Loud tapping from my newish supra, help please!

[dorachagi]

Hello all, this is my first post to the site. I acquired an 88 supra turbo about 2 months ago for $1000, spent another $1500 or so getting the engine running, new clutch, nice tires, etc. Ran great since, then a few days ago coming home the engine started making grinding noises a few blocks from my house and I noticed the oil pressure had fallen to about zero. After I got home (only drove it for about one more minute after the noise started) I check the oil and it's bone dry! Now, this is certainly my fault as I havent checked the oil in a few weeks, but my car doesn't smoke and never has any oil drips, I always check for puddles, so I don't understand how it could have been completely empty. Refilled the oil with good synthetic and almost all of the noise went away immediately, but there is now a pretty loud tapping coming from the head that seems to come on a bit over 2000 rpm, it increases speed with the engine, but it only seems to tap when the throttle is open (as soon as I let off the noise stops even when the revs are still up). There does not seem to be any power loss or hesitation, just the noise, and it's holding the oil fine now.
So I guess I have two questions:
1. Did the car really just consume that much oil that quickly? Does anyone else's supra do this too?
2. (The Important Question) What should I do about this tapping? Will it cause the engine more damage to run with it? Do I need a mechanic to look at it? Is it probably the valves?
Any suggestions would be greatly appreciated.

 

[Intothenight19]

A valve adjustment may be needed, my Supra sounds like it has a slight tap to it. Just my 2cents.

 

[oscolivar1]

well if it is more of a ticking/tapping then you prolly just have to adjust the valves.

if u think its a rod knock it more of a loud clunk. Think about something hitting the block repetitivley.

 

[loki2043]

if it was ran dry im 99.9% sure its rodknock... BUT it could also be the valves like the others say, try checking your exhaust mani to see if its loose, if it is you will hear the tapping from the valves

 

[89_turborunner]

When you say you checked the oil and it was "bone dry". do you mean no oil regisered on the dipstick, or there was no oil in the pan?

 

[3p141592654]

You can test for rod knock. Pull the sparkplug wires one by one. If it stops knocking, you've found your bad rod. If it doesn't stop, then go by a lottery ticket quick!

 

[dorachagi]

Thanks for the help all.
By no oil I meant that the dipstick was dry, I didn't take off the pan.
Now it's changed, for the better I think. Today was the first day I've let it run for a bit since it happened, just to warm up and get the oil around some more, and just a minute ago I went to check pulling the plugs off to see if it was rod knock and almost all of the tapping is gone. There is still a fast rattle tap sound, but nowhere near as loud and only very briefly when I really push the throttle hard, where as before even if I just feathered it up past 2000rpm it was very loud tapping. Is it possible some of the hydraulic lifters just ran out of oil and now enough has recirculated for them to come back to life?
So, what would you do from here? Get the valves adjusted? I figure it can't be rod knock or anything in the bottom end because the sound wouldn't have gone away. And would you drive the car like it is now or will it cause more damage to it?

 

[3p141592654]

The 7M valve train is inverted buckets and shims. No hydraulic lifters to bleed down on a 7M.

 

[Nick M]

Here is some more for you. You indicated it sounded like the tapping was on top.

Valve lash does not sound like engine knock from too much clearance. And the engine bearings are not the only place where clearance is needed to be checked. The cam journals that the inernet community thinks is normal to be scored have a clearance spec too. If you run low on oil, you will score the cam journal before the engine bearing.

That could be the noise.