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The manual doesn't specify the orientation of the pistons, it's a poor manual by today's standards... The T was on the passenger side and currently, I have only pulled #2. The piston is unmarked. I will crawl back under the car and check the rest of the T orientations tonight, but I am almost positive they are all slotted and all on the passenger side. I am planning on pulling some of the off center rods and checking the piston's wear patterns and wrist pins this weekend. The engine has a front and rear main plus a main between every piston. It spaces off the rear main with babbitt on both the front and back faces of that bearing. I checked the end play of the crank by pushing on the flywheel with both feet as hard as I could (braced against the seat) and measuring between the front facing babbitt and cheek on the crank, it's about .004" or .005". I could borrow a mag base dial indicator and check it that way if you think it would make a difference. I checked the side play of the rod bearings on the throws, they are all around .0025" to .004" by feeler gauge.

Scott

Just to be sure, try to get an authoritive answer or documentation on which side of the block that the T slot is supposed to go to. Mite consult other makes or later Packard manuals on this.

In all engines i've seen with T slot pistons the T slot is suppossed to be OPPOSITE the thrust side of the block. i.e should face the LEFT side (drivers side) of the block. The T slot is not an oiling slot as many people think. The T slot is an expansion joint and is the weak part of the piston. Not likely, but it is possible to run into solid skirted replacement pistons.

Look at the T slots to be sure they are not cracked. They usualy crack from the bottom of the piston skirt up to the hole at the bottom of the leg of the T slot. This crack can be difficult to see sometimes unless u grab the piston with your thumbs inside of each side of the piston and try to spread the skirt apart.

Hopefully someone has a manual or other reasonable documentation that will verify the T slot orientation or that will refute my claim.

Also compare the T slots to see if there are any obvious size and shape differences. I'm just curious if there are different T slots within the engine.

I believe that all Packard in-line Eights were 9 main bearing engines until the advent of the "120". Also in rebuilding you might want to take note that Packard had a change of heart about the positioning of the connecting rod bleed hole, this is covered in the 33/34 Service Letters. To paraphrase, "prior to the 9th series motors the connecting rod oil bleed holes were on the "leading" or oil filter side of the engine; starting with the 9th series they face the valve-side and subsequently the size of the bleed hole was reduced in size from a #30 to a #56 drill size for better oil control. However the rods shouldn't be switched in the earlier (than 9th series) motors because the bleed holes will not align with the crankshaft at the proper timing."

Just a note on pistons, the originals were "autothermic strut" design which have entirely different expansion characteristics than cast or forged pistons. When using replacement pistons, the original Packard piston skirt clearance specifications should be ignored and those of the new piston make used. Cast or forged pistons also require different clearances. Expansion slot on the valve side of the engine is the general rule for L-head engines.

Check Plymouth flatheads ca 1946. I think u will find that the cam is on the right side and the spec is to place the t slot to the left. Ditto for the T slot for Studebaker and Willys flatheads of the 40's and 50's. BUT DOUBLE CHECK my claim on those MAKES. I believe the T slot toward rite side also holds for the 30's - 50's inline OHV's of other makes.

One other thing to look for is any wrist pin offset of the piston pin bosses. THere mite not be any and then again there mite be. I've ran into both on the same engine depending on manufaturer of piston. The offset can be as little .010 inch and as much as 1/10 inch or none at all. That would help to determine the direction of the piston. You can NOT depend on the supplier of the piston to know wheather or not there is offset. U have to measure for it yourself.

Sorry, I'm not at all familiar with the Willys, Studebaker and Chrsyler engines and was thinking Packard pretty exclusively, though I didn't say so. Sorry 'bout that. But let me quote again an excerpt for the 33/34 Service Letters:

"Up to and including the Eighth Series motors this slot was on the left hand side, that is to say, on the same side as the oil filler. In the Ninth Series and in all later series the slot faces the valves. Either the early or late motors will operate satisfactorily with the slot on either side but we believe the present construction with the slot facing the valves will probably give a little quieter result and a little longer life. Either installation however might be used when fitting new pistons in the earlier blocks, and there is nothing incorrect in installing all pistons with the slot facing the valves."

Page 849 of Motors Auto Repair Manual of 1956.

Piston and rod assembly 1946 - 54 Packard and Clipper engines:

" WHen correctly assembled the oil spray hole and the slot in the piston should be on the cam shaft side".

So Owen was correct.

However i will comment that this is a POOR design if it places the T slot to the rite side of the engine.

Owen, thanks for the clarification in your last post about the T-slot. I didn't pick up on that in the earlier post about the oil bleed hole.

Quote: Like mine were

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It's not clear to me what i am looking at. They appear to be simply slotted pistons. NOT T-slotted. They are cracked into the oil ring groove???

I had a few of them cracked like that. I am not sure if these are original or not.

For the T-Slot good question? What do they consider it to be then?