Next up was fixing the chewed up gear in my speedometer. @mepstein came to the rescue yet again by donating a core to extract a replacement gear from.

Click to view attachment

Here's the old gear with the divot out of the side cause by me accidentally gluing the odometer gear shaft to the housing in the last odometer repair.

Click to view attachment

And here is the replacement gear in place.

Click to view attachment

The speedometer is nice and smooth again. No more bouncing needle. The speedo still often sticks on the peg after a full stop which is a mystery. I can find nothing that is binding and have cleaned the mechanism with brake cleaner and relubricated with clock oil several times. It almost acts like the peg stop is magnetized or something. I find myself looking for pot holes after coming to a full stop to bump the needle off the peg so the needle swings free again.

I had not been driving the car at night because I hadn't gotten round to aiming the headlights. I finally did that using these directions that were posted here on the World: https://www.danielsternlighting.com/tech/aim/aim.html

I like these LED Truck-Lites.

Click to view attachment

Click to view attachment

In pursuit of quiet, I followed a tip that @Dion posted and bought a different engine bay sound pad from RIX 914 parts https://www.rix914parts.com/store/p29/914_F...uction_Mat.html It is lightweight but denser than the closed cell foam pad I installed before.

Click to view attachment

Before removing the old pad, I took some sound measurements using the Decibal X app on my phone. I measured with the top on, windows rolled up and car outside in the driveway. Average measurements were:

82.1 dB @Idle (~1K rpm) 95.2 dB @3K rpm

Then I installed the new pad

81.0 dB @Idle 94.5 dB @3K rpm

Honestly, I was hoping for more than 1 dB sound reduction for my $185 investment, but I'll take every dB I can get. That doesn't tell the whole story either. Almost all of the sound reduction was at frequencies above 800 Hz which dropped the annoyance level more than the 1 dB would suggest. Also, most of the low frequency sound is coming from the muffler so I wouldn't expect the firewall pad to have much effect on that.

Her it is installed. I did not glue it in because the clips work just fine and I'd like to be able to pull it out if needed.

Click to view attachment

And now for some ignition news... Several weeks ago I replaced the copper spark plug wires to Pertronix wires for compatibility with the Ignitor III. Last weekend I decided to give the stocky and new SVDA dizzies another shot with the new wires. Unfortunately, I got the same result. The Pertronix worked fine when the engine was first started, but developed a progressively worse misfire as it warmed up. Watching with a timing light was startling. I'll bet #1 was only firing half the time and assume the same for all other plugs. In disgust, I put a set of points and condensor in the stock dizzy. Man do I hate points. What a PITA to adjust. I have always hated adjusting points but now it is worse knowing there is better technology available. PITA or not, they worked. The engine runs smooth and strong with the stock dizzy and vacuum advance AND retard connected. It might be my imagination, but the car seems to stink less of gas now too.

For now I have the stock dizzy installed with an old tired looking coil until I decide what to do.

Click to view attachment

No way will I stick with points. Fuch those things. However, after just a month I think I've learned I am not a carb guy. Don't get me wrong, the performance has been amazing even though they aren't properly tuned yet. I strongly suspect they are jetted a bit too rich which is expected given that I live at 6,000 feet. But they bring back nostalgia of the bad old days when every garage stank like gasoline from the fuel constantly evaporating out of carb fuel bowls and they are just a bit too fiddly for my liking.

I'm very strongly thinking of converting to microsquirt with ignition management. The more I read, the more I like. I may just run what I have for the summer and have a winter project to bring the fuel and ignition into the 21st century.

Regarding carbs I am in the same state of mind. Most of the noise on my car comes from carbs.. I see fuel injection in my future.. down the road as I have a 928 to get running 1st but I agree with carbs need to go thoughts.

Great minds... I have to brag about my custom air cleaner's ability to silence the carbs. I've had taking with and without sound measurements on the to-do list but haven't gotten round to it yet. In fact, I hadn't even driven the car without the cleaner installed to know if it was making any difference until a few nights ago. I was test driving the car after swapping dizzies and yet again forgot to tighten down the carb linkage so had to pull over about 5 miles from home to deal with my repeat stupidity. I decided to leave the air cleaner off until I got closer to home. As soon as I mashed on the throttle, I though "holy those things are loud!

