need diagnosis help with engine noise
 

I have no experience in diagnosing noises, so I hope someone can figure this out. From inside the car it sounds like halfway between a flutter and a rattle. The video I took with my phone with the window open makes it sound a lot more like a rattle but that's not as bad as it sounds in real life. The sound does not happen at idle or cruise, but only on acceleration. At first I thought it might be an exhaust leak, and then I started to get worried about a valvetrain problem or worse detonation. Like I said, I really don't know the difference between those sounds so I'm at a loss. Anyway, here's the video - please let me know what you think.

Sorry - having problems uploading the video.

What engine and heads do you have? What is the compression?

First thing, check your flywheel/converter bolts.

Did the noise start on its own, or after you did some work on the car?

It's a TKO so there are no converter bolts. Dumb question, but is it typical for the same issue to happen with the pressure plate and/or flywheel bolts? I'd have to drop the trans to retighten all of these obviously which is a pain to do in the driveway.

The noise started on its own. I have done lots of things to the car, but the only engine related things have been timing and carb tuning, and an intake swap so I'm not sure I caused the noise. Anything is possible though, I do have a tendency to fix one thing and mess up another. :(

The engine is the original 350 with a PPR stroker kit, KRE heads, I think the compression is around 10-10.5:1. I'm going out there again to try to get a video of the noise.

Got the video to work. Please give it a listen and let me know what you think it might be. Thanks.

http://www.youtube.com/watch?v=kFQ41...ature=youtu.be

Almost sounds like a rocker arm or lifter related to me.
Or maybe even exhaust leak?

Forgot to mention, I started out this spring by getting a similar problem in my car...it ended up being a blown head gasket between cylinders 4 and 6. Didnt lose any coolant it was just between the cylinders. I even posted a topic that is eerily similarly titles to yours:

http://forums.maxperformanceinc.com/...d.php?t=695593

interesting, I'll have to do a compression check.

OK, I'm now wondering if a different issue is related or not. Starting out of nowhere just last week, I am having very violent bucking when I hit the accelerator in any gear. If I'm very smooth and light it is fine, but if I step on it it really has problems. Idles fine and revs up in neutral fine, it only happens under load. If there is indeed a head gasket issue like 428GTO70 found, would these things all be related? I can live with the minor noise, but this bucking and jerking is really bad.

Hmm not sure what that could be, but I guess you could start with the suggestions I got in my thread. check plugs wires cap rotor and advance weights/springs under the cap. Could jump straight to a compression check while you have the plugs out. Hopefully yours is an easy fix. Bucking could possibly be fuel related i suppose also.

Eric, it could be the the coil cutting out under acceleration. Had that problem with my coil for the points distributor. Switched to HEI and problem solved.

sounds like a lean condition or detonation What is the timing set at? back it off a bit to see if the noise stops

Yeah, you know I was having ignition issues recently. I had to change out a bad MSD box last month. I also changed out the coil, rotor, and cap while I was at it since the contacts all looked a little burned. It's an HEI from Ace at PPR. It's a Chinese no name piece, but Ace says that they have been reliable and he uses lots of them. The only other things I could change are the plug wires and the plugs. Might be worth a try since they're relatively cheap.

It seems like the 2 problems are probably unrelated. I want to fix the bucking and jerking first as it makes driving really irritating and probably isn't doing the driveline any favors either. The fluttering/tapping/whatever sound will be next. I will back the tining down a little to see if it goes away though. It's at about 14 right now, maybe that's too much. The distributor is supposed to have 21 mechanical. Take that plus the vacuum advance and maybe it's just too far, I don't know. Should I back off the vacuum advance first? I would think that 35 total is just fine isn't it?

l have a 541 that likes 35 to 36 but more thanthat its on the edge. i have another 455 in the Judge (iron heads) that is content at 31 to 32 degrees......what are the engines temps when the noise is occuring?

i also noticed you are running a hyd roller. What distributer gear do you have on your combo?.....also how much vacuum are you making? maybe your holly system is not getting a good reading and its affecting the AFR readings causing the system to go lean?

Just more crap to check

OK, I fixed the bucking issue. Turns out that when I put in the new 6AL box, I ran the green/purple wires with the others to the HEI. They have to be separated according to MSD because of EMI. Moved them apart 4-5 inches and all is well again.

