My '85 MGM, "Maisa"

[Arquemann]

You have tried the long metal object or a auto stethoscope to isolate this?

Kinda louder from up top, all along the length really. No definite location.

[jaywish]

So you tried an auto stethoscope and it could not be isolated?

[Arquemann]

So you tried an auto stethoscope and it could not be isolated?

Used a tire iron, couldn't isolate it with that. Putting it on a head is louder than the intake, but the heads are quieter than the block. Front to back basically no difference, maybe a bit quieter all the way back.
Laying underneath the engine seems quieter than having my head close by up top.

[sly]

Sounds cam related by sound intensity... lifters are right there. Seems to point to the current theory.

[Arquemann]

Inspection passed, just one complaint; frame VIN is almost illegible. Shouldn't be much work to make it a bit better to see.
Inspector wasn't particularly fond of the noises my engine makes either, joked about an unapproved change of fuel type.

Yesterday I took off the driver side valve cover after running for a while, rockers were all tight, so nothing obvious wrong. Though the rockers were quite uniform in angle, I guess the rockers under spring pressure bleed down pretty fast.

Since the rattle doesn't seem to be going anywhere, I think I'll get the TV cable adjusted properly, tune the carb a bit and get some more miles on the engine. Then change the oil, back to 10W30 see what it does.

[friskyfrankie]

Curious to see what the change in viscosity does too. Doesn't sound like a gas/octane issue - too bad as that would be an easy fix!

[Arquemann]

AOD: adjusted
Belts: tight
AC: cold
Weather: hot
Inspection: valid
Rattle: yes
Car: filthy

I think it's time for the first cruise night with her.

30°C weather plus me romping on it for probably 20 minutes straight, oil pressure was down to about 40-45 psi at low idle, even with 20W50. Though that'll probably be as hot as it'll ever get.
I have a feeling the reman dizzy isn't doing timing things very nicely, I'll have to check and verify the vacuum & mechanical advance soon.

[Arquemann]

First run didn't go quite as well as I'd have hoped.
It idles low and lean now for some reason, more now than earlier today. Had to two-foot it most of the way out of town on the way home. Highway afr is fine, though it feels oddly sluggish at those speeds.
Definitely will have to check the operation of the distributor advance mechanisms. And check for vacuum leaks, if none found I'll re-set the idle mixtures.

[sly]

+1 check the distributor advance and make sure it's not locked in the advanced position (or just flopping straight out).

I like carbs for the easy adjustments, but I dislike them for general troubleshooting. I don't miss dealing with them until I have computer failures and a screwdriver would be able to "get me home" with a carb. I think you're on the right track though.

[Arquemann]

Carb nuts were a bit loose but it didn't seem to affect the idle afr. No leaks found anywhere else either.
The low and lean idle is probably a combo of having it adjusted a bit leaner than before and without the AC draw on the engine. 2 idle screws are now in sync properly and are both about 2,25 turns out. Idle steadies out around 14 afr in park w/o AC and about 15 in gear with ac on. Might end up richening it more if it doesn't like to play nice cold and it still might idle smoother when richer.

Other part of the idle was also the timing, initial was around 8-10°, now it's about 15°. More than it should probably, but here's why:
Popped off the vacuum advance and verified function with a vacuum pump. All in by 15 inHg of vacuum. That all in is barely 10° of vacuum advance. No wonder it felt sluggish at highway speeds, I had barely 20° of timing when cruising.

Mechanical advance is shit, I can move the distributor rotor back and forth and it's springy and moves freely, but as high as I dare to freerev the engine, I can't see any mechanical advance come in. Revving the engine the timing advance moves a couple degrees back from the initial and stays there. So the advance is there somewhere, but wants stupid high rpm. How unsurprising.

Now the engine idles smoother and better, it'll probably cruise a bit nicer with +5° of total advance. Dunno what to do with the distributor, only things it has going for it is the steel gear and it being a Motorcraft body. Replacement gears are dummy expensive.

Rattle is still alive and well.

[Arquemann]

Had a fella from our car club come over before cruise night today, we've been talking about the rattle for a while.
Of course my engine didn't get all the way hot while he was here, but he said that its just normal noise and quiet enough to not worry. "Dunworryboutit" kinda thing. He fired up the full roller 427 in his '34 Tudor and said the valvetrain was spot on in it too. Fuck me the noise that valvetrain made; it'd make me lose my shit.
His friend happened to be at the cruise night who happens to be a long time foxbody guy and he wanted to listen in too. He confidently said that the rattle is just roller lifter noise and pretty much every fox has it too, and complimented how smooth my engine runs (I don't really think it runs particularly smooth). Apparently roller small blocks have thick cast valve covers for a reason.

Dunno, I guess the rattle gets easily drowned out by other noise, but idling a hot engine in the driveway in a quiet suburb it just gets in my head. The lopo setup was such a sewing machine, bar the misfires.

Seems the most common answer to hearing the rattle live has been the "dunworryboutit", so guess I'll just try to do that...
But I can aim my worry at the distributor now. Though I know what's wrong and what I can do about it so, eh. That extra timing I put in it earlier today made quite a noticeable improvement, almost feels peppy!

[sly]

Yeah... these engines are not quiet. I do think yours is a little louder than most, but I don't think it sounds wrong. Reminds me of the 88 I had. I put 50-60K miles on that car and the noise never changed, just the amount of oil leaked.

[gadget73]

Sort out the distributor, that should make it happy. About 10 degrees vac seems reasonable but if you aren't getting any noticeable mechanical advance by 2000 rpm the springs are very wrong. That should probably be full in by 3500 rpm or so and very noticeably advanced by 2000. Have to play with a balance of advance limiting and advance curve.