For FI, I'm torn between a single throttle body using the stock plenum and intake setup, or ITBs with my custom (I'm making a stand against the hipster word "bespoke") air cleaner. Leaning toward ITB that I assume would be just as loud as carbs, but I have a cool solution that I worked really hard on. The engine bay just looks so much nicer.

[/quote]
For FI, I'm torn between a single throttle body using the stock plenum and intake setup, or ITBs with my custom (I'm making a stand against the hipster word "bespoke") air cleaner. Leaning toward ITB that I assume would be just as loud as carbs, but I have a cool solution that I worked really hard on. The engine bay just looks so much nicer.
[/quote]

Just because you use parentheses doesn’t let you off the hook.

The Bozeman Hipster has a ring to it but you probably need more cowbell. BTW, ITBs would be way cool with that ‘custom’ air cleaner.

I have thought about just using my carbs are throttle body's. On my 6 there are mfi ports in the heads so could use injectors there. Jpnovak has done that with good success.

@mb911

Can you post a link to any ITB with EFI setup using MFI ports. I’m not finding it. Could be really interesting.

Jpnovak makes the machined fittings. Not sure there is a link. He and I just spoke about them

I bet you haven’t noticed it. Pretty cool for me though. Your posts are about little piddly shftz things. Which means you are on the road. I am so pleased! Congratulations!

Kind of has me wondering about using my dual throat carbs with drilled manifolds for the injectors. I'm guessing just bolt on the appropriate TPS on each carb? Do jets need to be blocked off or anything? Seems like if only air is going through the carbs, it wouldn't matter.

Interesting idea. Next question would be what the value of a pair of lightly used Italian 40IDFs would be compared to the cost of buying drilled ITBs.

I wonder if drilled manifolds with bungs welded on there makes the most sense.. either way using itbs will maintain the intake noise. You could leave jets.. just need a tps off 1 carb.

Oh right... duh! Very interesting...

Yeah. That whole town is bespoke now with cowbell out the ass. In just 5 short years it has changed from a town I loved to one I can't stand to be in. COVID has only accelerated the spiral into hipster hell.

Ha ha. I did notice because I've been shocked out how well this car has run straight out of the box. In fact, I rolled over the first 1,000 miles after the rebuild today. A few impressions after returning to the 914 driver's seat after a 35 years absence:

1. The car is still the most f'ing fun car to drive ever! To be honest, I thought maybe my memories had inflated and romanticized fond memories. No! Not at all. In fact, I'm really driving a well sorted 914 for the first time and it remains just an incredible machine. So civil, yet raw.

2. Biggest surprise - wind noise. The last time I was driving a 914, the national speed limit was 55 mph (maybe it had been raised to 65). The difference between wind noise with top off at 65 vs 80+ mph is vast! I remember driving the Interstate all day with the top off and listening to a crappy radio. At 80+, the side windows really need to go up for comfort and forget about the radio. It shouldn't be a surprise, but I just hadn't thought about how much the speed limit has increased since those old days. This is more than outweighed by FINALLY being able to drive this car at the speeds it wants to go. What joy!

3. I'm not a carb guy as we've already discussed. There are many factors that have me leaning toward Microsquirt, but a big on is where I live. Home at 6,000 ft. and a day's drive could take me from 10K to 3,500 which is a big range for carbs. Microsquirt offers and affordable option to get true sequential EFI with modern ignition without having to split the case to swap out my mild carb cam. There is a lot of appeal there. I'm pretty sure we'll see more on this topic in this thread.

4. Sound - This engine does NOT sound like the box of buffalo farts that I think most Type 4 engines sound. Between the elephant feet valve adjusters an the M&B Specialties exhaust, the car has much more of a Porsche growl than Volkswagen clatter. Wonderful sound for those who like wonderful sounds. Unfortunately, it is too loud for me. It draws too much attention and even with no load and not moving, I'm getting nearly 95 dB inside the cockpit at moderate engine speeds. That's just not going to work. As was mentioned, I have the induction noise tamed with the air cleaner and have taken the sound deadening almost as far as I can go. Most of the sound level seems to be coming from the exhaust note so, reluctantly, I'm going to explore other options. First I will bolt on my Bursch "quiet" muffler to get a comparison. Then I will probably try swapping out the muffler for a Walker Quiet-Flow turbo style muffler. I found a part that should swap in easily for less than $50. I'm willing to shave a few ponies to gain some peace and quiet.

