Found out today, while doing some engine t/s'ing, that Chrysler chooses not to use hardened valve seats in our 4.0's. Learned this from a certified mechanic website used by the big guys to pass Q&A around. I always thought ALL valve seats were hardened ever since unleaded gas became mandatory.
How is this pertinent? It gets to be pertinent when you're looking for the reason for rough idle. Dinged up valve seats can cause inconsistent compression at idle, especially when some of those little dings catch carbon deposits.
What else? Didja know that a misfire can cause your torque converter to exhibit erratic behavior? Yep!

Maybe a couple of you gents will find that info helpful. I did.
Best to all,
Bob

 

Gotta link to that certified mechanic website and more specific to where it says hardened valve seats are not used??????........I'm from Missouri, the "show me" state. LOL

 

The 6-242 doesn't use separate valve seats, they are integral to the iron head (just as the valve guides are integral as well.)

They may have used local induction hardening to the valve seat area on the head - I don't know - but major damage to the valve seat area will require machining to head to accept a valve seat insert.

 

I think unleaded pitting valve seats got a little over hyped. Just my .02. Maybe it's more of an issue with high performance than it is for my 66 Ford 6 or old Toyota's.

 

Got a cert, or subscription to that info and those sightes? real shops pay good money to have access, so why should you get in for free?


And before you bash, i do, and i know i cant spell

 

 

Confused. Lol

 

What's the BFD about getting in for free.

 

If you go look at my original post, it says nothing about me getting on that site for free. It says nothing about it being me that was on the site.
Who was on the site is the Chrysler certified mechanic who owns the shop that was trying to get a handle on a problem with misfire for me. This gent is a former Chrysler engine tech in the Cherokee plant, and pretty much knows the 4.0 inside and out. My problem was a bit baffling, so he went searching for answers. Even his $20K diagnostic computer was at a loss to locate my miss. The miss was enough to tell the computer to unlock the converter due to loss of engine power.
And if it makes a difference, he does pay his dues for the site. I don't know the name of the site, I don't have the credentials to get on it anyway.
I posted this only as a source of info for anyone who chooses to look in that direction. Now and again even a blind sow finds an acorn, ya know?
Regards,
Bob

 

Yes. AMC started induction hardening the valve seats in it's I-6's in 1972.
Chrysler did not design the 4.0 head, nor did they make any valve seat decisions. That was done by AMC in Kenosha before Chrysler took over.
Chrysler made a few relatively minor head changes over the years including the infamous 0331 emissions redesign, but did not do away with the induction hardening. Heck, they ran the original AMC tooling until it finally wore out in '96 or '97.

 

I'm familiar with that idea - the 6-242 was released for the 1987 model year (as we all know,) and ChryCo bought AMC/Jeep ~AUG1988.

They revised the head three times:
#7120 (1991-1995,) had the intake ports raised slightly to reduce the change in direction in the intake port, which increased airflow slightly. This yielded nominally higher engine output.
#0630 (1996-1999,) reduced the exhaust ports slightly to improve catalyst light-off time (emissions mod.)
#0331 (1999-2006,) reduced the exhaust ports a bit more, modified the intake slightly, and the earlier ones (1999 to mid-2001) are the "#0331 Club" or "#0331 Card" heads that crack. The later (mid-2001 to 2006) heads with the TUPY foundry mark are revised to address this, although there was no official acknowledgement and no recall issued.

Likewise, ChryCo revised the block - I believe, twice.
1991 - Lightened the casting for NVH reasons and to save money on material.
1996 - Lightened the casting again (the addition of the main bearing cap brace isn't a "block modification," as it may be retrofitted to any 6-242 engine merely by replacing the main cap screws with the later screws - with 3/8"-16 stud tops - and fitting the brace.)

What I can't stand is that fuel with TEL ("regular" gas) isn't available anywhere in the US anymore, that I know of. However, CA can still fail you on emissions if you don't have the stupid little "restrictor" in place (it was to keep you from sticking a "regular" fuel nozzle into an "unleaded" vehicle, as it was slightly larger.)

Pretty much the only automotive fuel pumps that have larger nozzles than unleaded anymore are Diesels - and if you try to pump Diesel into a gasoline engine, you've got bigger problems and really shouldn't be driving (won't run anyhow.) So, why keep the requirement?

And, why are new vehicles still made with that stupid little restrictor? It's not necessary anymore (I don't think there are very many countries at all that still use TEL as an AKI improver additive...)

 

"And, why are new vehicles still made with that stupid little restrictor? It's not necessary anymore (I don't think there are very many countries at all that still use TEL as an AKI improver additive...)"

You can always fill up with leaded av fuel @ your local airport.

 

So the bottom line is, the valve seats, or the area where the valve seats, IS hardened.

 

Interesting...and thanks. Filled in some gaps in info that I had wondered about. I should clarify the Chrysler comments were not directed at you, but to the subject of the thread itself, that Chrysler "chose not to use hardened seats". That was not the case.

If I'm not mistaken, the "0331" head problem wasn't so much the redesign itself as the fact that (I believe) they finally replaced the old head tooling and casting fixtures along with the redesign, and had issues with the new setup.

 

That's technically "low lead" (not as much as regular, but a bit more than unleaded) as indicated by being specified as 100LL, 110LL, and 112LL.

And good luck getting it airports around here! If you're not putting your nozzle into an airplane, they'll come out and try to stop you.

Yes, even if you're using Jerry-cans.