Pre 99 headers on post 00 head

[Joshy]

G'day,

Probably a stupid question...

Why won't the pre 1999 headers fit on a post 2000 Wrangler? The earlier design looks much better and the single outlet would simplify the system.

I'm assuming it's one of three reasons:
1) the 00-06's had those pre cats in some parts of the world and they need to be retained;
2) the engine mount's in the way; or
3) the exhaust ports are higher in the head and the older headers won't fit the newer head.

Maybe I'm way off. I've tried searching but haven't had any luck.

Thanks for any advice

[SilverXJ]

A) The precats won't fit with the earlier headers.

B) With the precats you have 4 o2 sensors. This poses two problems: 1) You would need to correctly locate two bungs for the upstream o2 sensors. Bank 1 needs to see only cylinders 1-3 and bank two needs to see only cylinders 4-6. 2) You would need to do something about the after cat O2 sensors since you don't have a place for them nor a cat for them to monitor.

If you don't have the precats you can install the earlier header and just get some custom exhaust work done to mate it to the stock pipe.

The earlier headers will not get in the way of the engine mounts nor have issues covering the later head exhaust ports.

[Joshy]

That's sweet. Thanks champ!

The Wranglers don't have pre cats in Australia. Just one O2 sensor before the single cat under the skid pan and one after. That makes header selection and the rest of the system heaps better.

Thanks again

[SilverXJ]

The Wranglers don't have pre cats in Australia.

Then you are good to go.

However, one other option is to run a later header and do a true dual exhaust to the rear.

[jeepman]

I would just go with the proper header that matches your port size. Mopar actually installs the newer exhaust manifold on some 99's with the 0630 head so it should work the otherway just use the gadket thst matches your manifold of choice.

[SilverXJ]

The 0630 heads don't line up very well with the stock cast iron exhaust manifolds. I have never heard of Mopar doing that.

I know of no after market header that won't cover both head ports. The headers don't really match the port size as they are all significantly larger.

[jeepman]

I have seen Many 99's with the 0630 head and the newer 0331 (00+) exhaust manifolds
so I am speaking first hand knowledge. I believe this was an end of production thing but
have no confirmed reason for it. Regardless of the ports being offset, that doesn't mean
It still can't be done as the gasket that matches the manifold will block the offset and limit
the flow. But it's possible. I wouldn't do it but that doesn't mean it can't be done.

They have primarily been in WJ's...

[SilverXJ]

The WJ never had the 0630 head. All 0331s.

Regardless of the ports being offset, that doesn't mean It still can't be done as the gasket that matches the manifold will block the offset and limit
the flow.

It can be done but a) the gasket and manifold itself will significantly block the bottom of the port b) there will be limited sealing at the bottom of the port.

[jeepman]

Please stop calling me a lier. I have physically seen and removed this head on more then one occasion and as previously
stated with first hand knowledge. I unlike you I am speaking first hand, I was unaware
that you specifically have inspected every single 4.0l ever made which is what must make your
word gospel. I also said I wouldn't do it because it would block and restrict flow but could be done.

I don't see why you skip certain things said and focus on only certain things.

I understand a lot can be misunderstood on the Internet and I am no author but really I
was sure to be clear on having first hand experience and not speaking of just an opinion.

If you don't wish to understand what I say, no problem but I do not lie under any circumstance so I sure
would do it here.
If I have missuderstood you then I apologize

If you want to continue I will not as I have sure I have been clear.

Good day

[SilverXJ]

I am not calling you a liar, but your information is incorrect.

I have plenty of first hand experience with WJs to have seen enough to know that they never came with a 0630 head. If you think they did then answer this: Where did they mount the coil rail as the 0630 does not have bosses for coil rail mounting?

As for XJs I have heard that the 99s may have had a 0331 head as well, but again I and no one I know has ever seen one.

[jeepman]

XJ/TJ/WJ 99 is a cross over year for all 4.0L As with the 97 TJ so they get a little of old and a little of new sometimes.

That's why half the time you order a part for a crossover year it's WRONG and you either have to ask for
one year newer or older to get the correct part.

I make my living working on Jeeps and see them every day so I do not care about your limited exposure and or
opinion.

With your limited thinking if you only saw a Red Corvette that must mean that
every Corvette ever made must be Red as well.

[SilverXJ]

Sure you do, whatever you think.

Limited exposure.. lol. I'm sure in your mind you think I only work on my Jeeps. Wrong.

You still haven't told me what held the coil rail on to the 0630 head. I call BS.

[jeepman]

You really are that limited and no I am sure you never leave the house let alone work on anything.

I never claimed every 99 Jeep is one way or another just what I have experienced so you think whatever you want as I know what I have had my hands on so I dont really care what you think.

Your too closed minded to have a conversation with so bye bye and take care.

[SilverXJ]

And you have no idea what you are talking about or are just very confused.

The 0630 was never put on a 99 WJ. Period. Besides the fact that they simply did not do it there are other issues. 1) Using either gasket there would only be about 1/16" of sealing at the bottom of the exhaust port, 2) that same misalignment would kill flow, 3) There is not way to bolt on the coil rail to the 0630 head. Friction of the spark plug boots on the plugs is not enough to hold the rail on.

You never did answer that question of how the coil rail was secured, so we can surmise you never saw one and have no idea what you are talking about. Or are you going to say next that some 99 WJs had a distributor?

[jeepman]

I chose to no longer play your game and No, what we can Summarize is that your close minded and full of yourself...

I chose to no longer debate with you when your the most ignorant person I have ever dealt with and its my fault as We have had other discussions and you were just as arrogant then when you were wrong so why should I think you'd stop now...

And Sorry to be the one to break it to you BUD but you are NOT the foremost authority and regardless of your experiences you can not (with as must as you try) speak for everything ever built in the world as all your doing is showing others how simple and ignorant you are...

I don't' claim to speak for every engine out there or ever built hell maybe the one WJ I saw was a fluke but since I have seen the same thing on a XJ and a TJ from one owner vehicles I speak from what I have seen and worked on, and since your not likely to actually read what I say here I will let you think you won and I will walk away...

I will be unsubscribing to this so I don't have to read your ignorance anymore...

ONCE again Good day