Guys, I am so discouraged with this ongoing problem.

Over the winter, in an effort to address what I thought was a exhaust manifold leak causing a loud engine, I took the exhaust manifolds off, gave them and the head surface a quick clean, installed Remflex manifold gaskets, brand new bolts torqued to Remflex specs, new exhaust donut gaskets. I wrote a whole thread about the process, documented the whole thing. See here, https://classicoldsmobile.com/forums...d-leak-181758/

Anyway, I still have this "chug a lug" engine noise under light and medium acceleration. I can't quite tell if I am still getting the noise under full throttle because it's almost like the full throttle wide open engine noise overwhelms everything and it just sounds like a badass engine at high RPM. Honestly, the engine sounds the best when I floor it.

If I have the car in the garage and manually rev the crap out of it, it just sounds nice. Idles softly and quietly, no strange engine noises, just that sweet V8 roar. However, put it in gear and accelerate from the driveway and I'll hear it right away. You don't have to push it to make it happen, just general normal acceleration and it appears right away. I was checking the total timing the other day and had it up to about 3600 RPM in Park......no abnormal noises, just a sweet roar. I got a length of hose out the other day and went fishing around for leaks and I didn't find anything obvious. The noise doesn't sound like detonation to me. It sounds like an exhaust leak that only appears under acceleration/load. I could be wrong about that, I am just not sure as I just don't have the experienced ear. I used to have a 1985 Pontiac Grand Prix with a 305 in it. I remember if I cheaped out and used regular fuel, that thing would ping on hills on the highway and I think I remember that sound pretty clear (that's 30 years ago now). This just doesn't remind me of that. Once I get the Toro up to speed and let off, the noise goes away but if I have to put my foot into it a touch going uphill to hold my speed the noise re-appears. I mean, that's certainly a scenario where one would think it's detonation but it's not that kind of rattle (at least, I don't think so).

With regards to timing, it occurred to me that it's possible it is detonation due to over advanced timing or something but I went though it all and I found no smoking gun here. Initial timing is at 8 degrees, total timing is hitting 19 degrees max at 3600 RPM and I've driven it with the vacuum advance disconnected and plugged and that made no difference. 19 total is definitely not right so that's something I need to sort out but it shouldn't be detonating at that setting. With the vacuum advance connected I'll see about 30 degrees of total advance. I checked the harmonic balancer for slippage and it seemed to be very close. I also checked for timing chain slackness and I found there was around 8 degrees of harmonic balancer movement backwards before I noticed the rotor move so there's definitely some slack in the chain but nothing massive.

I use 91 octane fuel with VP racing octane booster. That's the best I can get around here unfortunately. Still, with these numbers it shouldn't be detonating like a SOB anyway. The timing is very conservative, I use the best fuel available, not sure what else I can do!

 

You've spent so much time on timing, that suggests something else. I use 91 octane alcohol gas here in CA and it takes a good deal of effort to get these old cars to run without knocking on that.

Well done on the octane booster. One experiment to run is see if 2 bottles of booster make a difference. Our gas tanks by contemporary standards are cavernous. As I recall the 66 Toro tank is 24 gallons. That's at least double the size of modern car gas tanks.

It's not legal here in CA, but if you can still get Xylene and Toluene, they can be used as an octane booster too. I did that here and there. See the 'net for home-brew octane booster recipes. I not all that sorry those chemicals are no longer available here. They are so strong, they can't be good for people interested in living long lives.

Next up before getting deep into it, has the carb been cleaned and serviced in the past 4-5 years? If the exterior is crusty and nasty, it's reasonable to expect that no one has cleaned & serviced the interior either. I'm not talking about just blasting spray cleaner down into it, I'm talking about disassembling the airhorn, checking it for straightness (flatness); cleaning the main body including fuel wells; measuring the primary rod "T" holder to be sure it's exactly the same height for both primary rod holes; and being sure you have no vacuum leaks from the always-in-motion throttle plates - particularly the primary side...

With carbs, cleanliness is next to godliness since the metering depends on tiny _clean_ passages to work right.

If it's not timing and it's not carb, another thing to check is the left side exhaust valve if there is one. It was a spring loaded thingy on the driver's side exhaust manifold that always seems to seize up from heating/cooling cycles. I eventually just removed mine or confirmed they're cranked open. I can't recall which. After that, you're into the exhaust system. All kinds of fun stuff can wear out in mufflers and create weird sounds.

Finally, you don't have that AIR injection thing, do you? That pump has vanes which can wear out and make weird noises too.

Hope this helps. Sorry you have to chase the un-fun stuff.

Cheers
Chris

 

Thanks Chris,

I might be able to get my hands on some VP race fuel. Next time the tank runs fairly low, I'll see if I can get some and throw it in just to see if it affects the noise. I'm betting it won't though. Carb is in excellent shape, I had it rebuilt a couple of years ago and it seems to run extremely well. I made sure to have all the correct metering rods and jets installed.

The thought had occurred to me about the AIR pump. The only thing about that is the engine is smooth, quiet, etc when unloaded. I can rev it right up in park and I don't hear any weird noises from that pump. If it was the pump making these noises, wouldn't it always do it?

