4.0 OHV exhaust manifold differences

[MarcosLopez77]

Im building a 4.0 ohv engine and have 3 different exhaust manifolds ive gathered over the years. all 3 of them fit but i notice they are all different castings. Was wondering if one is stronger or better than the other

heres what i have

-1990 2.9l exhaust manifolds
-1990 4.0l exhaust manifolds
-1998 4.0l exhaust manifolds

 

[PlumCrazy]

Are you running EGR?

 

[MarcosLopez77]

no egr

 

[JoshT]

For the most part the will flow the same, use the one that will fit your application best. If using a y-pipe use the manifolds that will match it. Otherwise use the one that seem to be most free flowing, least restrictions.

 

[MarcosLopez77]

thanks Josh, they all seem to bolt up to the y pipe im using which was originally connected to the 2.9 manifolds. the 98 manifolds which are still bolted on to the 98 block seem to have the least use on them so i might try to use those. Appreciate the info!

 

[cp2295]

98+ heads have bigger exhaust ports.

 

[PlumCrazy]

98+ heads have bigger exhaust ports.

^You are 100% incorrect....

The 98+ ports are smaller to increase velocity of the exhaust gasses entering the cats to basically heat them up faster to reduce emissions.

Don't post incorrect info if you are just making assumptions.

 

[MarcosLopez77]

^You are 100% incorrect....

The 98+ ports are smaller to increase velocity of the exhaust gasses entering the cats to basically heat them up faster to reduce emissions.

Don't post incorrect info if you are just making assumptions.

Plum Crazy i got a question. i noticed last night that my 90 2.9 y-pipe fits perfectly on the 98 manifold however the metal plate that the bolts go thru to attach to the manifold are spaced a bit narrower than the ones on the 98 y pipe. i havent tried to drill them out to make it a little wider yet, theres not a whole lot of room to drill. But i do have the 98 y pipe still that i can use only thing is it has 2 O2 sensors on it. I was wondering if i could replace 1 sensor with the one that matches up to my harness and plug the other O2 sensor hole with something and weld it?

 

[Destroyer000]

Plum Crazy i got a question. i noticed last night that my 90 2.9 y-pipe fits perfectly on the 98 manifold however the metal plate that the bolts go thru to attach to the manifold are spaced a bit narrower than the ones on the 98 y pipe. i havent tried to drill them out to make it a little wider yet, theres not a whole lot of room to drill. But i do have the 98 y pipe still that i can use only thing is it has 2 O2 sensors on it. I was wondering if i could replace 1 sensor with the one that matches up to my harness and plug the other O2 sensor hole with something and weld it?

yea that will work fine. your 90 computer was in the "simple" years. so basically the 02 is just gonna read off one bank and give both banks that reading if that makes sense. ive ran a few like that and my buddies truck is set up like that as well

 

[cp2295]

^You are 100% incorrect....

The 98+ ports are smaller to increase velocity of the exhaust gasses entering the cats to basically heat them up faster to reduce emissions.

Don't post incorrect info if you are just making assumptions.

Oh whoops, just the opposite, well I knew It was one or the other! thanks for correcting me

 

[MarcosLopez77]

yea that will work fine. your 90 computer was in the "simple" years. so basically the 02 is just gonna read off one bank and give both banks that reading if that makes sense. ive ran a few like that and my buddies truck is set up like that as well

What did you use to plug the extra hole with? Did u glue it or weld it?

 

[JoshT]

Have you got an old O2 sensor? IIRC they are NPT thread. Take it to the store and find a pipe plug that fits. Just snyg it in good and you are set. If you feel the need to seal it some high temperature RTV will do the job, smear a little on the threads and tighten it down good.

 

[PlumCrazy]

Have you got an old O2 sensor? IIRC they are NPT thread. Take it to the store and find a pipe plug that fits. Just snyg it in good and you are set. If you feel the need to seal it some high temperature RTV will do the job, smear a little on the threads and tighten it down good.

Nope....

O2 sensors are 18 x 1.5mm straight thread. You can buy plugs from just about any performance vendor (Jegs, Summit, Speedway, etc)

I personally would weld a new bung in at the Y so it picks up both banks and plug the other two, but that's just me.

http://www.summitracing.com/parts/aaf-all34150/overview/

 

[MarcosLopez77]

Nope....

O2 sensors are 18 x 1.5mm straight thread. You can buy plugs from just about any performance vendor (Jegs, Summit, Speedway, etc)

I personally would weld a new bung in at the Y so it picks up both banks and plug the other two, but that's just me.

http://www.summitracing.com/parts/aaf-all34150/overview/

plumcrazy thank you for the link. thats exactly what i need. i didnt realize they sold a bung. but since they do ill plug both of them like you said and add the other at the Y. Appreciate it man!