Hi guys,

Well, now I get to learn some more stuff! While I really like driving around with only a pair of old exhaust lines attached to my Dutra duals, clamped together, then run back to under the bed of my D100 truck, inspection time nears and I must go a tad more conventional for exhaust. Like adding a muffler. In rereading all the exhaust posts on the forum I decided on the muffler (kinda think I will use a flowmaster 70) then went to catalogs and shazaam, the flowmasters are 2 - 2.25" in and one 3" out. Then I realized that for my putting a muffler at rear of truck I'd have two pipes running about 7 feet to muffler.

Uhhh, how is best to plumb a single muffler in such a case...it seems the 2.25 pipes are the best, but do you collect the two pipes into a single collector (model number?) then run a single on back? And, how about that 3" out..way too big for us slanters, isn't it?

Thanks
rock
'64d100

I think I can help here. On my work truck I run full length headers to a Flowmaster "Y" (2.25 primaries to 3" ) .....then 3" pipe to a Flowmaster 50 Stainless....thence to a 3" tailpipe. But that is on a large V8.

On a slant I would go either1 7/8" or 2" Primaries about 32" long to a Flowmaster 2 1/2" "Y" http://store.summitracing.com/partdetai ... toview=sku ...then 2.5" pipe to Flowmaster 50 http://store.summitracing.com/partdetai ... toview=sku and thence to 2.5" tailpipe.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Rock,

Here's my advice: Use 2" primary tubes to a Y-pipe (flowmaster Y is best, but shop can make it too), then 2.5" out the back. Get the Y entrance at least 1 ft behind the trans x-member for best overall perf - closer to the motor will tend to degrade low end. I would advice against flowmasters - too boomy.

You live near one of the world's greatest exhaust shops, IMHO. R&J Custom Exhaust in Apex did a fabulous job on my 64 Dart for a reasonable price. By far the best work I've had done.

Lou

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Home of Slant6-powered fun machines since 1988

Sandy and Lou,

I am humbled by being the recipient of such good info so readily offered. Many many thanks guys and Thursday will see old red get both of your advices implemented. Lou, Boyette's turned me onto Robert at R&J a long time ago but I never had a vehicle I cared to put that good of a system on before this one..to avoid burning my valves on the 20 mile one way trip down I am going to have AAA flat bed the truck down there and a fabrication with the "Y" using 2" to the "Y' and 2.5" thereafter will commence and be done by Friday. I am now leaning towards a super turbo Robert suggested. But as you found out, with his service you get to try mufflers out until you get the sound you want! I am going stainless and wanted a chrome stack behind the cab, but that is too costly....sigh.

He says the Y close to the Dutras protects the low end torque...I don't need power past 4000 rpm for this truck.

Again, thanks guys,
rock
'64d100

If I read Lou's comments correctly, the Y should be far away from the manifolds to protect low end torque. About one foot beyond the cross member is going to be maybe 3 feet from the manifold outlet. The thing is, smaller primaries give you more low end torque, and I guess if you dump into a bigger collector too soon, you might lose some of that low end torque.

I put duals on mine, mostly for the look, and sound, as I'm told performance gains are minimal from duals. If you want to go duals, order a stock set of duals for your truck with a v-8, if they ever made such a thing, and then have the exhaust shop make you the header pipes to get to the tail pipes from the manifolds. I got my tail pipes from a guy in PA who bends pipes to stock profiles and ships them out UPS. It only took him two days. But I think you are on the right track now.
Sam

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Thanks Sam,

And upon rereading Lou's note I have to agree with your interpretation..so let's ask Lou...did you mean the joint between the inlet pipes of the Y and the 2 pipes coming to the Y from the exhaust manifolds should be behind my cross member? As sam says that is about 3 feet and it would be hard to locate a Y any closer. But Robert says close makes for MORE low end torque and in his custom fabricated Y he wants to put it in front of the crossmember, or about beside the starter and dipstick area. This is a 4500 lb truck with a 4 speed not planned for high end power, but at the same time I sure would like it to run like it does no with no muffler, only pipes extended back to truck bed.

Thanks,
rock
'64d100

The "tuned length" is going to be 32" to about 38". On Chev 250 6s with factory split manifold (about 80-82) the primary length is 32.5". Lou is saying 36" (I think this is based on Cameron Tilley research) .

Knowing this I would put the Y somewhere in this range based on convienience and pricing.

Because the manifold is a log type and the runners are not equal length Vizard might suggest making the Y where the short runner and primary length is close to 32" and the long runner is close to 38" . That way you increase your torque band by always having some cylinders close to optimum.

But...then again...I could be full of shyte....

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Yeah....Im the one who destroyed this rare, vintage automobile.....

Lots of good thoughts here. I meant to Y at least 1ft behind the X-member to protect low end. Cameron said 30-34" for a race engine with headers, but these are manifolds going into secondary pipes, and you want more low end than a race engine.

Personally, I wouldn't worry about driving it down to R&J, but that's me. I would put on short downpipes to keep exh out of the engine bay, or flatbed is easy too!

Lou

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Home of Slant6-powered fun machines since 1988