 

Here is a video from a couple of years ago when I was just starting to dig into this noise. You can hear the noises I'm referring to when I drop the RPMs down. Now, it's not nearly as loud since I replaced some of the exhaust gaskets but when you hear the engine RPM go right down, THAT is the noise. It's just really pronounced when you accelerate. The best way I can describe it is a "chug a lug puffing" sound. Kind of like a diesel tractor sort of thing. I dunno, hard to describe.

When the engine is idling now, I can't hear the noise at all. I've done a lot of work on this car since I made that video. Maybe I'll make another one.

 

I hear a tick. That's lifter or trunion slop.

KaThunk KaThunk KaThunk is a rod.

Tick tick tick is the exhaust or valve train.

 

All of those noises would get faster and maybe even louder when I rev the engine in neutral correct? I'm only getting the noise under load.

 

Looks like I can get VP C12 racing fuel locally. This is something like 110 octane leaded gas and it is NOT cheap! I'll gladly pay the extra $$ though just to definitively determine if this is a detonation issue or not.

 

Enjoy the racing fuel! Even if it's fleeting, it should be fun.

I'd be tempted to advance the he*ll out of the timing just to see what's up there...

 

Personally I think you are going the wrong direction. That engine should run just fine on 93 octane unleaded. If you put it in gear in the garage and hold the brake and up the throttle some what does it do ? It really is almost impossible to know what sound you are talking about in your video because the engine just sounds noisy to me in general.

Do you know anybody at a good modern repair shop ? If so they will almost certainly have a "smoke" machine for checking emission systems. Have them smoke the exhaust. It will find even the smallest exhaust leak.

Do you know any other car guys local that can listen to it for you and get a second opinion ?

 

With regards to heading in the wrong direction, I agree. I wish there was a sharp ear around here that could help me out.....I've yet to find one though.

Funny you mention the smoke machine.....I built one myself. I also built a handy little power supply out of an old computer to power it. See pictures. I'll try it next and see if I can find something.

I will try the brake/throttle thing too. That's a great idea. I'll try to record a video of the engine while I do it.

 

I'm bettin on a exhaust leak, still. Can you have someone inside brake torque car in reverse and you check w/ hose to ear under hood ??

 

Yeah I'll have to try something like that. I find it hard to trust people with a job like that, I'll have to chock the wheels too to be sure. Could be engine mounts flexing enough to open up exhaust leaks or something like that.

 

Made a couple quick videos while I had the chance this evening. In the first, and longest video, I could barely hear the noises I refer to. Maybe you can kinda hear it at 1:07. Even when I was hitting the throttle in gear with the brake on I couldn't really hear it. In the second quick video, I believe you can hear it better as it seems the noise is bouncing off the cars in the driveway and you can actually make it out.

 

I finally could hear the noise in the last video. No suggestions, clues or hints as to what it might be, but it's audible in the last video.

 

Start car, get it off the fast idle cam when still cold ish. Take a video. All angles, 30 seconds, just get the sounds. Remove all belts. Restart car and video for 30 sec. Shut down and reconnect. Compare videos.

Recommend stethoscope.

 

I think this whole thing is chasing a wild goose. I've listened to all your videos, and I can't hear anything but a nice-sounding engine. How much of a noise can it be if the only way you can hear it is to park it next to other cars and hear the echo as it bounces off those other cars? If it bounces off nearby cars, why doesn't it also bounce of the walls of your garage, which are much larger reflective surfaces than car fenders.

The human ear can be convinced to hear anything if the mind is convinced it is there. You're pulling your hair out trying to fix something that ain't broken.

Just drive the car and enjoy it.

 

It does sound really nice with no load on it. I think if you drove it though, you'd change your mind on that. I haven't been able to capture the noise properly but it is very audible when you're behind the wheel, particularly on hills. I'll do my best to try and capture it with another video.

 

Then my money is on an exhaust leak. Take it to a muffler shop and have them go over it from stem to stern.

I bought my '78 Toronado in 2017, and about a year or so later, after I had gotten it up and running after not being started in 13 years, I took it to a local shop that did some of its work on older cars, and they found that the right side exhaust manifold leaked where it attached to the engine. They removed the manifold and resurfaced the two mating surfaces. The car did run somewhat loudly before that, and this work quieted it down considerably. They told me that there was also a leak in one of the exhaust system seals and that I should take it a local muffler shop they recommended. I took it there, and they replaced that seal with no problems. The car sounded much better after all of this.

As I said, my money is on an exhaust leak. Probably not a very big one at that.

We don't need any more videos. You've already tried three times, and we haven't been able to hear it, which itself tells us something. Take it to Midas or somewhere and tell us what they say.

 

Turn the radio up! :-)

 

Ahh the soothing voice of reason. You guys always know just what to say to me.

 

As said, it could be valve train noise, the rocker arms do wear out. But it does sound like a minor exhaust leak. Get the timing fixed and enjoy!

 

Car engines will always sound a little different when driven under a load such as going up a hill than they sound when revved up in neutral or park. A small exhaust leak will be noticeable under engine loading.

I have a '66 Olds Toronado that sounds like your video's and there is nothing wrong with it. My "Toro" idles smoothly, doesn't ping, doesn't overheat, cruises at 75 MPH on the freeway just fine. I think you are trying to fix something that isn't broke.

 

I have a '66 Toro and the videos sound fine to me.