85Hokie
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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
BX24 - Won't Start
- Thread starter Ngiovan
- Start date
It is not like we are trying to get down to a thou or two. 18 thou would be ok but 10 thou or less would not be. It is surprising how much a few thou changes CR and compression
The carbon build up is causing a lot of variance in readings. Intake sides are reading as low as .008 inches and exhaust as large as .024.
Thinking I should clean them up to get a bit more consistency. Any recommendations on cleaning the pistons?
Thinking I should clean them up to get a bit more consistency. Any recommendations on cleaning the pistons?
North Idaho Wolfman
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Roloc disk, putty knife, scraper blade, wire brush
Just looking at the pictures it does not look like any of the pistons stick up from the block at all.
If you're getting .008 protrusion on one side of the piston, you have bent rods.
No sense even cleaning them up, as any other measurement wouldn't matter.
Plan on a complete rebuild with new rods, pistons, rings, and possibly oversized ring and pistons depending on what a bore gauge tells you the cylinders are at.
Just looking at the pictures it does not look like any of the pistons stick up from the block at all.
If you're getting .008 protrusion on one side of the piston, you have bent rods.
No sense even cleaning them up, as any other measurement wouldn't matter.
Plan on a complete rebuild with new rods, pistons, rings, and possibly oversized ring and pistons depending on what a bore gauge tells you the cylinders are at.
In your pictures,showing the protrusion, is the head gasket still in place?
Bill
Bill
85Hokie
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I did not think it was ............ but looking BACK at the pictures ...........it DOES seem to be on the block still!!!
Pic is with the gasket on, measurements were after removing it. Keen eye!
I'd clean it up and re-measure. I don't see how you'd get accurate measurements with all that gunk.
I'm no expert, but the evidence points toward bent rods.
Cleaned things up a bit last night. Wire brush did great. As some of you mentioned, cleaning didn't change my "low-side" readings at all. I can now see that the low side is below the deck, which is concerning.
Indications continue to point to bent rods. I'll keep tearing down today and post updates.
A few lingering questions I have:
Indications continue to point to bent rods. I'll keep tearing down today and post updates.
A few lingering questions I have:
- Is it common for all of the rods to bend in the same manner to the same (approximate) degree? All of my readings have the exhaust side at about .015-.02 and the intake side is below the deck.
- With bent rods and what I'd call a cambered piston position, I would expect the rotating assembly to be a bit harder to turn by hand.
- Assuming it's a bend in the rods, is that enough to cause 0 compression in two of the cylinders?
- Should I plan to pull the valves as well? I was trying to keep that as intact as possible, or at least reduce the chaos on my workbench
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Pulled the engine today and got it on a stand. Looking at the connecting rods, there’s a different type of bolt head on them. Anyone know what these are called?
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GreensvilleJay
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Torx, and ETorx only have 6 lobes. That's probably 12 point. Just try a 12 point socket or wrench.
* All the rods bending the same seems unlikely to me, it sounds a bit more like warping from overheating?Cleaned things up a bit last night. Wire brush did great. As some of you mentioned, cleaning didn't change my "low-side" readings at all. I can now see that the low side is below the deck, which is concerning.
Indications continue to point to bent rods. I'll keep tearing down today and post updates.
A few lingering questions I have:
- Is it common for all of the rods to bend in the same manner to the same (approximate) degree? All of my readings have the exhaust side at about .015-.02 and the intake side is below the deck.
- With bent rods and what I'd call a cambered piston position, I would expect the rotating assembly to be a bit harder to turn by hand.
- Assuming it's a bend in the rods, is that enough to cause 0 compression in two of the cylinders?
- Should I plan to pull the valves as well? I was trying to keep that as intact as possible, or at least reduce the chaos on my workbench
* Bent rods won't necessarily make it any harder to turn, they can just reduce the stroke a bit
* Bent rods probably won't cause low compression, that's usually from bad rings or bad valves
* I'd figure out the block issues before I messed with the head any more, you have enough there to figure out first.
But I'm just a shadetree mechanic, and I usually don't work inside the short block, so don't take my advice as gospel.
North Idaho Wolfman
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Bent rods will 100% change the compression ratio, thus reducing compression dramatically.
The compression of these engines usually happens in the last few cm of the stroke rising from paltry single digit numbers to 100 of pounds rather quickly.