Okay here is piece 1 of my 18:1 build, a set of 18:1 pistons from Diesel Direct, the pistons started life as stock 21:1 with shaved tops and reat treated and re-ceramic coated.

This will be a long process don't expect frequent postings until I start the actual build, I'm collecting parts now for the build. I'll add photos as I go with this thing.

I've got a lead on a crate military surplus 6.2 block I think I'll start with depending what they mean by crate; new in the crate block or a crated block with a bunch of other 6.2 parts. I'll be following this post http://www.dieselplace.com/forum/showthread.php?t=33614 for suggestions as I build mine also.

Make note of this, knkreb........

Make note of this, knkreb........
Teach me, oh great diesel one. . .

how much must be shaved off the top of the stock pistons to achieve 18:1..

thanks
brian

The answers are in individual posts for Boring, or 18:1 rebuild, or Too much Boost, so as not to hijak this one any further..........

Turbine Doc - feel free to eradicate this.

.050" iirc

I'll be watching this thread closely, TD. After I finished the Gear Drive Install this morning, I pulled the oil pan off to begin Girdle Install.

Main Web 3 & 4...Cracked. I'm gonna 'Girdle It' for the time being though.

Now I'm looking for a Block & Pistons.

TD - Why make pistons your first purchase?

Now you are locked into a 'Bore Size'.

Jumped the gun on a ebay purchase, now kicking myself for the decision, thought I was going to start with a fresh AM Gen short block, have recently done some digging and found "new & improved" AM Gen blocks aren't without it's own trail of tears of broken dreams (blocks).

This set may reappear on ebay, I tried to cancel the order but vendor says they could not cancel order as the shave down from 21:1 to 18:1 already occurred and only needed ceramic coat to finish the order and ship, so now I have a set of stock size 18:1's I'm having second thoughts on.

Are these Broken Dreams steering you away from this block?

What would be the preferred block then?

Is there a definate date(julian) as to when they were cast by Navistar?

The Project Truck has over a hunnerd thou on 18:1's - they used a regular block w\balanced crank...........................

I spent considerable time last nite with one who wishes to remain anon on this info, but someone with LOTS of been there done that, says old standby 599 block series avoid oil sprays unless that is what you have on hand, or even go with a 6.2 block with 6.5 heads, try to get one with front of block oil port to feed turbo oil, or tee into rear of block to feed oil to turbo, he does not like 18:1 unless you are adding lot of air & fuel (which I'll be doing) even then he has mixed feelings.

Thinks block cracks are more of a heat distribution rather than design weakness in block, 220 at front of engine & 280 at back of engine sets you up for thermal distress, which results in cracking more than hitting it hard. I'll be dropping my pan shortly just to see if I have a problem, if not I'll add 18:1 to this one if bores will match pistons, and probably try one of the rear of engine flow kits.

More homework to do still, as I said earlier I'm not rushing I only want to do this once, my GM block warranty is out by time, but I still have time on my 10 yr and 250 miles left on my 100K extended warranty I bought the truck in 2000.

There seems to be a great deal of controversy on "The Page" as to whether or not this temp equalization thing is a good idea. I read about first in a Hummer site, so I know it is a theory that is out there. I know Heath has a kit; would this fit the bill?

I would think that tapping the rear like the Heath kit does will at least balance the temp in the motor. I don't see how it won't work like many think. I also trust Heath as a vendor and doubt he is only in it for the money although I hope he is making it.

I don't see a negitive side either BUT I am still looking and reading about this idea.
Now back to subject TD was you thinking bout changing them out in your motor or still looking for a "new" stock block. You mention using a 6.2 block, wouldn't that give you the chance to match bore the block to your new pistons?

Too much meat to bore the 6.2 block maybe, 6.2 vs 6.5 dislp 300 cc I think I mite be able to make up the difference in displacement for block strength, yes the Heath balance flow kit is probably on the horizon for me (I think Spindrift got the one I was eyeballing, "way to go Spin;) ", he needed it more N me besides we shared a beer over it when I was working a job in Philly & I'm all better).

I'm still musing it over which way to go. If my stock block is sound, I just might use it as well, with some bottom end strengthening. If it has made 100K without coming apart I think it might hold some more. Since Diesel is a lubricant as well as a fuel, I expect to see minimal cylinder wear and maybe the stock 18:1s will be the ticket.

In the 5 years I have had it it has never been in overheat territory, I started with mods from day 1 that I owned it. gauges and exhaust were step 1, the truck was in mint condition when I bought it with 36K miles on it in 2000, no mud or dirt any where under the truck it never left the highway I believe I may have been 1st one to ever take it off pavement. Will maybe pull pan this weekend and see what I can see.

TD,

One other thing to keep in mind, select fit of pistons to bore is great for an engine that needs to last a long long time, but it takes a long time to brake in a tight engine to where you can poor the fuel to it and make some power. If your cylinders are in good shape, a clean up hone will just make the engine a little more broke in and should add in your quest for power. Check with penninsular diesel and see what they say about durability with the 18:1's as far as cracked blocks go. There are a lot of other engines out there that run a lot hotter in the rear than the front, including the cummins 6bt. My personal opinion is that the design of the 6.5 is what leads to main web cracks. Most cracks start at the point where the bore under cuts the main web, and the under cut is only on one side. The 6.5 bore under cuts more than a 6.2 does and hence another reason that 6.5's crack blocks more than 6.2's. Another factor could be that at the bottom of the bore, there is no radius in the machining, just a sharp 90 degree cut, in the world of machining, this is a no-no, sharp edges lead to cracks. A nice radius at the bottom of the bore, might be hard to do, but would certainly help. Good luck, I think you will be fine.:grd: