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Tahoe Motor Is Blown Up

Your .005" fall right in the middle of what we got here for specs, .004" to .006" on the rears. Maybe with the block-fill the cylinders deformed a bit down low (at concrete) or the fill retains heat more. Either way, think that a bore would be a good precaution, and go on the high side of clearances.... we only filled 3" (bottom of water-pump holes), but after seeing the galling that you got, we might be obligated to bore too.

Still am very impressed that neither the crank nor the block let go (we have not broke either yet), being that those two are what many of the horror stories are about....
 
Well I pulled the pan on my low compression 6.2 that has seen over 60 psi boost . Two of the rods are bent,the rest are still dead center on piston pin. I just think the rods should have lasted longer in the 6.5,and lowering the compression from 22.6 to 17.68 didn't help at all.
 
6.2 turbo said:
Well I pulled the pan on my low compression 6.2 that has seen over 60 psi boost . Two of the rods are bent,the rest are still dead center on piston pin. I just think the rods should have lasted longer in the 6.5,and lowering the compression from 22.6 to 17.68 didn't help at all.
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how do the bores look? did you check it to see which bearings are turned? IMO, that motor(6.2l) deserves another kick at the can...LOL
do you think the galling on the 6.5l was from the type of cement that you used( to much expansion with the heating cycles)? or because the spec was a bit to tight? or because the cement is retaining the heat more maybe.......
 
I will pull the 6.2 and check it out some more. I'm not sure about the concrete,it might only work in combination with water injection to keep the cyl wall temp down. I have two 6.2's the one in my 92 and a military one, both are 660 blocks. I'm leaning towards putting a 6.2 in the Tahoe. I still think a 6.2 will handle more cyl psi ,because the piston is smaller.
 
6.2 turbo said:
I will pull the 6.2 and check it out some more. I'm not sure about the concrete,it might only work in combination with water injection to keep the cyl wall temp down. I have two 6.2's the one in my 92 and a military one, both are 660 blocks. I'm leaning towards putting a 6.2 in the Tahoe. I still think a 6.2 will handle more cyl psi ,because the piston is smaller.
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yeah, the thicker cyl. walls wont hurt, thats for sure.....
 
And at some point determine how much boost is necessary. The fueling might drive a turbo to 60psi, but that doesnt mean it needed it. Perhaps an adjustable wastegate and dyno runs to see if there is increase in HP from 30psi, 40psi, 50psi, ect.... If you had a known fuel mass, could calculate the necessary boost to get the right air for fuel ratio. Maybe thats the next spread sheet I will make, just not this week.

More boost means more work and heat to compress it and expel it, so you never want too much. Why you dont want a lot for fuel economy when just cruising, dont need the engine doing more work compressing unnecessary boost. And at the high end of performance, you lose a lot of horsepower from having to do that work compressing extra boost and expelling higher backpressure.
 
I dropped my pump off today to get the cc's and timing checked. What is the normal max cc's of a DB2831 pump? MM3 and cc's are the same thing.
 
We are not sure to have seen anyone else do this and post up the #'s. One of the reasons we will do it too. I will look after, somewhere in all the papers here, we have the fuel and hp #'s that were on the rad support with the DB2831-4911 in the early 6.5L turbo trucks (we took this info off of all different trucks at the scrap yard). Maybe one of the members here can check his truck and post them up. This would give a baseline of what the pump originally was delivering. The "Moose pumps" (Oilburners), have flow #'s listed with them, but when we requested a little more info, none was forthcoming. Also, I am not 100% sure of my flow calculations with different plunger sizes, but his claims seemed to be pretty high for the dyno'd power his pumps are delivering. More than likely it is just me with my feeble out-dated math skills....LOL.

Really need to thank you for doing this, it is a good step forward. Buddy, had mentioned doing another spread-sheet with fuel/hp relationship......we all need the #'s to be able to plan and design better.
 
to convert cubic millimeters (mm^3) to cubic centimeters (cm^3) just divide by 1000 so 100mm^3 is 0.1CC. However, a lot of times people will give CC per 1000 events. So 100CC from some people's perspective is 100mm^3 per injection event.

I can calculate the BTU in an available volume of fuel at a given RPM, and convert that to HP. But knowing all of the losses from accessories drag, the fan clutch, metal friction, ect.. is kind of difficult.

