muffler Qs

[C-Pierce]

2 questions

1 I am backdateing my SC and i have heard that I need to buy a '74 only muffler- this is 2 in 1 out and wil work with the large bumpers- so is this correct?
2 is CIS better with factory baffled muffler or will any muffler work? I have als heard that the CIS dyno sheets done by many show that the factory muffler is the best possible combination of breathing and muffling and the these aftermarket 2 out deals really dont work as well as they say and could possibly hurt torque curves.

what do you think? I would love to hear it.

thanks
Chris

PS I am looking for a muffler that will work and heater boxes too!

[dlagerstrom]

By backdating, you are doing the heat exchangers and muffler, correct? The pre '74 or SSI style heat exchangers and a pre '74 muffler are the ticket. I put SSI and M&K 2 into 1. There are many options.

I would do a search on backdate and muffler to see some of the posts. There doesn't seem to be much real dyno information but most believe you will see around 10 horse improvement. You can do a 2 out muffler but they are louder and you have to modify the right rear valance to allow for the additional out pipe. Not sure if there is any performance gain but many do it for the sound.

Remember that you will also have to back-date some of the oil lines. Also, do a search on removing exhaust port nuts as you want to avoid breaking the exhaust studs if at all possible. I had to drill out 2 of mine as they broke.

I hope this helps. Good luck.

[Ole Petter]

It is correct that the pre 74 has 2 inlets.
The quoted "will hurt the touqe curve" has some truth, as the torqe low down will suffer. But the midrange will improve much, and so the top end.

I have fitted a second tail pipe on my OE muffler on the right side ( I also cut into the muffler and opened it up in the middle, where there are 2 pipes, one that goes to the right side and one that goes straight through the middle chamber. This so that the gasses can go to both tailpipes with the same lenght.) (see the threads on this forum "making a sports exhaust".

At first I drove with the system "open" and it made a lot of BEAUTIFUL noise, but in the end it was, well just too much. But the engine was transformed - in the low revs there was little power, but it really really came on song in the midrange and just took off and hit the rev limiter with a vengeance in full fury. The noise/music from 3500 revs was just awesome! But It was to much sound and I opened the muffler again and made a pipe from the mid chamber to the second exhaust-pipe (on the right side) exit. I now have a muffler "split in two", with equal lenght pipes at both sides. The pipe on the right side has no silencing, but is made of "spiralled flexible pipe" so the gas has some "damping". There is still noise, but it makes much music as well it growls beautifully then revs drops and dips. Idle is a bit coarse, but it is a compromise. I miss the insane mid/toprange though, the midrange is fine, but the top end is not stonking. At low revs things are just about as standard, it pulls "strongly" from 1300 revs in third gear.

I have some ideas with exhaust-valving to give me the best compromise... I my humble opinion the muffler is a bag of compromises at best, and the OE is maybe the best for noise, torque and very sensible - but quiet and restrictive in my view.

The CIS needs to be adjusted when you install a sportsmuffler, but is very happy to apply more juice. I had no problems with it at all.

You just have to ask yourself what you want. If you want more sound/power the muffler is a great place to start... It is for a reason the racers runs with megaphones!

Ole

[mb911]

the CIS should be adjusted after fitting ssi's or = to ssi exchangers

As to performance to all the aftermarket mufflers you will not see huge gains or losses with most aftermarket mufflers or stock for that matter. There are a couple mufflers that have a brick wall effect which would effect performance but sound will really be your issue and how loud or not so loud you want it. if looking for the sleeper kind of car go with a stock muffler/ansa if looking for agressive then go to pelicans muffler page write down all the different mufflers they sell and then go to youtube and have a listen. this will give you a much better basis for choosing most mufflers will gain or loose you in the neighbor hood of +/- 2-4 hp range the heat exchangers do most the work.. The other consideration is weight savings.

[C-Pierce]

Ole Peter, dont racers get rid of CIS? know the ones here do, megafones are usually done on carb motors from what I understand...

And MFI motors are best with a factory sport muffler or a factory 1out, as well.

from what I have heard.

thanks for the other input.
Chirs

[mb911]

Originally Posted by C-Pierce

Ole Peter, dont racers get rid of CIS? know the ones here do, megafones are usually done on carb motors from what I understand...

