I am taking a step towards getting rid of my Glasspaks* and re route my exh pipes, not because I dont like them ,but because the former owner ran the pipes straight back under the body , not in the tunnel ...and after lowering the car I get scraping..the glasspaks themselves are too far forward and gets crunched..
my question is this... would I be better off running just the transverse muffler behind the axle,with flowmaster or dynomax, or just have the two in front of the axle? my thinking is that just running transverse would give most clearance... and it should not be louder than the glasspaks , I assume with just the transverse... what am I thinking wrong, if anything?
if you look at my car on the pic below (online show) you can see where the glaspaks are low, right under the center...you can also see the shadow line of the pipe hanging under all the way from the front...
* probably going to the 'muffler man' this saturday to get it done.
I have been reading up on exausts and doing a lot of window shopping, and I'm probally going to go with a new exaust from the headers back. (No cheering from the peanuts' gallery Ash.)
From what I can gather and based on prices I have received and heard from others, it seems that the Pypes system is the most cost effective. Also, from the postitive replies from users of the system, it seems to create more power than custom exausts. It is a case of cashing in on sweat equity when you diy.
Pypes has a system with the transverse muffler, but if I recall, it's pretty high dollar. Based on what I have read, the claim is that the transverse muffler isn't that efficient. Whatever you decide keep in mind that H pipes or X pipes are major mandatory. Also you want to have the mufflers as far back as possible.
Bjorn...I would just get the custom stock dual exhaust system in the 2.5" diameter with Flowmaster's. The muffler's will be tucked up close to the floorpan anyways and you wouldn't have any muffler to ground interference. The transverse muffler would even tuck up higher under the car but I believe you would loose a little power with this muffle.
Need dual mufflers, right in front of the rear end. Flat, standard size that the car is made for. Add a transverse to that if you want, but not sure why anyone would want three mufflers. Lots do it, but its beyond me as to why.
Must have an X or H flow Cross in the system for real exhaust balance. I've researched that X is better for flow. Others will disagree.
2.5 inch mandrel-bent tubes all the way from the collectors to the exhaust tips, nothing less Bjorn!!
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?
looks like Ill be asking the shop for two in front of the axle and an H pipe ( sorry Nash , I`ve had more positives of H`s than X`s from people) ..the transverse will not go in , I just had that as an "instead" of the two, but if I use the two, thats enough...I`m not worried about the noise...not after the glaspaks...I may miss them ...LOL
I wouldn't go with blowmasters. I know they're popular and they do sound good when idling but they have a real bad intonation at around cruising rpms that vibrate everything in the car. Go with the dynomax with what they call roving fiberglass. Doesn't seem to hit that tone. Probably cost more but you get what you pay for.
Bjorn - PLEASE check out Jim Hand's book. He has way too much info on exhaust systems in there. Interestingly enough, the fastest muffler (a certain Dynomax) was also the quietest! He also highly recommends an X-pipe and not an H.
Hand backs up all of his assertions with reliable track testing.
Bjorn, My '68 has only the transverse muffler on it and I have no problems at all. It is, for the most part quiet at idle, but is as noisey as I care for on a driven car. I got the entire system from a POCI advertiser, I want to say Kapich or something like that. Fit & function was my primary concern rather than performance. Prior to this system, with headers I had only the two and no transverse. It never gave me problems, but I wanted a more original appearance since I'd put a set of long branch manifolds on it back in '88.
I installed pypes x pipe on my 69 coupe. The sound and fit are great. I bought mine from a mustang store on ebay I save about $100.00. Check this site out if you want to see the x pipe on a convertible http://pypesexhaust.com/gallery39.html
I need to do convertible and when I do it it will be with pypes
Bjorn, the H pipe is allowing gas and air to be pushed at near 90 degree angles! You call that free flow? If you are buying NEW you truly must go with the lesser resistant X pipe crossover. :p
Geesh, for a nice quiet guy, you've really stirred up a hornets nest here!!