But an important factor is fuel mass to air mass, when enough boost is enough. Knowing fuel volume and approximate temp, we can calculate how much air mass is needed. From that some calculation of boost based on air temp can be made to get the A/F ratio desired, like stoichiometry at max fuel output.
 
Went to Labrosse today, (our preferred scrap yard) and Jeff got the #'s off the valve cover of a 1992 6.5L TD......190 hp @ 59.5mm^2 @ 3500rpm. This will give an idea, of how much more your pump is flowing than the stock calibration.
 
turbonator said:
stoichiometry......now that is a word I need to look up in my dictionary:eek:
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I guess about 18:1 has been tested to be the best at peak performance, whereas actual stoichiometry is around 15:1 like a gasser. Its probably better being a little "lean" compared to stoichiomtery just to ensure the fuel is all combusted and potentially quicker.
 
I calculated the compression on my 6.2 it's 15.97-1. The cyl's are also a bit scarred. I talked to Peninsular today,their biggest pump is calibrated for 90 cc's.
 
Well I finaly called Bill. He was very surprised that I was bending rods,Peninsular was not surprised, they have seen it before. I beleive the only reason Bill can get away with high HP is beacause it is at much higher rpm. I was able to make over 40 psi boost at 2500 rpms,great for torque but bends the rods. I took the heads off of my Military 6.2 ,I might use that motor,and save the concreted block for something else. My low compression 6.2 needs pretty much machine work. I would patch the 6.5 back together,but I suspect the concrete causing heat problem.
 
I have used "Hard blok" many times, my build now is getting it also.....BUT YOU MUST TORK THE MAIN CAPS AND AS SOON AS YOU FILL ONE SIDE YOU MUST TORK A HEAD ON IT RIGHT THEN. Also machining after it cures for 3-4 weeks, if you don't you WILL get what you had happen, I know this from my own mistakes. My block is going to cure for at least 4 weeks, longer if the temp outside isn't warm. If you do one side at a time and let it sit for a week and then do the other side and let everything cure for a month, then rebore it and go from there it will be just fine. The cement will move the bottom end enough to warp the cly and cause trouble.

I have a almost new set of std 6.5 pistons that came out of my GEP motor that I am going to clean up and have for sale with pics soon, I can also ceramic coat & poly coat the sleeves if you need a nearly new set of 6.5 pistons. They will be for sale as is or coated, it will be a week or two before they will be in the sale section.

Chris
 
I know that it should have been bored afterwards. I'm more worried about very high cyl wall temp. This could mess with cyl psi,timing,and I also was gettig alot of carbon on the heads and piston. It was fuel carbon ,not oil.
 
My current 4974 is making 125cc of fuel on the '82 @3000. around 100cc @ 4100, Pump currently runs 100cc all the way to 5600 RPM (yeah, I'm f'ed if I break something in the drivetrain right now and the engine get's to do the "high idle").

I guess I'm getting away with murder on my 6.5 with concerns to rods. The engine has been beaten for 5 year with no bottom end failures. Maybe it's because of the Piston Oil Spray cooling, mine's a 1997 block. Cylinder to bore clearance was set at .004" 1-6 and .0045" 7&8. Of all the times I've had the head off no scoring whatsoever, no cylinder ridge either. Standard bore with shaved GM Pistons.

Your cylinder galling suggests the rods are being pulled off the pistons. Suggest finding a piston oil spray block, and at least a girdle in it.

6.2 vs 6.5 in regard to killing rods. Well, if you're galling cylinders, the 6.5 has more surface area on the bore size in which to grab the cylinder walls. The piston crown design is also dramatically different between the 6.2 and the 6.5. I think more heat consumes the piston in the 6.5 than the 6.2 due to ring position.

The boost numbers you're getting are awesome. I've been swaping turbos to try and get more boost because my ceiling is 35psi and still smoking (still have fuel to burn) right at the 1250 degree limit on a 1/2 mile run. 145 degree intake temp. S362 and S366 (the 66 made 35).

Thinking Twins right now... Like a S357 over S366.

That pro 52 you got seems to do the job though. Making me less-impressed with my Borg Warners.
 
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