2000+ 3x00 exhaust manifolds

[TheProfessor]

i got some 2000+ 3x00 exhaust manifolds to put on my 3.1 in my 93 retta my mechanic was saying he wasnt sure about the egr because the fitting on the manifold side of the hose is different and he wasnt sure if the crossover would work, not sure why he said that about the crossover but anyway i was hoping someone could shed some light on this for me so i can tell my mechanic how to do it
thanks
jayme

[jmgtp]

The 3100 exhaust manifolds wont bolt to 3.1 heads.

[TheProfessor]

yes they will
thats not the problem

[v6h.o.]

The 3100 exhaust manifolds wont bolt to 3.1 heads.

they bolt up fine, and they have no issues with port location.


the Crossover from the 3x00 will be needed, you cant use the old crossover. it has a 2 bolt flange on each end, where as the 3x00's use a 3 bolt flange, completely different and is required with the newer manifolds.

the EGR tube will likely be in a slightly different location but, the fitting's for the EGR are all the same thread. so it should thread in fine. but as to if your egr tube will work propely in relation to lenth and location?? cant say for sure.

the tricky part with those manifolds in the old J/L bodies is the angle and closeness the rear manifold points the exhaust exit at the firewall.

its tight like a tiger.....

[jmgtp]

I stand corrected
I thought the heads had different shaped ports between Gen II and III

[v6h.o.]

they are different shaped ports. the gen3's are a "D" shape, and the gen2's are a round port.

you cannot swap the other way around, the Round port gen2 manifolds Do NOT fit onto the "D" shaped gen3's, but you can do the gen 3 manifolds onto gen2 heads.

[Cliff8928]

The 3100 exhaust manifolds wont bolt to 3.1 heads.

the tricky part with those manifolds in the old J/L bodies is the angle and closeness the rear manifold points the exhaust exit at the firewall.

its tight like a tiger.....

Yes, it sure is. I even have the melted rack and pinion boot and bushings to prove it (there used to be a little leak there!). Now i have a new custom downpipe that i got made a week or so ago and it's much better. Although the heads of the bolts which retain the inner tierods look like they want to decapitate the oxygen sensor at times.

Is it possible to drill/tap the EGR port for the M18 oxygen sensor thread so that i can relocate it there?


Cliff Scott
89 BerettaGT
89 Volvo740

[v6h.o.]

Cliff to remedy this i wraped up my rear manifold with Header wrap to keep the heat from melting the rack, and the downpipe was wraped as well to keep from melting the shifter cables for the trans.

i dont know if you could tap the egr port for the oxygen sensor.... the way the egr bolts into the manifold is a bit different... but might be possible. hard to say.

what O2 sensor do you have in there cliff?? aftermarket replacement? or a Stock A/C delco(gm) sensor. i have a GM sensor in there and it clears fine. i do know a few guys have had issues with some other sensors due to extra bulkyness of the sensor.

[Cliff8928]

what O2 sensor do you have in there cliff?? aftermarket replacement? or a Stock A/C delco(gm) sensor. i have a GM sensor in there and it clears fine. i do know a few guys have had issues with some other sensors due to extra bulkyness of the sensor.

I have the stock ACDelco sensor that has been on my car for a long time (at least 6 years!) probably about time to change it!


Cliff Scott
89 BerettaGT
89 Volvo740

[SappySE107]

You can port out gen 2 manifolds to fit a gen 3, but its a lot of work. Really only worthwhile for a TGP owner who wants to use the stock TGP setup on a gen 3.

[mihela816]

Is there any advantage to the 3x00 manifolds as opposed to the 3.1 manifolds? Do you have to have a 3100 downpipe as well?