Cylinder bore measurements

JackFish

JackFish

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The first row is longitudinal, the second is across the bore.

--------top-middle-bottom

1-----3.682 3.681 3.684
-------3.687 3.677 3.687

2-----3.683 3.674 3.678
-------3.682 3.680 3.679

3-----3.682 3.679 3.679
-------3.682 3.679 3.679

4-----3.681 3.679 3.679
-------3.683 3.678 3.679

5-----3.679 3.677 3.679
-------3.683 3.679 3.677

6-----3.680 3.677 3.679
-------3.677 3.676 3.680

Do these measurements seem reasonable?
I haven't mic'ed a block before, so I guess accuracy is relative to experience and feel.
It is also a cold block with temps around freezing here.
So I need to decide if this block can just be honed and put back together.
The compression was very good before disassembly @ 166, 170, 174, 174 164 160.
I would like to spend as little as possible on this at the moment, so I'm hoping to use the old rings and pistons.
Whaddya think?
I want to have the machinist just hot tank, deck for flatness, hone, install cam bearings and cam.
I would like to reinstall the rotating assembly, if it can be reused without machine work.
 
Jackfish, on one there is a .005" difference.
If you can afford to do it right bore it.
If you do decide to just hone it make sure you use plain cast rings so they will conform to the out of round bores.
Make sure you hone it with at least a 320 grit flex ball hone.
Get a second opinion from your machinist.
I like perfection, but let your wallet be your guide.
However if you do bore it and install new pistons, use plasma-moly rings but hone with a 500+ grit. With plasma moly you want a very slick bore for proper ring seal. Bill
 
Thanks for your input.
I reamed the ridges today and finished the teardown:

Tomorrow it goes to the shop and they'll check everything.
I just don't want to buy new pistons. :(
 
8) those bore number are pretty good actually. a clean up bore would come in at .020 at most. it depends on what you are doing with this engine as to whether to bore it now or not. if you are looking at doing a cheap rebuild, then leave the bores alone, dont even hone them. i would however use a set of new moly faced rings as they will seat nicely on a glass smooth cylinder wall, and fresh set of bearings. use what ever cam you are planning to use, and run the engine for another 50k or so miles before considering boring the block.
 
Bore taper is not the only thing you need to measure if you plan putting used pistons back into those worn cylinders, you should also measure piston to bore clearances and see how out of spec those might be.

Basically, the more taper you have in a cylinder that you reuse without boring, the more rapidly you will cause ring fatigue with your new rings. This is because as the piston moves up and down in the bore, the rings must expand and contract to match the changing bore size. This movement quickly fatigues rings and ACCELERATES wear on the ring lands and cylinder bores (which are already worn with re-used pistons and non-bored cylinders). Ring fatigue is when the rings lose their ability to spring back and no longer effectively seal the bores. So while you may get 100K+ miles of good ring seal on an engine that was bored, you may only get 50K or less on tapered cylinders (this is also affected by compression ratio, piston to bore clearance, ring type and engine use).

Ford recommends a maximum taper of 0.005 without boring, most engine builders I have talked to say you should never go over 0.010, and even at that will not guarantee engine life or ring break-in over 0.005.

And even though moly rings are extremely easy to get to seat, I would still recommend at least honing the cylinders enough to remove the glaze. Honing marks not only help seat the rings, they also help reduce cylinder wear by cylinder wall oil retention/lubrication. If you use any other type of ring than moly, consider honing a minimum requirement.

Good luck! Let us know what you decide and how it works out.
 
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