Bad lifters can range from a tapping noise (kind of like a sewing machine) to sounds that are almost a dead ringer for rod knock.
A couple of clues –
Rod knock is very consistent and lifter noise can vary quite a bit with revs and time.
Rod knock, unless it is incredibly bad, is covered up by cold oil and high pressure. If it is rod knock it will get a lot worse as the oil temp goes up.
Oil pressure will drop a lot as the temp goes up if it is rod knock, it won’t change if it is a collapsed lifter.
Since you have new rods and bearings I would find it hard to believe it is rod knock – much more likely to be a collapsed lifter due to a long period of in activity.
As long as the oil pressure keeps up above 15-20 psi you will not be doing any damage. Run it some more to get some more diagnostic info. Use a long screw driver as a stethoscope and see if you can locate the source of the noise.
As they say – “Don’t Panic”

 

You can always do the old screwdriver listening technique or get a mechanics stethoscope(edit - that's what happens when you get taken away from your desk while typing - good one Chris LOL!!). You may have a bad one, it does happen. It might be worth pulling the cam tower to check them and test them. I have some spares, in oil, but I'm 13 days from being home but would be happy to loan you some good ones if you find a bad one.

Were the lifters in oil while you built the engine? Did you do the air test with them - hit the hole on the side and if they stayed hard on the button they're good?

I'd drain the oil, rig up through some cheese cloth, to see if I have any type of metal in there - an aquarium fish net with cheese cloth works well and keeps you clean -simple but effective; if not metal or sorts, this might offer some piece of mind.

 

If you haven't used your lifters for a long time, they can be very loud quite a long time. I ran to this once with the lifters which were unused over a year. It took over 20 minutes to have a normal sound.

 

Lifters are brand new Porsche lifters I had in oil before installing in the engine, and were rock hard before installing. However, the assembled engine has sat for a while, so that part of the equation fits descriptions of a collapsed lifter. I expected lifter "pump up" would take a while, but I was expecting a "tapping," not a "knocking" sound. I was not about to boldly ignore "knocking" for a prolonged period of time. I couldn't figure a reason for rod knock to develop given new bearings, assembly lube, and plenty of oil pressure, but doubt kicks in quickly and hard. So, I should allow the engine to continue running, so long as oil pressure is good and steady, and monitor? I have a set of spare rebuilt lifters from Markus Blaszak.

 

You didn't lube both sides of the rod bearing did you?

 

Alex,

Don't turn the engine over anymore! You are probably damaging the engine severly with every turn!

My offer of $100.00 for the car, as is, still stands. I would just take the money and be done with it.

Your friend,
Constantine

 

how about a little better description of the sound?
Does it change with RPM (louder or not)
Frequency? (at idle the engine is turning about 13 revs per second - a rod knock will occur at TDC and BDC but a lifter occurs only once every other revolution) so a really fried bearing will knock at 2x engine speed and a lifter will knock at ½ engine speed.
Here’s the realist view – if it is rod knock you are going to take the engine apart anyway – the crank is tough enough that you won’t damage it unless the oil pressure goes to 0. If it is lifter noise then no damage will occur (unless you run it to high RPM and hold it there). So – running it will not cause any additional significant damage….

 

Tarheel - No, fortunately my stupidity is limited.
Constantine - I'll take the car equivalent which is about two 928s!
Chris & others - Good points, I will give it a go later if I get a chance. Also, thanks for talking me off the ledge!

 

ive had a couple motors out- not even to rebuild them- just out for awhile and then when we started them back up they clicked/knocked for awhile. I knew they had to be a lifter and let the car get up to temp and gave it a couple of good revs and they pumped up and the tick went away. IM not saying this is your problem but could be- sometimes the lifters just refuse to pump up w/o a good surge of oil pressure to the top end.

 

Well guys, I gave it another try and things didn't get better. The car hasn't really been idling well, and engine revved up a little high, and knocking evolved into a sharper more metallic sound, like something gave, and the engine quit. Anyway, I'm going out of town for a few days. When I get back I'll do some exploratory surgery. Hopefully its up top. I'll report back. Thanks again.

 

Hopefully it will all work out for you. I feel your pain, my wife also HATES my 951, some just don't get it. But I do have to admit it, sometimes I hate it too.

 

Uhg. Our projects are so similar, I really feel for you. I'm very hopeful for you that it turns out to be nothing major. Fingers crossed.

 

Yeah me too, with a 3.0L project gathering speed in my garage. Best of luck.

 

Man that sucks. All that work over time. Just to break on first start up. Hope the best of luck.

 

Really sorry, if you want some help wrenching let me know.