...to me buying the parts resulting in this by 2013.
23 Mocked up for install.JPG
Total of about 5 years and nobody wants to get out the calculator, trust me.
 
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Where is that drool emoticon when you need one. hehehe You should have said it was Bill. He is just northeast of me here in WA. Little much for an afternoon drive but not terrible.
One different bearing did that? Must have been before he started using coatings on everything. I am thinking of doing some coatings for the first time just to stack things in my favor a bit. I'm a little paranoid about ring gaps at present. Some of the recommended gaps for turbocharged engines seem pretty wide to me.

That is a good looking engine there with a nice rarely seen paint finish on it. I like it.
 
consaka said:
...One different bearing did that? Must have been before he started using coatings on everything. I am thinking of doing some coatings for the first time just to stack things in my favor a bit. I'm a little paranoid about ring gaps at present. Some of the recommended gaps for turbocharged engines seem pretty wide to me.

That is a good looking engine there with a nice rarely seen paint finish on it. I like it.
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Thanks for the compliment on the motor. Would that it looked that good many years later but with the hood vents, it gets dirty pretty quick.
A word about the bearings. Diesel Depot built it with a cast crank and used Clevite bearings throughout except on the compression side of #7. For whatever reason, they used a King bearing which flattened out and it killed the motor before 20K miles. So DD gets the blame for killing 635s motor, I get the blame for buying it and Bill gets big credit for resurrecting the whole thing to what it is.
 
I'm scratching my head here big time because while I have rebuilt many engines over the years I do not consider myself the "expert" that I would expect diesel depot to be. That being said I do know that bearings are held in by the crush factor, which is very much built on size. In short mixing and matching different bearing shells is a serious no no. Least in my book it is. I haven't heard of King brand before but even if I was desperate enough to use it, I would use both shells and not just one.
And that, ladies and gentlemen, is why I build my own engines. My dad taught me mechanics when I was very small but these days he has been known to buy a long block now and then and every single time he does he regrets it. You just don't know what is in an engine unless you build it yourself.
 
Husker6.5 said:
Go with gapless rings on your 6.5 rebuild and don't second guess the decision. Makes a world of difference on blowby contamination and compression.
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I agree. I suspect that is one reason why I have never really had starting problems with my 18:1 pistons. Just goes to show if you built it right there is very little drawback to using those pistons in an IDI engine. This engine I am building now will also have 3 coatings on each piston. The head side along with the precups will also have a coating. Hopefully some insulation will help slow down the heat sink that occurs when cold cranking. Together it should be a little more efficient.
 
Just a suggestion, but I'm not sure heat coating the precups is the best idea. Looking at the original design of the precups in the heads, the fact they get hot is part of the way that the IDI works. By design, once they get hot, they tend to hold heat pretty well, which has it's drawbacks yes, in the form of heat transfer to the head, but it also helps to vaporize a fair amount of the fuel that gets swirled with the air inside the pre-cup by contact from the fuel with the hot surface, thus creating a greater atomization without the need for a high pressure injection system. So will a coated pre-cup transfer less heat to the head and more to the piston to create better power, or does the trade off result in less overall power because of the lack of atomization? It's a balance act. But IMO, attempting to get more heat outside of the precup and onto the piston presents its own obstacle in the form of orfice size and angle. So it's a lot of guess work sometime. Just my opinion.
 
Hmm I am not sure I follow completely. It is long well known that heat energy lost to the head and the piston and cylinder wall is lost efficiency. Every IC engine is a giant heat pump. If that heat gets cooled off you lose power and efficiency.
The interesting thing about the precups is two fold. They get to hot as evidenced by the cracks that form. They heat sink fairly quickly once they get hot due to their own thermal expansion. Ideally you want them insulated and heatsinked at the same time. This would help keep their temps low while enhancing efficiency.
Keep in mind that the heat barrier gets very hot on the surface but protects the metals underneath from the high temps. This helps keep more heat in the cylinder which we all know turns the crank.
If you study the Stirling engine concept you can understand just how fast heat(and thus cylinder pressure) can be lost. The "stirling effect" is one of the main reasons crank speed is so important in starting a diesel.
Like buddy showed, crank speed compression may only be 400psi something but running pressure can be 2000psi. It is not all lost to blowby. A good share is lost to the "stirling effect". You can see the difference when you compare a direct injection diesel with a comparable IDI engine. The reason the direct injection engines can run at such low compression ratios (17:1) is the decreased surface area which decreases losses due to the "stirling effect".
The insulating effect of these coatings means the compressed air temperature will be a bit hotter. Unfortunately these coatings can only provide a relatively small insulating effect. The theory I am working under is that a little is better than nothing.
 
I have pulled many heads with 150,000 + miles that the precups never cracked. Ask yourself why they doubled the cost of making the head by using the inconel precups instead of something cheap or just cutting the port into the cast head.

If you want to insulate between the precup and the head, I am all for it. But the specific inconel that was chosen is not the cheapest one, infact it is one of the most expensive ones- why? Because they want the precups getting as hot as possible and retaining the heat as much as possible. That way it is not heat cycling up and down in temperature.

And yes, ignition in the precup is a big helper. If it didnt matter you could just open the port wide open and the bigger you make it letting fuel get through quicker, the more power you would have. But many here learned a little port goes a long way.
 
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