questions on dual exhaust

[blkfordsedan]

lol yeah that motor is in rebuild time. lol it's getting bored .020 over and trying to find some good performance cams for it, but all the sites o go to like quit working when i get to waht i want lol and it sucks.

I believe one of the common tricks on a BP is to install a factory exhaust cam in lieu of the intake cam. Not sure what all is involved.......but you can't beat the price!

[hofficergrover]

i am confused by what you said about the cams? what do you mean? i don't know my dad is really the one that is helping me, but he isn't hear to explaine.

[blkfordsedan]

Honestly I thought about that, but I don't know like how I would I really don't have the tools to do extream exhaust work. I was planing on using what I have on the car and at the end getting a y well like a t that had the t part around lime 45 angels and run out before the tires.

Why don't you just go to Summit Racing and order a Flowmaster muffler with single inlet/dual outlet? I believe Summit even offers a "house" brand chambered muffler for less money. Then, all you need is some straight pipe, clamps & a couple 45's or 90's.

Splitting the manifold or header would sound great (IMO), but if it's like a V8, you really need to match exhaust pulses from the other cylinders to help scavenge exhaust for optimum flow. That's the theory behind "180 degree" headers. They match up the best cylinders (based on timing order) in the collectors to maximize scavenging, however, if the header is a 2-into-1 collector then breaking off of the two collector tubes shouldn't hurt too much.

As for running one pipe out each side, if you run a common muffler or a "Y" pipe then you should get pretty close to the same sound as just one outlet, only from each side. If you split the header, you'll get that chunky dead miss sound (like the old side pipes did in the 70's) unless you run both pipes out the back or the same side. If you change the length or bends of each pipe slightly, relevant to each other, you should get a nice dual tone sound.

Post some sound clips, whatever you do!

[blkfordsedan]

i am confused by what you said about the cams? what do you mean? i don't know my dad is really the one that is helping me, but he isn't hear to explaine.

Sorry, since you said cams (plural) and someone else mentioned a 1.8 stroker kit, I thought you had a BP engine. If you have the stock SOHC engine or a B6 then It doesn't apply. My bad.........

[hofficergrover]

haha ok i am going to stay with what i have but do a y or some thing close to it and run ou the side. i have a shorty cherry bomber on it and it sounded awsome but i want to try to have duals i like the look and hopfuly the sound.

[hofficergrover]

no i have the bp

[blkfordsedan]

^^^^ Don't remember where I saw it. Maybe it was an article I downloaded or something, but it probably had to do with a Miata. The cam profiles (lift, duration, etc.) are different between the intake cam and the exhaust cam on the DOHC engines. Dimensionally and physically they will interchange. One of the tricks is to replace the cam with the lowest lift and least duration with another used factory cam of the opposite gender. I would guess in the case of the BP they replace the Intake cam with an Exhaust cam from another BP. You may have to flip the cam end-for-end as well and machine it to accept the cam sprocket on the opposite end. I don't have a BP so I didn't commit it to memory. If you do some searching you should find all the details on a Mazda or Miata site.

[hofficergrover]

so your saying if i got another exhast cam and made it fit in the intakes spot that it would make more hp?

[blkfordsedan]

so your saying if i got another exhast cam and made it fit in the intakes spot that it would make more hp?

Actually, it's probably the Intake cam that is the "bigger" one on a BP ( just guessing, you would need to research it) so you would replace your exhaust cam with an Intake cam from another BP engine. But, yes, that's the basic idea. There may be some machine work involved, I seem to remember something about having to flip the cam end-for-end and reinstalling the sprocket on the opposite end or something.

[hofficergrover]

ooo ok il see what i can do thanks

[blkfordsedan]

I just spent a half hour searching the web for info on the cam swap and I can't find anything on it. I know I didn't just dream it...........................maybe someone else here has the info on it.

[pr0nst4r]

It's called the "ExhIntake" mod over in the Miata world.

Check out this thread on miata.net. This guy is one of the originals and you can probably find a write-up on it somewhere over there.

http://forum.miata.net/vb/showthread.php?t=18329&highlight=ExhIntake

Edit: The beauty of coming from the Miata world to another Mazda car... I got this for ya!

Edit2: Also this thread: http://forum.miata.net/vb/showthread...ight=ExhIntake

Edit3: And here: http://forum.miata.net/vb/showthread...ight=ExhIntake

Edit4: Check clubroadster.com too

[big_ty2003]

quit messing around and turbo it.

[pr0nst4r]

Quite the informative post you have there for someone that can't do exhaust work, so I don't think he'd be up to tackling a turbo system..

[big_ty2003]

lol, I guess your right.