I picked up two summit glasspacks and there is no in/out marked on them, now the inner core has louvers punched in them i feel that the open side of the louvers would go towards the header and the rounded closed end would go towards the tail end ??? any info. befor i weld thanks smile.gif

You can install them either way, but they are slightly quieter like you say, but don't last quite as long vs the other way, plus slightly noisier!!

That's why I like the W/D/T perforated inner core glasspacks b/c they are a true pipe dia. inside through them..

What is the inside pipe dia. on the Summit ones vs the in and out dia. b/c I'm wondering about how much the louvers choke them down???

pdq67

A straight through glasspack really doesnt have a flow direction...That said there are a couple small points to consider with the direction of the louvers.These louvers are really designed to allow high end sound waves to enter into the fiberglass packing.When these sound waves enter this fiberglass the sound waves are trapped and therefore stop moving thus canceling the sound produced by these sound waves .If you place these louvers with the packing faced twords the collector you will be exposeing these louvers to a little bit more heat , sound waves , water ( a natural by product of combustion ), carbon , air flow ect ect. In that direction you may get a decible or two more quieting than if faced in the other direction but the muffler life may be a small amount shorter as the packing is exposed to abit more of the exhaust blast then if faced in the direction of the tailpipes.... Either way the real problem with these types of mufflers is that the fiberglass does a great job of collecting and holding water... this is the main reason most glasspacks have reletivly short lifespans compared to non packed mufflers.

Pdq...sorry I didnt see your post ..you finished before me !! graemlins/beers.gif

What is it?? Great minds think alike???

Just had tooooo.... He, He!!!

And I do love them cackling, "cop-calling", W/D/T glasspacks!!

pdq67

Originally posted by pdq67:
And I do love them cackling, "cop-calling", W/D/T glasspacks!!

pdq67 ..many years ago,I had a 69 Caprice w/a 2 bbl. 265 HP 396..it had 2.56 gears,2.25" dual exhaust with 18" long glasspacks,and boy,tach it up to about 4500 in 1st gear (TH400) and letting off on the gas would sure let it cackel,crackel and pop..what a sound graemlins/thumbsup.gif

That's it!!!

And to make it deeper and more thoaty if you want, just run long ones or two short ones end to end.

Doing this tones them down and makes for the deeper "purr" and "cackle", imho....

pdq67

Pdq,

Right you are !!

Do you ( or anyone else ) happen to remember " Douglass Headers " from the 60's to early 70's ?

Anyhoo he was interviewed in an article in the book titled " Basic Cams , Valves , and Exhaust Systems "
copyright 1968.... that I have here.

In the article Howard Duglass said that a typical 18 in glass pack would lob off about 25% of the high end sound waves but if you put two 18 in glass packs in series ( edit Or a long 36 to 40 incher ) you would take care of approx 65 % of the high end sound waves..... and that would allow for the lower deeper quieter tone of the long glasspack systems.... simply the exhaust air spends more time in the muffler haveing the sound waves absorbed.

I've got a copy of that book!! It was about the first in my collection..

Then HPBook's "How to Hot Rod Chevy Small Blocks" was next....

pdq67

Originally posted by pdq67:
What is it?? Great minds think alike???

Just had tooooo.... He, He!!!

And I do love them cackling, "cop-calling", W/D/T glasspacks!!

pdq67 Don't forget to soak 'em with the hose when they are warmed up... listen for a crack graemlins/thumbsup.gif . there ain't nothin that sounds like a pair of blown out glass packs :D

I know that some of my friend way back when I was a kid would fill them up with used motor oil when they installed them new to supposedly help them burn out quicker!!

But this wouldn't work with the type that were packed with steelpack material so they didn't burn out like the cheaper glasspack packed mufflers...

BTW, Never heard of the water trick???

pdq67

Originally posted by pdq67:


BTW, Never heard of the water trick???

pdq67 well I learned about it when my uncle tought me on my car when I was 12 (17 now). My dad loved that :rolleyes: . oh well what are uncles for if they don't spoil you much? :D

A little pdq67 glasspack story a comin' on!!!

