I am taking apart a 454 that I got to rebuild. The casting reads "1006?286" (the ? is a raised blob of metal and not actually a question mark) and on the other side it's stamped GM 74, I believe.

The previous owner bought it from NYC, it was being used as a propane generator. He rebuilt the motor and changed the top end. Detonation cracked a piston and damaged the cylinder wall.

It's currently .032"-.033" over (my guess is it was bored directly to .030" and then it was honed afterwards). Upon closer inspection, every cylinder has been sleeved. It's a 4 bolt main, 2 piece rear main.


Would anybody know anything about this block? I read a few people had the same block and couldn't find any information on it (I assume it's originally a crate motor). It's a GM block, why would it be sleeved in all 8 cylinders? It just doesn't make any sense to me...

 

10068286

It's listed as a 90-91 Mark IV block but 91 was the first year of the Gen V block which has a 1 piece rear main. That would make it a 1990 engine since it has a 2 piece rear main. Last year of the Mark IV blocks and aftermarket parts are plentiful.

The block may have been bored out to the maximum and it was probably cheaper to just sleeve all 8 cylinders than to find another block.

If the cylinder wall is cracked, have it sleeved. If the damage isn't that bad then just pick up some new pistons and punch it out .060" over.

 

The cylinder wall isn't exactly damaged from the piston blowing apart, cylinders 1,3,5,7 all have some oxidation and cylinder one actually has some lightly pitted rust. The local shop told me it could be honed out but when I told him it was already .032-.033" over he said it would need to be bored then.

Thanks very much for the information though, I planned on going .060 but wanted to know some answers first. I read something about it being a 91 crate motor but then right afterwards I read about them changing two a one piece main in that year so I figured some fool just took a guess at the casting.

Last two concerns:
- They can bore a block that has been sleeved?
- Does sleeving make it stronger or weaker? (I figured they might have sleeved it because of something to do with how propane detonates?)

 

The key to sleeving is having it done properly. There's plenty of engines out there that get sleeves as part of a performance application.

 

Nothing wrong with sleeving a block. My block has 2 sleeves after throwing a rod and damaging the bottoms of 2 cylinders.

Sleeves are very thick. A good machine shop will bore the block out for a sleeve and leave a lip on the bottom. A frozen sleeve is then dropped into the bore and allowed to warm up. The interference fit is so tight that it will never come out. The top of the sleeve is then milled off flush to the deck surface.

Sleeving is common with the LS blocks. The factory walls are not thin enough for a good overbore. When the block is bored for the sleeve, it actually cuts right into the water jacket. The new sleeve gives a thicker wall for a safer overbore plus there's less wall distortion.

My Dart block has very thick cylinder walls. I can bore it out .100" over and still have .250" walls. Although a production BBC "could" be bored .100" over, it's more common to go .060 or .070. The walls start getting a little thin with more overbore. You could sleeve all 8 and do a .120" overbore.

 

Thank you very much Alky. It's truely very appreciated cause not even my "go to gear head" can answer the things you do and shops always just BS me.

 

Whilr perfectly "possible" and "acceptable" to sleeve even one hole in a block, let alone ALL of them, it usually costs more to do that, than to just go to the junkyard and pick up another one.

Evaluate the costs CAREFULLY before jumping on sleeving.

 

yes and no.

If a block has already had a lot of work done to it such as bored, line honed, decked etc, the cost of a sleeve or 2 is cheap. Picking up another used block means all that machine work needs to be redone. Since the Mark IV blocks stopped production in 1990, junkyard replacements are getting harder to find.

For me, I have a $3000 aftermarket block. It's cheaper to resleeve all 8 holes than to buy a new block.

 

The block is already sleeved in all 8 cylinders. I was just asking why in the world somebody would waste money doing that.

 

I got another question... I was talking to my neighbor and he has rebuilt many motors and brought up an idea. since the way I see it I probably have to bore it anyway, we are going to just hone it for now and let the rings compensate for the difference in the bore while we take measurements ... I'll need new pistons anyway since the one has the broken skirt but I'll also be measuring the gap in the rings and see if I can get oversized rings or rings with a greater tolerance to compensate for the difference in bore.

sound like a logical plan?

Also I am hearing two sides to this (like I said I have never touched a bottom end), my rod bearings are wearing evenly and smoothly but they are at the point were the metal is a different color. Do I buy new bearings only or if I buy new bearings do I need to get a new crank (or machined)?

 

Depends what pistons are currently in it and how much clearance there currently is. Cast, hypereutectic and forged all require different piston to wall clearances. If you hone it out, you may be able to get .001 or .002 oversized rings but if the wall gap is too great, the piston will be considered sloppy in the hole.

Forged pistons require the greatest gap as they expand the most. An engine with forged piston is noisy when it's cold until the pistons expand.

 

Alright, I knew certain kinds of pistons and rings had greater tolerances and expansion rates but this might be able to work out to my benefit... and if not I'll be back at square one anyway.