Quote Originally Posted by FMS88 View Post
How much oil is it using? Is it as bad as (or worse than) before the head replacement? Does it blow blue smoke all the time, or on start ups and mostly when accelerating from a stop? If it's a serious issue, best to address before worrying about the catalytic converter.

If the consumption is excessive, do a compression test and maybe a leak down test if the compression test results are concerning. If it passes these tests, the rings aren't the issue. Maybe they used low quality valve stem seals on the new head. Bad seals won't affect compression readings, but they will increase oil consumption.

Regarding your questions about the manifold and converters removal, I don't know for a fact, but it looks like there's room to remove everything together. To separate them, use plenty of WD40 and an impact driver. Hopefully they're available at Five 0 Motors.

If you do disassemble the manifold and cats, why not give the lower cat the same "treatment" as the upper cat? It would save the cost of a new lower cat. Or alternatively, why not get a set of Pacesetter headers which are about as costly as the lower cat? Both options aren't EPA compliant, but neither is treating the upper and replacing only the lower converter.
The Saga Continues to Evolve

FMS88 I have never measured oil used per miles driven but the oil used is about the same as before & after the new cylinder head install ~ just seems that every or every other gas fill that it needs at least 1/2 to one quart of oil ~ I put gas in the truck whenever it is 1/4 full and am not sure how much mileage it gets per gallon of gas ~ 5 years ago when we shipped the truck to Hawaii the best it ever got was 22 MPG ~ but, new tires caused a drop in MPG to about 18 to 20 ~ replacing the O2 sensor made a world of difference in smooth idle, no more miss & gray colored tailpipe BUT that only lasted two days ~ since taking the truck (1/26/23) on the H3 fwy for a 26 mile mission @ 60 MPH, it used half a tank of gas per the gauge WOW BAD WORSE EVER YET and I noticed going up the steep 3000 ft elevation the engine coolant temp gauge got up to 3/4 to 7/8 scale almost reaching the red mark ~ so, gas mileage is poop; the engine runs very warm on a steep grade; loss of power could not get over the Koolau Mtns in 4th gear as usual but had to use 3rd gear, and there is often a big lag of power now, as tho no fuel is getting to the engine but then after a moment it slowly picks up and goes (using a very slow gradual press on the accelerator usually prevents this nagging new miss) ~ my gut is telling me after seeing the front catalytic converter full of crud blocking the honeycombs that a fix is needed to the exhaust cats, at least ~

I hear you about damage to cats 'n should fix those problems before install of a new cat (truck had a recent history of coolant out the tailpipe & an O2 sensor that was toast and perhaps 35 years old..!? and, a history of burning some oil) all of which ruins cats ~

With regard to putting this California version truck back to legal C.A.R.B. smog standards you're right, it ain't gonna happen on my watch; it would cost too much and I doubt it will be shipped to Calif, but you never know ? anyway, since Hawaii only requires an EPA/FED style cat and since I have not yet checked MitsubishiPartsCentral about availability of that front case style cat inside the exhaust manifold; the plan is shaping up (if Big Red Auto supplies the rear FED cat) to install a new rear cat into the exhaust piping ~ hopefully a FED cat there might last near the 25,000 miles before getting plugged or rusting off and it should help prevent nasty exhaust smells ~

The direct fit Big Red cat is $300.00 free shipping to mainland

If Big Red Auto will not supply their cat then I will be forced to buy a cat from my local O'Reilly's which has C.A.R.B. cats for the truck but it would require me to cut weld fabricate the old piping onto the O'Reilly's cat priced @ $229.00 + $10.00 shipping ~

Heck, I still need to measure the O.D. of the exhaust piping; it must be either 2" or 2.25" as that is the size cats everyone sells; RockAuto lists the manifold to piping gasket size as 2.25"

At least Big Red Auto might be a source for folks needing a catalytic converter for these trucks..?

Do you think any California SMOG inspector or SMOG station is savvy enough to check the front cat being missing inside the exhaust manifold..? I think not but they sure as heck would look for the CARB # on the rear cat, yeah..?

I really appreciate your estimate that the manifold & cat could come out as one piece, not sure the difficulty of removing those two spring covered bolts holding exh manf to pipe, hmmm...

Life is Good
Aloha ~ George