For sound, I shot a horrible video on the last leg of my trip home today after rolling over 1,000 miles. I just had my cell phone on a crappy suction mount so it bounced around like crazy. Also, it is really smoky here today so the scenery looks pretty blah. The jitter adds a slow motion feel and does no justice to that actual drive. Speed limit on this road is 70 mph and I stuck to that through most of the curves. Didn't even come close to the car's limits. The video ends at the same place as the last video down our gravel road to the railroad tracks. No Porsches were harmed filming this video despite the seemingly violent ending.


https://www.youtube.com/watch?v=wt1V3pDzJA0

Roads like that would really make the last four years worthwhile. One of these days I’ll visit with a car a little closer to the road…but no worries about that 3 mile driveway.

i was only away from mine for 16 years. you did a sentence 3 times mine. hats off.

in relation to:

1. yep. fun factor off the scale.

2. i don't listen to radios (could not fit it back in rhd format anyway). i never drive it with the top on, always have the windows wound up. it only wants to drive at one speed, 80 mph. or about 15 mph over max speed limit in aus. i live in a nanny state where nanna has a moustache and wears jackboots. i have to be careful.
but it does not want to drive at 65mph or 110 kph.

3. love your aircleaner. but EFI is the way to go. i like my Kraftwerk vintage L jet. fahn fahn on ze autobahn.

4. watching vid you are right - at least your engine does not sound like buffalo farts, or down here wombat farts. mine is solid desert rat clatter coming out of a kombi exhaust. but the induction does get a nice tone around 3,000 to 4,500 on the L jet that makes you think for a moment you might be in a me 262. dream on.

you must be feeling like a pig in sh$t as we say down here.

What is interesting about this is that DRphil did testing on his car for dbs and he is seeing 84-86 dbs with my muffler. He does have fuel injection though.

So glad to see you on the road with this car!

95dB is pretty loud. Especially by modern car standards but this is a 1970's era Sports Car. You were supposed to hear it.

The 914 has no real engine mounts to speak of, a fiberglass Targa top that resonates and reflects noise. No serious cabin insulation. Ultra simple door and window seals. No real suspension isolation to speak of (and that's with the rubber bushings assumed). We won't even talk about the open screen mesh that's required for cooling air to be ingested for the air cooled motor. And inherently air cooled motors are louder than water cooled motors.

Benchmarking:
Miata gets all sorts of complaints from disgruntled owners that don't seem to have realistic expectations of what a convertible top sports car is vs. a modern sedan.

Sound level @ idle (dB) 49.7
@ Full throttle (dB) 84.3
@ 70 mph cruise (dB) 72.5
@ 70 mph top down (dB) 80.3
https://www.edmunds.com/mazda/mx-5-miata/20...est-specs1.html

I'm sure my 1st Gen 1990 was a bit louder since later models added rear glass window and I believe some additional sound proofing in the soft top. Personally, I had no issues with my Miata and thought it was indeed quiet compared to my 914 when I first bought the Miata.

Also remember dB levels are heavily related to filtering and weighting (dBA, dBC) or dBZ no weighting. Not sure what your smartphone app weighted.

Trimming 15dB is no small task.
Options:

Add something more substantial to the Targa top interior besides the simple Perlon monkey fur which is still better than nothing.

Add shoddy behind back pad in addition to Dynamat.

Add shoddy and Dynamat to front cabin firewall as far up under the dash as possible.

Make sure your window, door, and all Targa seals have good tight seal and compression. Use dollar bill test or better yet, leak trace powder.

https://www.kimballmidwest.com/803099.

Might consider making a noise baffle insert that could be put into either end of the heat exchanger inlet / outlet that runs though the longitudinal. I'd bet there is considerable noise with a very direct path via this tube. Have to balance airflow restriction to still have heat. Maybe even just foam wrap the exterior of the paper tubes but that won't do anything for noise getting ducted via the vents.

Even things like cloth trimmed seats have quite an effect on interior cabin noise vs. Vinyl and Leather. Cloth trimmed seats, door cards, and Back Pad could be in your future.

Can't wait to see what the mad scientist comes up with to quiet things down.

Again read my response above.. I would bet dollars to doughnuts that it is mostly intake.. if Drphil registers almost 10dbs less with the same muffler then that intake is your source.

First, I think we have to take the smart phone sound readings with a grain of salt without calibrating them to a known reference. I think the smart phone apps are good for measuring relative sounds of one treatment vs. another but I'd be a little leery of trusting the actual numbers. That said, taking various sound readings with my phone is very much in line with typical levels for things like quiet room, conversation, etc.

