I am installing a set of Sanderson headers on my bird.the collectors are 2 inch outlet . should i change the whole exhaust system to 2 inch or use a reducer to fit the stock pipes. thanks for the help  55birdman

55Birdman  Hickory NC

Wow. Your Thunderbird looks just like a Sunbeam Tiger I used to have. Pretty cool.



I'd suggest that you not use 2" pipes if you want maximum power because they're too big. I'll try to remember to do a web search for the formula for pipe size, but I'm thinking that 1 7/8" would be better. Of course, you'd want a crossover and mismatched mufflers, too.



The mismatched mufflers will prevent the system from droning when you hit a certain RPM. I won/lost an argument with a muffler shop about this. They wanted to put exact match mufflers on it and when I asked for mismatched mufflers I got an argument. I finally prevailed on the mufflers but they got the last laugh when they jacked the price of the system. But at least my exhaust system doesn't drone.



Needless to say that I won't be going back to Boise Muffler.



If you're thinking that 1 7/8" is nearly the same as 2" here's the math;



area of 2" pipe = 3.142 square inches

area of 1 7/8" pipe = 2.761 sq/in



The 2" pipe is 14% bigger than the 1 7/8" pipe. It's not intuitive that a 2" pipe that is a 1/8" bigger diameter than a 1 7/8" diameter pipe, or 6%, has a 14% bigger area.



Try this link;



http://victorylibrary.com/mopar/header-tech-c.htm



Looks like a 1 3/4" might be even better.



By the way, the 'mismatch' between the collector size and the exhaust pipe size can actually be good for power.


Best regards,



Paul Menten

Meridian, Idaho

what do you mean by mismatched mufflers? I am not sure . thanks 55birdman

55Birdman  Hickory NC

55

       Being a "Hot Rodder" I'd vote for the larger diameter and let it drone. What good is a quiet Y Block anyhow. We've been quiet for too long now.

                                

Frank/Rebop

Bristol, In ( by Elkhart) 

here here!!!!!!! HIP HIP HORRAY

55Birdman  Hickory NC

I preferr the larger just for the sake of the engine breathing better, even too the point of going to 2 1/4 inch because by the time they put all the bends in the pipe you're bascially back down to 2 inch anyway from the way the bends are crimped.If they can mandrel bend then 2 in would be fine. Since the tailpipes on my 56 t-bird were made in a regular muffler shop I went to 2 1/5 inch pipes to come out with 2 1/4 inch over all.

-Gary Burnette-

I think 2" will be ok.  I think that's what I had on the truck with the rams horn manifolds on the old engine.  I don't know how your gearing is.  Mine is a 3.70 by the VIN plate but the tag on the rear drive looks like is says 3.89 - it's hard to tell, the tag's been smashed.  The old engine had a few goodies but it wasn't spectacular.

If the engine's stock, keep it smaller.  If you've done some work to it or plan to do some work to it, go a little larger.  Consider that if you go a little larger now, future modifications will be less likely to be restricted by the exhaust system.

I now have a 2 1/2" system with an X crossover with the new engine and the torque is great.  They seem to work well with the combination.  It is loud when I get on it.  I'll be trying some Hooker Aeroflows to quiet it down some.  The glass packs sound nice but I know that I'll be seeing the blue lights if I leave them on.  Plus I plan to start driving it regularly again and I don't want to annoy the neighbors.

Lawrenceville, GA

I've noted references to exhaust crossovers before on this site. I have a question about it. I was under the impression that they aren't really all that beneficial on a Y-Block (or a Flat head, for that matter) because neither engine uses what I'll call the "Chebie" firing order. Can someone enlighten me on the subject?     

Paul

There are very basic studies that have been run (pressure gauges in the exhaust tubing) that show that both crossover pipes and "X" pipes (like Charlie's new outfit seen elsewhere) reduce total back pressure in cars with mufflers (outlet restriction). We are not talking about individually tubed extractors, firing orders or exotica here - gas pressure only. At relatively low RPM, engines like low back pressure - engines with narrow lobe centers and large overlap numbers have problems with reversion in closed, muffled systems. 

 
 Steve Metzger       Tucson, Arizona

PCmenton,

The referenced site deals with header design.  How do you apply it to tailpipe diameter?   I'm trying to optimize tailpipe diameter for low rpm torque and am interested, and have been thinking about 1 7/8 inch also.  Currently the pipes are 1 3/4.  Your idea of mismatched mufflers is interesting.  Had not heard that before but it makes some sense.  The glasspacks on my truck side exit 1 foot behind my cab, and at a certain constant rpm on the interstate the sound gets doubly loud.

Mike

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.