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Old 01-23-2020, 06:54 AM   #1
FFG
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Headers, muffler, cat

We've got a manifold leak and I'm going to replace the headers with Doug Thorley as the Banks system is too much money and the Thorley system has good reviews. For an Itasca Passage, 1994, 7.4 big block gas engine. I'm looking at the THY306Y2-C but do I have D port cylinder heads or do I have smog fittings as this add an "S" to the product code. Reason I ask is that its going to cost me around $350 to get to the UK including customs charges so I can't afford to get it wrong. Also looking at a different muffler (upgraded and maybe a tad louder) but struggling to find one that matches the existing which is cylindrical, 20" long as has a top inlet and bottom outlet (both 3") and has the number 15666316 stamped on the bottom of it - any recommendations? Also shoud I replace the CAT which is flat (around 18" long and 12" wide by arppox 3.5" tall) and has AC, Made in USA on the bottom of it - again any recommendations. Hopefully get better mpg and with the bonus of additional torque. Engine has done 59k miles.
Also need a new O2 sensor so loking at a Bosch - think its a 15726 from Summit Racing. Thanks in advance.
FFG
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Old 01-23-2020, 02:24 PM   #2
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Quote:
Originally Posted by FFG View Post
We've got a manifold leak and I'm going to replace the headers with Doug Thorley as the Banks system is too much money and the Thorley system has good reviews. For an Itasca Passage, 1994, 7.4 big block gas engine. I'm looking at the THY306Y2-C but do I have D port cylinder heads or do I have smog fittings as this add an "S" to the product code. Reason I ask is that its going to cost me around $350 to get to the UK including customs charges so I can't afford to get it wrong. Also looking at a different muffler (upgraded and maybe a tad louder) but struggling to find one that matches the existing which is cylindrical, 20" long as has a top inlet and bottom outlet (both 3") and has the number 15666316 stamped on the bottom of it - any recommendations? Also shoud I replace the CAT which is flat (around 18" long and 12" wide by arppox 3.5" tall) and has AC, Made in USA on the bottom of it - again any recommendations. Hopefully get better mpg and with the bonus of additional torque. Engine has done 59k miles.
Also need a new O2 sensor so loking at a Bosch - think its a 15726 from Summit Racing. Thanks in advance.
FFG
A curious note here, why the oxygen sensor, do you plan on adding a programmable efi system on this rv?

Header material and wall thickness is critical to long term survival..
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Old 01-24-2020, 01:38 AM   #3
FFG
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Probably won't be able to get the old one out so for a few extra dollars I may as well change it. Hate to be in a position where I can't re-use it and have to spend a fortune in postage to the UK and wait a few weeks to get it.
FFG
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Old 02-06-2020, 05:45 PM   #4
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I have a 1993 Winnebago Chieftain TBI 454. I put Thorley headers on. The Y pipe slip connector under the trans sucks. Do yourself a favor and weld it instead of clamping. After it popped apart on me on a trip I bought a lap band clamp. Hopefully it holds till I can get back to my welder. I cut out the stock muffler and cat and went with the largest magnaflows I could get. Purrs. And yes replace the oxygen sensor. They get lazy over time. Just a standard 15 dollar one should be all you need. Muffler is a magnaflow 13740 and cat is a 95509. Bought them off amazon.
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Old 02-06-2020, 05:47 PM   #5
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And as for smog fitting....you should be able to tell on the current exhaust or find a smog pump on the motor I think.
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