Packard Forum Index » General

hi there i have a question can the engine cylinder block can pistons be replaced with out removing the sump,which means fitting the pistons from the bottom of the the cylinder,i have rebuid one of these engines before and it was a pain dropping the pistons from the top. the engine in question is a spare but the valves are seized i bit and the block is rusty.i want to remove the block strip and clean replaced the valves and rings.it looks like it can be done but looks tricky may be the are special tools which i dont know about,any advice is greatly apriciated Dave

I can't give you a definitive answer but the factory procedure was pistons out from the top, connecting rods out from the bottom (because the big end of the rod is larger than the bore), and the reverse to reinstall. I guess if you want to install pistons from the bottom you might be able to but getting a ring compressor in there won't be fun, if even possible; obviously the crankshaft has to be removed. But since the head must already be off the cut the ridge and hone, why not do it the obvious way?

Doing it the factory way is a bit of a chore to fit the piston pins. You heat the pins in hot water (160? IIRC), have a friend push the rod up from below, and then fit the hot pin into the piston and rod. Not fun with all the head studs in the way.

I made a pilot using an old wrist pin with .001 turned off it and chamfered one end.

Then I put a long wire through the small end so I could pull the rod up for assembly. Feed the wire through the piston, followed by the pilot, followed by the pin from the opposite side. This took a lot of pain out of the process.

I also made up sleeves out of heavy tape to prevent the crank from being nicked by the process and used plastic tubes on any rod bolt threads.

If you want to be really fancy you can turn out a drift that will slide through the pin and pilot to hold the assembly in perfect alignment. How about that?

If the motor was out of the car I stood the thing upright on a piece of wood and worked horizontal at bench height.

The bottom of the cylinders should have a relief to allow the rod to be brought higher. If the block has been sleeved those reliefs have to be restored otherwise you will have problems.

Big end bearings larger than the bore is common in diesel engines so you might find a video demonstration somewhere.

thanks for your advises they must have had some tool I reckon to take the pain out of the job, i remember trying to fit from the bottom before it started to work then the block wobbled about so I then gave up and did it the hard way.it would make the job so much easier if you could slip the block off fit a new set of pistons slip and new one on.
i was shown a set of piston ring clamps the other day which where able to wrap around the pistons and then clamped with ratchet plyers once the piston is fitted it can be unwrapped and slid out i may have a go do some swearing give up and do it the hard way i will see what happerns and let you know cheers dave

You have the option of separating the bores from the crankcase (leaving the crankcase in the chassis if it's already there), fitting the pistons and rods to the block, and lowering the fitted assembly to the crankcase and connecting the big ends of the rods. I've seen it done that way but not done it myself in that manner.

If you don't like the Eight you'll hate the V-12.

I wouldn't try the pre-assembled block method without eight ring compressors. The eight standard ring compressors from Lisle will hold the rods high enough to avoid interference. Without the crankcase in the way it's a little faster, but the rod bolts should be removed and sometimes they aren't very cooperative. So I always played it safe used the standard method.

After some thought, I think the piston and rod assemblies will go in from the bottom with the block on the bench. But you still need eight ring compressors to hold the rods up.
Packard sold reconditioned long blocks so this must have been the way they built those motors.