Still having the other noise. I'm thinking it's either a header leak or rocker arms need to be relashed/adjusted. I'll post back on that when I get under the hood again.

Revisiting this again. I took the vacuum advance hose off of the carb and plugged the port. Drove it to dinner, about 20 minutes. I did not get the noise anymore which was good, but the idle dropped about 500 rpm and the water temp went up 15-20 degrees. Would someone tell me what this means?

Sound's like the vac can is giving it too much advance and its pinging badly? I would limit it down to arount 10-14 degrees, so you end up around 40-44 total

Damn! I snipped a razor blade to size and super glued it to the vacuum advance according to advice on threads here so that the upturned arm can only travel 1/8" under vacuum. I was hoping this would get rid of my noise, but it didn't. I guess it was still a good idea, but back to the drawing board for me on this noise. I'm starting to wonder if it's not just some random metallic rattle or vibration. Whatever it is, it's driving me nuts. Anyone have any other ideas? I've got a dial back light on order that also measures RPM, so I'm going to write down all the specs of the mechanical advance curve and post them. Maybe that will mean something.

As an aside, while in the distributor I noticed that the button had melted itself into the cap. Tons of reading here explained it to me, but it seems there are strong disagreements as to how to solve it. I'm also ordering the low resistance button from MSD and a new cap. If that one melts, it's on to an external coil.

Your exhaust system might be toast in the muffler baffle area(rusted out,banging around in there,popping),..how old are those mufflers?..They can restrict power and clog up everything including your brain!!

very good thought, thanks. Unfortunately they're brand new Magnaflows. The sound seems like it's coming from right in front of me, driver's side engine bay. Of course, since my ears on on that side, and my driver's side window is open, I can't say for sure that's really where it is coming from.

The exhaust actually sounds awesome if anyone is thinking about Magnaflows.

OK seriously, I'm going to light my car on fire. On the way home tonight I was hearing a faint ticking sound, so I popped the hood and one of the 2 rearmost plug wires on the HEI is arcing off the firewall. It's not loose, I pushed down on it. It's actually arcing right through the boot itself. That big dumb HEI is so tight up against the firewall you can barely even get your fingers in there. WTF do I do now? This is not only annoying, but I would think rather dangerous as well. I am seriously about through with these damn HEIs, it's been one problem after another with melting buttons, loose connections, screwed up advance canisters, etc.

Can someone help me with the arcing issue? If I can solve that and the tuner gets me in good shape this weekend, maybe I'll be OK with keeping the damn thing.

Small body HEI? Were the plug wires damaged in any way to cause this? Once they start arcing they will never stop.

What's the gap on the plugs? Didn't see that mentioned...

no, a regular HEI (they're freaking huge). I haven't pulled the plugs yet to check them. It's running the internal coil with an MSD 6AL box. Maybe the boot is cut or something, I don't know.

I think he may have been suggesting you to use a small body hei to gain firewall clearance. If you are arcing I would definitely check the wires out. Is it possible that you have bad wires and thats what was causing the issues before(burned button) etc? Im no expert but its an idea. How old are the wires? check that plug wire for a split boot at least.

Ahh I see. I've thought about a small body, and I may end up going that way. I think the arcing was from a small split in the rubber boot. It was my fault as usual - That particular plug would not "snap" down on the terminal like it should and it was always loose. I tried to pinch it with some pliers and likely tore the boot a bit.
With that said, I am pretty sure it wasn't causing the issues with the melted button. This arcing just started, it was very audible which is why I found it. The melting cap was happening prior to this. I have come to the conclusion that when using a CD box with an HEI, you MUST use the low resistance button, and even then some guys still melt. It has been suggested by someone here that you should move the coil outside tyhe cap with a modified dust cover, which I looked at. But at that point, why not just buy a Pro billet anyway - I mean you're already going to an box, coil, and dizzy setup anyway, plus you gain the firewall clearance.

Oh, and a new set of wires is on the way. For now, I've swapped that particular wire to a different spot so it isn't up against the firewall or anything else it could arc to.

I had a noise close to this. Fan was hitting bottom of the shroud. I didn't notice it until I looked real close,because it only happened while driving down the road. It's worth a look. Good luck. < Mike >

Thanks. I wouldn't be surprised at all if the noise is something totally unrelated to the engine and I'm just paranoid. One thought I had was that it's something under the dash that rattles/vibrates. The mystery continues. :)