I plan to take more measurements, but am getting 95 dB from about 4ft. directly behind the center of the car with "idling" at 1,1000 rpm. That was before I had dialed the idle down to a more civilized 750 rpm. The sound is definitely loudest behind the exhaust pipe. As I said, the intake noise is really loud without the air cleaner on and much quieter with it, but I need to do a lot more testing to figure out how much is coming from where.

I am not naive about what is possible with these cars and the miata numbers are what I would love.

i run whats called a kombi (bus for USA) quiet muffler. made of stainless steel i picked up about 20 years ago. (now a vintage item, i believe it was aus manufactured and might have even been lying on a shelf since the 1980s or so even when i got hold of it).
i found out about the quiet bit taking it slightly apart to reweld the exhaust coupling brackets on the other way around. the end chambers of the muffler have inlet pipes inside that connect to the exhaust flange and feed into the central chamber of the muffler.

the muffler that was originally on the car for many years i have kept. it differs from the quiet muffler - the end chambers that the exhaust feeds into are empty and are kind of echo chambers? i can barely read the stamps still on it. its a Lange. suspect it was a called a "sport muffler". ie louder, probably not much else, definitely not performance. we are talking vw muffler options here, not aftermarket. there was more than one sort of vw factory muffler.

i am pretty sure my memory isn't so bad that i'm wrong saying it used to be louder with that original muffler. some of that would have been down to shot baffles in the central chamber.

mine is almost turbine quiet at highway speeds in 4th or 5th. top off/windows up - 70 miles per hour - you can converse inside it without shouting. its quiet enough to surprise people. i get none of that low frequency throaty sound yours seems to have in the video. but video sound is tricky to judge. but mine sounds like a vw, not a porsche, though most 356s i see sure sound vw to me.

its still noisy around town at lower speeds accelerating - whatever you do that engine is sitting there banging away like a hammer on an anvil six inches from the back of your spine. i swear its noisier doing that than when its out on the highway at cruise. in fact out on the highway, when i first fitted the michelin XAS i was getting this high pitched tyre "roar" that was more like a scream. i thought my transaxle was kaput from sitting for 16 years - until i figured out what was going on. the tyres have since quietened right down. but thats how quiet the engine was, i was getting into citroen owner territory having a whinge about tyre roar. i do own a citroen,.........(an xm, so i do get the pursuit of silence thing as a diversion).

i've got a mate with a speedster set up with delorto carbs, small air cleaners and a sport exhaust system. its pretty loud. even when its at cruise. he was one of the folks surprised how quiet the 914 is at cruise when he took a ride. i can hear a lot of induction noise whenever i go for a ride in that speedster.

one last thought. i pretty much run a full stainless exhaust system. heat exchangers and muffler. why i jumped at the quiet muffler i came across 20 years ago it was SS. and i am sure that also makes a difference. you don't get that low boom you have with mild steel mufflers and exhaust system. the cost is it sounds awful when its cold, like a real tin can sound. it does improve once the the whole exhaust system warms up. but its not a comforting performance sound when its all stone cold.

I agree but I find your scenario very odd. My -6 is very quiet and it's the same muffler you have. My carbs make all the noise. 95 dbs is really loud and think there is something missing here. I wonder what your DD would register by comparison?

I'm a bit perplexed myself. So I set up my phone 2 ft. off the ground and 5 ft. behind the 914 and took measurements at idle (~800 rpm). I get consistent reading from 94.5 to about 96 and usually within a few tenths of 95. I also measured sound right behind the rear glass and above the engine lid and got about 97 db.

I took a short video of cold start of the car with the sound measurement setup. Unfortunately you can't read the meter because of sun glaring off the clear coat over spray on my screen protector. I should replace that. With headphones and the volume turned up pretty loud, this does a decent job of capturing what I'm hearing.


https://www.youtube.com/watch?v=fbXbSoBGeXQ


And here are readings with the same setup from a couple of our other cars:

1991 Nissan Pathfinder (beater truck with slight exhaust leak): 82 db.

2006 Honda CRV: 74 db

Sitting quietly in the house: 44 db

there is a good article here.
measuring sound level of air cooled beetle.

https://www.bksv.com/en/knowledge/blog/sound/quietest-cars

done in sones, but conversion to db is here.

https://www.industrialfansdirect.com/pages/...-decibel-levels

the figures for the beetle are pretty much in line with what other guys are getting with the quiet mufflers. though the figure at full thrash is pretty high at around 71.66 sone or in excess of 87db probably approaching 95db. at cruise (130kmh) its 56 sone or 86db.
the figures are probably measured inside the car too.
i would have thought the factory would have been aiming at around 85db or so with 914s back in the day. that was probably a legislated drive by level back in that era they had to get to.

you must be getting a lot of induction noise. that measurement above the engine grille would likely be the induction for the most part and it seems higher than exhaust level.

