BRUNO's 78-308 muffler odyssey - Ferrari Life
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post #1 of 32 Old 10-08-2002, 02:37 PM Thread Starter
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BRUNO's 78-308 muffler odyssey

Well I removed the muffler from my 78-308gtb. I cut a whole in the top under the heat shield.I now know why you get more exhaust from the driver side as opposed to the other.The 2 come in off the cats into a common area in the top half (where I cut) of the muffler.They combine and pressure forces it through the holes in the plate you are looking at.It then gets forced through at the bottom of the muffler on the right (in pic.passenger side when on car.muffler is siiting as mounted in car and up is up).It then goes to the right through a chamber and into the large tube(you cant really see it here but there are 2 tubes under the plate with the wholes 1 large 1 small) it then passes through this tube to the other side of the muffler into a common area which then goes to the 2 tips on the drivers side,then there is a smaller tube as mentioned,that takes whats left back across the muffler and out the 2 tips on the passenger side.This is why the drivers side blows harder as air,gas etc. under pressure always takes the least path of resistance.They should have made the inlets to the tips on the drivers side smaller to balance the release out of both sides.Now if I want I got to remove the 2 tubes and see if the bottom one is collapsed inside or blocked as I suspect.I get almost no exhaust from my passenger side.If I tear it up anymore it will be very hard to weld back together.Any questions please post.
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post #2 of 32 Old 10-08-2002, 03:57 PM
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Bruno, I see what you are talking about. Other than opening it up from the bottom and checking it that way is the only way to get at the pipes. Even then it might not be accessible. Maybe you should consider using the "Flowmaster" and design the pipes to fit.
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post #3 of 32 Old 10-08-2002, 04:06 PM
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Another thought. since you have the muffler out is there any way you can snake from the pipes back into the muffler and check for a restriction, like convertor crap. Also a spring flex pick up tool about 2 ft. long with a crows foot on the end is a good tool to use to get hold of the restriction. But I gotta tell ya that my 79 GTS is the same way with hardly any exhaust coming out of the pass. side. My muffler looks like it is new. My car is also low mileage. I know other guys have had this problem and I checked with Ferrari Of Atlanta and the service mgr. said it was normal.
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post #4 of 32 Old 10-08-2002, 04:16 PM Thread Starter
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I will try the snake ideal and the pickup tool. I can see why it all wants to come out 1 side.I must say though that it is a design flaw and even though they all do it a free flowing design that distributes more evenly will work better.i ordered one from Stebro.They say it will bolt right in and it is stainless.I will let you knmow what I find. When you say you get little from the exhaust at your passenger side how much is little/ I get almost none. Remember this is all in search of my problem of car acting up when good and hot.My problem is heat related and this is my next logical step.After this I am going to unhook (not remove) All emission controls and try that. I'll keep you posted.
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post #5 of 32 Old 10-08-2002, 06:06 PM Thread Starter
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You know I was thinking.If you block off the drivers side pipes with your car running the pressure should send the exhaust all to the other side.If it does not the pipe is bad in your muffler .Now that I took one apart I know the test.Oh well cant win them all.
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post #6 of 32 Old 10-09-2002, 01:47 PM Thread Starter
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Well I opened up the muffler more.A lot more.The tube from the drivers side back to the passenger side tips was blocked!!! It was blocked at the end where it goes into the common area for both tips on the passengers side. It bends upward at about a 30 degree angle at the exit. Thus making it a prime spot for blockages. I posted pics of the material that came out. I do not know if this is where this material was originally located at. I know this is where it got stuck. This explains why I had almost no flow from passenger tips. Material is a wood like cork substance like honeycomb.It is neither wood or cork in my opinion. I suspect all 308 mufflers will block at this location once this substance blocks up. I have designed a way to inspect this with little damage to muffler in future. I cut mine all up. It must be the work I do.I am not happy with something when it fails.I must know why and how to prevent it next time. Will keep site posted. Waiting for new muffler to arrive. Please post any questions.
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post #7 of 32 Old 10-09-2002, 04:23 PM
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Bruno, I can't remember if you took off your cats or not I don't yhink you did because you were looking for test pipes. However, what you have there is pieces of the "cat guts." If you remove your cats and look inside you will probably see where the stuff has popped out of the cat. This honeycomb material was used in some American cars as well such as Chrysler. That crap has screwed up more mufflers and caused more performance problems then you can believe. Although when I removed my cats and checked them and everything was intact and I still have little pressure coming out of the pass. side. What idea do you have to check or remove the blockage of pieces within the muffler?
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post #8 of 32 Old 10-09-2002, 04:34 PM Thread Starter
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Now you got to remember I have access to a lot of tools and equipment. After taking it apart I can now measure to spots where you can drill (with hole saw 1.5" will be fine) or even plasma cut. and proceed to visually inspect and run a "snake". I used a long tubing spring made for bending copper tubing.worked grreat,through the tube.I do not see the big tube blocking as it is straight with no offsets or bends.However if enough crap blew in I guess it's possible.The little tube will block at the bend where it sets up about 30 degrees before discharging into the common area for the 2 passenger side tips.I recommend anybody in doubt block off the drivers side with a couple of rags and see if the flow picks up out of the other side.If it does not a block is evident. If you are going to open it up let me know I will email you dimensions.Or even better I can make a template up and fax it to you or mail it.You will need a good 1/2" drill and a good high speed metal bit 1.5" should suffice.Or a plasma cutter.To reweld it will be no problem if you just cut a couple of clean 1.5" holes into it.Also if the big tube did block you would have reduced exhaust from the drivrs side also.The big tube is very important as it carries the flow for all 4 tips through it until it gets to the drivers side chamber.Post any questions.
