Keep cyl/valve in wrong position or correct?
 

I'm in the tear down phase of a 2.7 rebuild (needs casesavers and probably valve guides although I haven't got far enough to figure out if that has been done before or not).
Anyway, the motor has been poorly rebuilt in the past. PO claims no knowledge of it. All the cylinders and valve assemblies were marked with position numbers, but for some reason whoever put the block together last time paid no attention to the numbers they stamped on. Example: in position 1 I have a cyl marked 3 and vavle assembly marked 5. :confused: I'm waiting on the cam tools so don't know if the pistons are marked yet or not. But on the low quality of the rebuild I've seen so far, I'm not counting on anything once inside.

Cylinders are stamped Mahle, so I'm assuming Nikasil, and since the engine ran well aside from oil leaks and loose studs, my plan is to just re-ring the pistons and reuse both the pistons and cylinders.

So someday when I get to put the puzzle back together, should I keep them in the random order they are in now, or put them back in the original factory order (assuming the stamps are correct)? Or does it even really matter at this point?

Its important to keep the right piston with the right cylinder and the right rocker on the right cam lobes. At this point you will probably need to have everything measured and do the best part matching possible by size.

For the purpose of keeping the heads, cam carriers and cylinders properly clamped down you will need to pay careful atention to the cylinder and head height measurements since at this point you can not assume that any of this was correctly done at the last rebuild.

350HP930,
Thanks,
For my clarification though, when you reference "the cylinder and head height measurements" are you refering to deck height and valve to piston clearances or something additional?

Pat

The head height I am referring to is the distance between the head-cylinder sealing surface and the cam carrier mounting surface.

To properly seat, seal and stress the heights of the cylinders (from deck to case sealing surface) and the head height need to be the same on each bank, and if not special thickness cylinder base gaskets need to be used to match the heights.

If not the cylinder, head and cam carrier stresses will be abnormal and heads, cylinders and case sealing surfaces wont clamp properly.

If its bad enough damage to the camshaft and carrier can also occur.

If you are going with unknown piston and camshaft changes you will also need to be check the valve clearance (the kind between the piston, head and valve).

When rebuilding, the cylinder heads do not need to be matched to a particular cylinder location. It's common to mark them so you can observe wear patterns and match them up once they are cleaned up. Just about the only thing that needs to be consistent is that you need to keep track of your rockers if you are not regrinding your cams. Check out the section in the Engine Rebuild book for more info on this topic...

-Wayne

Thanks Wayne, Read the book more or less cover to cover twice and am refering to it often. But you didn't have a section on what to do when morons get in there before you and start messing things up.
:D