95-97 db is on the verge of industrial deafness material if exposed for long enough periods.


--------

is it possible the snorkel design of your air cleaner is actually amplifying sound.
i only say this because of something i have seen on an NSU RO80 and a citroen GS birotor, both of which ran the wankel engine. the air cleaner is quite a complex and strung out piece of equipment on those cars that incorporated what was basically a muffler to keep the engine quiet - the rotary engine not having valves but ports was inherently loud - almost like a 2 stroke.
they both have a long snorkel, but it goes into a tapering silencer cylinder before feeding into the filter section.

Brent I would like to look at that muffler this winter. I am half wondering if I sent you the wrong muffler. Pretty sure I didn't but want to make sure and I can make it quieter for you even if it is the right muffler. But again it is so odd that Phil gets about 85 dbs with gt3 tail pipes.

i knew i had seen a db level for a 914 published in contemporary road tests back in the 70s.

Car and Driver, 1973, 2.0 L. 80db @ 70 mph constant speed.
presumably with the top on because they describe the targa top being superior to canvas roofs at speed. so it is possible.
it seems right too, i can conduct a conversation in mine with a passenger, with the roof off at 65mph on a good road surface without straining or raising my voice much.

Hi Ben. Would love to get your assessment. I've wondered the same thing about whether I got the quiet muffler. I can tell you it does not look like the quiet mufflers on your website. Mine is a single straight cylinder rather than the 3-section curved ones on our site. 2-1/2 diameter tailpipe too if that helps. Seems big but I don't know your design.

Anyway, it is off the car now so I can send it at any time. The Bursch is on getting ready to take it for a test drive. I'll probably run this muffler for the rest of the summer anyway because it will soon have a wide band bung so I can test AFR. I'm getting 91 db 5 ft behind the car.

Thanks for posting the measurements. I've read that C & D article several times but had forgotten they had a sound measurement there.

There is still some work to be done on the intake, but that is not where the bulk of the noise was coming from. Especially not at idle with the butterflies on the carbs nearly closed. It is obvious from outside the car and inside as well that is is the exhaust. I wasn't really surprised by 97 db over the engine grill though. These engines are not quiet. Lot's of valve clatter etc. and that is mostly what you hear up there in addition to the lub of the muffler. The important thing is that the sound deadening and window are preventing a lot of that noise from entering the cabin.

I don't have the snorkel installed because I haven't chopped down the support bracket yet to match the lowered height of the cleaner. Still on the to-do list. I still have adding a resonator and/or redirecting the opening to the left side of the car instead of to the front as options to play with for future sound control. I think there may be a few db to be shed there, but that is going to be more refinement than addressing the main problem.

I did not get a chance to test drive the car with the Bursch installed tonight like I hoped. That will have to wait until tomorrow. But a quick drive down the gravel road is encouraging because all I heard was the sound of the roof squeaking and the suspension bouncing on the uneven road. Having those drown out the engine is a very good sign. I also didn't feel like I was disturbing the neighbors driving by. Even a "quiet" Bursch is not known for being a quiet muffler so having this much progress feels like I'm on the right track. I'll get some measurements on road tests tomorrow.

Now to figure out why Ben's muffler is so loud. I'm more and more leaning toward it being the wrong model which would be wonderful news.

i have a bit of stuff on file re factory vw mufflers i found when i was modifying mine to fit properly. back then i was trying to figure out if there was any real difference between 1.8 mufflers and kombi mufflers. i ended up figuring there was none apart from exhaust inlet mounting plates orientation.

there are some german test figures for the standard kombi muffler that jp group make.

test = 91db at 3,450 revs stationary. 79db on the move. i think measured at 1.5m from the exhaust outlet for the stationary one. the bursch is probably not far off that.

i did not want a loud 914 either. i think part of its original design ethos was to be relaxed at high speed on the autobahn.

thinking about it, the shape of the snorkel is a sound suppression resonator of sorts anyway - tapering down tube.

attached a picture of the fairly extreme snorkel/silencer on the wankel in a citroen birotor. NSUs had all the same components but arrayed a differently in the engine bay.

