My old engine block cracked on the outer bolts on the main webbing in at least 3 places.
New engine will be a 6.5L with 23.5:1 compression, cast high silicon pistons, forged rods and used cast Iron GM crank. Engines like this put out 330 to 350 ftlb of torque and 160 to 170 hp and hopefully I get around 25mpg on the highway like I did with the 6.2 in my suburban.
Not sure if it cracked because of 26 years of continous daily use or what. I am not sure how long it was cracked just found it when pulling the engine apart.
I am buying a new block with improved metalurgy and an improved casting for one.
What else can I do to make sure it doesn't crack?

 

REALLY? , 23.5:1 with a cast crank?

a 6.5L @23.5:1 with those numbers and 25mpg, im sorry but that makes no sense

i assume you mean like a dart little-m or something similar?

 

Pretty sure he's talking about a diesel engine

 

lol yup your right^ never even though of that cuz i was thinking gas motors and 6.5 L is about a 396 stroker or sbc 400

 

Are you planning to put this in your third gen???

 

i'd just look it over for any rough areas in the casting
that could cause "stess risers" and then smooth those
areas with a die grinder i think 6.5 diesel is '92 and
newer,so that probably has quite a few improvements
over the '82-91 version.
BTW the 5.7 car diesel can be converted into a real stout
,tough 350 olds gas engine,use heads off of a 403 as i
recall,82-87version is much improved over original 1978
-81 versions

 

This is one of the few places some one can ask a hard question and get a good answer so I figured it wouldn't hurt to ask.
The suburban is the support vehicle for my camaro, since the truck is down I can't do any thing to my car until I get the truck fixed.
Yes the engine is a 6.5L chevy diesel. The on road factory 6.5L engines run about 20.2:1 compression, my cracked 6.2L block ran 22.5:1 compression.
The engine I want to build will be a 6.5 and use slightly different "marine" pistons for a total compression of 23.5:1.
Also the now cracked 6.2L got over 25mpg burning straight diesel, with a TH700, 3.08 gears on 2wd in a 5800lb suburban. It got more like 21mpg when I first got it back in 2005, I have done a few mods to increase power and improve fuel economy, like building a ram air intake, putting a bigger side dump exhaust on and converting to electric fans.
The cast crank in the 6.2 and 6.5 engines have 2.400'' rod jornals, 2.95'' Mains and it weighs in at about 80lb. I am pretty sure that is larger than a genV BBC crank. Thats how the cast crank can take out rageous compression and boost, its just really big.
Under boost, usually the pistons or stock head gasket fail before the cast crank.

The new block was talking about will be something like the AM General blocks where they improved the casting and use Molybdenum insted of Nickel to harden the cast Iron.

"i'd just look it over for any rough areas in the casting
that could cause "stess risers" and then smooth those
areas with a die grinder"
Ok I did that to the heads a little, didn't think to do it to the under side of the block. I will be sure to check it out. when I get it.

I have read a little about using main studs insted of bolts to prevent main web cracking, but when you switch to studs down there I also read that its a good idea to have the bore reline honed since the block is loaded differently with the new hard ware.
Does anyone know anything about that?

I was reading about using blockcreate to prevent block cracking but I think that is more for applications where you have so much power its warping the block. I can only make about 190hp and 380tq at the most running N/A.
I don't think it would help me any?

 

are u using a turbo? your 6.2 didn't have one correct? The intake should bolt right over to the 6.5 but i would look for a turbo if i were u. Did u look into EGTs? Just keep an eye on temps can cause cracked heads, damaged pistons, etc....check out the link
http://bankspower.com/techarticles/s...T-is-Important

 

Nope no turbo.
I am going to stick with N/A for now. When It comes to diesels a non turbo mechanical controled 6.2L~6.5L diesel is about as simple as killing a snake with a shovel.
I have been running around with a "J-code" intake manifold from a non turbo 6.5L for the last year or so.
Ever since I redid the exhaust my EGTs have not been able to hit 1200'F. I had the EGT up to 1300'F a few times for a few seconds after I turned up the fuel rate adjustment screw on the injector pump.
After cleaning nearly a 1/4'' of sluge out of the intake ports, porting the heads, installing file fit rings, and adding .3L of displacement it might be time for another injector pump fuel rate adjustment.