Finally past treading water, tough year. So...

Have a 425 motor pulled apart 22 years ago. Oiled and bagged in garage. The last rebuild 22 years ago had not more than 10 miles. We were young and did not know of bank angle. We swapped out the motor for a 455.

I purchased and it's been sitting ever since. Checking the motor and it's all factory with original timing chain, sprockets, pistons, heads rebuilt and standard bore.

Reading the manual, I noted that the block and pistons were stamped. Sure enough, block has 1357 stamped c, dd, dd, none and 2468 stamped c, l, cc and dd.

Pistons stamped 1357- c, c, dd, dd and 2468 stamped dd, l, c and c.

This was really exciting as all were in spec and bores had little use, no marks and only one had some noted pitting.

Will refresh, but I believe the last rebuild only did gaskets, heads, springs, lifters re-ring and cam. The bearings are standard.

It ran like crap under 2 k but over it pulled. Another truth of wrong cam.

Now going to rebuild And have a question, should I rematch the pistons to the original place as the factory did? I stamped all main caps and pistons to place as removed. Should I worry about changing pistons only or the rod with pistons or leave be?

The one that threw me for a loop was "l" (L) as it was .010 over size both piston and bore and were correctly matched.

So long story short, since the last rebuild may have 10 miles should I worry about placing pistons back to factory placement as it is oblivious the last rebuild did not know this.

Also noteworthy, the oil pressure popped fram, ac delco and other oil filters, I mean popped the metal, expanded. We finally used an oversized K&N filter which contained the pressure.

Something was wrong and all of us figured it was a bad build and replaced with the 455.

Would piston clearances do this ? The bearings, all show very little wear as well as bores, heck they still have cross hatch and are not glazed. I'm a novice and think perhaps oil pump or clogg. Visually, all galleys look fine, cam, main and lifters as well as bearings matched holes. Will find out if oil pump was issue or clearances. Have not checked crank yet and wil update.

Going to rebuild with and for my 13 year old, all stock with afreshen up.

Thoughts?

Want torque so 232 / 245 ish with 110 and lift to match.

Will update with pics. It's got v markings on pistons and virtually no dish.

Pretty happy finding the stampings. Are these usually found when building an Olds motor?

Nice to be back, Dave.

 

You have to start over. Balance everything. Mike everything and fit the pistons to the best bore. Zero deck it and mill the intake face on the heads. When you measure lifter preload you might have to shim the pedestals. Your engine was built with a lot of precision and attention to detail. Reassemble it with the same attention. Those marks are not unusual.

 

you should indeed keep the parts where the factory put them.

Pistons and bores were ABCD for std bore variations, and I think KLMN or JKLM for 0.010 variants. So, you cannot use the L piston in any other bore, and vice versa. Double letters were also used, as you point out. Maybe you can add photos, esp. of the uncommon "L" stamps?

if the rings were replaced, you likely do NOT have 0.010 oversize rings in the L bore. Live with that, get 0.010 over rings for it, or re-bore to thirty over or so.

If you blew the filter apart, either the filter was bad or the relief valve is stuck/ installed backwards. If the RV is working properly, your oil pressure will never exceed its setting. When it does, the excess oil is returned to the oil pump inlet, and pressure stops building.