Click to view attachment

The ones pictured on the website are my 1st 10.. I later changed to a single straight muffler for ease of build. All the tail pipes are 2.5 inch.

Thanks for the clarification. Was hoping that might be an easy solve to the mystery. Just let me know when is the most convenient time for me to send it to you for inspection.

Pm me. I am going to make a new one and just trade you out the one you have and then sell it to cover costs.

Sound good?

Yet another example of Ben's character. I have dealt with Ben on a few things and always found him to be a 100% stand-up guy. We are very fortunate to have his skill/experience set making parts for our cars.

Sounds fantastic Ben and way above what I expected. I hope you know I did not intend this to turn into a referendum on your muffler. The quality, of course, is impeccable and I bought it knowing that you can't know how any muffler is going to sound on a particular vehicle until you try it.

I got a chance to test the Bursch at highway speeds last night and it is a mixed bag. It is noticeably and measureably quieter from outside the car but is still a loud muffler. I'd say it is at the limit of what is acceptable, but is a step in the right direction. Inside the cabin, it does sound quieter but the numbers don't support that. db levels at all rpms and speeds are barely lower than before. However, the frequency distribution is much different from before. Unfortunately the free app doesn't let me save the traces but there is less energy in the very low frequency range which feels easier on the ears.

I'm not confident of the numbers the phone app is providing other than relative sounds levels between conditions/treatments. I noticed it seems more sensitive to certain frequencies which isn't much of a surprise for a phone microphone. So I ordered a modestly priced sound level meter that got good reviews from people who appear to know what they are talking about to provide a reference.

The most noticeable difference is that at highway speeds, I now hear the wind whistling through a couple small gaps i the window weather stripping I've needed to address but have been surprised they didn't make more noise. Turns out they did, I just could hear it. Also, the engine noise is more noticeable than it was before. It sounds mostly like mechanical racket but I will be experimenting with the intake snorkel and possibly additional/other sound deadening. I think I'm on the right track to try to get the exhaust as quiet as possible first and then work through other components one step at a time.

No worries either way let's get this figured out for you. My 914-6 is incredibly quiet except for the intake and -6 engine whine

@mb911 Thanks Ben! What kind of sound deadener are you using on the firewall? I think I'm getting pretty good attenuation there, but wondering if there are additional gains to be made.

This is the one I went with.
High tech and very, very lightweight.

https://www.aasesales.com/products/c6a-r142...eeb51&_ss=r

I used contact cement to apply it to the firewall.
Very happy with it.

Click to view attachment

Ending up shaving or trimming the upper edge such that the engine lid "swang" freely if you know what I mean????

That's the one I have in mine now too (bought it from RIX 914 Parts but looks like the same material/part). I measured a 1 db reduction in interior noise compared with the cheaper closed foam/foil face underhood liner I installed first. I did not cement mine in as that type of mat shouldn't depend on tight bonding to the panel that constrained layer masses like Noico do. I also have Noico stuck on the firewall behind the sound pad. Seems like a quality product, but mad scientist would love to know how it compares with the heavy oem slab. Unfortunately mine has lost most of the probably asbestos fiber so wouldn't be a good test.

Just noico and 1/2" aviation insulation with perlon over it.

As a generalized statement about NVH, sound transmission loss effectiveness increases with increasing mass. That is why OEM mats (internal & external) are so heavy.

If you don’t mind the weight there were advantages to the heavy OEM barriers.

Generally speaking the light weight, fibrous, or foam barriers are only going to serve to absorb mid to high frequency. For low frequency and structural boominess, you want mass and constrained layer solutions.

FYI - Dynamat (and Noico) are a mixed mass & constrained layer solution. You can add double or triple layers of Dynamat to build mass. Check the specs on Dynamat vs Noico. My recollection is that Noico had less mass per square foot but don’t flame me if I’m wrong. Don’t have numbers in front of me.

Nope, you are correct about Dynamat vs. Noico. I also don't have the numbers but remember that Dynamat is slight thicker/more mass. There was also a sound attenuation test I ran across that showed Dynamat outperforming the competitors, but the difference was small compared to the triple price of Dynamat.

