Help me diagnose engine noise, Ford 2.3 Turbo

[Too Fordy]

Hello! I have a 1973 240z with an 88 turbocoupe 2.3 and T5 tranny.

- The engine has been making a rattle I'm having a hard time diagnosing. It seems to only occur around 2-3k rpm and is not present at idle. I've recorded some good audio so you guys can tell me what you think. Any input is appreciated. Thanks!

Video link: https://www.youtube.com/watch?v=5fIA...ature=youtu.be

[Barry Donovan]

transiton of vac to boost or something..
peculiar sound, like a diesel valves.

[Too Fordy]

Is sounds very much like its coming from the top end, like right under the valve cover. Is it something to be concerned about?

[DanStokes]

Hey 2:40 - welcome!

Here's where I make my usual suggestion for these kind of issues. You need to find a shop with a dyno with a PAU (power absorbtion unit) like a Mustang, SuperFlo or similar. Most DynoJets are inertia only and don't apply much or any load during a cruise. Anyhow, chuck the car up on the dyno, load it a bit, and then you can get out your stethoscope and pinpoint the exact area of the noise. If you're pretty sure it's under the valve cover it would be a good idea to score a VC from PnP and cut the top out before heading to the dyno so you can swap it out and listen/observe the likely problem area. You can do this on the road - if you don't mind driving with the hood up and can run fast enough for long enough (not finding a sarcasm smilie).

Seriously, folks tend to forget about the dyno as a diagnostic tool and only think of it to measure results. This is exactly the type of situation where the dyno is your friend. I have a local shop that is very reasonable for this type of testing as long as I have everything ready so he isn't wasting time waiting for me to get my act together - of course, time = money for him.

Good luck!

Dan