Opinion on X pipe design

[eric8]

So this is what my muffler shop installed when I told them I wanted an X pipe for my mild 400hp 383. This is 2.25” pipe. I’ve had a rich WOT condition that no amount of jetting or carb swapping has been able to tune out and this is one of the last things I’m thinking could be a culprit.

Most X pipes I have seen are a Siamesed design where 2 pipes merge together. This design on mine appears quite restrictive and the more I look at it, both pipes are having to neck down to one small section of 2.25” tubing. I have been told that a restrictive exhaust can cause a misfire and make a wideband O2 read rich. Thoughts on this particular X pipe being restrictive enough to cause this?

[EDC]

HARM Mufflers and exhaust.

Best system we have even used.

[Schurkey]

Misfire produces a false-lean indication on an O2 sensor.

The oxygen doesn't combine with the fuel, so there's a heap of free O2 in the exhaust stream, which drives the O2 sensor to report a lean condition.

That's a mess of an "X-pipe", but "restrictive = misfire = rich" is not what's happening.

[cpmotors]

So this is what my muffler shop installed when I told them I wanted an X pipe for my mild 400hp 383. This is 2.25” pipe. I’ve had a rich WOT condition that no amount of jetting or carb swapping has been able to tune out and this is one of the last things I’m thinking could be a culprit.

Most X pipes I have seen are a Siamesed design where 2 pipes merge together. This design on mine appears quite restrictive and the more I look at it, both pipes are having to neck down to one small section of 2.25” tubing. I have been told that a restrictive exhaust can cause a misfire and make a wideband O2 read rich. Thoughts on this particular X pipe being restrictive enough to cause this?

Suggest you find someone who takes pride in the work they do, as that is not cutting it.

[lefty o]

ive seen worse junk cobbled up as exhaust, but id still not be too happy with that.

[bob460]

Looks like you took it to a plumbing shop not a exhaust shop.......

[steve cowan]

So this is what my muffler shop installed when I told them I wanted an X pipe for my mild 400hp 383. This is 2.25” pipe. I’ve had a rich WOT condition that no amount of jetting or carb swapping has been able to tune out and this is one of the last things I’m thinking could be a culprit.

Most X pipes I have seen are a Siamesed design where 2 pipes merge together. This design on mine appears quite restrictive and the more I look at it, both pipes are having to neck down to one small section of 2.25” tubing. I have been told that a restrictive exhaust can cause a misfire and make a wideband O2 read rich. Thoughts on this particular X pipe being restrictive enough to cause this?

i think it could be your issue in my opinion.
where it is joined at the X could be full of slag for all we know,only one way to find out.
i can see the restriction causing more back pressure leading to combustion contamination etc,i would cut the system off and start again.

[Bill Chase]

Khaos motorsports out of Grand Rapids Michigan makes a nice stainless 2.5" and 3" x pipe for a very good price. Quality matches x pipes costing twice as much.

No affiliation with them, just blown away at the quality and price, great customer service and a real American shop ran by a couple gear heads. Check them out.

[shoedoos]

OP, any chance you can expand on the comment: "rich WOT condition that no amount of jetting....."

What parts of the carb did you play with?

[eric8]

Thanks for all the responses. I was confused about what I had said earlier. A clogged exhaust or high back pressure can cause a wide band to read rich. But Shurkey is correct in that a misfire will cause a lean indication.

So far I’ve gone through a brand new Quick Fuel 750 SS that came stock with 72/80 jetting and went all the way down to 64/68 jetting and it still ran pig rich at WOT. Same behavior with a brand new AVS2 edelbrock 800. Even after going down 2 stages lean on the primary metering rods and 2 stages lean on the secondary jets.

I’ve come to the conclusion that my issue HAS to be this x pipe or either the position of my o2 sensor is causing it to read faulty under wide open throttle. I have the AEM wideband that says to install 18” from the head. I didn’t follow this and put the o2 in the factory bung in the manifolds I had to use which is closer than 18” to the head.

[eric8]

Well update. I’m here at a [different] muffler shop now. They cut off the x pipe and sure enough, there was slag all in the crossover and it probably necked down to a 1-1/2 diameter hole. They are welding in a magnaflow x pipe as well as moving my o2 sensor further back to around 24” from the head. Fingers crossed.

[lefty o]

thats a pretty big pile of steamy crap.

[EXCELLENCE AUTO]

Plumbers (on) Crack!

[motormonkey]

Oh dang, that's horrible. Somebody took the x pipe design to literal and gave you single exhaust.
Nice to hear it's fixed.

[eric8]

Well it does seem peppier now (shocker). But my old problem of pig rich mixtures at wide open throttle still remains. I think I may try a new AVS2 650 cfm Edelbrock and see how it responds. The 750 QF and an 800 Edelbrock seem just like they are too much, regardless of jetting changes.