What's interesting about the OE mat is that not only does it have the heavy tar-like coating, but the fiber portion is also dense and heavy. I would have reused mine except for the fact that it is shot. I contemplated spraying this new mat with several coats of rubberized undercoating to create a bit of a mass layer on the engine side. I did that with the uxel foil faced foam. Does the relative location of the mass vs fiber matter? Effectively, I now have the reverse of the factory mat with thick fiber on the engine side and then Noico butyl mass stuck to the firewall. The total weight savings over the OE mat is still substantial. I'm too lazy to look up the numbers I posted before to update with the new mat number.

I'm also wondering about something like this to either replace or add to the rubber sheet on the interior side of the firewall. https://www.amazon.com/Self-Adhesive-Automo...;language=en_US

Traveling to Rt66 I took the plunge and tried Hey Siri with my phone for directions. With highway noise Siri couldn’t understand me and I sure as heck couldn’t hear her. I didn’t add much sound deadening, which is fine. But not in line with the rest of the world.

That's no test. Siri, Google, Cortana (remember her?) Alexa... none of them can understand me in a dead silent room. Oh wait, Google did understand me once when I got so mad I spewed out just the right series of profanity to get this response, "Okay, one of us needs to take a breath, and I don't have lungs." I have never been able to replicate it, but oh how I have tried...

You're lucky your phone did not report you to the authorities.

Yup something like that on interior over the top of the Noico.

Seems pretty similar to DynaPad 4 layer urethane pad coming in around 1lb/sf. That is still probably less mass/sf than OEM interior pad but is a good mass add in addition to the Noico.

https://www.dynamat.com/wp-content/uploads/...l-Sheet_Web.pdf

Looks like the Dynapad is thicker @ 3/8" vs 1/4" I have Noico on the engine side of the firewall, not on the interior. Right now on the inside, I just have the factory rubber pad that goes behind the backpad. I have enough Noico to do the inside too but trying not to get too crazy with weight unless I have to.

I still need to work on reducing the sound being produced first. I'm thinking reduce exhaust as much as possible first as that is still the main culprit and makes the car obnoxious outside as much as inside. Then dial in the intake although I really don't think that is a major source. I don't think I can do much about the mechanical noise. Then work on sound dampener. Once I have the better sound meter in hand, I might throw the ratty original firewall mat in and see how it compares just for grins.

Snorkel, test drive, and running like

Had some errands to run in town today so decided to finally get the snorkel installed on the lowered air cleaner properly. Two adjustments needed to be made. One was to lower the support bracket to match the new, lower height of the plenum box. The other was to shorten the snorkel itself because I did not account for the backward "lean" of the firewall in front of the engine, or the thickness of the sound pad. The snorkel barely fit.

Click to view attachment

I lopped off more than an inch off the tip. Ooh, that doesn't sound good Well, I did it anyway.

Click to view attachment

Click to view attachment

After a bit of reshaping the bugle flare on the end, here is "Shortie" snapped onto the lowered bracket.

Click to view attachment

Then I hit the open road to further check out sound levels. With the top off and windows up, I hit the Interstate at 75-80mph. The first thing I noticed was that the engine noise has completely disappeared and it is all wind noise at that speed. That is a switch because before, the exhaust note was very noticeable at any speed as you could hear in the previous driving video. Today I couldn't hear the engine at all at highway speed and I really tried. The next indicator was being able to order lunch at a drive-thru window while the car was idling. Before I had to shut the engine off to be able to hear. Then I found a shady spot to park to eat my lunch and got pretty good evidence the sound levels I'm getting on my phone are not reliable. With the engine off on a very quiet back road and the radio playing at a relatively low volume, the Decibel X app read an average of 100 db! I'm confident I was not anywhere near ear damaging sound levels. It will be interesting to see how the sound meter I ordered compares. I do think the app is decent at reading relative loudness even if the actual numbers are off.

It runs like shit
I noticed my ignition misfiring on my last test drive a few nights ago and suspect the old ratty coil I put in to pair with the points was going bad so I ordered a new Bosch blue coil which should be here this week. I rechecked the dwell just to make sure the points hadn't gotten out of adjust and it was still spot on. As I ran errands today, the misfires and jerky engine got worst and it started backfiring slightly at low engine speeds. Every time it misses, the tachometer jumps which makes me think coil. I guess the other possibility is fouled plugs from carbs running too rich. I'll pull the plugs to inspect when the engine is cooled down and still need to get the lambda installed to measure AFR.