'68 428 HO M3 Monster, 4-on-the-floor! Need I say more?
Keith , yes thats Dougs car ,he sent me that directly (from PY) but its not that easy...if you look , his car had to get a spacer ,looks like 1 - 2" deep for the X brace to fit the pipes under... I am still worried about scraping , notice my car is lowered...I am changing pipes etc to get more space under , so I`m worried about getting rid of the pipe under ,but replacing it with a lowered X brace... and Nash , yes this is excactly why I keep asking , stirring the hornets up...lol.. the H is lots easier to install, less space req`d (I think) than the X that takes more room lengthwise (maybe?)....the X brace(only converts) is an item to be aware of... I understand H is more restrictive than the X , but in my case H would be less restrictive than nothing , which I have now... it may even come to use nothing, who knows...until I see an H with a X brace I have no clue to see the difference to/from a X pipe... and I dont want to delete the X brace...I rather then not connect the pipes...
as I keep telling Drew , its not "just" hp that counts...LOL
Thanks Johhny , someone already did... and its a X pipe , but not a convertible there...it works great on coupes...
and for Keith, this is Dave Boulducs answer re my question re the X brace...: "it was too tight...a 2" exhaust would fit.....thats all....some suggested that using the blocks defeated the brace integrity....dont notice any diff....have yet to bottom out
Tom Hand (Jim's son) has been to my home and he concluded the kits required the spacers for the brace, which disables the emergency brake.
Let me know if you squeeze and H or X pipe in on your convertible. I ended up with a custom exhaust, single muffler behind the gas tank, but no resinators or H/X pipes.
Johnny ... I dont want to disable the emerg,. brake, the H or X is a "hopeful" ,but if not possible without lowering the X brace (which I think may defeat the endresult of what I`m trying to do (clearance under the car, trying to get the pipes up from the ground, into the 'tunnel'), I`ll go without the 'connection'....I first thought of going with only the transverse muffler behind the axle ,for clearance, but have been convinced that going with two in front of the axle instead is better...(less back pressure with dual exh and mufflers than with a transverse, I`ve been told) I`ll let you know how it goes... also the shop that will be doing it is run by the brother of one of our HALF guys so I hope I`ll get a great 'system'....
and under side of one of the pics of Doug Boulducs car shws the emerg brake cable wrap around the lowered X brace...I was curious to how that would work...obviously it doesnt...
I have an "H" pipe on my 69 vert but I also have a 4-spd which makes it fit easier. I have pics but they are on my old hard drive and I don't know how to access them yet. Pete
Bjorn...If you're running headers which hang low to the ground, the X or H head pipe might not be a good idea as this will hang lower also in your present "lowered" condition. I would think it would be OK for a car which hasn't been lowered more than stock. Also, make sure that the muffler installer adjusts the tailpipes away from the gas tank or the springs so you won't have any pipes banging around when you hit a bump.
Ken, I have no headers ,I run stock exhaust manifolds. my current tailpipes are in there ok, even though tight.. ,and the new should be in exact same location... I am only taking the pipes that are UNDER the body, under the floor areas and sticking them in the tunnel where they should be, then will have two mufflers in the stock location...mostly intersted in to what extent I can use an H or X in conjunction with the convertible X brace , without lowering the X brace...
Peter , yes with the automatic I have less room...if you had access it would probably have helped...since it looks like you are theonly one with H pipe and convertible...
maybe someone else has it too? the preferred pic would be of an 69 conv. w/ X brace, and automatic and a H pipe...
