Valve - Piston Clearance Question
 

I'm realizing that I should do the valve / piston clearance check on my 2.7 rebuild that will use SC grind cams with 8.5 Alusil 'European S' pistons (so labeled by Zim's in 1999, when I bought them for a song.)

I'm thinking of attaching rods 1 and 4 to the crank, checking the deck height for 1 and 4, and from there mounting the four remaining cylinder barrels, bolt up cam towers, and check the clearance, maybe do a sigh of relief, and then tear it down and build it for real.

The question: after the tear down, I think I should re-clean the case, including the bearings. Can I reuse these nearly-new bearings, or should I install new.

John.

What are you inclined to resolve?
Stroke is the same, 2.7 or 3,0
Euro pistons are cut for actual S cams, cam timing being in excess of 5 mm
C-2 cams won't set any higher than 2.0mm with spec being 1.25.
You're not going to touch anything.
Bruce

1. These are CIS 'Euro S' Alusil piston/cylinders. Are we talking about the same thing?

2. The case has been machined so that it could be line bored, so it's not quite as wide as it was out of the box, so dimensions are different, and not in my favor.

3. I really want to know about how obsessive I should be about installing, removing, and then reinstalling the crankshaft and rod bearings.

I can see no reason why you would not use your bearings. If I read your post correctly they are new bearings, never been run, only test fitted?

Gordon: what I'm thinking is that the bearings deform (change shape) when pressed into their spots. Does removing and then reinstalling create an issue? I have no trouble imagining that it can, but is it enough to be an actual problem.

Look at it another way. When pro engine builders pre-assemble an engine to check clearances, by using a bore gauge & not plasti-gauge, they then disassemble it and build it back up again. They don't discard the bearings or use different bearings, or else they introduce a variable that would throw off their calculated clearances.

Bearings don't permanently deform. Yes, there is a "crush" that occurs but that is a known occurrence and the shape of the bearing accounts for that. The bearings also have some spring in them to assist in retaining the bearing in the bore halve.

Thanks, Kevin. One less thing to worry about :-)

John

You shouldn't have to tear apart the short block (rods torqued onto pistons, case torqued together, along with everything inside it) to adjust piston to valve clearance. You find you don't have enough, pull the cylinders and all that goes with/above them, and add thicker shims, etc. Same if you need to reduce clearance by some machine work on heads, or to chamfer, or whatnot.

When the case was line bored, didn't the machinist check to see if the tops of the spigots were all where they need to be?

The case was done by Competition Engineering, and yes, he went
over the spigots. I've got lots of bucks into this engine, and I don't
want to wreck it by overlooking something. In the Rebuilding the
911 Engine book, Wayne recommends to assemble the engine and
measure the head-valve clearance as the engine turns through
possible collision zones. Once satisfied that it's not going to grenade
I tear it down and seal it up. I don't mind the putzing around, but
if it's really not necessary... This seems to be overkill in my case as
I've got CIS pistons with a SC grind camshaft. But one never knows
what might happen ;-)

In the next few days, I'll build it up enough to check the deck height.
if I need thicker base gaskets, I'll get those, and then it's on to the
piston / valve clearance check...

Ya know, this thing might run by the end of Summer :-)

Ha! Deck Height with 0.25 shims is maybe .45, so I'm looking
at thicker shims. I have no idea about the history of this motor.
I found it on PP back in 2006, and paid lotsa bucks for it. The rods
and crank were good, the case had case savers, and from there
it went to h@ll, but Walt over at Competition Engineering brought
it back to spec.

Last week I was trying to fit my pistons into the cylinders, and was
having a lot of trouble with those pesky thin oil control rings. I found
an adjustable 'ring cone' make by Total Seal. Once adjusted, it's
the cat's meow, and it beats the stuffing out of the compression ring
pliers that I bought... Line it up, shove the piston in, and open a
diet pepsi ;-)

Anyway, it was really sweet to drop the crank into the case, tighten up
the case through bolts and turn the crank... smooth as glass. Maybe
in the next ten days I'll have the case finished.

The boring of the case, (shaving the halves) and touching up the spigots could be why your under on deck. Just a note too, when I had the heads they were surfaced off .030 but not marked, which is a bit over what is normal so check your valve to piston closely

Thanks for that bit of info, Craig. At this point, I'm going
to do it 'by the book.' I'll pay close attention to the piston
- valve clearance measurements.