appropriate exhaust size/muffler choice 1500

[caseyjones955]

I will be adding a header and leaving the engine otherwise pretty stock (except for the not yet selected carb/intake--webber, SU or dual SUs).

Along w/the header I will be doing the complete exhaust. I am wondering what an appropriate size exhaust will be for an engine w/only these mods?

I would like to open it up a little but not so much that low end drivability suffers. Give it a nice tone but not real loud. I was thinking a small flowmaster?? any other good chioces? 1.5", 1.75" big enough for this little mill?

Thanks.

Tony

 

[JPSmit]

muffler? /ubbthreads/images/graemlins/devilgrin.gif

 

[jlaird]

There is a thread here some place that gives all the info you need.

 

[caseyjones955]

I searched archives before asking and didnt find anything, Ill try some other terms and see what comes up.

 

[Baz]

Picked this up, I vaguely remember the thread Jack was talking about, but this may help...
BCF Thread

 

[jlaird]

Tell ya what it was Jollyrogers post/answer that gave all the details..

 

[jlaird]

Here ya go

https://www.britishcarforum.com/ubbthread...true#Post248596

 

[Baz]

That's the one Jack. Knew it was in there somewhere.

 

[jlaird]

Some of this stuff needs to be in the knowledge base, but who or what makes that decision and does it I have no clue.

 

[Baz]

There is supposed to be a 'contributor', I agree, a lot of stuff gets recycled and would be nice to have a central point for things like this that are fairly standard.
Anyhow, who the contributor is, I don't know either...

 

[caseyjones955]

Excellent, thats the info I was looking for. Thanks for linking the thread!

Tony

 

[ChrisS]

[ QUOTE ]
Some of this stuff needs to be in the knowledge base, but who or what makes that decision and does it I have no clue.

[/ QUOTE ]
Is this what you want?
https://www.britishcarforum.com/lore/article.php?id=081

 

[jlaird]

Was more intrested in this part actually.

<!--[if !supportLists]-->• <!--[endif]-->I didn't really need to replace my exhaust several years ago and wrestled with a few questions that you are asking, but haven't quite asked? What works and sounds best. Questioning everybody about exhaust back pressure, and getting a lot of different answers. What Vizard says is no back pressure is the best. Anybody that tells you otherwise, just hasn't tuned the carbs correctly. It is a system, and does not work independently. The largest diameter that works is better; I went with a 2" ID. The muffler shop bent the pipe and put an oval muffler on it and I have been really happy with it since.

<!--[if !supportLists]-->• <!--[endif]-->Actually the size of the pipe IS very important. A mild tuning likes a 1 3/4 inch tube all the way to the rear. A full on car(11 to 1 or more with .5" lift and 290+ duration) likes a 2" pipe all the way back. Kicking the exhaust out in front of the rear wheel works ok only at7500 plus and limits the throttle response/drivability.
The velosity of the exhaust affects the intake charge greatly. Basically if you slow the exhaust by going to a larger diameter pipe you will reduce the scavenge effect that pulls a fresh charge of fuel into the combustion chamber. A nice can type hi flow muffler of the proper size will work great. Some "glasspacks can inhibit gas flow. A mild tuning will work fine with a glasspack and pipe of 1 3/4" size.

 

[Baz]

Chris, very helpful. Appreciate it.