I would like to add my two cents if you do not mind. An exhaust system is a subject that has many options. Many people have their own experiences and opinions as to what to do and how to get there. So you have to ask yourself what are your objectives? Ground clearance appears to be the most important. Second is performance. (H/X pipe)Third is sound(?) If it were my car: I would go with a high flowing muffler that Tom Hand suggested to me. Dynomax #17725. This is a 2.5" dual inlet/outlet transverse muffler. It will give you the flow (performance) you are after, and the ground clearance. I would look into an H pipe when they get your car up on the rack. If it looks like it might interfere with the trans or hang too low, I would scrap that idea. This muffler should sound similar to your glasspacks. (aggressive/raspy)The Hands have done some extensive track and bench testing of mufflers. Their recommendations are well respected in the Pontiac community. Some "High Flowing" aftermarket mufflers do not flow as well as one thinks! Good luck with your project.
Were does a person buy a complete exhaust for a 1968 firebird convert.I really don't want a transverse system.I do have long branch exhaust manifolds.Any help would be great.Thanks Mike
What do you mean it's not JUST about HP! There's no such thing as TOO much! LOL
Bjorn, you should be able to get an x-pipe or an H-pipe system to work on your car. I would be willing to bet we could put my current 2.5 inch exhaust with the H-pipe in your car without issues with the cross brace. Remember mine was ticked way up in the tunnel.
Robert , Yes I think he does...I`ve ridden in it...but he`s got headers..and may connect a little differently? looking for stock exh. with H and 2.5 " pipe and X brace... oh well, tomorrow I`ll know how/if it works, just wanted to be able to pre-order muffler I decide on , but it will just have to work out.... again my main concern is clearance.....car runs fine...worst case I could even stick with 2 1/4 pipes again...its only a 400...
I love the sound of your G-packs. Just to add my $.02, When I had my exhaust done I had the H pipe installed just to maintain accessibility to the transmission etc. I think I would use the X pipe if I were to do it again. The biggest problem I had was the clearance between the trunk floor and the exhaust pipe where it runs over the axle. They ran it so tight that it clunked against the body and was also hitting the leaf springs when I went over bumps. Make sure to stick your nose under the car before accepting it. I had to go back 3-4 times before they finally pulled it out and did it correctly.
Bjorn, my old system also bumped against the leaf springs. If you want run 2.5" pipes over the axle and out the back, its a very tight fit. I think thats gonna be a bigger issue for you than the x pipe. I now have the stock muffler setup, with the pipes fabricated at the shop. He had to use 1.5" going over the axle. Not saying you can't use bigger pipes, it'd just be tough. I'm happy with the new system.
Got it done today,,, sounds great...only got to drive 2 miles back home,but felt good, tomorrow will be test day...got 2.5" from the 2 1/4" 'starter" pipe, that hooks on to my stock exh manifold, got a H pipe in , runs great by the 2 sched. 40 Flowmasters that I ended up using to my TA splitters ...got the clearance I wanted...test drive hopefully will tewll how performs, Ill also find out if ANY scraping happens where I used to scrape...I assume not. Thanks to all who responded with Ideas , photos etc
Bjorn...You've got the perfect exhaust system now!...I'm sure you'll like the way those Flowmasters "growl" when you "get on it" I'm glad everything worked out for you.
Thanks Ken, yes I am very happy now...sound is good , runs good (did before too), but for some reason it seems to start easier when cold , not the same need for the choke!?? , cant figure that out ,seems to me it should have no effect on it ,but seems to... had to go back , because one pipe was a little too close to the body as it went over the rear axle and at BIG bumps hit the body....
haven`t had enough time or great weather l;ately to really take her out for a good spin ,but soon...
and going in to my office garage ,where I used to scrape , I get about 2" clearance!!
</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> The biggest problem I had was the clearance between the trunk floor and the exhaust pipe where it runs over the axle. They ran it so tight that it clunked against the body and was also hitting the leaf springs when I went over bumps. </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">thats excactly what happened Brent! but no problem with leaf springs....took it in today ,they gave me 1/2" more clearence to the body, we`ll see...
...and after lowering the car I get scraping..the glasspaks themselves are too far forward and gets crunched.. 
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