Block do's and dont's

[Robyn]

After having been through a real nightmare with the 6.5 Block that I bought for DaHoooley there comes to mind some very real points to consider.

With so many of the 6.2 blocks at 25 years old or older and the 6.5 blocks as much as 18 years old now there are several things to consider aftger you have gotten your NEW prize home to work on.

For sure, there are a lot of shops out there that will do a reman in some very odd and often unscrupulous ways.

Cylinder boring is a common thing and is to be considered a normal part of refurbishing an engine block.

Some of these engines will even see the mainline remachined.

This is no biggy either.

I will not go into depth on the mainline cracks here as we have beaten that to death elswhere for many years.


The focus of this thread is the Block DECKS.

These engines, as they near the 200K mark or sooner in some cases will have errosion around the two front cylinders where the gaskets fire ring sits.

This is due to coolant sitting right up to the stainless steel fire ring.
Along with the two dissimilar metals the electrolysis process starts and eventually the block will develop a small groove where the ring sat.

Now in and of itself, this is not a big deal. The block is set up and machined to give a fresh new surface.

Here is where the problems start.

Bubba's Garage and machine scalps off .014" off of one side and .009" off the other and does not bother to stamp the upper rail as to this fact.

Ten years later after you drag this hunk of Iron home (Happy as a clam) is when the trouble starts.

A bare block tells few stories at a glance.

Its also not impossible to have a block with one side STD and one thats been cut. (ask me how I know this)

Here is the important point.

As soon as you find a good block to drag home. If you have to pay much, get it in writing that the thing will be CRACK FREE and also that the decks will be usable or at least STD height.

Next thing, right after you get the new little beastie all scrubbed up and clean, get it upside down and drop in a set of old bearings and a crank.

Next, stuff in two piston/rod assemblies (dont need rings just bearings) and turn these suckers to TDC and check where the top of the piston is in relationship to the deck.

The piston should (if the deck is stock) come to right at flush to no more than a couple thou. out of the hole.

If the decks have been cut you will soon know it.

Now just because a deck has been cut before is not a death sentence as long as the surface is good.

Let say that one side is cut .010" and the surface is good with no errosion then just install the thicker Felpro gasket.

If, lets say the other side is at STD and needs to be cut, just have that side machined and your off to the rodeo.

NOW
Let say that one side has been cut and the surface is nasty, at this time you can save yourself a BUTTLOAD of $$$$$ and a bigger pile of embaracement by getting the thing all ready to build, then finding this out.

ASK ME HOW I KNOW THIS

There is the possibilities of doing special pistons with heigher pin centers or cut tops and then reballance and OH $Hit frank more $$$$$$$

Before you pour a lot of $$$$ at a potential engine be sure and check this out.

The main line crack things is certainly repairable and I have done many of these with success.

The deck issue is one situation to avoid at all costs.

Now if you find a block with this issue and you want to build you plans around special pistons and or other tricks, have at it, just be aware that this issue is lurking out there and may strike at any time.

The stock of good usuable 6.5/6.2 Blocks is dwindling every day at a fairly fast rate due to normal attrition.

These engines are not like the little mouse motors that GM made a Bazzzzzzillion of.

One thing for sure, I myself would certainly not be afraid to use a new block from one of the online sellers instead of spending a buttload of $$$$$ trying to revive a questionable old 6.5 block thats been hacked, chopped and otherwise mollested over the last 20+ years.

I understand that the HUMMER is being phased out by the military and so if this happens, the likelyhood that the P400 and the optimizer 6500 will also soon go away.

The whole reason for these engines was to supply a reliable engine for the HMMWV.

The 6.5 will likely be around for some time BUTTTTTTTTT I suspect that the sources for parts are going to eventually fall back to used stuff and the aftermarket.

In closing

Just be sure of what you have before you spend a dime on machining and such.

I have a lovely little YELLOW block sitting in the corner now with over $800 tied up in it thats not going to give back what I poured into it.

Even the engine rebuilder suppliers dont check this stuff so you are going to be the only thing between success and failure here.

Good luck

Missy