And MFI motors are best with a factory sport muffler or a factory 1out, as well.

from what I have heard.

thanks for the other input.
Chirs

pretty much BS (MFI statement)so most of the guys I deal with on a regular basis and they are very well respected on this board along with others as well as the porsche world engine builders/tuners

[C-Pierce]

I prefer the sleeper look, I dont need Bling! I also hate hate hate the loud mufflers that are on these little rice burners here in my town. what a joke! If the stock muffler is the best compromise then that is what I shall do.

the big question is; are all mufflers 74 back the same? or is 74 a special year for the tail pipe. 74 cars were big bumper/short hood cars but had the 2in1 out muffler- so is that muffler special? or was it the same as all pre 74 cars (ie long hood) cars?

Thanks
Chris

[C-Pierce]

Originally Posted by mb911

pretty much BS (MFI statement)so most of the guys I deal with on a regular basis and they are very well respected on this board along with others as well as the porsche world engine builders/tuners

So what I heard was wrong? maybe I skewed the info..... what have you "heard"? what is the truth/ dyno result?

maybe that should be another thread?

Chris

[mb911]

Originally Posted by C-Pierce

So what I heard was wrong? maybe I skewed the info..... what have you "heard"? what is the truth/ dyno result?

maybe that should be another thread?

Chris

Truth be told I deal with high end porsche engine builders and race shops all day every day. we have had extensive conversations about this as I supply them with mufflers for their needs. Not one of the shops that I deal with give any validity to the claim the MFI can only use stock mufflers most suggest that simple "correct" tuning will make any issue disappear

[mb911]

Originally Posted by C-Pierce

I prefer the sleeper look, I dont need Bling! I also hate hate hate the loud mufflers that are on these little rice burners here in my town. what a joke! If the stock muffler is the best compromise then that is what I shall do.

the big question is; are all mufflers 74 back the same? or is 74 a special year for the tail pipe. 74 cars were big bumper/short hood cars but had the 2in1 out muffler- so is that muffler special? or was it the same as all pre 74 cars (ie long hood) cars?

Thanks
Chris

go for the ansa then the dansk will be too loud for your needs IMHO along with the other aftermarket mufflers

[C-Pierce]

So mb911 you are obviously a person who would/should know the real answer to my question. are pre 74 muffler tail pipes shaped differently becuse of the different bumper or they the same?
I would assume that the (if there was a difference) current manufacturing process would make it backwardly compliant so it would work on both. but If I were to buy a muffler with a pre '74 manufacture date on it at say a swap would I have an issue with fitment?

thanks
Chris

[C-Pierce]

I am also surprised you didnt suggest a MK- got any samples?

sell me on it..

Chris

[RWebb]

MFI _is_ more sensitive to muffler choice than CIS or some others - partly due to the fact that the cam design is less constrained - i.e. one can be at much higher rpms. That does not mean that most mufflers will not work fine with your car/cam/etc.

Get Bruce Anderson's book for more info on this. Beyond that, some of this info is secret; but unless you race that need not concern you.

[RoninLB]

mb's comments on design are superior than anything i can offer besides that I inspected his at Hershey and they are noticeably very well built.

[My prejudice comes from staring at high end tuna tower design and welds.]


many pelicanheads love them.

[mb911]

Originally Posted by C-Pierce

So mb911 you are obviously a person who would/should know the real answer to my question. are pre 74 muffler tail pipes shaped differently becuse of the different bumper or they the same?
I would assume that the (if there was a difference) current manufacturing process would make it backwardly compliant so it would work on both. but If I were to buy a muffler with a pre '74 manufacture date on it at say a swap would I have an issue with fitment?

thanks
Chris

The tail pipes are in different locations for bumper exits and heights so they don't swap back and forth very easily. so you need a 74 up muffler which have a ton to choose from but would suggest the ansa because it will be very quiet compared to all the rest

[mb911]

Originally Posted by C-Pierce

I am also surprised you didnt suggest a MK- got any samples?

sell me on it..

Chris

Not my purpose in answering the question plus I am not real sure it would fit your needs of the sleeper.. I hope you find what you are looking for.

[C-Pierce]

Originally Posted by mb911

The tail pipes are in different locations for bumper exits and heights so they don't swap back and forth very easily. so you need a 74 up muffler which have a ton to choose from but would suggest the ansa because it will be very quiet compared to all the rest

That is what I thought! it only makes sense... thanks, boy it took a long time to get to that answer.

And I was joking about the possibilty of selling me on your product I Have heard them.


thanks for the input though.

Chris