blk406

I am going to be putting on 69' style side exhaust on my 69' BB427 and have read they are pretty restrictive. My question is which system is the best performance wise to put under the 69' covers? It seems allen, and sweet thunder are 2 options. I don't want it ridiculously loud, but want the BB to breath as best as possible. Anybody have any recommendations?

Corey_68

I have stock pipes on my BB and to me they can be loud at times. ST and Allen pipes sound great but many have chimed in that they are too loud. I'm installing a LS2/6speed and with be removing the stock pipes and building my own set to go under the covers.

Alan 71

Hi blk,
For years I've read that the 69 side exhaust system was quite restrictive, even more restrictive than the stock under car exhaust.
As far as sound is concerned I think part of the problem, (or pleasure), is that the outlet is about 2' from your left ear!
But, boy do they look good!
Regards,
Alan

These are 69 covers painted black.

Faster Rat

I have the Allen's oversized 2-1/2" and just like the orange warning sticker on their shipping carton stated "THESE PIPES ARE LOUD." Unfortunately, less restriction equates to more noise. The original or repro factory side exhaust are really just 2 parallel tubes with holes between them...an inlet on the end of the top one and an outlet on the other end of the bottom one. Very little muffling is going on. With the T-Tops on, the drone inside the car could be bothersome on a long trip. Around town, it sure is a lot of fun to annoy other drivers while idling at traffic lights. The neighbor two houses down tells me his windows rattle when I start the car.

The only thing I don't like about them is the exhaust pipes are not mandrel bent, which undoubtedly causes some unecessary restriction. If you go with them, make sure to have them shipped in pieces and do the fitment and tack welding on your car, with the covers in place. I really don't think stainless is necessary. The aluminized steel will last a long time and doesn't look quite as non-original. They can provide you with new GM repro covers for a discount...which I believe all come from Paragon.

Here is a link to 4 YouTube videos I made using a cheap still camera, so the sound is not real good..but you can get the idea.

http://www.youtube.com/watch?v=mqNXJ9FBNZM

69Vett

I have the BB 454 Sweet Thunder oversize tubes, I found them to be quite comapared to other similar exhaust systems,
I was slightly dissappointed they were not louder.

blk406

Alan, beautiful 71' you have there.

FasterRat, sweet car you have there as well. That info and those videos are a big help, thanks.

I'm going to try to listen to the sweet thunders and try to figure out which one is louder. I imagine they are pretty similiar.

HamadUP

my car came with Allen's side exhaust (the 2.5 in.) and it was loud to my taste, but worst of all, I was really shocked when I saw that much better performance when I switched to a normal undercar exhaust, that thing is so restrictive, maybe I gained 40 HP or so just by going to the under car exhaust, my car was a '71 big block stock.

blk406

So, would it be less restrictive to use my own pipe with sts baffles? What is the biggest pipe that fits under the 69' covers?

Ganey

Very "restrictive".

427 435 HP
Actual nos. w/ engine on dyno & off road sidepipes are 368 HP @ 5750. TQ 419 @ 3500.

69VetteFla

I have a '69 SB 350/350 with factory side pipes. Not sure how restrictive they are because never ran w/o them but they sound nice - not too loud but loud enough.
Click on the images below - they are videos:

Roma

I changed from a performance exhaust :



to original side exhaust



My feeling is that I loose some power, but the look and sound is ways better

Alan 71

Hi Ganey,
PLEASE don't take any offence!!!!
I believe you know that "off road'" and "sidepipes" don't go together.
'Off road' refers to the optional undercar exhaust with less baffles in the muffler so may have been less restrictive than the standard undercar exhaust.
I've always been intrigued with side exhaust and like the truth to be known about them. Even the down side to them.
Regards,
Alan

Faster Rat

Any exhaust silencing system creates backpressure, causing a drop in performance. I guess if one is into street racing it would be important. If going to the strip is your thing, slap on some open headers. When I give somebody a ride that has never experienced the sound and feel of a BB muscle car, I ususally take the opportunity mash the pedal to the floor at least once. Then I have all that I can do to hang on to the wheel and keep it going straight down the road, hoping that some 42 year old item doesn't let go. I am amazed that I haven't even gotten a ticket in 7 years. Performance? I don't need no more stinkin' performance.

Ganey

Alan
There was a pic. & it was factory side pipes, so maybe they should not have called them "off road".
I suppose you know side pipes came from lakes pipes which were run open.
I found out about restrictive exhaust on my first car when it blew the straight through glass packs off & exploded w/ power!

Faster Rat

...and she purrs like a kitten til the lake pipes roar.

- Little Deuce Coupe by The Beach Boys

I remember when my greaser buddy across the street put fake ones on his '56 Ford convertible back in the early '60s...just as a decoration, along with the pair of foam dice hanging from the rear view mirror.

Ganey

I mounted the glass packs so that a hard job of the throttle would blow them back & the hangers would hold them out of the way.
We would start lining up & I would blow them off. Too late now.

blk406

Ok, so I guess it's either Allen or Sweet Thunder. I am leaning towards sweet thunder because of their performance 2 1/4" inner baffle tube diameter. http://www.sweet-thunder.com/corvett...pes_68_74.html Both are 2 1/2 pipe. And their prices are almost identical.

WESCH

Hi

But even the 2 1/4 " sweet thunder pipes have 2 in parallel running muffler tubes that seem to be interconnected by longitudinal holes somehow.
Doesn't anybody build just a straight through glasspack muffler single tube like the HOOKER high flow glass pack muffler ?

That would be the least restrictive.

Rgds. Günther

Faster Rat

When I got my car the original factory side exhaust system had been replaced with painted blue glass pack mufflers, stenciled with the name of some company in Benicia, CA. They also put in a crossover tube in the exhaust pipes, similar to what all new Harleys have. Let me tell you, it sounded like crap (puff-puff-puff) and as far as the restriction went...hard to tell because my engine needed rebuilding.

blk406

OK, here's the update. I bought the sweet thunder 2.5" baffle system. I installed it the other day. Sounds great, not too loud and definetly not too quiet when you step on it. No annoying drone on the highway. Performance wise I don't feel a difference, which I am happy with. I just didn't want to lose performance.

On a side note, to anybody that wanted 69' side exhaust, DO NOT let leg burns or heat sway your decision. I have read that, and was a little nervous about one of my kids touching the exhaust after a drive. The ceramic insulators inside the covers work perfectly. I can immediately touch the side covers after a long hard drive, no problem. Just warm. I'll try to post a pic of the system tomorrow. Loving it!