Since I want a throatier exhaust than stock on my '61 I thought of using one of those Thrush glasspack (a.k.a. cherrybomb) mufflers. The engine is a bone stock '72 vintage 2bbl 350 SBC and I'll be running the stock 2" diameter single exhaust with a Y-pipe. An oldtimer mechanic friend of the family warned me against the glasspack because of its straight-through design which, according to him, doesn't provide enough back pressure and causes some valve issues (valve float he said) above 3500rpm. I tend to under-rev if anything but I do on the rare occasion wind it out a bit, especially while merging on the highway for example. Anyways, I always thought valve float was caused by over-revving or bad valve train geometry or weak springs but I'm not an expert lol. Anywho, the oldtimer recommended one of the Thrush Turbo mufflers instead saying that it will still give a throaty sound and provide the needed back pressure. The reason I'm planning to go with the Thrush line of mufflers is first for the sound and 2nd because at just over $40 at Crappy Tire they're less than 1/2 the price of the stock replacement muffler.
What are your guys' thoughts/opinions? Any validity to the valve float claim?
What about open headers on race cars? What about the millions of vehicles running around in cowboy country with glasspacks on them???
My pickup came out of Swift Current and the only reason I pulled off the 13+ years old Cherry bombs a few months ago was because the system was so badly rusted out it was falling off the truck!
__________________
1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Glass packs sound can annoy you due to noise and "drone" ... that's all I've heard.
__________________
Prince Edward Island
'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.
Glass packs sound can annoy you due to noise and "drone" ... that's all I've heard.
Ya, that's another reason for worry. Might be fun for the first few miles but then when the novelty wears off the annoyance factor will kick in when all I'm looking for is a relatively throaty sound without pissing off the neighbors too much. I went on the Thrush website (thrushexhaust.com) and youtube for sound samples but of course on youtube it's hard to gauge the actual 'loudness' of the setup and even on the Thrush website the sound samples of the glasspacks and the Turbo both sound pretty much the same and it's hard to guage the loudness difference. Also, the website doesn't mention what engine the exhaust is on or even if the samples for each muffler were taken in the same conditions (i.e. mic distance from exhaust, etc) and on the same vehicle/engine combo.
"cowboy country" ? (that be us out here in Cowgary?)
I was thinking more like southwest SK where my truck is from, but "Cowgary" gave me a good laugh, never heard that before! I guess there's some cowboy hats in Alberta also...
At any rate, seems like there's more glasspacks west of us than in Manitoba.
__________________
1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
All I can add to the conversation is that back in the '80s a buddy of mine installed one of these Thrush glasspacks on his 305 '78 Pontiac Phoenix (single exhaust). It was louder than stock but I didn't think it had a very good sound, probably because it was coming through the single tailpipe - didn't have that nice stereo rumble of dual exhausts. It was noisy around town and did have that drone on the highway - we didn't mind so much because we were young (lol), but I don't think it helped the car much - reminded me more of a car with a rusted out muffler than "performance" exhaust.
Don't have any recommendations as I'm not sure what the other brands would sound like thru single exhaust, but wouldn't recommend the glasspack.
On myu Fathers 67 Sat. GTX with stock exhaust it would "chirp" the tires in all 3 gears when pushing the pedal tpo the floor.
he changed them to glass Packs (cheaper then stock) and it would float the valves just before shifting..
__________________
Surrey BC
1963 Acadian Beaumont Sport Deluxe http://www.63acadian.com/
I'm reminded of a story Dad told me about a musician he knew in scotland who thought a solid brass exhaust would be a good thing ... didn't end well. An exhaust is like a musical instrument .. no, it's not like one ... it is a musical instrument. There's all sorts of harmonics and pressures interplaying. Even just moving the muffler about on the length of the exhaust pipe can make or break a system. There's really too many things to say that this one thing will make or break it. That said ... a 350 through a single 2" pipe .. I don't think lack of back pressure is going to be a serious issue. But at the same time ... a good turbo or vortex muffler isn't all that much more than $40 ... and I can't stand spending a dime at Commie tire.
I've got dual glasspacks with a crossover pipe on my '63. Sounds fantastic and not annoying in the slightest. Also have the exhaust running straight out the back. But for a single system, I'm not too sure.
Glasspacks can sound like crap on one car and good on another. I don't like glasspacks with headers. I had a 58 Plymouth with a 318 and glasspacks (no headers) and it sounded pretty good.
Walker had a perfomance muffler back in the sixties. Deep throaty sound with no crack, snap & pop. Not sure if Walker still around ?? At the time they cost about 2 x glass packs
Hmmm, so I see some varying responses. Some think glass is too loud, some that it's fine. I guess it's a matter of personal opinion. Any perfoamance improvements I'm not so much concerned about since the engine is stock with a 2bbl and a single exhaust. heh heh What does concern me however is the few people who chimed in on the valve float issue, that's definitely worrisome. Although, with a single exhaust you'd figure there'd be enough backpressure in the system to avoid any engine issues. That is if in fact glasspacks do cause valve float and such.
I think Carl meant that glasspacks are 'redneck' lol but of course I 'ain't calling any Cowgarians redneck' Now where's that copy of Deliverance?
I used to live in Manitoba back in the 70's and there wasn't not one 'redneck' to be seen.......oh yeah really, I worked with a couple of them from Gypsumville, what a pair!!!
Regarding the Deliverence reference....'Paddle faster boys, I hear banjos'....buy a couple of glasspacks & if you get tired of them or you suffer from hearing loss, sell 'em on ebay and try something else. Back in the day the old Corvair turbo muffler was the 'hot ticket' for an exhaust system.
__________________
1949 Pro Street Meteor Coupe, 468 BBC, 4L80E, Narrowed 9" 3.50 posi
1966 Biscayne post, 427 L72, M21, 4.11's 16600 original miles
1966 Hemi Satellite 4 gear 59K original miles 1968 Z28 302MO, M21, 3.73's, cowl plenum induction
Pick up a glasspack and put it on. I don't think they're that pricey (I've seen them for $35 online), so you won't be out so much money if you don't like it.
As far as the valve float issue goes, I really can't see it being a problem. I've seen so many cars running over the years with glasspacks or open pipes - my buddy ran small block Chevs on the ovals in his street stocker for many years with open pipes on a stock 350 and there never was a problem. Sounds to me like an old tale that just got passed down over the years - they're fun to hear but you can't put much merit in them.
Now where's that copy of Deliverance? 
I know from experience that there is NO performance advantage.