vt324

Newly rebuilt 324 with about 100 miles on it. Now when I start it the valve train rattles and the lifters have to pump back up then it smooths out like normal. Is there a check valve in the pump that has failed letting the oil drain back into the pan??

coldwar

You failed to mention the interval in operation when noisy lifters at start up is happening, few minutes, hour, week, month?

Let's assume lifter condition and pre-load considering thickness of head gasket is at spec since the valve train does quiet down once oil pressure builds. Lifter bleed down aside from all else was a problem since new, hence the bleed down test for clean lifters using the bench tool for this purpose.

Also assuming oil pressure is nominal, say 40+psi cold indicating general bearing clearances.

Would have helped to know what type, brand and viscosity oil you chose, and what oil filter is installed.

Also assuming the camshaft has broken in properly if new, and all lifters are rotating in operation.

This being said most of the time your condition will find the source of fast bleed down of all or most lifters being excessive rear main bearing clearance, even if bearing is new. A single or couple noisy lifters might merit close checking of all parts associated with that valve train, and perhaps faulty check valve in the single lifter. Noisy lifters at cold start up is pretty common with early Oldsmobile.

vt324

Ah, let me fill in the blanks. I was rushing this morning to get to an engagement.
The engine is a fresh rebuild and has been solid since the initial break in. The 100 miles are just short runs around town as we were working on other issues with the transmission, rear gearing and steering. Have never had any issues with lifter noise until this week when I started the engine to move the car. Running VR1 15w40 and the stock filter with a Wix element. Oil pressure has always been right around 60 on start up and a bit lower after warm up but nothing that would be of concern IMHO.
Lifters are small block Chevy with custom length pushrods as recommended by the machine shop who has rebuilt several Olds engines. Engine is a 54 bored to 371 specs with 371 pistons and a set of number 10 heads with all new guides, valves and adjustable rockers.
The rattle I am experiencing goes away quickly, probably within 5 to 10 seconds. Perhaps I am just being an alarmist here, but it seemed odd that it would just begin doing this so quickly after it has been running fine during these short runs. I am dropping the oil pan to repair a rear seal leak which has been the only thing that has been aggravating with this build. On my 2nd Best replacement but this time around I am going back to a rope seal. While the pan and rear main is off, I will check the clearance of that rear main to see if it is in spec.
Thanks for the input

Tedd Thompson

When you had the rebuild done were the cam and lifters replaced or at least examined? Were SBC lifters used as replacement for stock lifters, that was a common swap in the past as they were cheap and common to get. Noisy lifter rattle on start up was also a common result. And if mine I would do an oil change with a high zinc oil and see if that might help, doubtful if that is your problem because they do quiet down after time, but that did help on a 394 that I once had that had sticky lifter issues after a rebuild...Tedd

vt324

Thanks for the reply, Tedd. The engine was completely overhauled with all new parts including a cam from Ross Racing in Ohio. I have used high zinc oil and a small amount of zinc additive for additional .insurance. Currently running with Valvoline VR1 15w40 which is what we have used before and after breakin. This may be just one of two lifters that are causing the rattle. I have to look into this further when time permits.

Tedd Thompson

Years ago with your same results, I tried the SBC lifters as Oldsmobile lifters were at that time over $14 dollars a peace and hard to find and I think the Chevy lifters were somewhere around $2.50 each. They are nearly the same but not exactly. Both are 921 diameter, but are ( I think) 8 thousand shorter and the valve is not in the same location. Sorry to say I pulled it down and replaced the lifters before any damage or wear on the cam. Before you give up you might flush your engine real well and change your oil to a high detergent diesel oil like Rotella t 6 that will sometimes free up sticky lifters. I wouldn't think 8 thousands would not require new push rods but I may be wrong on this, its been a while and my memory isn't what it uses to be...Tedd