Back when I was about 16.5 years old, I ran around, (b/c Dad had died early), like I was outta control.. (AND I NEVER BOTHERED ANYBODY EXCEPT MYSELF AFTER IT WAS ALL SAID AND DONE WITH!!!!)

I had noisy glasspacks on my old '57 Chevy and always made it a point ta down-shift and rack them off every time I came and went around our country town of about 450 people!

Well I came into town one Sat. morning early and a girl, (that was a friend), classsmate's Dad and Boss was working at the Blacksmith Shop I hung around at b/c the Owner took a liking to me..

They told me flat out to quit making so much noise OR I was gonna get a ticket for hotrodding!!!

I laughed and left AND got ta thinking about that so went over to the gas station where I worked on my car at AND stole a couple of old mufflers off two junk cars and came back and asked my Blacksmith Buddy if he would gas weld them on my car??

He did and I left town to get cleaned up so I could run around that evening and when I came back to town, sure enough, there sat "John Bull" in his Cruiser right where I always down-shifted to rack her off!!

I down-shifted right in front of him AND was stone stock quiet AND He just looked at me and cranked up and drove outta town..

THAT's when I finally picked up on the fact that I did have some friends in the little hick town I lived around!!

And to this day, I dearly love that guy's daughter that is my classmate b/c she has always has been a great friend of mine!!! AND I mean all these years b/c we will be going to our 40th H/S Class Reunion the next time we have one!!!!

pdq67

My story about glass packs isnt nearly as much fun... Circa 1975 a friend had a 1970 Road Runner..
12-1 383 Isky 505 lift 310 dur cam , 750 Holley , Keith Black headers with glass packs , 4 speed , 4.10 gears , L60-15's ect ect... Turbo muffler were just starting to become popular then but Bob didnt have them yet.... Anyhoo we were wrenching on the car and I was underneith installing the driveshaft and Bob was doing something with the engine.... Well he didnt see me so he needed to fire it up.... And did so.... I was by the 8 3/4 rear end about to button it up ( right next to the turn downs )...when all of a sudden my world sort of explodes with a huge ROAR of VERY LOUD HOT EXHAUST blasting on me !!! Fortunatly I was pretty thin and wiggled my way out of there VERY QUICKLY !! I was not a happy camper .... I can say this it was not anything I ever wanted to do again! I can laugh at it now as that was nearly 30 years ago.... But I wasnt laughing then graemlins/clonk.gif graemlins/clonk.gif Hehehehee

bolt on header glasspacks were what I used to run, no turndowns and no tailpipes. The floorboards sure got warm. They made a consistant sound with no crackle but they sure were loud. The local parts stores stocked them along with the thrush and regular bullet types, turbo styles used to rip open at the seam often so most around here wouldn't use them. The good ol days :D

Paul, I'm suprised you never heard of the water trick with glasspacks especially since you are from this part of the country. That used to be THE thing to do with new ones...get 'em good and hot and then blast a water hose up in there. You would know you was doing good when you could hear them creak and pop :D My first vehicle was a'69 chevy truck with a WAY worn out original 307. It burned a quart of oil every 65 miles...a true mosquito fogger. I had a single exhaust and 18" glasspack on it, and my buddy had a '72 chevy truck with duals and 24" glasspacks. We was sitting next to the school building and decided to water down the mufflers. Well, when I fired mine up with a tailpipe full of water, it shot out this thick, nasty stream of black goo (years worth of old burnt up motor oil and water mixed) that literally stuck to the freshly painted white cinder block school building. The principle was not pleased :D

He, He!!

Kinda like back in H/S getting put in detention and having ta pound the chalk outta the erasures!! Used the red brick on the side of the School Bldg to beat against!!

I bet the white chalk marks are still there!!

He, He!!

pdq67