In Search Of - Vibration

rlphvac said:
Wedge some blocks of wood cut into angled pieces and wedge them between your pipes and the floor or frame use about 3 per side that should take any exhaust noise out then remove them 1x1 to isolate the problem and it may be as simple as the hanger you changed
Click to expand...

Will do !

In the meantime I took it out for another test drive and checked a few things.

It seems that the vibration/rumble comes and goes between 2500 and 3200. Above 3200 it seems to be gone.

It idle the exhaust tips seem to shake a lot. They don’t seem to be firmly located.

I popped under the car and checked the hangers.


The look pretty flimsy to me. Maybe it worked for a very mild 350.... but not so much for a high performance V8 ?

I will need to measure the exhaust pipes again but to me they look closer to 2 than 2.5 inches.

Muffs are some kinda Flowmasters.

DF30192C-599B-4F4D-B3AF-2816C2841AA9.jpeg

BFDD1FA5-AA90-42CE-8CDA-1ED759117E47.jpeg


“The Original 40 series muffler delivers an aggressive exterior and interior tone. If you're looking for that original Flowmaster sound this is the muffler is for you. Constructed of 16 gauge aluminized steel and fully MIG welded for maximum durability.
Features:
  • Durable fully welded 16 gauge aluminized steel
  • Aggressive Sound Exterior Exhaust Tone
  • Noticeable Interior Resonance
  • Excellent Street/Strip and Off Road application”
Noticeable Interior resonance? Mmm. Too loud means I’m too old.
 
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Been doing a lot of reading about C3 corvettes, glass bodies and, Flowmaster 40 muffs... and I think I’m experiencing droning.

Droning apparently is a resonance that is felt in the cabin, not just heard. It’s not uncommon in C3 corvettes with loud muffs and usually happens at a set RPM band.

Changing mufflers is one solution. Car Chemistry inserts is another. Finally a cross pipe can also help.

New mufflers and or exhaust pipes can get pricey quick, especially shipping the whole kit and kaboodle over here.

Inserts behind the collectors, I think are the easiest and cheapest solution... but there will be a price to pay in power.

Finally a crossover might help - splitting and diminishing the pulses. It’s not too expensive... excluding labor, which may be hard to find here. And it may make dropping the exhaust a pain later on.

I think the best idea is to start with the inserts and see if that make a difference.
 
Summit has X pipes, cut your exhaust clamp one in and if it works, tie some kind of support to the exhaust and you’re in business!
SUM- 642122 is 85 bux
 
FWIW I ordered off of summit some Car Chemistry inserts and a couple of brackets. Fingers crossed plz.
 
Wow- they came in fast.

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Reading the instructions on and in box, it seems that if you are just running pipes, the insert should be placed after the collector.

If you’re running muffs, you can put them in the tail pipes.

These inserts do not look very sophisticated.

The fit is super tight, I think mainly because my tailpipes are slightly ovalled-out. The instructions say to grind off a few thousandths, but there not very much meat on the discs.

I think another option would be to simply pound them in, understanding that they will never be coming back out.

I think I’m ok with that, because if this fails, I think the next step is to swap out my mufflers with known quieter ones.
 
stop!
your making me bang my head on the table
I really wish you were local,
this is a common issue that a custom exhaust would help resolve,
and a custom or modified exhaust could be a noticeable benefit here
https://www.chevydiy.com/c3-corvette-modifying-exhaust-systems/
one more in an endless list of reasons anyone seriously into modifying cars need a decent welder and to learn the required skills to use it.

the baffles that you show are unlikely to do more than restrict exhaust flow and reduce peak power
, yes they may reduce the (drone at lower rpms but thats also unlikely to be worth the resulting loss in power),
inserts and baffle in exhaust pipes,
rarely produce any where near the expected reduction in sound expected.
exhaust pipe exits must extend at least 2" past the body and ideally curve back/downward toward the road surface behind the car
the cross sectional area of the holes in those baffles you show is significantly less than an open exhaust pipe they slide inside.


they make very inexpensive exhaust pipe expansion tools for similar issues
480.jpg

https://www.harborfreight.com/medium-tail-pipe-expander-63703.html?_br_psugg_q=exhaust+pipe+expander

Id also suggest use of an x-pipe and kit. mounted as close to the header collectors as space allows under the car (yeah its limited in a c3 vette)
https://www.summitracing.com/parts/sum-642122
sum-642122_w.jpg


but that will require a welder
generally oxy-acetylene torch use , is about the most flexible
and some fabrication and accurate measuring skills

there are exhaust pipe inserts that maintain the same open cross sectional area as open pipe

http://garage.grumpysperformance.com/index.php?threads/building-an-exhaust-system-for-your-car.1166/

https://www.jegs.com/i/Dynatech/329...B_o0V3V3TFtnBKUL_mGm4R4sgc-6Cr6AaAhSdEALw_wcB

related info you'll benefit from reading through:D
http://garage.grumpysperformance.com/index.php?threads/exhaust-h-pipe-leading-into-a-x-pipe.15118/

http://garage.grumpysperformance.com/index.php?threads/x-or-h-pipe.1503/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.com/index.php?threads/building-an-exhaust-system-for-your-car.1166/

http://garage.grumpysperformance.com/index.php?threads/replacing-entire-exhaust-on-a-c3.9296/

http://garage.grumpysperformance.com/index.php?threads/exhaust-system-tools.2002/
 
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:p :p:p:p I guess you’re right. I do have a buddy that has one of those expanders. I’ll ask him if I can borrow it.

I’m going to see if a shop here (friend of a friend) can do that crossover.
 
Soooo this came in

730EC67A-65C8-4B7B-8D35-582510D67F05.jpeg 288C2EC2-C10E-4660-8EF9-AE26DAF3648D.jpeg

Will it be beefy enough to slightly expand my tail pipes is anyone’s guess.

We find out tomorrow and we also see if it has any effect on what I think is droning.
 
I agree with Grumpy; I just can’t see these things being anything else other than a restriction and power-robbing. However, I have read good reviews with respect to drone control. At the very least I hope to find out whether the vibration I feel is droning or not.

The plan after this is to install a cross pipe to offset the inserts.

After that... side pipes or quieter muffs.
 
Fail.

The cheap tool was not able to put (remove) a dent from the Flowmaster tail pipes.

I’m not in the mood to start putzing around to put these inserts into the exhaust pipes behind collectors.

I think I’m now at considering just the cross-over, getting new quieter muffs or a whole new exhaust.
 
Well folks, I ordered the exhaust crossover kit grumpy suggested above.

https://www.summitracing.com/parts/sum-642122

There’s a small garage around the corner and the mechanic there says he can do it.

Let’s hope this solves the problem. I will also be asking him to go through the exhaust hangers to make sure things are squared away there too.
 
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