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post #9 of 32 Old 10-09-2002, 04:38 PM Thread Starter
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This thing is not easy to cut through.I tried a sawzall with regular blades with little success.I ended up using a gas powered cut off saw with carbide tip.Works great but a lot of work to put back together.I suspect carbide blades in sawzall will work.A nibbler should also work.I will put hole in it with hole saw and let you know bits to get. Give me couple of days to get to it.Still waiting for new muffler and test pipes. My cats are off but I will not be putting them back on.I will be using the stebro test pipes we discussed. I find stebro to be very economical.I will let you know about sound and quality and fit as soon as they get here.
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post #10 of 32 Old 10-09-2002, 08:46 PM
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Have you checked your cats to see if they are broken. They gotta be or you wouldn't have the honeycomb pieces. So you are saying that the pass. side pipes can't be snaked up far enough to reach the blockage. Right? The muffler would have to be cut at a certain area. Am I correct? Thanks, Magoo
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post #11 of 32 Old 10-10-2002, 07:59 AM Thread Starter
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My original cats were hollowed out.Pobably after they failed.Peices must have went into muffler and were not recovered. I do not se how you will be able to fish through tips make turn into tube and push out to otherside with muffler intact.If you do and manage to push it back it will eventually block again.Let me remove 1 of the tips and see if that makes it possible to fish through. I'll keep you posted. Did you start car and try to block 1 side with rags to see if other side increased?
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post #12 of 32 Old 10-10-2002, 08:01 PM
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Not yet but I intend to do it. However the pressure will still increase somewhat over the old pressure simply because there is some pressure now and it should increase regardless. I don't think mine has the problem unless some one put 2 new cats on it after they broke apart. I kinda doubt that especially since mine has low mileage. I still would like to know what your findings are. Also when I had the muffler off there was no rattling around. Of course again if there was a problem they could be wedged in there. Keep in touch bud and let me know what you find. Wouldn't this be odd if it was causing the cut off of your car causing a pressure back up then when the pressure released the car would start again. I've seen weird things like that happen.
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post #13 of 32 Old 10-11-2002, 08:05 AM Thread Starter
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Thats what I'm wondering.I had an Audi that had a blocked cat and did the same thing.We'll see the Stebro should be here today.If it comes I'll post picks before I install it. Still examining the old muffler and ways to diagnose it without cutting it open.
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post #14 of 32 Old 10-11-2002, 09:07 AM
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My cat had been blown out as I found when I pulled the engine all apart, I got a straight pipe prior to finding out so I'll make the swap anyways. My muffler (stock) has been cut apart by someone, presumably because the cat guts had clogged it. It seems to work pretty well, eventually though I'm gonna look to swap for tubi or the likes.
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post #15 of 32 Old 10-11-2002, 03:03 PM Thread Starter
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Bretm dont buy nothing yet.Wait till I get this stebro muffler and install it.If the sound and fit is right the price is good and it is the way to go, They say it is only 3-4 db louder and combined with the test pipes should give a deeper v8 sound. They are giving me a week to see if I like the sound or I can return it. Problem is .IT STILL AINT HERE!!!!!!!!!
Where did they cut your muffler open at. Both ends?
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post #16 of 32 Old 10-12-2002, 07:06 PM
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Bruno, I would think that opening up the muffler at both ends doesn't give you the access to the pipe where the pipe is blocked. After looking at yours what do you think?
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post #17 of 32 Old 10-13-2002, 11:48 AM Thread Starter
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Correct Magoo. Thats why i aked him where they opened it up at. The muffler I have here was allegedly "repaired" and where they opened it was both ends and that isnt enough.So far the best solution I have is drilling holes at 2-4 locations to inspect muffler and reweld it. Still dont have new muffler or test pipes.. I am ging to remove the tips from the old muffler to see if that allows you to maybe fish something into the smaler tube.I'll keep you posted. Even with my drilling holes theory you might want to drill 6 or more to inspect every chamber and possible fault area in muffler. Cant wait to get new one on car and see if my stumbling after car is good and hot goes away!!!!!! Of course now it's cool out but I'll find a good traffic jam somewhere.
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post #18 of 32 Old 10-15-2002, 03:21 PM Thread Starter
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Still no muffler. Looks like Stebro B.S'd me on the availability. Hopefully this week in time for weekend. Hate missing fall drive season.
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post #19 of 32 Old 10-15-2002, 05:36 PM
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Bruno, Lets hope they are better then ferrari who takes 2 yrs to deliver a car.
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post #20 of 32 Old 10-16-2002, 09:31 PM
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The whole bottom of it was cut open from one side to the other, then I assume that cut section was flapped down to allow access into the chambers inside, then rewelded up. I repainted the stock muffler to make it look nicer. Will be cool to hear what how you like the Strebo, there was a modified 512bbi with the strebo at work awhile ago, very very mean car and sounded the part.
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